WorldWideScience

Sample records for continuous wave lasers

  1. Continuous wave laser irradiation of explosives

    Energy Technology Data Exchange (ETDEWEB)

    McGrane, Shawn D.; Moore, David S.

    2010-12-01

    Quantitative measurements of the levels of continuous wave (CW) laser light that can be safely applied to bare explosives during contact operations were obtained at 532 nm, 785 nm, and 1550 nm wavelengths. A thermal camera was used to record the temperature of explosive pressed pellets and single crystals while they were irradiated using a measured laser power and laser spot size. A visible light image of the sample surface was obtained before and after the laser irradiation. Laser irradiation thresholds were obtained for the onset of any visible change to the explosive sample and for the onset of any visible chemical reaction. Deflagration to detonation transitions were not observed using any of these CW laser wavelengths on single crystals or pressed pellets in the unconfined geometry tested. Except for the photochemistry of DAAF, TATB and PBX 9502, all reactions appeared to be thermal using a 532 nm wavelength laser. For a 1550 nm wavelength laser, no photochemistry was evident, but the laser power thresholds for thermal damage in some of the materials were significantly lower than for the 532 nm laser wavelength. No reactions were observed in any of the studied explosives using the available 300 mW laser at 785 nm wavelength. Tables of laser irradiance damage and reaction thresholds are presented for pressed pellets of PBX9501, PBX9502, Composition B, HMX, TATB, RDX, DAAF, PETN, and TNT and single crystals of RDX, HMX, and PETN for each of the laser wavelengths.

  2. Coherence manifestation in a continuous-wave laser

    NARCIS (Netherlands)

    Eichhorn, M.; Pollnau, Markus

    We extend the existing theory of continuous-wave lasers by systematically considering spontaneous emission. In a simple rate-equation approach, the laser eigenvalue, defined as the ratio of coherent photons coupled out of the resonator divided by the number of photons coupled in via spontaneous

  3. Tapered Diode-pumped continuous-wave alexandrite laser

    OpenAIRE

    2013-01-01

    Tapered diode-pumped continuous-wave alexandrite laser Ersen Beyatli,1 Ilyes Baali,2 Bernd Sumpf,3 Götz Erbert,3 Alfred Leitenstorfer,4 Alphan Sennaroglu,1 and Umit Demirbas2,4,* 1Laser Research Laboratory, Departments of Physics and Electrical-Electronics Engineering, Koç University, Rumelifeneri, Sariyer, Istanbul 34450, Turkey 2Laser Technology Laboratory, Department of Electrical and Electronics Engineering, Antalya International University, 07190 Dosemealti, Antalya,...

  4. Toward continuous-wave operation of organic semiconductor lasers

    Science.gov (United States)

    Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

    2017-01-01

    The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

  5. Continuous wave infrared laser deposition of organic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yaginuma, Seiichiro [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Yamaguchi, Jun [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Haemori, Masamitsu [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Itaka, Kenji [Department of Advanced Materials Science, Graduate School of Frontier Sciences, Univesity of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568 (Japan); Matsumoto, Yuji [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Kondo, Michio [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Koinuma, Hideomi [Department of Advanced Materials Science, Graduate School of Frontier Sciences, Univesity of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568 (Japan)

    2007-04-15

    We developed a continuous-wave infrared laser molecular beam epitaxy (CW-IR-LMBE) optimized for the fabrication of organic semiconductor films. The crystal quality of these organic thin films deposited by CW-IR-LMBE was substantially the same as those deposited by thermal evaporation. Due to the possibility of quick switching of evaporation sources, CW-IR-LMBE is especially advantageous for rapid screening of composition, thickness, and fabrication parameters in materials and device optimization based on combinatorial technology.

  6. Continuous-wave organic dye lasers and methods

    Science.gov (United States)

    Shapira, Ofer; Chua, Song-Liang; Zhen, Bo; Lee, Jeongwon; Soljacic, Marin

    2014-09-16

    An organic dye laser produces a continuous-wave (cw) output without any moving parts (e.g., without using flowing dye streams or spinning discs of solid-state dye media to prevent photobleaching) and with a pump beam that is stationary with respect to the organic dye medium. The laser's resonant cavity, organic dye medium, and pump beam are configured to excite a lasing transition over a time scale longer than the associated decay lifetimes in the organic dye medium without photobleaching the organic dye medium. Because the organic dye medium does not photobleach when operating in this manner, it may be pumped continuously so as to emit a cw output beam. In some examples, operation in this manner lowers the lasing threshold (e.g., to only a few Watts per square centimeter), thereby facilitating electrical pumping for cw operation.

  7. Continuous-wave laser particle conditioning: Thresholds and time scales

    Science.gov (United States)

    Brown, Andrew; Ogloza, Albert; Olson, Kyle; Talghader, Joseph

    2017-03-01

    The optical absorption of contaminants on high reflectivity mirrors was measured using photo thermal common-path interferometry before and after exposure to high power continuous-wave laser light. The contaminants were micron-sized graphite flakes on hafnia-silica distributed Bragg reflectors illuminated by a ytterbium-doped fiber laser. After one-second periods of exposure, the mirrors demonstrated reduced absorption for irradiances as low as 11 kW cm-2 and had an obvious threshold near 20 kW cm-2. Final absorption values were reduced by up to 90% of their initial value for irradiances of 92 kW cm-2. For shorter pulses at 34 kW cm-2, a minimum exposure time required to begin absorption reduction was found between 100 μs and 200 μs, with particles reaching their final minimum absorption value within 300 ms. Microscope images of the surface showed agglomerated particles fragmenting with some being removed completely, probably by evaporation for exposures between 200 μs to 10 ms. Exposures of 100 ms and longer left behind a thin semi-transparent residue, covering much of the conditioned area. An order of magnitude estimate of the time necessary to begin altering the surface contaminants (also known as "conditioning") indicates about 200 μs seconds at 34 kW cm-2, based on heating an average carbon particle to its sublimation temperature including energy loss to thermal contact and radiation. This estimation is close to the observed exposure time required to begin absorption reduction.

  8. The Q-factor of a continuous-wave laser

    NARCIS (Netherlands)

    Eichhorn, M.; Pollnau, Markus

    We define the finite Q-factor of a continuous-wave lasing resonator as the energy of coherent photons stored in the resonator at a given time over the energy of these coherent photons lost per oscillation cycle.

  9. Study on 660-nm quasi-continuous-wave intracavity frequency-doubled Nd:YAG laser

    Institute of Scientific and Technical Information of China (English)

    Tao Wang(王涛); Jianquan Yao(姚建铨); Baigang Zhang(张百钢); Guiyan Zang(臧贵艳); Peng Wang(王鹏); Yizhong Yu(于意仲)

    2003-01-01

    A quasi-continuous-wave intracavity frequency-doubled Nd:YAG laser which operates at 660 nm is studied.By using a flat-flat laser cavity, 2 Kr-lamps, KTP crystal and an acousto-optically Q-switch, 2-W outputpower at 660 nm is obtained. The relationship between laser cavity length and output power is analyzed.

  10. Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode

    Science.gov (United States)

    Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

    2015-11-01

    Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

  11. Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode.

    Science.gov (United States)

    Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

    2015-11-16

    Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

  12. Interlaminar damage of carbon fiber reinforced polymer composite laminate under continuous wave laser irradiation

    Science.gov (United States)

    Liu, Yan-Chi; Wu, Chen-Wu; Huang, Yi-Hui; Song, Hong-Wei; Huang, Chen-Guang

    2017-01-01

    The interlaminar damages were investigated on the carbon fiber reinforced polymer (CFRP) composite laminate under laser irradiation. Firstly, the laminated T700/BA9916 composites were exposed to continuous wave laser irradiation. Then, the interface cracking patterns of such composite laminates were examined by optical microscopy and scanning electron microscopy. Finally, the Finite Element Analysis (FEA) was performed to compute the interface stress of the laminates under laser irradiation. And the effects of the laser parameters on the interlaminar damage were discussed.

  13. Characterization of Chirped Pump Four-Wave Mixing in Nonlinear Fibers using only Continuous-Wave-Lasers

    DEFF Research Database (Denmark)

    Lillieholm, Mads; Guan, Pengyu; Møller-kristensen, M. S.

    2017-01-01

    We propose a novel fiber characterization method that reveals the four-wave mixing bandwidth for chirped pump operation, using two tunable continuous-wave-lasers. The method accurately predicts the bandwidth for optical time lenses with broadband multi-carrier input......We propose a novel fiber characterization method that reveals the four-wave mixing bandwidth for chirped pump operation, using two tunable continuous-wave-lasers. The method accurately predicts the bandwidth for optical time lenses with broadband multi-carrier input...

  14. Continuous-wave, single-frequency 229 nm laser source for laser cooling of cadmium atoms

    CERN Document Server

    Kaneda, Yushi; Merzlyak, Yevgeny; Yamaguchi, Atsushi; Hayashida, Keitaro; Ohmae, Noriaki; Katori, Hidetoshi

    2016-01-01

    Continuous-wave output at 229 nm for the application of laser cooling of Cd atoms was generated by the 4th harmonic using two successive second harmonic generation stages. Employing a single-frequency optically pumped semiconductor laser as a fundamental source, 0.56 W of output at 229 nm was observed with a 10-mm long, Brewster-cut BBO crystal in an external cavity with 1.62 W of 458 nm input. Conversion efficiency from 458 nm to 229 nm was more than 34%. By applying a tapered amplifier as a fundamental source, we demonstrated magneto-optical trapping of all stable Cd isotopes including isotopes $^{111}$Cd and $^{113}$Cd, which are applicable to optical lattice clocks.

  15. Comparison of photosensitivity in germanium doped silica fibers using 244 nm and 266 nm continuous wave lasers

    DEFF Research Database (Denmark)

    Jensen, Jesper Bo; Varming, Poul; Liu, B.;

    2001-01-01

    Diode pumped continuous-wave UV lasers offer an interesting alternative to frequency doubled argon-ion lasers. We report the first photosensitivity comparison using these lasers on deuterium loaded standard telecommunication fibers and unloaded experimental fibers....

  16. Advanced Sine Wave Modulation of Continuous Wave Laser System for Atmospheric CO2 Differential Absorption Measurements

    Science.gov (United States)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.

    2014-01-01

    NASA Langley Research Center in collaboration with ITT Exelis have been experimenting with Continuous Wave (CW) laser absorption spectrometer (LAS) as a means of performing atmospheric CO2 column measurements from space to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission.Because range resolving Intensity Modulated (IM) CW lidar techniques presented here rely on matched filter correlations, autocorrelation properties without side lobes or other artifacts are highly desirable since the autocorrelation function is critical for the measurements of lidar return powers, laser path lengths, and CO2 column amounts. In this paper modulation techniques are investigated that improve autocorrelation properties. The modulation techniques investigated in this paper include sine waves modulated by maximum length (ML) sequences in various hardware configurations. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit perfect autocorrelation properties down to one cycle per code bit. In addition, a method is presented to bandwidth limit the ML sequence based on a Gaussian filter implemented in terms of Jacobi theta functions that does not seriously degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

  17. Matched Template Signal Processing for Continuous Wave Laser Tracking of Space Debris

    Science.gov (United States)

    Raj, S.; Ward, R.; Roberts, L.; Fleddermann, R.; Francis, S.; McClellend, D.; Shaddock, D.; Smith, C.

    2016-09-01

    The build up of space junk in Earth's orbit space is a growing concern as it shares the same orbit as many currently active satellites. As the number of objects increase in these orbits, the likelihood of collisions between satellites and debris will increase [1]. The eventual goal is to be able to maneuver space debris to avoid such collisions. We at SERC aim to accomplish this by using ground based laser facilities that are already being used to track space debris orbit. One potential method to maneuver space debris is using continuous wave lasers and applying photon pressure on the debris and attempt to change the orbit. However most current laser ranging facilities operates using pulsed lasers where a pulse of light is sent out and the time taken for the pulse to return back to the telescope is measured after being reflected by the target. If space debris maneuvering is carried out with a continuous wave laser then two laser sources need to be used for ranging and maneuvering. The aim of this research is to develop a laser ranging system that is compatible with the continuous wave laser; using the same laser source to simultaneously track and maneuver space debris. We aim to accomplish this by modulating the outgoing laser light with pseudo random noise (PRN) codes, time tagging the outgoing light, and utilising a matched filter at the receiver end to extract the various orbital information of the debris.

  18. Nitinol laser cutting: microstructure and functional properties of femtosecond and continuous wave laser processing

    Science.gov (United States)

    Biffi, C. A.; Tuissi, A.

    2017-03-01

    Thermal processing can affect the properties of smart materials, and the correct selection of the best manufacturing technology is fundamental for producing high tech smart devices, containing embedded functional properties. In this work cutting of thin superelastic Nitinol plates using a femtosecond (fs) and continuous wave (CW) laser was studied. Diamond shaped elements were cut to characterize the kerf qualitative features; microstructural analysis of the cross sections allowed identification of thermal damage characteristics introduced into the material during the laser processes. A thermally undamaged microstructure was observed for fs laser cutting, while CW was seen to be characterized by a large heat-affected zone. Functional properties were investigated by differential scanning calorimetry and tensile testing of laser cut microelements and of the reference material. It was seen that the martensitic transformation behavior of Nitinol is not affected by fs regime, while cw cutting provokes an effect equivalent to a high temperature thermal treatment in the material surrounding the cutting kerf, degradating the material properties. Finally, tensile testing indicated that superelastic performances were guaranteed by fs regime, while strong reduction of the recoverable strain was detected in the CW processed sample.

  19. Developing a narrow-line laser spectrometer based on a tunable continuous-wave dye laser

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chun; Lv, Shasha; Bi, Jin [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Fang [College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China); Li, Liufeng; Chen, Lisheng [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan 430071, China and Laboratory of Atomic Frequency Standards, Chinese Academy of Sciences, Wuhan 430071 (China)

    2014-08-15

    We present the development of a dye-laser-based spectrometer operating at 550–600 nm. The spectrometer will be used to detect an ultra-narrow clock transition ({sup 1}S{sub 0}-{sup 3}P{sub 0}) in an Ytterbium optical lattice clock and perform high-resolution spectroscopy of iodine molecules trapped in the sub-nanometer channels of zeolite crystal (AlPO{sub 4}-11). Two-stage Pound-Drever-Hall frequency stabilization is implemented on the tunable continuous-wave dye laser to obtain a reliable operation and provide stable laser radiations with two different spectral linewidths. In the first-stage frequency locking, a compact home-built intracavity electro-optic modulator is adopted for suppressing fast frequency noise. With an acquisition time of 0.1 s the 670-kHz linewidth of the free-running dye laser is reduced to 2 kHz when locked to a pre-stabilization optical cavity with a finesse of 1170. When the pre-stabilized laser is locked to a high-finesse optical cavity, a linewidth of 1.4 Hz (2 s) is observed and the frequency stability is 3.7 × 10{sup −15} (3 s). We also measure and analyze the individual noise contributions such as those from residual amplitude modulation and electronic noise. The ongoing upgrades include improving long-term frequency stability at time scales from 10 to 100 s and implementing continuous frequency scan across 10 GHz with radio-frequency precision.

  20. Continuous-wave operation of a room-temperature Tm: YAP-pumped Ho: YAG laser

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We report a continuous-wave (CW) 2.1-μm Ho:YAG laser operating at room temperature pumped by a diode-pumped 1.94-?m Tm:YAP laser.The maximum output power of 1.5 W is obtained from Ho:YAG laser,corresponding to Tm-to-Ho slope efficiency of 17.9% and diode-to-He conversion efficiency of 5.6%.

  1. High power all-solid-state quasi-continuous-wave tunable Ti: sapphire laser system

    Institute of Scientific and Technical Information of China (English)

    Lei Zou; Xin Ding; Yue Zou; Hongmei Ma; Wuqi Wen; Peng Wang; Jianquan Yao

    2005-01-01

    This paper reports a high power, all-solid-state, quasi-continuous-wave tunable Ti:sapphire laser system pumped by laser diode (LD) pumped frequency-doubled Nd:YAG laser. The maximum tuned output power of 4.2 W (797 nm) and tuned average power of 3.7 W were achieved when fixing the Ti:sapphire broadband output power at 5.0 W and applying 750-850 nm broadband coated mirror.

  2. Er-doped fiber ring laser gyroscopes operating in continuous waves

    Institute of Scientific and Technical Information of China (English)

    Jingren Qian; Jue Su; Xuxu Wang; Bing Zhu

    2007-01-01

    A direction related polarizer was inserted into a ring laser cavity to eliminate one of the two eigen-modes as well as spatial hole burning of the gain medium in a bidirectional Er-doped fiber ring laser. Thus, a fiber ring laser gyroscope (FRLG) operating in continuous wave was demonstrated. A beat signal of over 30-dB noise was observed and a good inear relation between the beat frequency shift and cavity rotation rate was obtained.

  3. Above room temperature continuous wave operation of a broad-area quantum-cascade laser

    Science.gov (United States)

    Semtsiv, M. P.; Masselink, W. T.

    2016-11-01

    We describe the design and implementation of a broad-area (w ≈ 30 μm) quantum-cascade laser operating in a continuous wave mode up to heat-sink temperatures beyond +100 °C. The room-temperature emission wavelength is 4.6 μm. The temperature gradient in the active region of such a wide laser stripe is essentially perpendicular to the epitaxial layers and the resulting steady-state active region temperature offset scales approximately with the square of the number of cascades. With only 10 cascades in the active region, the threshold electrical power density in the current quantum-cascade laser in the continuous-wave mode is as low as Vth × Ith = 3.8 V × 0.9 kA/cm2 = 3.4 kW/cm2 at room temperature for 2 mm-long two-side high-reflectivity coated laser stripe. A 4 mm-long one-side high-reflectivity coated laser stripe delivers in continuous-wave mode above 0.6 W at +20 °C and above 1.3 W at -27 °C (cooled with a single-stage Peltier element). A 2 mm-long two-side high-reflectivity coated laser stripe demonstrates continuous-wave lasing up to at least +102 °C (375 K). The thermal conductance, Gth, ranges between 235 W/K cm2 and 140 W/K cm2 for temperatures between -33 °C and +102 °C. This demonstration opens the route for continuous-wave power scaling of quantum-cascade lasers via broad-area laser ridges.

  4. Photoacoustic overtone spectroscopy of liquids with continuous wave laser excitation

    Science.gov (United States)

    Manzares, Carlos; I

    1991-06-01

    To study overtone absorptions in condensed phases, a technique is presented which uses a piezoelectric detector, lock-in amplification and a cw dye laser modulated at frequencies from 10 to 120 kHz with an acousto-optic modulator. Acoustic resonance frequencies calculated for a cylindrical cell are observed experimentally using liquid Si(CH 3) 4 as the sample. The acoustic signal is found to be proportional to the laser power. The fifth overtone of the CH streching mode of Si(CH 3) 4 has been recorded pure and in solutions with CCl 4. With a 1% solution of Si(CH 3) 4 in CCl 4, an absorbance of approximately 1 × 10 -5 cm -1 is detected with a dye laser power of 55 mW.

  5. Correction of walk-off-induced wavefront distortion for continuous-wave laser

    Science.gov (United States)

    Zou, Hongxin; Chen, Guozhu; Wu, Yue; Shen, Yong; Liu, Qu

    2016-09-01

    We theoretically and experimentally investigate the wave front distortion in critically phase-matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM00 mode efficiently. Theoretically, we simulate the correction effect of 266-nm laser generated with SHG. The experiment results accord well with the theoretical simulation and an above 80% TEM00 component is obtained for 266-nm continuous-wave laser with a 4.8°-walk-off angle in beta barium borate (BBO) crystal. Project supported by the National Natural Science Foundation of China (Grant No. 91436103) and Research Programme of National University of Defense Technology, China (Grant No. JC15-02-03).

  6. Characterization of a Continuous Wave Laser for Resonance Ionization Mass Spectroscopy Analysis in Nuclear Forensics

    Science.gov (United States)

    2015-06-01

    OF A CONTINUOUS WAVE LASER FOR RESONANCE IONIZATION MASS SPECTROSCOPY ANALYSIS IN NUCLEAR FORENSICS by Sunny G. Lau June 2015 Thesis...IONIZATION MASS SPECTROSCOPY ANALYSIS IN NUCLEAR FORENSICS 5. FUNDING NUMBERS 6. AUTHOR(S) Sunny G. Lau 7. PERFORMING ORGANIZATION NAME(S) AND...200 words) The application of resonance ionization mass spectroscopy (RIMS) to nuclear forensics involves the use of lasers to selectively ionize

  7. Dual-frequency injection-locked continuous-wave near-infrared laser

    CERN Document Server

    Gavara, Trivikramarao; Sasaki, Yusuke; Kawashima, Takuya; Hamano, Hiroaki; Yoshizaki, Ryo; Fujimura, Yuki; Yoshii, Kazumichi; Ohae, Chiaki; Katsuragawa, Masayuki

    2016-01-01

    We report a dual-frequency injection-locked continuous-wave near-infrared laser. The entire system consists of a Ti:sapphire ring laser as a power oscillator, two independent diode-lasers employed as seed lasers, and a master cavity providing a frequency reference. Stable dual-frequency injection-locked oscillation is achieved with a maximum output power of 2.8 W. As fundamental performance features of this laser system, we show its single longitudinal/transverse mode characteristics and practical power stability. Furthermore, as advanced features, we demonstrate arbitrary selectivity of the two frequencies and flexible control of their relative powers by simply manipulating the seed lasers.

  8. [Multi-harmonic analysis of quasi-continuous-wave laser modulation absorption spectroscopy].

    Science.gov (United States)

    Qi, Ru-bin; Du, Zhen-hui; Meng, Fan-li; Li, Jin-yi; Gao, Dong-yu; Xu, Xiao-bin; Chen, Wen-liang; Xu, Ke-xin

    2012-03-01

    Numerous harmonic components such as multiple frequency, sum frequency and difference frequency of multiple modulation signals were found in quasi-continuous-wave (QCW) diode laser modulation absorption spectroscopy. Then, the authors analyzed these harmonic components' existence in terms of non-linear interactions of laser and gas absorption line. And the signals' characteristics were studied experimentally. The results shows that there are some sum frequency and difference frequency components that have larger amplitudes compared to the second harmonic wavelength modulation spectroscopy signal (2f-WMS) commonly used in tunable diode laser spectroscopy (TDLAS), and it may improve the detection sensitivity of QCW modulation spectroscopy.

  9. Continuous-wave anti-Stokes Raman laser based on phase-matched nondegenerate four-wave mixing.

    Science.gov (United States)

    Zaitsu, Shin-ichi; Imasaka, Totaro

    2015-01-01

    We demonstrate phase-matched nondegenerate four-wave mixing (FWM) in a high-finesse optical cavity using a gaseous Raman-active medium pumped by two independent continuous-wave lasers. Efficient upconversion is achieved for pump beams at different wavelengths under phase-matched conditions by optimizing the total dispersion of the hydrogen-filled optical cavity. The independent control of the pump-beam polarizations leads to further enhancement of the upconversion efficiency arising from a larger Raman gain than that in degenerate FWM. This approach offers a promising alternative for a narrow-linewidth tunable light source for highly precise laser spectroscopy.

  10. Continuous wave channel waveguide lasers in Nd:LuVO4 fabricated by direct femtosecond laser writing.

    Science.gov (United States)

    Ren, Yingying; Dong, Ningning; Macdonald, John; Chen, Feng; Zhang, Huaijin; Kar, Ajoy K

    2012-01-30

    Buried channel waveguides in Nd:LuVOlaser writing with the double-line technique. The photoluminescence properties of the bulk materials were found to be well preserved within the waveguide core region. Continuous-wave laser oscillation at 1066.4 nm was observed from the waveguide under ~809 nm optical excitation, with the absorbed pump power at threshold and laser slope efficiency of 98 mW and 14%, respectively.

  11. Highspeed laser welding of steel using a high-power single-mode continuous-wave fiber laser

    Science.gov (United States)

    Drechsel, J.; Loeschner, U.; Schwind, S.; Hartwig, L.; Schille, J.; Exner, H.; Huebner, P.; Eysert, A.

    2013-02-01

    Since a few years, high brilliance laser sources find their way into laser material processing. Laser micro processing by applying high brilliance laser radiation up to 3 kW of continuous wave laser power in combination with ultrafast beam deflection systems has been successfully demonstrated in 2008 for the first time. In the fields of laser welding, high brilliant laser radiation was mainly used for micro welding, but up to now the macro range is still insufficiently investigated. Hence, this study reports on detailed investigations of high speed laser welding of different steel grades, performed with a high power single mode fiber laser source. The laser beam was deflected relative to the sample by using both a fast galvanometer scanner system with f-theta focusing objective and a linear axis in combination with a welding optic, respectively. In the study, the mainly process influencing parameters such as laser power, welding speed, thickness of the metal sheets, angle of incidence and laser beam spot size were varied in a wide range. The weld seam quality was evaluated by structural analyses, static tensile tests and EDX measurements. Finally, the laser welding process has been optimized for different weld seam geometries, for example bead-on-plate welds and butt welds.

  12. Self-referencing a continuous-wave laser with electro-optic modulation

    CERN Document Server

    Beha, Katja; Del'Haye, Pascal; Coillet, Aurélien; Diddams, Scott A; Papp, Scott B

    2015-01-01

    We phase-coherently measure the frequency of continuous-wave (CW) laser light by use of optical-phase modulation and f-2f nonlinear interferometry. Periodic electro-optic modulation (EOM) transforms the CW laser into a continuous train of picosecond optical pulses. Subsequent nonlinear-fiber broadening of this EOM frequency comb produces a supercontinuum with 160 THz of bandwidth. A critical intermediate step is optical filtering of the EOM comb to reduce electronic-noise-induced decoherence of the supercontinuum. Applying f-2f self-referencing with the supercontinuum yields the carrier-envelope offset frequency of the EOM comb, which is precisely the difference of the CW laser frequency and an exact integer multiple of the EOM pulse repetition rate. Here we demonstrate absolute optical frequency metrology and synthesis applications of the self-referenced CW laser with <5E-14 fractional accuracy and stability.

  13. Solutions of kW Continuous-wave All-fiber Laser

    Energy Technology Data Exchange (ETDEWEB)

    Yan Dapeng; Li Libo; Liu Xiaoxu [Wuhan Raycus Fiber Laser Technologies Co., Ltd, Wuhan (China); Min Dayong, E-mail: dyan@raycuslaser.com [Wuhan HuaGong Laser Engineering Co., Ltd, Wuhan (China)

    2011-02-01

    Solutions of kW continuous-wave (CW) all-fiber laser are proposed. In our solutions, master oscillator power amplifier (MOPA) configuration is applied. Output power of master oscillator is 10W, and then is amplified to 70W with 1st pre-amplifier and next scaled up to 400W. Finally, 400W fiber laser is used as a basic power unit, and 1000W all-fiber laser can be achieved by means of beam combining with large core double clad fiber (DCF) combiner. In this solution, fiber laser has good stability and reliability for dispersion coupling of pump source and inhibition of photon darkening effect in the fiber. In addition, this solution assures us realize a 1000W all-fiber laser product easily, and the cost is low.

  14. Continuous-wave and actively Q-switched Nd:LSO crystal lasers

    Science.gov (United States)

    Zhuang, S.; Li, D.; Xu, X.; Wang, Z.; Yu, H.; Xu, J.; Chen, L.; Zhao, Y.; Guo, L.; Xu, X.

    2012-04-01

    With a fiber coupled laser diode array as the pump source, Nd-doped Lu2SiO5 (Nd:LSO) crystal lasers at 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions were demonstrated. The active Q-switched dual-wavelength lasers at about 1.08 μm, as well as continuous-wave (CW) and active Q-switched lasers at 1357 nm are reported for the first time, to the best of our knowledge. Considering the small emission cross-sections and long fluorescence lifetime, this material possesses large energy storage ability and excellent Q-switched properties. The special emission wavelength at 1357 nm will have promising applications to be used in many fields, such as THz generation, pumping of Cr3+:LiSAF, repumping of strontium optical clock, laser Doppler velocimeter and distributed fiber sensor.

  15. Damage analysis of CMOS electro-optical imaging system by a continuous wave laser

    Science.gov (United States)

    Yoon, Sunghee; Jhang, Kyung-Young; Shin, Wan-Soon

    2016-08-01

    EOIS (electro-optical imaging system) is vulnerable to laser beam because EOIS focuses the incident laser beam onto the image sensor via lens module. Accordingly, the laser-induced damage of EOIS is necessary to be identified for the counter-measure against the laser attack. In this study, the damage of CMOS EOIS and image sensor induced by CW (continuous wave) NIR (near infrared) laser was experimentally investigated. When the laser was emitted to CMOS EOIS, a temporary damage was occurred first such as flickering or dazzling and then a permanent damage was followed as the increase of laser irradiance and irradiation time. If the EIOS is composed of the optical equipment made of heatresistant material, laser beam can penetrate the lens module of EOIS without melting the lens and lens guide. Thus, it is necessary to investigate the damage of CMOS image sensor by the CW laser and we performed experimentally investigation of damage on the CMOS image sensor similar with case of CMOS EOIS. And we analyzed the experiment results by using OM (optical microscopy) and check the image quality through tomography. As the increase of laser irradiance and irradiation time, the permanent damage such as discoloration and breakdown were sequentially appeared.

  16. Flow speed of the ablation vapors generated during laser drilling of CFRP with a continuous-wave laser beam

    Science.gov (United States)

    Faas, S.; Freitag, C.; Boley, S.; Berger, P.; Weber, R.; Graf, T.

    2017-03-01

    The hot plume of ablation products generated during the laser drilling process of carbon fiber reinforced plastics (CFRP) with a continuous-wave laser beam was analyzed by means of high-speed imaging. The formation of compression shocks was observed within the flow of the evaporated material, which is an indication of flow speeds well above the local speed of sound. The flow speed of the hot ablation products can be estimated by analyzing the position of these compression shocks. We investigated the temporal evolution of the flow speed during the drilling process and the influence of the average laser power on the flow speed. The flow speed increases with increasing average laser powers. The moment of drilling through the material changes the conditions for the drilling process and was confirmed to influence the flow speed of the ablated material. Compression shocks can also be observed during laser cutting of CFRP with a moving laser beam.

  17. Stable, continuous-wave, intracavity, optical parametric oscillator pumped by a semiconductor disk laser (VECSEL).

    Science.gov (United States)

    Stothard, D J M; Hopkins, J-M; Burns, D; Dunn, M H

    2009-06-22

    We report relaxation oscillation free, true continuous-wave operation of a singly-resonant, intracavity optical parametric oscillator (OPO) based upon periodically-poled, MgO-doped LiNbO3 and pumped internal to the cavity of a compact, optically-excited semiconductor disk laser (or VECSEL). The very short upper-laser-state lifetime of this laser gain medium, coupled with the enhancing effect of the high-finesse pump laser cavity in which the OPO is located, enables a low threshold, high efficiency intracavity device to be operated free of relaxation oscillations in continuous-wave mode. By optimizing for low-power operation, parametric threshold was achieved at a diode-laser power of only 1.4 W. At 8.5 W of diode-laser power, 205 mW of idler power was extracted, indicating a total down-converted power of 1.25 W, and hence a down-conversion efficiency of 83%.

  18. Characterization/Selection of a Continuous Wave Laser for RIMS Analysis in Nuclear Forensics

    Science.gov (United States)

    Lau, Sunny; Alves, F.; Karunasiri, G.; Smith, C.; Isselhardt, B.

    2015-03-01

    The effort to implement the technology of resonance ionization mass spectroscopy (RIMS) to problems of nuclear forensics involves the use of multiple lasers to selectively ionize the elements of concern. While current systems incorporate pulsed lasers, we present the results of a feasibility study to determine alternative (Continuous Wave) laser technologies to be employed for analysis of the actinides and fission products of debris from a nuclear detonation. RIMS has the potential to provide rapid isotope ratio quantification of the actinides and important fission products for post detonation nuclear forensics. The current approach to ionize uranium and plutonium uses three Ti-Sapphire pulsed lasers capable of a fundamental wavelength range of 700-1000 nm. In this work, we describe the use of a COTS CW laser to replace one of the pulsed lasers used for the second resonance excitation step of plutonium near 847.282 nm. We characterize the critical laser parameters necessary to achieve high precision isotope ratio measurements including the stability over time of the mean wavelength, bandwidth and spectral mode purity. This far narrower bandwidth laser provides a simpler setup, more robust hardware (greater mobility), and more efficient use of laser irradiance.

  19. Resonantly pumped continuous-wave mode-locked Ho:YAP laser

    Science.gov (United States)

    Duan, X. M.; Lin, W. M.; Cui, Z.; Yao, B. Q.; Li, H.; Dai, T. Y.

    2016-04-01

    In this paper, we report a continuous-wave mode-locked Ho:YAP laser for the first time to our knowledge. Mode-locked pulse was produced by using an acousto-optic modulator. A 1.91-μm Tm-fiber laser as the pump source, at incident pump power of 25.9 W, the maximum output power of 2.87 W at 2117.8 nm was achieved in continuous-wave mode-locked regime. Pulse as short as 254.8 ps was obtained at repetition frequency of 81.52 MHz. In addition, the beam quality factor M 2 value of 1.6 was obtained.

  20. Two micron continuous wave laser vaporesection for the treatment of benign prostatic hyperplasia

    Institute of Scientific and Technical Information of China (English)

    Wei-Jun Fu; Bao-Fa Hong; Yong Yang; Jiang-Ping Gao; Lei Zhang; Wei Cai; Yao-Fu Chen; Xiao-Xiong Wang

    2008-01-01

    @@ Dear Editor. I'm Wei-Jun Fu, from Department of Urology, Chi-nese People's Liberation Army General Hospital, Military Postgraduate Medical College, Beijing, China. We write to you to present an observation on the safety and clini-cal effects of RevoLix 70 W 2 micron continuous wave laser vaporesection for the treatment of obstructive be-nign prostatic hyperplasia (BPH).

  1. Effect of scanning speed on continuous wave laser scribing of metal thin films: theory and experiment

    Science.gov (United States)

    Shahbazi, AmirHossein; Koohian, Ata; Madanipour, Khosro

    2017-01-01

    In this paper continuous wave laser scribing of the metal thin films have been investigated theoretically and experimentally. A formulation is presented based on parameters like beam power, spot size, scanning speed and fluence thresholds. The role of speed on the transient temperature and tracks width is studied numerically. By using two frameworks of pulsed laser ablation of thin films and laser printing on paper, the relation between ablation width and scanning speed has been derived. Furthermore, various speeds of the focused 450 nm continuous laser diode with an elliptical beam spot applied to a 290 nm copper thin film coated on glass, experimentally. The beam power was 150 mW after spatial filtering. By fitting the theoretical formulation to the experimental data, the threshold fluence and energy were obtained to be 13.2 J mm-2 and 414~μ J respectively. An anticipated theoretical parameter named equilibrium~border was verified experimentally. It shows that in the scribing of the 290 nm copper thin film, at a distance where the intensity reaches about 1/e of its maximum value, the absorbed fluence on the surface is equal to zero. Therefore the application of continuous laser in metal thin film ablation has different mechanism from pulsed laser drilling and beam scanning in printers.

  2. Low-Cost Fabrication of Printed Electronics Devices through Continuous Wave Laser-Induced Forward Transfer.

    Science.gov (United States)

    Sopeña, Pol; Arrese, Javier; González-Torres, Sergio; Fernández-Pradas, Juan Marcos; Cirera, Albert; Serra, Pere

    2017-09-06

    Laser-induced forward transfer (LIFT) is a direct-writing technique that allows printing inks from a liquid film in a similar way to inkjet printing but with fewer limitations concerning ink viscosity and loading particle size. In this work, we prove that liquid inks can be printed through LIFT by using continuous wave (CW) instead of pulsed lasers, which allows a substantial reduction in the cost of the printing system. Through the fabrication of a functional circuit on both rigid and flexible substrates (plastic and paper), we provide a proof-of-concept that demonstrates the versatility of the technique for printed electronics applications.

  3. Highly Nonlinear Luminescence Induced by Gold Nanoparticles on Glass Surfaces with Continuous-Wave Laser Illumination

    CERN Document Server

    Wu, Yong; Toro, Ligia; Stefani, Enrico

    2015-01-01

    We report on highly nonlinear luminescence being observed from individual spherical gold nanoparticles immobilized on a borosilicate glass surface and illuminated by continuous-wave (CW) lasers with relatively low power. The nonlinear luminescence shows optical super-resolution beyond the diffraction limit in three dimensions compared to the scatting of the excitation laser light. The luminescence intensity from most nanoparticles is proportional to the 5th--7th power of the excitation laser power and has wide excitation and emission spectra across the visible wavelength range. Strong nonlinear luminescence is only observed near the glass surface. High optical nonlinearity excited by low CW laser power is related to a long-lived dark state of the gold nanoparticles, where the excitation light is strongly absorbed. This phenomenon has potential biological applications in super-resolution and deep tissue imaging.

  4. Pseudo-random noise-continuous-wave laser radar for surface and cloud measurements

    Science.gov (United States)

    Matthey, Renaud; Mitev, Valentin

    2005-03-01

    Laser radar (lidar) application may require an instrument with compact size, long life of the components, low consumption and eye-safety. One possibility to achieve these features is to use a continuous-wave (cw) diode laser as lidar transmitter. A practical way to perform range-resolved measurements with a cw laser diode is the pseudo-random noise (PRN) modulation. This paper presents a compact PRN-cw lidar, using a 370-mW cw diode laser and an APD as detector. Daytime measurements of cloud base and topographic surface are demonstrated with the PRN-cw lidar technique, where the range detection exceeds 2 km. The detection of the topographic surface is performed with integration time of some tens of milliseconds during daytime and some tens of microseconds during night-time.

  5. Continuous wave operation of quantum cascade lasers with frequency-shifted feedback

    Energy Technology Data Exchange (ETDEWEB)

    Lyakh, A., E-mail: arkadiy.lyakh@ucf.edu [Pranalytica, Inc., 1101 Colorado Ave., Santa Monica, CA 90401 (United States); NanoScience Technology Center, University of Central Florida, 12424 Research Pkwy, Orlando, FL 32826 (United States); College of Optics and Photonics, University of Central Florida, 304 Scorpius St, Orlando, FL 32826 (United States); Barron-Jimenez, R.; Dunayevskiy, I.; Go, R.; Tsvid, G.; Patel, C. Kumar N., E-mail: patel@pranalytica.com [Pranalytica, Inc., 1101 Colorado Ave., Santa Monica, CA 90401 (United States)

    2016-01-15

    Operation of continuous wave quantum cascade lasers with a frequency-shifted feedback provided by an acousto-optic modulator is reported. Measured linewidth of 1.7 cm{sup −1} for these devices, under CW operating conditions, was in a good agreement with predictions of a model based on frequency-shifted feedback seeded by spontaneous emission. Linewidth broadening was observed for short sweep times, consistent with sound wave grating period variation across the illuminated area on the acousto-optic modulator. Standoff detection capability of the AOM-based QCL setup was demonstrated for several solid materials.

  6. Non-Markovian dynamics in pulsed and continuous wave atom lasers

    CERN Document Server

    Breuer, H P; Kappler, B; Petruccione, F

    1999-01-01

    The dynamics of atom lasers with a continuous output coupler based on two-photon Raman transitions is investigated. With the help of the time-convolutionless projection operator technique the quantum master equations for pulsed and continuous wave (cw) atom lasers are derived. In the case of the pulsed atom laser the power of the time-convolutionless projection operator technique is demonstrated through comparison with the exact solution. It is shown that in an intermediate coupling regime where the Born-Markov approximation fails the results of this algorithm agree with the exact solution. To study the dynamics of a continuous wave atom laser a pump mechanism is included in the model. Whereas the pump mechanism is treated within the Born-Markov approximation, the output coupling leads to non-Markovian effects. The solution of the master equation resulting from the time-convolutionless projection operator technique exhibits strong oscillations in the occupation number of the Bose-Einstein condensate. These os...

  7. Frequency doubled high-power disk lasers in pulsed and continuous-wave operation

    Science.gov (United States)

    Weiler, Sascha; Hangst, Alexander; Stolzenburg, Christian; Zawischa, Ivo; Sutter, Dirk; Killi, Alexander; Kalfhues, Steffen; Kriegshaeuser, Uwe; Holzer, Marco; Havrilla, David

    2012-03-01

    The disk laser with multi-kW output power in infrared cw operation is widely used in today's manufacturing, primarily in the automotive industry. The disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency and high reliability with low investment and operating costs. Additionally, the disk laser is ideally suited for frequency conversion due to its polarized output with negligible depolarization losses. Laser light in the green spectral range (~515 nm) can be created with a nonlinear crystal. Pulsed disk lasers with green output of well above 50 W (extracavity doubling) in the ps regime and several hundreds of Watts in the ns regime with intracavity doubling are already commercially available whereas intracavity doubled disk lasers in continuous wave operation with greater than 250 W output are in test phase. In both operating modes (pulsed and cw) the frequency doubled disk laser offers advantages in existing and new applications. Copper welding for example is said to show much higher process reliability with green laser light due to its higher absorption in comparison to the infrared. This improvement has the potential to be very beneficial for the automotive industry's move to electrical vehicles which requires reliable high-volume welding of copper as a major task for electro motors, batteries, etc.

  8. High-power Yb-doped continuous-wave and pulsed fibre lasers

    Indian Academy of Sciences (India)

    B N Upadhyaya

    2014-01-01

    High-power laser generation using Yb-doped double-clad fibres with conversion efficiencies in excess of 80% have attracted much attention during the last decade due to their inherent advantages in terms of very high efficiency, no misalignment due to in-built intracore fibre Bragg gratings, low thermal problems due to large surface to volume ratio, diffraction-limited beam quality, compactness, reliability and fibre-optic beam delivery. Yb-doped fibres can also provide a wide emission band from ∼1010 nm to ∼1170 nm, which makes it a versatile laser medium to realize continuous-wave (CW), Q-switched short pulse, and mode-locked ultrashort pulse generation for various applications. In this article, a review of Yb-doped CW and pulsed fibre lasers along with our study on self-pulsing dynamics in CW fibre lasers to find its role in high-power fibre laser development and the physical mechanisms involved in its generation has been described. A study on the generation of high-power CWfibre laser of 165Woutput power and generation of high peak power nanosecond pulses from acousto-optic Q-switched fibre laser has also been presented.

  9. Glassy behavior in a one-dimensional continuous-wave erbium-doped random fiber laser

    Science.gov (United States)

    Gomes, Anderson S. L.; Lima, Bismarck C.; Pincheira, Pablo I. R.; Moura, André L.; Gagné, Mathieu; Raposo, Ernesto P.; de Araújo, Cid B.; Kashyap, Raman

    2016-07-01

    The photonic analog of the paramagnetic to spin-glass phase transition in disordered magnetic systems, signaled by the phenomenon of replica symmetry breaking, has been reported using random lasers as the photonic platform. We report here a demonstration of replica symmetry breaking in a one-dimensional photonic system consisting of an erbium-doped random fiber laser operating in the continuous-wave regime. The system is based on a unique random fiber grating system which plays the role of random scattering, providing the disordered feedback mechanism. The clear transition from a photonic paramagnetic to a photonic spin-glass phase, characterized by the Parisi overlap parameter, was verified and indicates the glassy random-fiber-laser behavior.

  10. Wavelength modulation spectroscopy based on quasi-continuous-wave diode lasers

    Institute of Scientific and Technical Information of China (English)

    Rubin Qi; Zhenhui Du; Dongyu Gao; Jinyi Li; Kexin Xu

    2012-01-01

    A modified wavelength modulation spectroscopy (WMS) based on the self-heating effect of the tunable diode laser when driven in quasi-continuous-wave (QCW) mode is investigated.A near-infrared distributed feedback (DFB) diode laser working at the QCW mode is employed as the QCW light source,and CO2 is selected as the target gas.The characteristic of the QCW second harmonic (2f) line profile is analyzed through a comparison with that of the traditional CW WMS with the same system.A noise-equivalent absorbance of 3.2× 10-5 Hz-1/2 for CO2 at 1.58 μm is obtained with 18-m optical path.The QCW WMS lowers the dependence on lasers and expands selectivity,thus verifying the feasibility of the method.%A modified wavelength modulation spectroscopy (WMS) based on the self-heating effect of the tunable diode laser when driven in quasi-continuous-wave (QCW) mode is investigated. A near-infrared distributed feedback (DFB) diode laser working at the QCW mode is employed as the QCW light source, and CO2 is selected as the target gas. The characteristic of the QCW second harmonic (2f) line profile is analyzed through a comparison with that of the traditional CW WMS with the same system. A noise-equivalent absorbance of 3.2×l0-5 Hz-1/2 for CO2 at 1.58 μm is obtained with 18-m optical path. The QCW WMS lowers the dependence on lasers and expands selectivity, thus verifying the feasibility of the method.

  11. Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers.

    Science.gov (United States)

    Eigenwillig, Christoph M; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R; Klein, Thomas; Jirauschek, Christian; Huber, Robert

    2013-01-01

    Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future.

  12. Deep drilling of silica glass by continuous-wave laser backside irradiation

    Science.gov (United States)

    Hidai, Hirofumi; Saito, Namiko; Matsusaka, Souta; Chiba, Akira; Morita, Noboru

    2016-04-01

    We propose a novel method for drilling of silica glass based on the continuous-wave laser backside irradiation (CW-LBI) phenomenon. The method allows drilling to be performed by single-shot irradiation using a CW laser. A spindle-shaped emission is generated in the bulk glass and is then guided to the glass surface, and at the instant that the beam reaches the surface, the glass material is ejected. The glass ejection process occurs for a time of ~250 μs. A hole that is similar in shape to that of the spindle-shaped emission is left. The hole length tended to increase linearly with increasing laser power. The laser power dependence of the spindle-shaped emission propagation velocity is also linear, and the velocity increases with increasing laser power. The hole diameters were smaller in the case where the laser focus position was set on the glass surface, and these diameters increased with increasing defocusing. The maximum hole depth reached more than 5 mm. Through-hole drilling was demonstrated using a 3-mm-thick glass substrate.

  13. High power, low divergent, substrate emitting quantum cascade ring laser in continuous wave operation

    Directory of Open Access Journals (Sweden)

    D. H. Wu

    2017-03-01

    Full Text Available We demonstrate a surface grating coupled substrate emitting quantum cascade ring laser with high power room temperature continuous wave operation at 4.64 μm. A second order surface metal/semiconductor distributed-feedback grating is used for in-plane feedback and vertical out-coupling. A device with 400 μm radius ring cavity exhibits an output power of 202 mW in room temperature continuous wave operation. Single mode operation with a side mode suppression ratio of 25 dB is obtained along with a good linear tuning with temperature. The far field measurement exhibits a low divergent concentric ring beam pattern with a lobe separation of ∼0.34°, which indicates that the device operates in fundamental mode (n = 1.

  14. Flow angle dependent photoacoustic Doppler power spectra under intensity-modulated continuous wave laser excitation

    Directory of Open Access Journals (Sweden)

    Yu Tong

    2016-02-01

    Full Text Available Photoacoustic Doppler (PAD power spectra showing an evident Doppler shift represent the major characteristics of the continuous wave-excited or burst wave-excited versions of PAD flow measurements. In this paper, the flow angle dependences of the PAD power spectra are investigated using an experiment setup that was established based on intensity-modulated continuous wave laser excitation. The setup has an overall configuration that is similar to a previously reported configuration, but is more sophisticated in that it accurately aligns the laser illumination with the ultrasound detection process, and in that it picks up the correct sample position. In the analysis of the power spectra data, we find that the background power spectra can be extracted by combining the output signals from the two channels of the lock-in amplifier, which is very useful for identification of the PAD power spectra. The power spectra are presented and analyzed in opposite flow directions, at different flow speeds, and at different flow angles. The power spectra at a 90° flow angle show the unique properties of symmetrical shapes due to PAD broadening. For the other flow angles, the smoothed power spectra clearly show a flow angle cosine relationship.

  15. Histologic evaluation of laser lipolysis comparing continuous wave vs pulsed lasers in an in vivo pig model.

    Science.gov (United States)

    Levi, Jessica R; Veerappan, Anna; Chen, Bo; Mirkov, Mirko; Sierra, Ray; Spiegel, Jeffrey H

    2011-01-01

    To evaluate acute and delayed laser effects of subdermal lipolysis and collagen deposition using an in vivo pig model and to compare histologic findings in fatty tissue after continuous wave diode (CW) vs pulsed laser treatment. Three CW lasers (980, 1370, and 1470 nm) and 3 pulsed lasers (1064, 1320, and 1440 nm) were used to treat 4 Göttingen minipigs. Following administration of Klein tumescent solution, a laser cannula was inserted at the top of a 10 × 2.5-cm rectangle and was passed subdermally to create separate laser "tunnels." Temperatures at the surface and at intervals of 4-mm to 20-mm depths were recorded immediately after exposure and were correlated with skin injury. Full-thickness cutaneous biopsy specimens were obtained at 1 day, 1 week, and 1 month after exposure and were stained with hematoxylin-eosin and trichrome stain. Qualitative and semiquantitative histopathologic evaluations were performed with attention to vascular damage, lipolysis, and collagen deposition. Skin surface damage occurred at temperatures exceeding 46°C. Histologic examination at 1 day after exposure showed hemorrhage, fibrous collagen fiber coagulation, and adipocyte damage. Adipocytes surrounded by histiocytes, a marker of lipolysis, were present at 1 week and 1 month after exposure. Collagen deposition in subdermal fatty tissue and in reticular dermis of some specimens was noted at 1 week and had increased at 1 month. Tissue treated with CW laser at 1470 nm demonstrated greater hemorrhage and more histiocytes at damage sites than tissue treated with pulsed laser at 1440 nm. There was a trend toward more collagen deposition with pulsed lasers than with CW lasers, but this was not statistically significant. Histopathologic comparison between results of CW laser at 980 nm vs pulsed laser at 1064 nm showed the same trend. Hemorrhage differences may result from pulse duration variations. A theoretical calculation estimating temperature rise in vessels supported this

  16. Highly efficient 1063-nm continuous-wave laser emission in Nd:GdVO4.

    Science.gov (United States)

    Lupei, V; Pavel, N; Sato, Y; Taira, T

    2003-12-01

    Highly efficient 1-microm continuous-wave laser emission in 3-mm-thick, 0.5- and 1.0-at. % Nd:GdVO4 crystals longitudinally pumped at 879 nm into the laser emitting level is reported. Under Ti:sapphire pumping, the slope efficiency in absorbed power is approximately 80% for both crystals, while the slope efficiency, the optical-to-optical efficiency (at 1700-mW pump power), and the laser threshold in incident power are 79%, 78%, and 31 mW for 0.5-at. % Nd and 80%, 77%, and 40 mW for 1.0-at. % Nd, respectively. The slope efficiency is close to the quantum defect limit, the difference being fully accounted for by the residual optical losses. Under 879-nm diode laser pumping, the slope efficiency and the optical-to-optical efficiency in absorbed power of the 0.5-at. % Nd:GdVO4 crystal are 60% and 53%, owing to poorer superposition of the pumped and the laser mode volumes.

  17. Design and Fabrication of a Chip-based Continuous-wave Atom Laser

    CERN Document Server

    Power, E P; Vanderelzen, B; Herrera-Fierro, P; Murphy, R; Yalisove, S M; Raithel, G

    2012-01-01

    We present a design for a continuous-wave (CW) atom laser on a chip and describe the process used to fabricate the device. Our design aims to integrate quadrupole magnetic guiding of ground state Rb atoms with continuous surface adsorption evaporative cooling to create a continuous Bose-Einstein condensate; out-coupled atoms from the condensate should realize a CW atom laser. We choose a geometry with three wires embedded in a spiral pattern in a silicon subtrate. The guide features an integrated solenoid to mitigate spin-flip losses and provide a tailored longitudinal magnetic field. Our design also includes multiple options for atom interferometry: accomodations are in place for laser-generated atom Fabry-Perot and Mach-Zehnder interferometers, and a pair of atomic beam X-splitters is incorporated for an all-magnetic atom Mach-Zehnder setup. We demonstrate the techniques necessary to fabricate our device using existing micro- and nano-scale fabrication equipment, and discuss future options for modified desi...

  18. Continuous-wave yellow laser generation at 578 nm by intracavity sum-frequency mixing of thin disk Yb:YAG laser and Nd:YAG laser

    Science.gov (United States)

    Ma, Gangfei; Yang, Jianming; Tan, Huiming; Tian, Yubing; Yao, Wenming; Ju, Qiaojun; Zhang, Long; Chen, Jiansheng; Wu, Xiaodong; Gao, Jing

    2017-07-01

    We report a continuous-wave yellow laser at 578 nm obtained by doubly resonant intracavity sum-frequency mixing of thin disk Yb:YAG laser and Nd:YAG laser with a LBO nonlinear crystal. Single-wavelength laser operation at 578 nm by using a silica etalon as a wavelength selector and dual-wavelength operation at 578 nm and 582 nm are obtained with maximum output powers of 100 mW and 136 mW, respectively. The single wavelength operating power stability value in 30 min was 4.7%, which was improved ∼21.6%, compared with that of dual-wavelength operation.

  19. Sodium vapor cell laser guide star experiments for continuous wave model validation

    Science.gov (United States)

    Pedreros Bustos, Felipe; Holzlöhner, Ronald; Budker, Dmitry; Lewis, Steffan; Rochester, Simon

    2016-07-01

    Recent numerical simulations and experiments on sodium Laser Guide Star (LGS) have shown that a continuous wave (CW) laser with circular polarization and re-pumping should maximize the fluorescent photon return flux to the wavefront sensor for adaptive optics applications. The orientation and strength of the geomagnetic field in the sodium layer also play an important role affecting the LGS return ux. Field measurements of the LGS return flux show agreement with the CW LGS model, however, fluctuations in the sodium column abundance and geomagnetic field intensity, as well as atmospheric turbulence, induce experimental uncertainties. We describe a laboratory experiment to measure the photon return flux from a sodium vapor cell illuminated with a 589 nm CW laser beam, designed to approximately emulate a LGS under controlled conditions. Return flux measurements are carried out controlling polarization, power density, re-pumping, laser linewidth, and magnetic field intensity and orientation. Comparison with the numerical CW simulation package Atomic Density Matrix are presented and discussed.

  20. Measuring the Absolute Height and Profile of the Mesospheric Sodium Layer using a Continuous Wave Laser

    CERN Document Server

    Butler, D J; Redfern, R M; Ageorges, N; Fews, H

    2003-01-01

    We have developed and tested a novel method, based on LIDAR, of measuring the height and profile of the mesospheric sodium layer using a continuous wave laser. It is more efficient than classical LIDAR as the laser is on for 50% of the time, and so can in principle be used during laser guide star adaptive optics observations. It also has significant advantages over direct imaging techniques because it does not require a second telescope, is almost independent of the atmospheric conditions, and avoids triangulation problems in determining the height. In the long term, regular monitoring using this method would allow a valuable database of sodium layer profiles, heights, and return flux measurements to be built up which would enable observatory staff astronomers to schedule observations optimally. In this paper we describe the original experiment carried out using the ALFA laser guide star system at Calar Alto Observatory in Spain. We validate the method by comparing the LIDAR results with those obtained from s...

  1. Evaluation of weld porosity in laser beam seam welds: optimizing continuous wave and square wave modulated processes.

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, Chad M. (Honeywell FM& T, Kansas City, MO); Perricone, Matthew; Faraone, Kevin M. (Honeywell FM& T, Kansas City, MO); Roach, Robert Allen; Norris, Jerome T.

    2007-02-01

    Nd:YAG laser joining is a high energy density (HED) process that can produce high-speed, low-heat input welds with a high depth-to-width aspect ratio. This is optimized by formation of a ''keyhole'' in the weld pool resulting from high vapor pressures associated with laser interaction with the metallic substrate. It is generally accepted that pores form in HED welds due to the instability and frequent collapse of the keyhole. In order to maintain an open keyhole, weld pool forces must be balanced such that vapor pressure and weld pool inertia forces are in equilibrium. Travel speed and laser beam power largely control the way these forces are balanced, as well as welding mode (Continuous Wave or Square Wave) and shielding gas type. A study into the phenomenon of weld pool porosity in 304L stainless steel was conducted to better understand and predict how welding parameters impact the weld pool dynamics that lead to pore formation. This work is intended to aid in development and verification of a finite element computer model of weld pool fluid flow dynamics being developed in parallel efforts and assist in weld development activities for the W76 and future RRW programs.

  2. Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zajnulina, M.; Giannone, D.; Haynes, R.; Roth, M. M. [innoFSPEC-VKS, Leibniz Institute for Astrophysics, An der Sternwarte 16, 14482 Potsdam (Germany); Böhm, M. [innoFSPEC-InFaSe, University of Potsdam, Am Mühlenberg 3, 14476 Golm (Germany); Blow, K. [Aston Institute of Photonic Technologies, Aston Triangle, Birmingham B4 7ET (United Kingdom); Rieznik, A. A. [Instituto Tecnologico de Buenos Aires and CONICET, Buenos Aires (Argentina)

    2015-10-15

    We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.

  3. Continuous-wave, single-frequency 229  nm laser source for laser cooling of cadmium atoms.

    Science.gov (United States)

    Kaneda, Yushi; Yarborough, J M; Merzlyak, Yevgeny; Yamaguchi, Atsushi; Hayashida, Keitaro; Ohmae, Noriaki; Katori, Hidetoshi

    2016-02-15

    Continuous-wave output at 229 nm for the application of laser cooling of Cd atoms was generated by the fourth harmonic using two successive second-harmonic generation stages. Employing a single-frequency optically pumped semiconductor laser as a fundamental source, 0.56 W of output at 229 nm was observed with a 10-mm long, Brewster-cut BBO crystal in an external cavity with 1.62 W of 458 nm input. Conversion efficiency from 458 nm to 229 nm was more than 34%. By applying a tapered amplifier (TA) as a fundamental source, we demonstrated magneto-optical trapping of all stable Cd isotopes including isotopes Cd111 and Cd113, which are applicable to optical lattice clocks.

  4. High Efficient Continuous-Wave Ho: YAG Laser Pumped by a Diode-pumped Tm: YLF Laser at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    DUAN Xiao-Ming; YAO Bao-Quan; ZHANG Yun-Jun; SONG Cheng-Wei; GAO Jing; JU You-Lun; WANG Yue-Zhu

    2008-01-01

    We present a high efficient continuous wave Ho:YAG laser pumped by a diode-pumped Tm:YLF laser with a Fabry-Perot etalon tuning at 1.91 μm. The maximum output power reaches 7.2 W when the absorbed pump power is 10.8 W.The slope efficiency (relative to the absorbed power) is 74.1%,and the Tm:YLF to Ho:YAG optical conversion efficiency of 60%,then the diode-to-Holmium optical conversion efficiency achieved is 21.0%.The wavelength is 2090 nm when the transmission of output coupler is larger than 20%.The beam quality factor is M2 ~ 1.15 measured by the travelling knife-edge method.

  5. Comparison of femtosecond laser and continuous wave UV sources for protein-nucleic acid crosslinking.

    Science.gov (United States)

    Fecko, Christopher J; Munson, Katherine M; Saunders, Abbie; Sun, Guangxing; Begley, Tadhg P; Lis, John T; Webb, Watt W

    2007-01-01

    Crosslinking proteins to the nucleic acids they bind affords stable access to otherwise transient regulatory interactions. Photochemical crosslinking provides an attractive alternative to formaldehyde-based protocols, but irradiation with conventional UV sources typically yields inadequate product amounts. Crosslinking with pulsed UV lasers has been heralded as a revolutionary technique to increase photochemical yield, but this method had only been tested on a few protein-nucleic acid complexes. To test the generality of the yield enhancement, we have investigated the benefits of using approximately 150 fs UV pulses to crosslink TATA-binding protein, glucocorticoid receptor and heat shock factor to oligonucleotides in vitro. For these proteins, we find that the quantum yields (and saturating yields) for forming crosslinks using the high-peak intensity femtosecond laser do not improve on those obtained with low-intensity continuous wave (CW) UV sources. The photodamage to the oligonucleotides and proteins also has comparable quantum yields. Measurements of the photochemical reaction yields of several small molecules selected to model the crosslinking reactions also exhibit nearly linear dependences on UV intensity instead of the previously predicted quadratic dependence. Unfortunately, these results disprove earlier assertions that femtosecond pulsed laser sources provide significant advantages over CW radiation for protein-nucleic acid crosslinking.

  6. Continuous-wave Raman laser pumped within a semiconductor disk laser cavity.

    Science.gov (United States)

    Parrotta, Daniele C; Lubeigt, Walter; Kemp, Alan J; Burns, David; Dawson, Martin D; Hastie, Jennifer E

    2011-04-01

    A KGd(WO₄)₂ Raman laser was pumped within the cavity of a cw diode-pumped InGaAs semiconductor disk laser (SDL). The Raman laser threshold was reached for 5.6 W of absorbed diode pump power, and output power up to 0.8 W at 1143 nm, with optical conversion efficiency of 7.5% with respect to the absorbed diode pump power, was demonstrated. Tuning the SDL resulted in tuning of the Raman laser output between 1133 and 1157 nm.

  7. Agile laser safety glasses for protection against continuous wave laser sources

    Science.gov (United States)

    Smith, David C.

    2007-02-01

    A concept for laser safety glasses is demonstrated where the laser intensity itself introduces phase distortion on the transmitted laser beam and is therefore self-limiting. The absorbed light in the polycarbonate glass heats it and changes its index of refraction. A coating on the surface produces a non-uniform intensity pattern on the transmitted laser beam. This non-uniform intensity results in a non-uniform phase distortion which destroys the coherence of the laser and does not allow the cornea to focus the laser strongly on the retina. The absorption in the glass is the same for all laser wavelengths (the glass is sometimes referred to as a neutral density filter) and therefore the safety glasses are good for all laser wavelengths. The amount of laser absorption required to meet the ANSI standard for max allowable exposure is a transmission of 0.1% and this is experimentally verified by the data obtained. This attenuation is sufficient to protect the eye from damage until the heating and phase distortion kicks in. Once this happens, the protection is better - the higher the incident intensity. Experimental demonstration of the effectiveness of the prototype has been obtained at 488 mm (blue light) and 514 mm (green light) from an argon ion laser with laser duration from 0.04 seconds to 0.25 seconds. The data shows that as you increase the laser intensity beyond a certain value the intensity at the focus of a lens actually decreases, and further increases in intensity lowers the focal plane intensity even further. For the phase distortion safety glasses, we can calculate the transmission which meets the ANSI standard where the phase distortion is optimum. Thus our glasses not only meet the ANSI standard but provide protection for any higher laser intensity. The optical quality of the prototype was very good with no fogging, or optical distortion of transmitted laser, and after the experiment, the prototype returned to the identical optical quality with no

  8. Diode-pumped continuous wave tunable and graphene Q-switched Tm:LSO lasers.

    Science.gov (United States)

    Feng, T L; Zhao, S Z; Yang, K J; Li, G Q; Li, D C; Zhao, J; Qiao, W C; Hou, J; Yang, Y; He, J L; Zheng, L H; Wang, Q G; Xu, X D; Su, L B; Xu, J

    2013-10-21

    We have investigated the lasing characteristics of Tm:LSO crystal in three operation regimes: continuous wave (CW), wavelength tunable and passive Q-switching based on graphene. In CW regime, a maximum output power of 0.65 W at 2054.9 nm with a slope efficiency of 21% was achieved. With a quartz plate, a broad wavelength tunable range of 145 nm was obtained, corresponding to a FWHM of 100 nm. By using a graphene saturable absorber mirror, the passively Q-switched Tm:LSO laser produced pulses with duration of 7.8 μs at 2030.8 nm under a repetition rate of 7.6 kHz, corresponding to pulse energy of 14.0 μJ.

  9. High-efficiency frequency doubling of continuous-wave laser light

    CERN Document Server

    Ast, Stefan; Schönbeck, Axel; Lastzka, Nico; Steinlechner, Jessica; Eberle, Tobias; Mehmet, Moritz; Steinlechner, Sebastian; Schnabel, Roman

    2011-01-01

    We report on the observation of high efficiency frequency doubling of 1550 nm continuous-wave laser light in a nonlinear cavity containing a periodically poled potassium titanyl phosphate crystal (PPKTP). The fundamental field had a power of 1.10 W and was converted into 1.05 W at 775 nm, yielding a total external conversion efficiency of (95 \\pm 1)%. The latter value is based on the measured depletion of the fundamental field being consistent with the absolute values derived from numerical simulations. According to our model, the conversion efficiency achieved was limited by the non-perfect mode-matching into the nonlinear cavity and the pump power available. Our result shows that cavity-assisted frequency conversion based on PPKTP is well suited for low-decoherence frequency conversion of quantum states of light.

  10. Nearly-octave wavelength tuning of a continuous wave fiber laser

    Science.gov (United States)

    Zhang, Lei; Jiang, Huawei; Yang, Xuezong; Pan, Weiwei; Cui, Shuzhen; Feng, Yan

    2017-01-01

    The wavelength tunability of conventional fiber lasers are limited by the bandwidth of gain spectrum and the tunability of feedback mechanism. Here a fiber laser which is continuously tunable from 1 to 1.9 μm is reported. It is a random distributed feedback Raman fiber laser, pumped by a tunable Yb doped fiber laser. The ultra-wide wavelength tunability is enabled by the unique property of random distributed feedback Raman fiber laser that both stimulated Raman scattering gain and Rayleigh scattering feedback are available at any wavelength. The dispersion property of the gain fiber is used to control the spectral purity of the laser output. PMID:28198414

  11. Advanced sine wave modulation of continuous wave laser system for atmospheric CO2 differential absorption measurements

    CERN Document Server

    Campbell, Joel F; Nehrir, Amin R

    2014-01-01

    A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate online and offline wavelength transmitted and received channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit optimal autocorrelation properties down to one cycle per code bit with zero off mainlobe values to within numerical precision. In addition, a method is presented to bandwidth limit the ML sequence based on a filter implemented in terms of Jacobi theta functions that does not significantly degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

  12. Continuous-wave Raman generation in a diode-pumped Nd3+:KGd(WO4)2 laser.

    Science.gov (United States)

    Demidovich, A A; Grabtchikov, A S; Lisinetskii, V A; Burakevich, V N; Orlovich, V A; Kiefer, W

    2005-07-01

    Continuous-wave Raman generation in a compact solid-state laser system pumped by a multimode diode laser is demonstrated. The Stokes radiation of stimulated Raman scattering at 1.181 microm is generated as a result of self-frequency conversion of the 1.067 microm laser radiation in Nd3+:KGd(WO4)2 crystal placed in the cavity. The Raman threshold was measured at 1.15 W of laser diode power. The highest output power obtained at the Stokes wavelength was 54 mW. The anomalous delay of Raman generation relative to the start of laser generation (the oscillation buildup) due to slow accumulation of Stokes photons in the cavity at low Raman gain and Raman threshold dependence not only on the laser intensity but also on the time of laser action are observed.

  13. Room temperature continuous wave InGaAsN quantum well vertical cavity lasers emitting at 1.3 um

    Energy Technology Data Exchange (ETDEWEB)

    CHOQUETTE,KENT D.; KLEM,JOHN F.; FISCHER,ARTHUR J.; SPAHN,OLGA B.; ALLERMAN,ANDREW A.; FRITZ,IAN J.; KURTZ,STEVEN R.; BREILAND,WILLIAM G.; SIEG,ROBERT M.; GEIB,KENT M.; SCOTT,J.W.; NAONE,R.L.

    2000-06-05

    Selectively oxidized vertical cavity lasers emitting at 1294 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave at and above room temperature. The lasers employ two n-type Al{sub 0.94}Ga{sub 0.06}As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55 C. These lasers exhibit the longest wavelength reported to date for vertical cavity surface emitting lasers grown on GaAs substrates.

  14. Continuous-wave and Q-switched performance of an Yb:YAG/YAG composite thin disk ceramic laser pumped with 970-nm laser diode

    Institute of Scientific and Technical Information of China (English)

    Hong Cai; Jun Zhou; Hongming Zhao; Yunfeng Qi; Qihong Lou; Jingxing Dong; Yunrong Wei

    2008-01-01

    Using front face-pumped compact active mirror laser (CAMIL) structure, we have demonstrated an Yb:YAG/YAG composite ceramic disk laser with pumping wavelength at 970 nm. The laser has been operated in both continuous-wave (CW) and Q-switching modes. Under CW operation, laser output power of 1.05 W with 2% transmission output coupler was achieved at the wavelength of 1031 nm. Qswitched laser output was gotten by using an acousto-optic Q-switch. The repetition rate ranged from 1 to 30 kHz and the pulse width varied from 166 to 700 ns.

  15. Welding Stainless Steels and Refractory Metals Using Diode-Pumped Continuous Wave Nd:YAG Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, T A; Elmer, J W; Pong, R; Gauthier, M D

    2004-09-27

    This report provides an overview of a series of developmental welding studies performed on a 2.2 kW Rofin Sinar DY-022 Diode Pumped Continuous Wave (CW) Nd:YAG welder at Lawrence Livermore National Laboratory (LLNL). Several materials systems, ranging from refractory metals, such as commercially pure tantalum and vanadium, to austenitic stainless steels, including both 304L and 21-6-9 grades, are examined. Power input and travel speed are systematically varied during the welding of each materials system, and the width, depth, and cross sectional area of the resulting weld fusion zones are measured. These individual studies are undertaken in order to characterize the response of the welder to changes in these welding parameters for a range of materials and to determine the maximum depth of penetration of which this welder is capable in each materials system. The maximum weld depths, which are on the order of 5.4 mm, are observed in the 21-6-9 austenitic stainless steel at the maximum laser power setting (2200 W) and a slow travel speed (6.4 mm/sec). The next highest weld depth is observed in the 304L stainless steel, followed by that observed in the vanadium and, finally, in the tantalum. Porosity, which is attributed to the collapse of the keyhole during welding, is also observed in the welds produced in tantalum, vanadium, and 304L stainless steel. Only the 21-6-9 austenitic stainless steel welds displayed little or no porosity over the range of welding parameters. Comparisons with similar laser welding systems are also made for several of these same materials systems. When compared with the welds produced by these other systems, the LLNL system typically produces welds of an equivalent or slightly higher depth.

  16. Fabrication of room temperature continuous-wave operation GaN-based ultraviolet laser diodes

    Science.gov (United States)

    Zhao, Degang; Yang, Jing; Liu, Zongshun; Chen, Ping; Zhu, Jianjun; Jiang, Desheng; Shi, Yongsheng; Wang, Hai; Duan, Lihong; Zhang, Liqun; Yang, Hui

    2017-06-01

    Two kinds of continuous-wave GaN-based ultraviolet laser diodes (LDs) operated at room temperature and with different emission wavelengths are demonstrated. The LDs epitaxial layers are grown on GaN substrate by metalorganic chemical vapor deposition, with a 10 × 600 μm2 ridge waveguide structure. The electrical and optical characteristics of the ultraviolet LDs are investigated under direct-current injection at room temperature. The stimulated emission peak wavelength of first LD is 392.9 nm, the threshold current density and voltage is 1.5 kA/cm2 and 5.0 V, respectively. The output light power is 80 mW under the 4.0 kA/cm2 injection current density. The stimulated emission peak wavelength of second LD is 381.9 nm, the threshold current density the voltage is 2.8 kA/cm2 and 5.5 V, respectively. The output light power is 14 mW under a 4.0 kA/cm2 injection current density. Projects the supported by the National Key R&D Program of China (Nos. 2016YFB0401801, 2016YFB0400803), the National Natural Science Foundation of China (Nos. 61674138, 61674139, 61604145, 61574135, 61574134, 61474142, 61474110, 61377020, 61376089), the Science Challenge Project (No. JCKY2016212A503), and the One Hundred Person Project of the Chinese Academy of Sciences.

  17. Continuous-wave laser operation of diode-pumped Tm-doped Gd3Ga5O12 crystal

    Science.gov (United States)

    Wang, Yi; Lan, Jinglong; Zhou, Zhiyong; Guan, Xiaofeng; Xu, Bin; Xu, Huiying; Cai, Zhiping; Wang, Yan; Tu, Chaoyang

    2017-04-01

    We report on a diode-pumped Tm:Gd3Ga5O12 (GGG) laser at 2004 nm operated in continuous-wave mode with two-mirror linear cavity configuration. The maximum output power reaches 0.58 W with laser threshold absorbed pump power of about 0.39 W and overall slope efficiency of about 18.4%, which is believed to be the highest output power for Tm:GGG laser up to now. The Tm:GGG laser shows obvious thermally induced saturation of the output power, which indicated that power and efficiency scaling could be furtherly realized by more efficient thermal removal of the laser crystal.

  18. High speed video shooting with continuous-wave laser illumination in laboratory modeling of wind - wave interaction

    Science.gov (United States)

    Kandaurov, Alexander; Troitskaya, Yuliya; Caulliez, Guillemette; Sergeev, Daniil; Vdovin, Maxim

    2014-05-01

    Three examples of usage of high-speed video filming in investigation of wind-wave interaction in laboratory conditions is described. Experiments were carried out at the Wind - wave stratified flume of IAP RAS (length 10 m, cross section of air channel 0.4 x 0.4 m, wind velocity up to 24 m/s) and at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m, wind velocity up to 10 m/s). A combination of PIV-measurements, optical measurements of water surface form and wave gages were used for detailed investigation of the characteristics of the wind flow over the water surface. The modified PIV-method is based on the use of continuous-wave (CW) laser illumination of the airflow seeded by particles and high-speed video. During the experiments on the Wind - wave stratified flume of IAP RAS Green (532 nm) CW laser with 1.5 Wt output power was used as a source for light sheet. High speed digital camera Videosprint (VS-Fast) was used for taking visualized air flow images with the frame rate 2000 Hz. Velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave profile. The mean wind velocity profiles were retrieved using conditional in phase averaging like in [1]. In the experiments on the LASIF more powerful Argon laser (4 Wt, CW) was used as well as high-speed camera with higher sensitivity and resolution: Optronics Camrecord CR3000x2, frame rate 3571 Hz, frame size 259×1696 px. In both series of experiments spherical 0.02 mm polyamide particles with inertial time 7 ms were used for seeding airflow. New particle seeding system based on utilization of air pressure is capable of injecting 2 g of particles per second for 1.3 - 2.4 s without flow disturbance. Used in LASIF this system provided high particle density on PIV-images. In combination with high-resolution camera it allowed us to obtain momentum fluxes directly from

  19. Thermal effects of continuous wave CO sub 2 laser exposure on human teeth: An in vitro study

    Energy Technology Data Exchange (ETDEWEB)

    Miserendino, L.J.; Neiburger, E.J.; Walia, H.; Luebke, N.; Brantley, W.

    1989-07-01

    The thermal effects of continuous wave carbon dioxide laser irradiation on human teeth were investigated. Internal temperature changes were monitored by means of electrical thermistors implanted within the pulp chambers of 20 extracted, unerupted human molar teeth. One-hundred test exposures at various powers and durations were obtained. Linear regression/correlation analysis of the data suggests a direct relationship between the independent variable, exposure energy (joules), and the dependent variable, internal temperature, under the conditions of this study.

  20. Watt-Level Continuous-Wave Emission from a Bi-Functional Quantum Cascade Laser/Detector

    Science.gov (United States)

    2017-04-18

    materials, which makes their integration on Si particularly dicult. Heterogeneous integration using transfer techniques allows both single device and wafer...mixing process and low dispersion in this device. At higher currents the spectrum widens to about 80 cm−1. The spectra at the bias of highest WPE is...Elliott, S. N.; Sobiesierski, A.; Seeds , A. J.; Ross, I.; Smowton, P. M.; Liu, H. Electrically pumped continuous-wave IIIV quantum dot lasers on silicon

  1. High-efficiency multipass Ti:sapphire amplifiers for a continuous-wave single-mode laser.

    Science.gov (United States)

    Georges, P; Estable, F; Salin, F; Poizat, J P; Grangier, P; Brun, A

    1991-02-01

    We present the amplification of a continuous-wave single-mode ring dye laser in Ti:sapphire. A peak gain of 2 x 10(6) has been obtained in a passive multipass amplifier, which yielded 20-nsec pulses of 0.7-mJ energy at 780 nm. We discuss the advantages of this passive multipass amplifier in comparison with a regenerative amplifier that we have also developed. By second-harmonic generation we obtained high-peak-power UV pulses from the amplified single-mode laser.

  2. Field test of an all-semiconductor laser-based coherent continuous-wave Doppler lidar for wind energy applications

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Dellwik, Ebba; Hu, Qi

    The wind energy industry is gaining interest in prevision of the rotor inflow for turbine control. The potential benefits are increased power production due to better alignment of the rotor to the mean wind direction as well as prolonged lifetime of the turbine due to load reductions. Several lidar......-produced all-semiconductor laser. The instrument is a coherent continuous-wave lidar with two fixed-focus telescopes for launching laser beams in two different directions. The alternation between the telescopes is achieved by a novel switching technique without any moving parts. Here, we report results from...

  3. Accumulating microparticles and direct-writing micropatterns using a continuous-wave laser-induced vapor bubble.

    Science.gov (United States)

    Zheng, Yajian; Liu, Hui; Wang, Yi; Zhu, Cong; Wang, Shuming; Cao, Jingxiao; Zhu, Shining

    2011-11-21

    Through the enhanced photothermal effect, which was achieved using a silver film, a low power weakly focused continuous-wave laser (532 nm) was applied to create a vapor bubble. A convective flow was formed around the bubble. Microparticles dispersed in water were carried by the convective flow to the vapor bubble and accumulated on the silver film. By moving the laser spot, we easily manipulated the location of the bubble, allowing us to direct-write micropatterns on the silver film with accumulated particles. The reported simple controllable accumulation method can be applied to bimolecular detection, medical diagnosis, and other related biochip techniques.

  4. Characteristic time scales of coalescence of silver nanocomposite and nanoparticle films induced by continuous wave laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Paeng, Dongwoo; Grigoropoulos, Costas P., E-mail: cgrigoro@berkeley.edu [Department of Mechanical Engineering, University of California Berkeley, Berkeley, California 94720-1740 (United States); Lee, Daeho [Department of Mechanical Engineering, Gachon University, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of)

    2014-08-18

    In-situ optical probing has been performed to analyze and compare the characteristic coalescence time scales of silver ion-doped polyvinylalcohol nanocomposite (Ag-PVA NC) and polyvinylpyrrolidone-capped silver nanoparticle (Ag-PVP NP) films subjected to continuous wave laser irradiation. The Ag-PVA NC yielded conductive metallic patterns by photothermal reduction of PVA, formation of nanoparticles from silver ions and their subsequent coalescence. On the other hand, Ag-PVP NP thin films produced conductive patterns through only coalescence of nanoparticles. Upon laser irradiation, Ag-PVA NC and Ag-PVP NP films exhibited different coalescence characteristics.

  5. All-solid-state continuous-wave laser systems for ionization, cooling and quantum state manipulation of beryllium ions

    CERN Document Server

    Lo, H -Y; Kienzler, D; Keitch, B C; de Clercq, L E; Negnevitsky, V; Home, J P

    2013-01-01

    We describe laser systems for photoionization, Doppler cooling and quantum state manipulation of beryllium ions. For photoionization of neutral beryllium, we have developed a continuous-wave 235 nm source obtained by two stages of frequency doubling from a diode laser at 940 nm. The system delivers up to 400 mW at 470 nm and 28 mW at 235 nm. For control of the beryllium ion, three laser wavelengths at 313 nm are produced by sum-frequency generation and second-harmonic generation from four infrared fiber lasers. Up to 7.2 W at 626 nm and 1.9 W at 313 nm are obtained using two pump beams at 1051 and 1551 nm. Intensity fluctuations below 0.5 % per hour (during 8 hours of operation) have been measured at a 313 nm power of 1 W. These systems are used to load beryllium ions into a segmented ion trap.

  6. Continuous-wave supercontinuum laser based on an erbium-doped fiber ring cavity incorporating a highly nonlinear optical fiber

    Science.gov (United States)

    Lee, Ju Han; Takushima, Yuichi; Kikuchi, Kazuro

    2005-10-01

    We experimentally demonstrate a novel erbium-doped fiber based continuous-wave (cw) supercontinuum laser. The laser has a simple ring-cavity structure incorporating an erbium-doped fiber and a highly nonlinear dispersion-shifted fiber (HNL-DSF). Differently from previously demonstrated cw supercontinuum sources based on single propagation of a strong Raman pump laser beam through a highly nonlinear fiber, erbium gain inside the cavity generates a seed light oscillation, and the oscillated light subsequently evolves into a supercontinuum by nonlinear effects such as modulation instability and stimulated Raman scattering in the HNL-DSF. High quality of the depolarized supercontinuum laser output with a spectral bandwidth larger than 250 nm is readily achieved.

  7. Modulated and continuous-wave operations of low-power thulium (Tm:YAP) laser in tissue welding.

    Science.gov (United States)

    Bilici, Temel; Tabakoğlu, Haşim Ozgür; Topaloğlu, Nermin; Kalaycioğlu, Hamit; Kurt, Adnan; Sennaroglu, Alphan; Gülsoy, Murat

    2010-01-01

    Our aim is to explore the welding capabilities of a thulium (Tm:YAP) laser in modulated and continuous-wave (CW) modes of operation. The Tm:YAP laser system developed for this study includes a Tm:YAP laser resonator, diode laser driver, water chiller, modulation controller unit, and acquisition/control software. Full-thickness incisions on Wistar rat skin were welded by the Tm:YAP laser system at 100 mW and 5 s in both modulated and CW modes of operation (34.66 Wcm(2)). The skin samples were examined during a 21-day healing period by histology and tensile tests. The results were compared with the samples closed by conventional suture technique. For the laser groups, immediate closure at the surface layers of the incisions was observed. Full closures were observed for both modulated and CW modes of operation at day 4. The tensile forces for both modulated and CW modes of operation were found to be significantly higher than the values found by conventional suture technique. The 1980-nm Tm:YAP laser system operating in both modulated and CW modes maximizes the therapeutic effect while minimizing undesired side effects of laser tissue welding. Hence, it is a potentially important alternative tool to the conventional suturing technique.

  8. Self-organized micro-holes on titania based sol-gel films under continuous direct writing with a continuous wave ultraviolet laser

    Energy Technology Data Exchange (ETDEWEB)

    Bakhti, S.; Destouches, N.; Gamet, E.; Reynaud, S. [University of Lyon, F. 42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 18 Rue Pr. Lauras F-42000 Saint-Etienne (France); University of Saint-Etienne, Jean Monnet, F-42000 Saint-Etienne (France); Balan, L. [Institut de Sciences des Materiaux de Mulhouse, CNRS UMR 7361, Universite de Haute Alsace, 15 rue Jean Starcky, 68057 Mulhouse (France)

    2013-05-27

    The microstructuring of titania based sol-gel films is investigated by direct writing with a continuous wave ultraviolet laser beam emitting at 244 nm. Depending on the exposure conditions, the films exhibit a volume expansion, a volume shrinkage, a self-shaped delamination, or are damaged. This paper is mainly focused on the regime where spontaneous local delamination occurs, which corresponds to a narrow range of laser irradiances and writing speeds. In this regime, self-organized round-shape micro-holes opened on the substrate are generated.

  9. Continuous-wave to pulse regimes for a family of passively mode-locked lasers with saturable nonlinearity

    Science.gov (United States)

    Dikandé, Alain M.; Voma Titafan, J.; Essimbi, B. Z.

    2017-10-01

    The transition dynamics from continuous-wave to pulse regimes of operation for a generic model of passively mode-locked lasers with saturable absorbers, characterized by an active medium with non-Kerr nonlinearity, are investigated analytically and numerically. The system is described by a complex Ginzburg–Landau equation with a general m:n saturable nonlinearity (i.e {I}m/{(1+{{Γ }}I)}n, where I is the field intensity and m and n are two positive numbers), coupled to a two-level gain equation. An analysis of stability of continuous waves, following the modulational instability approach, provides a global picture of the self-starting dynamics in the system. The analysis reveals two distinct routes depending on values of the couple (m, n), and on the dispersion regime: in the normal dispersion regime, when m = 2 and n is arbitrary, the self-starting requires positive values of the fast saturable absorber and nonlinearity coefficients, but negative values of these two parameters for the family with m = 0. However, when the spectral filter is negative, the laser can self-start for certain values of the input field and the nonlinearity saturation coefficient Γ. The present work provides a general map for the self-starting mechanisms of rare-earth doped figure-eight fiber lasers, as well as Kerr-lens mode-locked solid-state lasers.

  10. Bandwidth scaling and spectral flatness enhancement of optical frequency combs from phase-modulated continuous-wave lasers using cascaded four-wave mixing.

    Science.gov (United States)

    Supradeepa, V R; Weiner, Andrew M

    2012-08-01

    We introduce a new cascaded four-wave mixing technique that scales up the bandwidth of frequency combs generated by phase modulation of a continuous-wave (CW) laser while simultaneously enhancing the spectral flatness. As a result, we demonstrate a 10 GHz frequency comb with over 100 lines in a 10 dB bandwidth in which a record 75 lines are within a flatness of 1 dB. The cascaded four-wave mixing process increases the bandwidth of the initial comb generated by the modulation of a CW laser by a factor of five. The broadband comb has approximately quadratic spectral phase, which is compensated upon propagation in single-mode fiber, resulting in a 10 GHz train of 940 fs pulses.

  11. A highly efficient directional molecular white-light emitter driven by a continuous-wave laser diode

    Science.gov (United States)

    Rosemann, Nils W.; Eußner, Jens P.; Beyer, Andreas; Koch, Stephan W.; Volz, Kerstin; Dehnen, Stefanie; Chatterjee, Sangam

    2016-06-01

    Tailored light sources have greatly advanced technological and scientific progress by optimizing the emission spectrum or color and the emission characteristics. We demonstrate an efficient spectrally broadband and highly directional warm-white-light emitter based on a nonlinear process driven by a cheap, low-power continuous-wave infrared laser diode. The nonlinear medium is a specially designed amorphous material composed of symmetry-free, diamondoid-like cluster molecules that are readily obtained from ubiquitous resources. The visible part of the spectrum resembles the color of a tungsten-halogen lamp at 2900 kelvin while retaining the superior beam divergence of the driving laser. This approach of functionalizing energy-efficient state-of-the-art semiconductor lasers enables a technology complementary to light-emitting diodes for replacing incandescent white-light emitters in high-brilliance applications.

  12. Theoretical and experimental investigations of quasi-continuous wave diode arrays side-pumped Yb:YAG slab laser

    Institute of Scientific and Technical Information of China (English)

    Wu Hai-Sheng; Yan Ping; Gong Ma-Li; Liu Qiang

    2004-01-01

    An analytical model of quasi-continuous wave (quasi-CW) diode array side-pumped slab laser for Yb:YAG oscillator in long-pulse free-running has been developed based on the CW model. In this model we first introduce a new parameter,pump pulse width, and make the model available for use in the quasi-CW model. We also give an analytical equation of laser delay time to calculate the laser pulse width. A detailed model is also presented for a new structure laser design, taking account of the geometry of Yb:YAG slab. A quasi-CW diode array side-pumped Yb:YAG slab laser is investigated theoretically and experimentally. Experiments yield a quasi-CW output energy up to 20.36 mJ with the laser pulse width of 654.55μs at 1049 nm when the diode arrays operate at 25 Hz and 1 ms pulse width. The crystal dimensions are 3 mm×8 mm× 1 mm and the doping density is 10 at.%. The experimental results are in good agreement with the predictions of the theoretical model.

  13. Reducing temperature dependence of the output energy of a quasi-continuous wave diode-pumped Nd:YAG laser.

    Science.gov (United States)

    Lee, Kangin; Kim, Youngjung; Lee, Sijin; Kwon, Jin Hyuk; Gwak, Jin Seog; Yi, Jonghoon

    2013-08-20

    It is demonstrated by numerical modeling that spectrally dispersed compound pumping diodes and low-loss pumping chamber reduced the temperature dependence of the output energy of quasi-continuous wave diode-pumped Nd:YAG lasers considerably. Several compound diodes with different spectral profiles were tested for pumping. The laser energy was calculated as a function of diode temperature from -30°C to 60°C. When a compound diode with a flat-top spectrum was used for pumping, the mean laser energy was 83% of the maximum energy of a Nd:YAG laser pumped by a diode with a narrow bandwidth. In addition, a compound diode with three emission lines was tested for pumping. When the wavelength gap between the adjacent emission lines of the pumping diode was in the range of 3-10 nm, the mean energy of the Nd:YAG laser became similar to that of a Nd:YAG laser pumped by a diode with a flat-top spectrum.

  14. Low power continuous wave-laser seed irradiation effect on Moringa oleifera germination, seedling growth and biochemical attributes.

    Science.gov (United States)

    Urva; Shafique, Hina; Jamil, Yasir; Haq, Zia Ul; Mujahid, Tamveel; Khan, Aman Ullah; Iqbal, Munawar; Abbas, Mazhar

    2017-05-01

    Recently, laser application in agriculture has gained much attention since plant characteristics were improved significantly in response of pre-sowing seed treatment. Pre-sowing laser seed treatment effects on germination, seedling growth and mineral profile were studied in Moringa olifera. M. olifera healthy seeds were exposed to 25, 50, 75mJ low power continuous wave laser light and grown under greenhouse conditions. The seedling growth and biochemical attributes were evaluated from 10-day-old seedlings. The germination parameters (percentage, mean germination time), vigor index, seedling growth (root length, seedling length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight) enhanced considerably. The laser energy levels used for seed irradiation showed variable effects on germination, seedling growth and mineral profile. The mineral contents were recorded to be higher in seedling raised from laser treated seeds, which were higher in roots versus shoots and leaves. The effect of laser treatment on seedling fat, nitrogen and protein content was insignificant and at higher energy level both nitrogen and protein contents decreased versus control. Results revealed that M. olifera germination, seedling growth and mineral contents were enhanced and optimum laser energy level has more acceleratory effect since at three laser energy levels the responses were significantly different. Overall the laser energy levels effect on germination and seedling growth was found in following order; 75mJ>50mJ>25mJ, where as in case of fat, protein and nitrogen contents the trend was as; 25mJ>50mJ and 75mJ. However, this technique could possibly be used to improve the M. olifera germination, seedling growth, and minerals contents where germination is low due to unfavorable conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Different photodynamic effect between continuous wave and pulsed laser irradiation modes in k562 cells in vitro

    Science.gov (United States)

    Klimenko, V. V.; Bogdanov, A. A.; Knyazev, N. A.; Rusanov, A. A.; Dubina, M. V.

    2014-10-01

    Photodynamic therapy is a cancer treatment method is used primarily continuous mode laser radiation. At high power density irradiation occurs intense consumption of molecular oxygen and this caused hypoxic tumor tissue, which leads to inefficiency PDT. In this paper, pulsed and continuous irradiation modes during PDT photosensitizer Radachlorin were compared. A mathematical model for the generation of singlet oxygen 1O2 in tumor cells during photodynamic therapy with tissue oxygenation was developed. Our study theoretically and experimentally demonstrates the increased singlet oxygen generation efficiency in a pulsed irradiation mode compared to continuous wave mode with the same power density 20mW/cm2. Experimental in vitro showed that pulsed irradiation mode mostly induces apoptosis k562 tumor cells at irradiation doses of k562 1.25 - 2.5J/cm2 while the continuous mode induced necrosis.

  16. Efficient and high-power laser-diode single-end-pumped Nd:YVO4 continuous wave laser at 1342 nm

    Institute of Scientific and Technical Information of China (English)

    Zhang Yu-Ping; Zheng Yi; Zhang Hui-Yun; Wang Peng; Yao Jian-Quan

    2006-01-01

    A compact, efficient and high-power laser diode (LD) single-end-pumped Nd:YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.

  17. A scheme for recording a fast process at nanosecond scale by using digital holographic interferometry with continuous wave laser

    Science.gov (United States)

    Wang, Jun; Zhao, Jianlin; Di, Jianglei; Jiang, Biqiang

    2015-04-01

    A scheme for recording fast process at nanosecond scale by using digital holographic interferometry with continuous wave (CW) laser is described and demonstrated experimentally, which employs delayed-time fibers and angular multiplexing technique and can realize the variable temporal resolution at nanosecond scale and different measured depths of object field at certain temporal resolution. The actual delay-time is controlled by two delayed-time fibers with different lengths. The object field information in two different states can be simultaneously recorded in a composite hologram. This scheme is also suitable for recording fast process at picosecond scale, by using an electro-optic modulator.

  18. Systematic analysis of DNA damage induction and DNA repair pathway activation by continuous wave visible light laser micro-irradiation

    Directory of Open Access Journals (Sweden)

    Britta Muster

    2017-02-01

    Full Text Available Laser micro-irradiation can be used to induce DNA damage with high spatial and temporal resolution, representing a powerful tool to analyze DNA repair in vivo in the context of chromatin. However, most lasers induce a mixture of DNA damage leading to the activation of multiple DNA repair pathways and making it impossible to study individual repair processes. Hence, we aimed to establish and validate micro-irradiation conditions together with inhibition of several key proteins to discriminate different types of DNA damage and repair pathways using lasers commonly available in confocal microscopes. Using time-lapse analysis of cells expressing fluorescently tagged repair proteins and also validation of the DNA damage generated by micro-irradiation using several key damage markers, we show that irradiation with a 405 nm continuous wave laser lead to the activation of all repair pathways even in the absence of exogenous sensitization. In contrast, we found that irradiation with 488 nm laser lead to the selective activation of non-processive short-patch base excision and single strand break repair, which were further validated by PARP inhibition and metoxyamine treatment. We conclude that these low energy conditions discriminated against processive long-patch base excision repair, nucleotide excision repair as well as double strand break repair pathways.

  19. Selective mucosal ablation using CO2 laser for the development of novel endoscopic submucosal dissection: comparison of continuous wave and nanosecond pulsed wave

    Science.gov (United States)

    Ishii, K.; Watanabe, S.; Obata, D.; Hazama, H.; Morita, Y.; Matsuoka, Y.; Kutsumi, H.; Azuma, T.; Awazu, K.

    2010-02-01

    Endoscopic submucosal dissection (ESD) is accepted as a minimally invasive treatment technique for small early gastric cancers. Procedures are carried out using some specialized electrosurgical knifes with a submucosal injection solution. However it is not widely used because its procedure is difficult. The objective of this study is to develop a novel ESD method which is safe in principle and widely used by using laser techniques. In this study, we used CO2 lasers with a wavelength of 10.6 μm for mucosal ablation. Two types of pulse, continuous wave and pulsed wave with a pulse width of 110 ns, were studied to compare their values. Porcine stomach tissues were used as a sample. Aqueous solution of sodium hyaluronate (MucoUpR) with 50 mg/ml sodium dihydrogenphosphate is injected to a submucosal layer. As a result, ablation effect by CO2 laser irradiation was stopped because submucosal injection solution completely absorbed CO2 laser energy in the invasive energy condition which perforates a muscle layer without submucosal injection solution. Mucosal ablation by the combination of CO2 Laser and a submucosal injection solution is a feasible technique for treating early gastric cancers safely because it provides a selective mucosal resection and less-invasive interaction to muscle layer.

  20. Surface-emitting terahertz quantum cascade lasers with continuous-wave power in the tens of milliwatt range

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Gangyi, E-mail: gangyi.xu@mail.sitp.ac.cn [Institut d' Electronique Fondamentale, Univ. Paris Sud, UMR8622 CNRS, 91405 Orsay (France); Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Li, Lianhe; Giles Davies, A.; Linfield, Edmund H. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS9 2JT (United Kingdom); Isac, Nathalie; Halioua, Yacine; Colombelli, Raffaele, E-mail: raffaele.colombelli@u-psud.fr [Institut d' Electronique Fondamentale, Univ. Paris Sud, UMR8622 CNRS, 91405 Orsay (France)

    2014-03-03

    We demonstrate efficient surface-emitting terahertz frequency quantum cascade lasers with continuous wave output powers of 20–25 mW at 15 K and maximum operating temperatures of 80–85 K. The devices employ a resonant-phonon depopulation active region design with injector, and surface emission is realized using resonators based on graded photonic heterostructures (GPHs). GPHs can be regarded as energy wells for photons and have recently been implemented through grading the period of the photonic structure. In this paper, we show that it is possible to keep the period constant and grade instead the lateral metal coverage across the GPH. This strategy ensures spectrally single-mode operation across the whole laser dynamic range and represents an additional degree of freedom in the design of confining potentials for photons.

  1. Laser-tissue interaction of a continuous-wave 2-μm, 3-μm cascade oscillation fiber laser: sharp incision with controlled coagulation layer thickness

    Science.gov (United States)

    Arai, Tsunenori; Sumiyoshi, Tetsumi; Naruse, Kyota; Ishihara, Miya; Sato, Shunichi; Kikuchi, Makoto; Kasamatsu, Tadashi; Sekita, Hitoshi; Obara, Minoru

    2000-06-01

    We studied coagulation layer controlled incision with newly developed continuous wave 2 micrometer, 3 micrometer cascade oscillation fiber laser in vitro. Since this laser device simultaneously oscillates 2 micrometer and 3 micrometer radiation, we could change tissue interaction by arranging power ratio of 2 micrometer to 3 micrometer radiation. About one watt of total irradiation power with various power ratios was focused to extracted fresh porcine myocardium or anesthetized rabbit on an automatic moving stage to obtain line incision. Macro photograph and microscopic histology were used to observe tissue interaction phenomenon. The incised specimen showed that precise cutting groove with thin coagulation layer was attained by a 3 micrometer based radiation, meanwhile addition of 2 micrometer radiation to 3 micrometer radiation made coagulation layer thicker. A heat conduction simulator using finite-element method was used to qualitatively explain obtained coagulation layer thickness. This precise incision with controllable side coagulation layer may effective to control bleeding during incision, for instance, for skin, liver, and kidney incisions. Pure continuous wave radiation of 2 micrometer and 3 micrometer may eliminate stress wave induced tissue damage which is frequently found in Ho:YAG and/or Er:YAG tissue interactions. Moreover, sapphire fiber might offer flexible power delivery to this new laser to establish endoscopic application and/or to improved beam handling.

  2. Continuous-wave singly resonant optical parametric oscillator placed inside a ring laser

    DEFF Research Database (Denmark)

    Abitan, Haim; Buchhave, Preben

    2003-01-01

    A cw singly resonant optical parametric oscillator (SRO) was built and placed inside the cavity of a ring laser. The system consists of a diode-end-pumped Nd:YVO4 ring laser with intracavity periodically poled lithium niobate as the nonlinear gain medium of the SRO. When the laser was operated...... the laser was coupled with the SRO. The results show that it is preferable to couple a SRO with a unidirectional ring laser....

  3. Frequency-modulated continuous-wave laser radar using dual vertical-cavity surface-emitting laser diodes for real-time measurements of distance and radial velocity

    Science.gov (United States)

    Kakuma, Seiichi

    2017-02-01

    A frequency-modulated continuous-wave (FMCW) laser radar capable of real-time displaying the distance to a target object and its radial velocity as their corresponding frequency spectra is developed. The system employs a pair of oppositely frequency-swept vertical-cavity surface-emitting laser diodes (VCSELs). This makes possible simultaneous detection of beat signals induced by the increment (up-ramp) and decrement (down-ramp) in laser frequencies. By mixing these two beat signals, their sum and difference frequencies are directly obtained without arithmetic processing such as averaging and subtraction. Results of the test experiments adopting axially moving block gauges as target objects show that both the distance and given velocities are accurately determined from the spectrum of the frequency mixer.

  4. High-power and high-efficiency operation of an all-solid-state,quasi-continuous-wave,titanium sapphire laser system

    Institute of Scientific and Technical Information of China (English)

    Quanfu Wei(魏权夫); Xin Ding(丁欣); Wuqi Wen(温午麒); Lijuan Fan(范丽娟); Jianquan Yao(姚建铨)

    2004-01-01

    High-power and high-efficiency operation of an all-solid-state, quasi-continuous-wave, titanium sapphire laser is obtained with a diode-laser-pumped frequency-doubled Nd:YAG laser as the pump source. A maximum output power of 2.5 W is obtained for 16-W power of 532-nm pump light. A much higher conversion efficiency of 15.7% is obtained when at the maximum output power.

  5. Mechanistic investigation of doxycycline photosensitization by picosecond-pulsed and continuous wave laser irradiation of cells in culture

    Energy Technology Data Exchange (ETDEWEB)

    Shea, C.R.; Hefetz, Y.; Gillies, R.; Wimberly, J.; Dalickas, G.; Hasan, T. (Massachusetts General Hospital, Boston (USA))

    1990-04-15

    In order to elucidate the photophysical mechanisms of cellular phototoxicity sensitized by doxycycline, MGH-U1 human bladder carcinoma cells in vitro were treated with 20.7 microM doxycycline and irradiated with either a pulsed (lambda = 355 nm, pulse duration = 24 ps) or a continuous wave (lambda = 351 nm) laser. Cumulative radiant exposure and irradiance were systematically varied in experiments with both lasers. Phototoxicity was assessed by epifluorescence microscopy of unfixed cells using rhodamine 123 labeling of mitochondria. With the continuous wave source, the cumulative radiant exposure required for induction of phototoxic injury was independent of irradiance. With the 24-ps-pulsed source, a significantly lower cumulative radiant exposure was required to induce the phototoxicity when the peak irradiance was 5.8 x 10(7) or 1.3 x 10(8) watts cm-2 compared with when peak irradiance was either lower (6.0 x 10(6) watts cm-2) or higher (7.6 x 10(8) watts cm-2). The measured fluorescence lifetimes of doxycycline in buffered saline solution were longer than the laser pulse duration of 24 ps. The increased efficiency of photosensitization at the optimal peak irradiance in the ps domain appears to result from sequential multiphoton absorption involving higher excited states of the singlet manifold. At the highest irradiance studied, on the other hand, reduced efficiency of photosensitization is attributed to increased photodegradation of doxycycline from higher excited states by processes such as photoionization. A model consistent with these observations is presented along with calculations, based on simple rate equations, that fit the essentials of the proposed model.

  6. Continuous-wave theory of Yb:YAG end-pumped thin-disk lasers.

    Science.gov (United States)

    Jafari, Ahmad Khayat; Aas, Mehdi

    2009-01-01

    The fundamental principles of the operation of a thin-disk laser are presented. We derived equations from a set of coupled rate equations that predict that the characteristics of a laser are affected by the Boltzmann occupation factors of the pump and the laser states simultaneously. The model is used to investigate the influence of the effective parameters on the operational efficiency of an end-pumped Yb:YAG disk laser. Based on our results, we examined laser output power as a function of output coupler reflectivity, crystal thickness or doping concentration, number of the pump beam passes, and temperature.

  7. Portable hyperspectral imager with continuous wave green laser for identification and detection of untreated latent fingerprints on walls.

    Science.gov (United States)

    Nakamura, Atsushi; Okuda, Hidekazu; Nagaoka, Takashi; Akiba, Norimitsu; Kurosawa, Kenji; Kuroki, Kenro; Ichikawa, Fumihiko; Torao, Akira; Sota, Takayuki

    2015-09-01

    Untreated latent fingerprints are known to exhibit fluorescence under UV laser excitation. Previously, the hyperspectral imager (HSI) has been primarily evaluated in terms of its potential to enhance the sensitivity of latent fingerprint detection following treatment by conventional chemical methods in the forensic science field. In this study however, the potential usability of the HSI for the visualization and detection of untreated latent fingerprints by measuring their inherent fluorescence under continuous wave (CW) visible laser excitation was examined. Its potential to undertake spectral separation of overlapped fingerprints was also evaluated. The excitation wavelength dependence of fluorescent images was examined using an untreated palm print on a steel based wall, and it was found that green laser excitation is superior to blue and yellow lasers' excitation for the production of high contrast fluorescence images. In addition, a spectral separation method for overlapped fingerprints/palm prints on a plaster wall was proposed using new images converted by the division and subtraction of two single wavelength images constructed based on measured hyperspectral data (HSD). In practical tests, the relative isolation of two overlapped fingerprints/palm prints was successful in twelve out of seventeen cases. Only one fingerprint/palm print was extracted for an additional three cases. These results revealed that the feasibility of overlapped fingerprint/palm print spectral separation depends on the difference in the temporal degeneration of each fluorescence spectrum. The present results demonstrate that a combination of a portable HSI and CW green laser has considerable potential for the identification and detection of untreated latent fingerprints/palm prints on the walls under study, while the use of HSD makes it practically possible for doubly overlapped fingerprints/palm prints to be separated spectrally. Copyright © 2015 Elsevier Ireland Ltd. All rights

  8. High-Power Continuous-Wave Directly-Diode-Pumped Fiber Raman Lasers

    Directory of Open Access Journals (Sweden)

    Tianfu Yao

    2015-11-01

    Full Text Available We describe novel fiber Raman lasers pumped directly by spectrally combined high power multimode laser diodes at 975 nm and emitting at 1019 nm. With a commercial multimode graded-index fiber, we reached 20 W of laser output power with a record slope efficiency of 80%. With an in-house double-clad fiber, the beam quality improved to M2 = 1.9, albeit with lower output power and slope efficiency due to higher fiber loss. We believe this is the first publication of a fiber Raman laser cladding-pumped directly by diodes.

  9. Intensity-Modulated Continuous-Wave Laser Absorption Spectrometer at 1.57 Micrometer for Atmospheric CO2 Measurements

    Science.gov (United States)

    Lin, Bing

    2014-01-01

    Understanding the earth's carbon cycle is essential for diagnosing current and predicting future climates, which requires precise global measurements of atmospheric CO2 through space missions. The Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission will provide accurate global atmospheric CO2 measurements to meet carbon science requirements. The joint team of NASA Langley Research Center and ITT Exelis, Inc. proposes to use the intensity-modulated, continuous-wave (IM-CW) laser absorption spectrometer (LAS) approach for the ASCENDS mission. Prototype LAS instruments have been developed and used to demonstrate the power, signal-to-noise ratio, precision and accuracy, spectral purity, and stability of the measurement and the instrument needed for atmospheric CO2 observations from space. The ranging capability from laser platform to ground surfaces or intermediate backscatter layers is achieved by transmitted range-encoded IM laser signals. Based on the prototype instruments and current lidar technologies, space LAS systems and their CO2 column measurements are analyzed. These studies exhibit a great potential of using IM-CW LAS system for the active space CO2 mission ASCENDS.

  10. Room-temperature continuous-wave electrically injected InGaN-based laser directly grown on Si

    Science.gov (United States)

    Sun, Yi; Zhou, Kun; Sun, Qian; Liu, Jianping; Feng, Meixin; Li, Zengcheng; Zhou, Yu; Zhang, Liqun; Li, Deyao; Zhang, Shuming; Ikeda, Masao; Liu, Sheng; Yang, Hui

    2016-09-01

    Silicon photonics would greatly benefit from efficient, visible on-chip light sources that are electrically driven at room temperature. To fully utilize the benefits of large-scale, low-cost manufacturing foundries, it is highly desirable to grow direct bandgap III-V semiconductor lasers directly on Si. Here, we report the demonstration of a blue-violet (413 nm) InGaN-based laser diode grown directly on Si that operates under continuous-wave current injection at room temperature, with a threshold current density of 4.7 kA cm-2. The heteroepitaxial growth of GaN on Si is confronted with a large mismatch in both the lattice constant and the coefficient of thermal expansion, often resulting in a high density of defects and even microcrack networks. By inserting an Al-composition step-graded AlN/AlGaN multilayer buffer between the Si and GaN, we have not only successfully eliminated crack formation, but also effectively reduced the dislocation density. The result is the realization of a blue-violet InGaN-based laser on Si.

  11. Laser Diode Pumped 1.54μm Er:Yb:Phosphate Glass Continuous Wave Compact Laser

    Institute of Scientific and Technical Information of China (English)

    孟凡臻; 宋峰; 张潮波; 丁欣; 商美茹; 张光寅

    2003-01-01

    We report a cw Er3+ :Yb3+ co-doped phosphate glass laser pumped by a laser diode. The maximum output power of 78.3mW and a slope efficiency of 15.25% were achieved. The laser spectral region was from 1532nm to 1535nm, with the peak laser wavelength at 1534nm. The laser modes and time stability were also measured.The thermal effect had little influence on the output in our experiment.

  12. A parametric study of the output of the optically pumped continuous wave CF4 laser

    NARCIS (Netherlands)

    Hartemink, M.; Godfried, H.P.

    1993-01-01

    A parametric study of laser output versus CF4 pressure and temperature was performed and correlated with a model for the gain in the system, which includes the relevant relaxation processes. Lasing in CF4 was observed at temperatures below 170 K. Cooling the CF4 gas, the output power of the laser in

  13. Gain-switched all-fiber lasers and quasi-continuous wave supercontinuum generation

    DEFF Research Database (Denmark)

    Larsen, Casper

    densities, and high spatial coherence. In this work the feasibility of applying gain-switched all-fiber lasers to SC generation is investigated. It is motivated by the simplicity of the architecture and the ability to scale the optical output power of such fiber lasers. The physics of fiber lasers...... are reviewed to understand the mechanisms involved in gain-switching. A detailed numerical model is provided to give deep insight into the different stages of pulse generation. A simplied model is also developed to derive an analytic expression for the pulse duration. Extensive experiments with gain-switching...... of fiber lasers with a variety of different configurations are carried out. The peak power, pulse duration, bandwidth, and scaling with repetition rate are thoroughly described. General guidelines are submitted to enable designing of gainswitched fiber lasers with specifically tailored properties...

  14. Spectroscopic properties and continuous-wave laser operation of Yb:Bi₄ Si₃ O₁₂ crystal.

    Science.gov (United States)

    Wang, Han; Chen, Yujin; Huang, Jianhua; Gong, Xinghong; Lin, Yanfu; Luo, Zundu; Huang, Yidong

    2014-09-08

    Yb3+:Bi4Si3O12 single crystal with Yb3+ concentration of 5.7 at.% has been grown successfully by the Czochralski method. The energy level positions of Yb3+ in Bi4Si3O12 crystal were determined based on the absorption and fluorescence spectra. The peak absorption cross-section is 0.98 × 10−20 cm2 at 976 nm and the peak emission cross-section is 0.57 × 10−20 cm2 at 1035 nm. The fluorescence lifetime of the excited multiplet is 1.26 ms. Diode-pumped continuous-wave laser operation around 1038 nm has been demonstrated in the Yb3+:Bi4Si3O12 crystal with a slope efficiency of 27% and maximum output power of 240 mW.

  15. Low-threshold room-temperature continuous-wave operation of a terahertz difference-frequency quantum cascade laser source

    Science.gov (United States)

    Fujita, Kazuue; Ito, Akio; Hitaka, Masahiro; Dougakiuchi, Tatsuo; Edamura, Tadataka

    2017-08-01

    The performance of a room-temperature continuous-wave (CW) terahertz source based on intracavity difference-frequency generation in a mid-infrared (λ ∼ 6.8 µm) quantum cascade laser with a dual-upper-state active region is reported. The fabricated buried heterostructure device, with a two-section buried distributed feedback grating, operates at two mid-infrared wavelengths and demonstrates a terahertz output of 2.92 THz with a very low threshold current density of 0.89 kA/cm2 in pulsed operation. Consequently, despite an epitaxial-side-up mounting configuration, the device achieves CW operation at room temperature in which a low CW threshold current density of 1.3 kA/cm2 is obtained.

  16. Distributed feedback quantum cascade lasers operating in continuous-wave mode at λ ≈ 7.6 μm

    Science.gov (United States)

    Jinchuan, Zhang; Lijun, Wang; Wanfeng, Liu; Fengqi, Liu; Lihua, Zhao; Shenqiang, Zhai; Junqi, Liu; Zhanguo, Wang

    2012-02-01

    Distributed feedback (DFB) quantum cascade lasers (QCLs) in continuous-wave (CW) mode emitting at λ ≈ 7.6 μm are presented. Holographic lithography was used to fabricate the first-order distributed feedback grating. For a high-reflectivity-coated QCL with 14.5-μm-wide and 3-mm-long cavity, CW output powers of 300 mW at 85 K and still 10 mW at 270 K are obtained. Single-mode emission with a side-mode suppression ratio (SMSR) of about 30 dB and a wide tuning range of ~300 nm in the temperature range from 85 to 280 K is observed.

  17. High power continuous wave atomic Xe laser with radio frequency excitation

    Science.gov (United States)

    Vitruk, P. P.; Morley, R. J.; Baker, H. J.; Hall, D. R.

    1995-09-01

    Radio frequency discharges in Ar/He/Xe gas mixtures have been studied in the range 5-150 MHz, and the importance of the ion sheaths in Xe laser excitation has been recognized. The discharge data have been used to improve the cw Xe laser performance, and efficiencies up to 0.8% observed. Area scaling in the slab geometry has been studied for α discharge excitation at 49 MHz, and multimode cw laser power up to 5.5 W has been observed. High quality beams have been produced at 4.9 W using a hybrid waveguide/unstable resonator.

  18. High-Power Diode-Side-Pumped Intracavity-Frequency-Doubled Continuous Wave 532 nm Laser

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yu-Ping; ZHANG Hui-Yun; ZHONG Kai; LI Xi-Fu; WANG Peng; YAO Jian-Quan

    2007-01-01

    @@ An efficient and high-power diode-side-pumped cw 532nm green laser based on a V-shaped cavity geometry, and capable of generating 22.7 W green radiation with optical conversion efficiency of 8.31%, has been demonstrated. The laser is operated with rms noise amplitude of less than 1% and with M2-parameter of about 6.45 at the top of the output power. This laser has the potential for scaling to much higher output power.

  19. A Continuous-Wave Diode-Side-Pumped Tm:YAG Laser with Output 51 W

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-Fu; CUI DaFu; XU Zu-Yan; XU Yi-Ting; LI Cheng-Ming; ZONG Nan; XU Jia-Lin; CUI Qian-Jin; LU Yuan-Fu; BO Yong; PENG Qin-Jun

    2008-01-01

    A compact diode-side-pumped Tm:YAG laser is presented, which can output 51 W of cw power at 2.02μm. The Tm:YAG rod is side pumped by nine diode arrays with the central wavelength of 783nm and the with bandwidth of about 2.5 nm at 25℃. To decrease the thermal effect on the both ends and dissipate the heat effectively, one composite Tm:YAG rod with the undoped YAG end caps and the screw threads on the side surface of the rod is used as the laser crystal. The maximum optical-to-optical conversion efficiency of the 2.02-μm laser output is 14.2%, with a slope efficiency of 26.8%.

  20. Pulpal response to irradiation of enamel with continuous wave CO sub 2 laser

    Energy Technology Data Exchange (ETDEWEB)

    Powell, G.L.; Morton, T.H.; Larsen, A.E.

    1989-12-01

    Selected dog's teeth, in vivo, were exposed to carbon dioxide (CO{sub 2}) laser power densities ranging from 13 to 102 J per cm{sup 2}. The teeth were extracted 48 h postlasing, fixed with 10% neutral buffered formalin, decalcified with Kristensen's solution, processed, sectioned, stained, and evaluated for pulpal damage. No pulpal damage was observed when compared with nonlased control teeth. It appears that carbon dioxide laser power densities of approximately 13 to 102 J per cm{sup 2} could be used to irradiate enamel of teeth without damage to the pulp.

  1. Diode Stack End-Pumped Nd:GdVO4 Continuous Wave Slab Laser

    Institute of Scientific and Technical Information of China (English)

    ZHANG Heng-Li; ZHANG Huai-Jin; LI Dai-Jun; WANG Ji-Yang; SHI Peng; Haas Rüdiger; LI Hong-Xia; JIANG Min-Hua; DU Keming

    2005-01-01

    @@ We report a diode stack end-pumped Nd:GdVO4 slab laser with a near-diffraction-limited beam. The output power of 45.8 W at 1064nm is obtained under the pumping power of 147W, with the optical-optical conversion efficiency of 31.2%, and the slope efficiency is 39.6%.

  2. Continuous wave operation of distributed feedback quantum cascade lasers with low threshold voltage and low power consumption

    Science.gov (United States)

    Xie, Feng; Caneau, Catherine; LeBlanc, Herve P.; Coleman, Sean; Hughes, Lawrence C.; Zah, Chung-en

    2012-03-01

    We demonstrated the room temperature continuous wave (CW) operation of mid-infrared distributed feedback (DFB) quantum cascade lasers (QCLs) made of strain balanced GaInAs/AlInAs material on InP substrates for sensing CO2 isotope and N2O gas for potential applications that need battery powered portable devices in a sensor network. For the former device at 4.35 μm wavelength, we demonstrated a low threshold voltage of less than 8 V for battery operation and a near circular far field pattern with small divergent angles of 33 by 28 degrees full width at half maximum (FWHM) in vertical and horizontal directions, respectively, for easy collimation. For the latter device at 4.5 μm wavelength, we demonstrated a low CW threshold power consumption of 0.7 W at 20 °C. A side mode suppression ratio (SMSR) of 30 dB was achieved within the whole operating current and temperature ranges for both lasers.

  3. Generating 2 micron continuous-wave ytterbium-doped fiber laser-based optical parametric effect

    Science.gov (United States)

    Paul, M. C.; Latiff, A. A.; Hisyam, M. B.; Rusdi, M. F. M.; Harun, S. W.

    2016-10-01

    We report an efficient method for generating a 2 micron laser based on an optical parametric oscillator (OPO). It uses a long piece of a newly developed double-clad ytterbium-doped fiber (YDF), which is obtained by doping multi-elements of ZrO2, CeO2 and CaO in a phospho-alumina-silica glass as a gain medium. The efficient 2 micron laser generation is successful due to the presence of partially crystalline Yb-doped ZrO2 nano-particles that serve as a nonlinear material in a linear cavity configuration and high watt-level pump power. Stable self-wavelength double lasing at 2122 nm with an efficiency of 7.15% is successfully recorded. At a maximum pump power of 4.1 W, the output power is about 201 mW.

  4. Continuous-wave high specific output power Ar-He-Xe laser with transverse RF excitation

    NARCIS (Netherlands)

    Udalov, Yu.B.; Peters, P.J.M.; Heeman-Ilieva, M.B.; Witteman, W.J.; Ochkin, V.N.

    1994-01-01

    A transverse RF excited gas discharge has been successfully used to produce a CW Ar-He-Xe laser. A maximum output power of 330 mW has been obtained from an experimental device with 37 cm active length and a 2.25 (DOT) 2.25 cm2 cross-section. This corresponds to a specific output power of about 175 m

  5. Crude Oil Remote Sensing, Characterization and Cleaning with ContinuousWave and Pulsed Lasers

    Science.gov (United States)

    2015-01-23

    Oceanography Division Stennis Space Center, MS 39529-5004 NRL/JA/7330--14-2317 NASA Headquarters Attn: Laurie Friederich Mail Code 210.H, Bldg. 17, Rm...N111 Greenbelt, MD NASA Approved for public release, distribution is unlimited. We demonstrate a successful combination of several optical methods of...pulsed lasers SPIE meeting of The Optics and Photonics 17-AUG - 21-AUG-14, San Diego, CA, Unclassified SPIE meeting of The Optics and Photonics

  6. Low power continuous wave laser induced optical nonlinearities in saffron ( Crocus Sativus L.)

    Science.gov (United States)

    Nasibov, H.; Mamedbeili, I.

    2010-12-01

    We report on the low power CW laser induced nonlinear optical responses of Saffron (stigmata of Crocus Savitus L.) ethanol and methanol extracts. The optical nonlinearities were investigated by performing Z-scan measurements at 470 and 535 nm wavelengths. At both wavelengths the material has a strong nonlinear refraction, mainly of thermal origin. However, only at 470 nm wavelength the material exhibit pronounced saturable nonlinear absorption. Long-term (70 days) stability measurements indicated that the nonlinearities in the Saffron extracts are due to their nonvolatile components. This study shows that there is great potential for Saffron extracts to be used in nonlinear photonic applications.

  7. A compact, continuous-wave terahertz source based on cascade laser and a miniature cryocooler

    OpenAIRE

    Richter, Heiko; Greiner-Bär, Michael; Pavlov, Sergey; Semenov, Alexei D.; Wienold, Martin; Schrottke, Lutz; Giehler, M.; Hey, R.; Grahn, H.T.; Huebers, H. -W.

    2010-01-01

    We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum-cascade laser (QCL) with a compact, low-input-power Stirling cooler. The QCL, which is based on a two-miniband design, has been developed for high output and low electrical pump power. Special care has been taken to achieve a good thermal coupling between the QCL and the cold finger of the cooler. The whole system weighs less than 15 kg including the cooler and power supplies. The maxim...

  8. Room-temperature continuous-wave operation of Ti:sapphire buried channel-waveguide lasers fabricated via proton implantation

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; Eason, R.W.; Laversenne, L.; Moretti, P.; Borca, C.N.; Pollnau, M.

    2006-01-01

    Fabrication and laser operation of proton-implanted Ti:sapphire buried channel waveguides is reported for the first time to our knowledge. Without any postimplantation annealing of the structures, continuous laser operation near 780 nm was demonstrated at room temperature at an absorbed pump power t

  9. Room temperature continuous wave operation of 1.33-μm InAs/GaAs quantum dot laser with high output power

    Institute of Scientific and Technical Information of China (English)

    Qin Han; Hongling Peng; Ronghan Wu; Zhichuan Niu; Haiqiao Ni; Shiyong Zhang; Xiaohong Yang; Yun Du; Cunzhu Tong; Huan Zhao; Yingqiang Xu

    2006-01-01

    @@ Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-Mw output power at ground state of 1.33-1.35μm for a 20-μm ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy (MBE) growth conditions,the QD density per layer is raised to 4 × 1010 cm-2. The laser keeps lasing at ground state until the temperature reaches 65 ℃.

  10. Widely tunable, narrow line width and low optical noise continuous-wave all fiber Er:Yb co-doped double-clad ring laser

    Science.gov (United States)

    Guesmi, Khmaies; Bahloul, Faouzi; Semaan, Georges; Meng, Yichang; Salhi, Mohamed; Sanchez, François

    2017-01-01

    In this paper, we report a widely tunable, narrow linewidth, low noise continuous-wave double-clad Er:Yb doped fiber ring laser. Tunability is demonstrated in wide range spanning from 1520 to almost 1620 nm covering the C and L spectral bands. The cavity design is optimized in order to achieve the largest tuning range with very high optical signal-to-noise ratio (SNR). The output coupling ratio greatly influences the tuning range of the laser while the position of the spectral filter determines the SNR. The obtained laser exhibits a tuning range over 98 nm with a nearly constant SNR of about 58.5 dB.

  11. Ruby Emission in the Range 400-800 nm with Excitation by Continuous-Wave CO2 Laser Pulses

    Science.gov (United States)

    Marchenko, V. M.; Kiselev, V. V.

    2017-01-01

    Thermal emission spectra of ruby single crystals in the range 400-800 nm were studied experimentally as functions of the intensity at 10.6 μm of exciting pulses ( 0.5 s) from a continuous-wave electrical-discharge CO2 laser. Spectra at excitation intensity 1-20 kW/cm2 were superpositions of the thermal emission continuum of the sapphire crystal lattice in the range 600-800 nm and selective emission spectra of Cr3+ that were observed for the first time for ruby and consisted of R-lines at 695 nm; N-lines at 715 nm; 2 T 1, 4 T 2 → 4 A 2 transition bands at 672 and 643 nm; and 4 T 1, 2 T 2 → 4 A 2 transition bands at 530 and 490 nm that were not observed in the luminescence spectrum. Time dependences of the shapes of selective emission spectra, quenching and shifts of the R 1 line, and the temperature dependence of ruby luminescence spectra were investigated.

  12. Photobleaching and phototoxicity of KillerRed in tumor spheroids induced by continuous wave and pulsed laser illumination.

    Science.gov (United States)

    Kuznetsova, Daria S; Shirmanova, Marina V; Dudenkova, Varvara V; Subochev, Pavel V; Turchin, Ilya V; Zagaynova, Elena V; Lukyanov, Sergey A; Shakhov, Boris E; Kamensky, Vladislav A

    2015-11-01

    The purpose of this study was to evaluate photobleaching of the genetically encoded photosensitizer KillerRed in tumor spheroids upon pulsed and continuous wave (CW) laser irradiation and to analyze the mechanisms of cancer cell death after the treatment. We observed the light-dose dependent mechanism of KillerRed photobleaching over a wide range of fluence rates. Loss of fluorescence was limited to 80% at light doses of 150 J/cm(2) and more. Based on the bleaching curves, six PDT regimes were applied for irradiation using CW and pulsed regimes at a power density of 160 mW/cm(2) and light doses of 140 J/cm(2) , 170 J/cm(2) and 200 J/cm(2). Irradiation of KillerRed-expressing spheroids in the pulsed mode (pulse duration 15 ns, pulse repetition rate 10 Hz) induced predominantly apoptotic cell death, while in the case of CW mode the cancer cells underwent necrosis. In general, these results improve our understanding of photobleaching mechanisms in GFP-like proteins and show the importance of appropriate selection of treatment mode for PDT with KillerRed. Representative fluorescence image of two KillerRed-expressing spheroids before and immediately after CW irradiation.

  13. Tunable, continuous-wave Ti:sapphire channel waveguide lasers written by femtosecond and picosecond laser pulses.

    Science.gov (United States)

    Grivas, Christos; Corbari, Costantino; Brambilla, Gilberto; Lagoudakis, Pavlos G

    2012-11-15

    Fabrication and cw lasing at 798.25 nm is reported for femtosecond (fs) and picosecond (ps) laser-inscribed channel waveguides in Ti:sapphire crystals. Lasing in channels written by fs (ps) pulses was obtained above a threshold of 84 mW (189 mW) with a maximum output power and a slope efficiency of 143 mW (45 mW) and 23.5% (7.1%), respectively. The emission wavelength was tuned over a 170 nm range by using a birefringent filter in an external cavity.

  14. Transurethral dividing vaporesection for the treatment of large volume benign prostatic hyperplasia using 2 micron continuous wave laser

    Institute of Scientific and Technical Information of China (English)

    SUN Dong-chong; YANG Yong; WEI Zhi-tao; HONG Bao-fa; ZHANG Xu

    2010-01-01

    Background The safety and efficiency of transurethral laser resection of the prostate to treat benign prostatic hyperplasia have been verified. However, this method does still not manage large volume prostates efficiently. To tackle this problem, we have designed a method of "transurethral dividing vaporesection of prostate" using a 2 micron continuous wave laser. The aim of this study was to evaluate the safety and efficiency of this method in the management of large prostates (>80 ml).Methods In this study, 45 cases of benign prostatic hyperplasia with a median prostatic volume of (123.7±26.7) ml (range, 80.2-159.8 ml) were treated by the same surgeon under epidural anesthesia. During the surgery, superapubic catheters were needed, and saline solution was used for irrigation. First, the prostate was divided longitudinally into several parts from the bladder neck to the prostatic apex, and then gradually incised transversely chip by chip. Intraoperative blood transfusion rate, postoperative complications, maximum urinary flow rate, International Prostate Symptom Score and quality of life scores were recorded for statistical analysis using SPSS 16.0 software.Results Intraoperatively, no transurethral resection syndrome was observed, and no blood transfusions were needed.The resected prostatic chips were easily flushed out of the bladder through the resectoscope sheath without the use of a morcellator. Median vaporesection time was (95.0±13.2) minutes (range, 75-120 minutes), and the median retrieved and removed prostatic tissue were (25.2±5.1) g (range, 15.5-34.7 g) and (75.4±16.4) g (range, 43.8-106.1 g), respectively. Median catheter time and hospital stay were (3.3±0.9) days (range, 3-5 days) and (4.8±1.8) days (range, 3-9 days), respectively. After a follow-up of 6 to 12 months, two patients had stress urinary incontinence and three had anterior urethral strictures. Satisfactory improvement was seen in maximum urinary flow rate, International Prostate

  15. Fully vectorial laser resonator modeling of continuous-wave solid-state lasers including rate equations, thermal lensing and stress-induced birefringence.

    Science.gov (United States)

    Asoubar, Daniel; Wyrowski, Frank

    2015-07-27

    The computer-aided design of high quality mono-mode, continuous-wave solid-state lasers requires fast, flexible and accurate simulation algorithms. Therefore in this work a model for the calculation of the transversal dominant mode structure is introduced. It is based on the generalization of the scalar Fox and Li algorithm to a fully-vectorial light representation. To provide a flexible modeling concept of different resonator geometries containing various optical elements, rigorous and approximative solutions of Maxwell's equations are combined in different subdomains of the resonator. This approach allows the simulation of plenty of different passive intracavity components as well as active media. For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail. As a numerical example the beam quality and output power of a flash-lamp-pumped Nd:YAG laser are improved. To that end we compensate the influence of stress-induced birefringence and thermal lensing by an aspherical mirror and a 90° quartz polarization rotator.

  16. Elimination of continuous-wave component in a figure-eight fiber laser based on a polarization asymmetrical NOLM

    Science.gov (United States)

    Hernández-Escobar, E.; Bello-Jiménez, M.; Pottiez, O.; Ibarra-Escamilla, B.; López-Estopier, R.; Duran-Sánchez, M.; García Ramírez, M. A.; Kuzin, E. A.

    2017-07-01

    The operation of a nonlinear optical loop mirror (NOLM) with polarization-dependent transmission was analyzed to perform high-quality ultrashort optical pulses in a figure-eight fiber laser configuration. The design of the NOLM is based on a symmetrical coupler, a loop of highly twisted low-birefringence fiber and a quarter-wave retarder (QWR) to provide polarization asymmetry. Pedestal-free optical pulses were obtained by careful adjustment of the NOLM low-power transmission, which is easily realized in our setup by rotation of the QWR. The laser is capable of operating in both the conventional soliton and the noise-like pulse regimes. Optical pulses as short as 1.39 ps were observed at the fundamental repetition frequency of 0.8 MHz. The effectiveness of the proposed scheme is demonstrated by the elimination of low-intensity radiation at the laser output.

  17. Continuous-wave and Q-switched operation of a compact, diode-pumped Yb3+:KY(WO4)2 planar waveguide laser.

    Science.gov (United States)

    Bain, F M; Lagatsky, A A; Kurilchick, S V; Kisel, V E; Guretsky, S A; Luginets, A M; Kalanda, N A; Kolesova, I M; Kuleshov, N V; Sibbett, W; Brown, C T A

    2009-02-02

    A diode-pumped LPE-grown Yb:KYW planar waveguide laser is demonstrated in a microchip monolithic cavity configuration. Output powers as high as 148 mW and thresholds as low as 40 mW were demonstrated during continuous-wave operation. Pulses of 170 ns duration with maximum pulse energy of 44 nJ at a 722 kHz repetition rate were generated when Q-switched using a semiconductor saturable absorber mirror.

  18. Effects of continuous wave and fractionated diode laser on human fibroblast cancer and dermal normal cells by zinc phthalocyanine in photodynamic therapy: A comparative study.

    Science.gov (United States)

    Navaeipour, Farzaneh; Afsharan, Hadi; Tajalli, Habib; Mollabashi, Mahmood; Ranjbari, Farideh; Montaseri, Azadeh; Rashidi, Mohammad-Reza

    2016-08-01

    In this experimental study, cancer and normal cells behavior during an in vitro photodynamic therapy (PDT) under exposure of continuous wave (CW) and fractionated mode of laser with different irradiation power and time intervals was compared and investigated. At the first, human fibroblast cancer cell line (SW 872) and human dermal normal (HFFF2) cell line were incubated with different concentrations of zinc phthalocyanine (ZnPc), as a PDT drug. The cells, then, were irradiated with a 675nm diode laser and the cell viability was evaluated using MTT assay. Under optimized conditions, the viability of the cancer cells was eventually reduced to 3.23% and 13.17%, and that of normal cells was decreased to 20.83% and 36.23% using CW and fractionated diode lasers, respectively. In general, the ratio of ZnPc LD50 values for the normal cells to the cancer cells with CW laser was much higher than that of the fractionated laser. Subsequently, cancer cells in comparison with normal ones were found to be more sensitive toward the photodynamic damage induced by ZnPc. In addition, treatment with CW laser was found to be more effective against the cancer cells with a lower toxicity to the normal cells compared with the fractionated diode laser.

  19. Quasi-continuous-wave 589-nm radiation based on intracavity frequency-doubled Nd:GGG/BaWO4 Raman laser

    Science.gov (United States)

    Liu, Yang; Liu, Zhaojun; Cong, Zhenhua; Men, Shaojie; Rao, Han; Xia, Jinbao; Zhang, Sasa; Zhang, Huaijin

    2016-07-01

    Quasi-continuous-wave (QCW) 589-nm radiation was realized based on a frequency-doubled crystalline Raman laser. The fundamental wave with macro-micro-pulse trains was generated from an acousto-optically Q-switched QCW diode side-pumped Nd:GGG laser. Intracavity Raman conversion was accomplished by a BaWO4 crystal and the second harmonic generation was finished by a KTP crystal. Under a pumping power of 126.0 W with a macro-pulse frequency of 300 Hz and duration of 300 μs, the maximum 589 nm output power of 4.2 W was obtained at a micro-pulse frequency of 33.3 kHz. The micro-pulse width was 13.6 ns.

  20. Waves in continuous media

    CERN Document Server

    Gavrilyuk, S L; Sukhinin, S V

    2017-01-01

    Starting with the basic notions and facts of the mathematical theory of waves illustrated by numerous examples, exercises, and methods of solving typical problems Chapters 1 & 2 show e.g. how to recognize the hyperbolicity property, find characteristics, Riemann invariants and conservation laws for quasilinear systems of equations, construct and analyze solutions with weak or strong discontinuities, and how to investigate equations with dispersion and to construct travelling wave solutions for models reducible to nonlinear evolution equations. Chapter 3 deals with surface and internal waves in an incompressible fluid. The efficiency of mathematical methods is demonstrated on a hierarchy of approximate submodels generated from the Euler equations of homogeneous and non-homogeneous fluids. The self-contained presentations of the material is complemented by 200+ problems of different level of difficulty, numerous illustrations, and bibliographical recommendations.

  1. Nanoshell-mediated targeted photothermal therapy of HER2 human breast cancer cells using pulsed and continuous wave lasers: an in vitro study.

    Science.gov (United States)

    Khosroshahi, Mohammad E; Hassannejad, Zahra; Firouzi, Masoumeh; Arshi, Ahmad R

    2015-09-01

    In this study, we report the apoptosis induction in HER2 overexpressed breast cancer cells using pulsed, continuous wave lasers and polyvinylpyrrolidone (PVP)-stabilized magneto-plasmonic nanoshells (PVP-MPNS) delivered by immunoliposomes. The immunoliposomes containing PVP-MPNS were fabricated and characterized. Heating efficiency of the synthesized nanostructures was calculated. The effect of functionalization on cellular uptake of nanoparticles was assessed using two cell lines of BT-474 and Calu-6. The best uptake result was achieved by functionalized liposome (MPNS-LAb) and BT-474. Also, the interaction of 514 nm argon (Ar) and Nd/YAG second harmonic 532-nm lasers with nanoparticles was investigated based on the temperature rise of the nanoshell suspension and the release value of 5(6)-carboxyfluorescein (CF) from CF/MPNS-loaded liposomes. The temperature increase of the suspensions after ten consecutive pulses of 532 nm and 5 min of irradiation by Ar laser were measured approximately 2 and 12 °C, respectively. The irradiation of CF/MPNS-loaded liposomes by Ar laser for 3 min resulted in 24.3 % release of CF, and in the case of 532 nm laser, the release was laser energy dependent. Furthermore, the comparison of CF release showed a higher efficiency for the Ar laser than by direct heating of nanoshell suspension using circulating water. The percentage of cell apoptosis after irradiation by Ar and 532 nm lasers were 44.6 and 42.6 %, respectively. The obtained results suggest that controlling the NP-laser interaction using optical properties of nanoshells and the laser parameters can be used to develop a new cancer therapy modality via targeted nanoshell and drug delivery.

  2. Continuous-wave and Q-switched operation of a resonantly pumped Ho³⁺:KY₃F₁₀ laser.

    Science.gov (United States)

    Schellhorn, Martin; Parisi, Daniela; Eichhorn, Marc; Tonelli, Mauro

    2014-03-01

    We report continuous-wave and repetitively Q-switched operation of a resonantly pumped Ho3+:KY3F10 laser at room temperature. End pumped by a Tm3+-doped silica fiber laser operating at 1938 nm, a maximum laser power of 7.8 W was obtained at a wavelength of ∼2041  nm for 21 W of absorbed pump power, corresponding to a slope efficiency of 60.7% with respect to absorbed power. At a repetition rate of 10 kHz up to 0.78 mJ, energy per pulse was demonstrated with pulse widths of 100 ns. The beam propagation factor (M2) was measured to be <1.26 at the maximum output power.

  3. Absorption and wavelength modulation spectroscopy of NO2 using a tunable, external cavity continuous wave quantum cascade laser.

    Science.gov (United States)

    Karpf, Andreas; Rao, Gottipaty N

    2009-01-10

    The absorption spectra and wavelength modulation spectroscopy (WMS) of NO(2) using a tunable, external cavity CW quantum cascade laser operating at room temperature in the region of 1625 to 1645 cm(-1) are reported. The external cavity quantum cascade laser enabled us to record continuous absorption spectra of low concentrations of NO(2) over a broad range (approximately 16 cm(-1)), demonstrating the potential for simultaneously recording the complex spectra of multiple species. This capability allows the identification of a particular species of interest with high sensitivity and selectivity. The measured spectra are in excellent agreement with the spectra from the high-resolution transmission molecular absorption database [J. Quant. Spectrosc. Radiat. Transfer 96, 139-204 (2005)]. We also conduct WMS for the first time using an external cavity quantum cascade laser, a technique that enhances the sensitivity of detection. By employing WMS, we could detect low-intensity absorption lines, which are not visible in the simple absorption spectra, and demonstrate a minimum detection limit at the 100 ppb level with a short-path absorption cell. Details of the tunable, external cavity quantum cascade laser system and its performance are discussed.

  4. Coded continuous wave meteor radar

    OpenAIRE

    2015-01-01

    The concept of coded continuous wave meteor radar is introduced. The radar uses a continuously transmitted pseudo-random waveform, which has several advantages: coding avoids range aliased echoes, which are often seen with commonly used pulsed specular meteor radars (SMRs); continuous transmissions maximize pulse compression gain, allowing operation with significantly lower peak transmit power; the temporal resolution can be changed after ...

  5. Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet

    OpenAIRE

    Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

    2015-01-01

    We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and ...

  6. Secondary Austenite Morphologies in Fusion Zone of Welded Joint after Postweld Heat Treatment with a Continuous Wave Laser

    Institute of Scientific and Technical Information of China (English)

    Heping Liu; Xuejun Jin

    2012-01-01

    In order to improve the weldability of duplex stainless steels,obtaining more secondary austenite in the weld metal is an effective way.Therefore,optimizing the secondary austenite by changing its morphology,volume fraction and stability may be expected to enhance the ductility of the weld.The secondary austenite morphologies in the fusion zone of the laser continuously heat treated welds of 2205 duplex stainless steel were investigated.The secondary austenite morphologies were found to be influenced by different laser power level.The secondary austenite with penniform,freely grown and dendritic shape appeared in the course of 4,6 and 8 kW continuous heat treatment,respectively.It was found that there were three kinds of morphologies of secondary austenite in the fusion zone treated by different power,i.e.,widmannst¨atten austenite,grain boundary austenite and intragranular austenite.The results demonstrated that the mechanism of the secondary austenite formation was a displacement mechanism during the initial austenite lath formation and a diffusion mechanism during cooling.The nitrides provided the nitrogen for the transformation and at the same time acted as nucleation sites for the secondary austenite.

  7. Generation of silicon nanocrystals by damage free continuous wave laser annealing of substrate-bound SiO{sub x} films

    Energy Technology Data Exchange (ETDEWEB)

    Fricke-Begemann, T., E-mail: fricke-begemann@llg-ev.de; Ihlemann, J. [Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen (Germany); Wang, N.; Peretzki, P.; Seibt, M. [IV. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany)

    2015-09-28

    Silicon nanocrystals have been generated by laser induced phase separation in SiO{sub x} films. A continuous wave laser emitting at 405 nm is focused to a 6 μm diameter spot on 530 nm thick SiO{sub x} films deposited on fused silica substrates. Irradiation of lines is accomplished by focus scanning. The samples are investigated by atomic force microscopy, TEM, Raman spectroscopy, and photoluminescence measurements. At a laser power of 35 mW corresponding to an irradiance of about 1.2 × 10{sup 5 }W/cm{sup 2}, the formation of Si-nanocrystals in the film without any deterioration of the surface is observed. At higher laser power, the central irradiated region is oxidized to SiO{sub 2} and exhibits some porous character, while the surface remains optically smooth, and nanocrystals are observed beside and beneath this oxidized region. Amorphous Si-nanoclusters are formed at lower laser power and around the lines written at high power.

  8. 205 nm continuous-wave laser: application to the measurement of the Lamb shift in hydrogen; Laser continu a 205 nm: application a la mesure du deplacement de lamb dans l'hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Bourzeix, S

    1995-01-15

    The subject of this thesis is the construction of an experimental set-up, and in particular of a tunable continuous-wave laser at 205 nm, for the measurement of the ground state Lamb shift in atomic hydrogen. Chapter 1 deals with the Lamb shift from a historical point of view, and with the interest of its measurement, for metrology and test of quantum electrodynamics. Chapter 2 is devoted to the theory of the hydrogen atom. The principle of the experiment is based on the comparison of two frequencies which are in a ratio of 4: those of the two-photon transitions of 2S-6S or 2S-6D and 1S-3S. Chapter 3 describes the experimental set-up used to measure the 2S-6D transition which is excited by a titanium-sapphire laser at 820 nm. The 205 nm light required to excite the 1S-3S transition is generated by two frequency-doubling of the titanium-sapphire laser, made in non-linear crystals placed in enhancement cavities. Chapter 4 is entirely devoted to the frequency-doubling. After a recall of non-linear optics, the enhancement cavities are described in detail, as well as the results we achieved. At last chapter 5 describes the research for a signal on the 1S-3S transition: the construction of a ground state atomic beam, and the development of the detection system. This work has led to a preliminary measurement of the ground state Lamb shift in atomic hydrogen: L(1S) = 8172.850 (174) MHz whose result is in very good agreement with both the previous measurements and the most recent theoretical results. (author)

  9. In-process monitoring and feedback control for stable production of full-penetration weld in continuous wave fibre laser welding

    Science.gov (United States)

    Kawahito, Yousuke; Ohnishi, Terumasa; Katayama, Seiji

    2009-04-01

    Laser micro-welding has been applied for device sealing in electronics and automobile industries. Welding of corners in goods and products is a problem owing to easier formation of a weld with burn-through, shallow penetration or a non-bonded part when a drastic change in the welding speed or laser power occurs. This research was therefore undertaken with the objective of obtaining a fundamental knowledge of in-process monitoring and feedback control for the stable production of a full-penetration weld with a constant bead width on the bottom surface irrespective of the changes in the laser power and the welding speed. Variation in weld penetration geometry was investigated by rapid deceleration and acceleration in the welding speed during lap welding of pure titanium thin sheets with a continuous wave (CW) single-mode fibre laser beam. The rapid deceleration in the welding speed led to a considerable change in the full-penetration weld geometry or a partially penetrated weld (if the power was accordingly reduced), resulting in the difficulty in the stable production of a full-penetration weld bead. The heat radiation intensity measured from the laser-irradiated area was useful as an in-process monitoring signal for detecting the molten pool size on the laser-irradiated surface. However, the utilization of monitoring of heat radiation was difficult for predicting the weld bead width on the bottom surface due to the formation of partial penetration or the change in the penetration shape. The laser power was controlled at a 4 ms interval according to the heat radiation signal in order to adjust the weld bead width on the laser-irradiated surface to the target weld penetration geometry affected by thermal storage. Consequently, the feedback-controlled laser power produced a stable full-penetration weld with the designed bead width on the bottom surface irrespective of the rapid deceleration of the welding speed and the corresponding decrease in laser power

  10. In-process monitoring and feedback control for stable production of full-penetration weld in continuous wave fibre laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Kawahito, Yousuke; Ohnishi, Terumasa; Katayama, Seiji, E-mail: kawahito@jwri.osaka-u.ac.j [Joining and Welding Research Institute (JWRI), Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2009-04-21

    Laser micro-welding has been applied for device sealing in electronics and automobile industries. Welding of corners in goods and products is a problem owing to easier formation of a weld with burn-through, shallow penetration or a non-bonded part when a drastic change in the welding speed or laser power occurs. This research was therefore undertaken with the objective of obtaining a fundamental knowledge of in-process monitoring and feedback control for the stable production of a full-penetration weld with a constant bead width on the bottom surface irrespective of the changes in the laser power and the welding speed. Variation in weld penetration geometry was investigated by rapid deceleration and acceleration in the welding speed during lap welding of pure titanium thin sheets with a continuous wave (CW) single-mode fibre laser beam. The rapid deceleration in the welding speed led to a considerable change in the full-penetration weld geometry or a partially penetrated weld (if the power was accordingly reduced), resulting in the difficulty in the stable production of a full-penetration weld bead. The heat radiation intensity measured from the laser-irradiated area was useful as an in-process monitoring signal for detecting the molten pool size on the laser-irradiated surface. However, the utilization of monitoring of heat radiation was difficult for predicting the weld bead width on the bottom surface due to the formation of partial penetration or the change in the penetration shape. The laser power was controlled at a 4 ms interval according to the heat radiation signal in order to adjust the weld bead width on the laser-irradiated surface to the target weld penetration geometry affected by thermal storage. Consequently, the feedback-controlled laser power produced a stable full-penetration weld with the designed bead width on the bottom surface irrespective of the rapid deceleration of the welding speed and the corresponding decrease in laser power

  11. All-solid-state continuous-wave frequency-doubled Nd:YAG-BiBO laser with 2.8-W output power at 473 nm.

    Science.gov (United States)

    Czeranowsky, C; Heumann, E; Huber, G

    2003-03-15

    We report on a diode-pumped Nd:YAG laser with 4.6 W of linear polarized continuous-wave (cw) output power on the 4F3/2 --> 4I9/2 transitions at 946 nm. Three different crystals, cut for critical type I phase matching at room temperature, are used for the intracavity frequency doubling of the laser: 10-mm-long LiBaO5 (LBO), an 8-mm-long beta-BaB2O4 (BBO), and a 10.4-mm-long BiB3O6 (BiBO) grown by FEE GmbH. Up to 2.8 W of cw output power in the blue spectral range at 473 nm has been achieved with the BiBO crystal (2.1 W with BBO and 1.5 W with LBO).

  12. High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection

    Energy Technology Data Exchange (ETDEWEB)

    Centeno, R.; Marchenko, D.; Mandon, J.; Cristescu, S. M.; Harren, F. J. M., E-mail: F.Harren@science.ru.nl [Life Science Trace Gas Facility, Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University, P.O. Box 9010, NL-6500 GL Nijmegen (Netherlands); Wulterkens, G. [TechnoCentrum, Radboud University, Heyendaalseweg 135, 6525AJ Nijmegen (Netherlands)

    2014-12-29

    We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm{sup −1} (∼24% of the center wavelength) at 8 μm, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10{sup −8 }cm{sup −1 }Hz{sup −1/2} was obtained.

  13. Tunable continuous-wave dual-wavelength laser by external-cavity superluminescent diode with a volume Bragg grating and a diffraction grating

    Science.gov (United States)

    Zheng, Yujin; Kurita, Takashi; Sekine, Takashi; Kato, Yoshinori; Kawashima, Toshiyuki

    2016-10-01

    We demonstrate the tunable continuous-wave dual-wavelength laser based on a double external-cavity superluminescent diode (SLD). The double external cavity consisted of a volume Bragg grating (VBG) and a diffraction grating bracketing the SLD's two facets. The VBG was used as an output coupler to enable the external-cavity SLD to achieve a stable wavelength. A narrow bandwidth of 0.25 nm was achieved in single-wavelength operation. The diffraction grating served as an end mirror to create another tunable wavelength external cavity for the SLD. A wavelength tuning range of 23 nm was achieved. The laser output of the double external-cavity SLD had a tunable spectral separation with dual-wavelengths from +6.42 to -16.94 nm. An output power of up to 37.7 mW was achieved with a frequency difference of 7.1 THz.

  14. Intracavity control of a 200-W continuous-wave Nd:YAG laser by a micromachined deformable mirror.

    Science.gov (United States)

    Vdovin, G; Kiyko, V

    2001-06-01

    A silicon micromachined membrane deformable mirror with a diameter of 10 mm, reflectivity of better than 99.8%, and a surface deflection range of 3mum has been used for intracavity control of an industrial 200-W cw Nd:YAG laser. When it was placed in the resonator, the mirror demonstrated continuous (more than 40-h) stable operation under an ~550-W cw optical load, with beam diameters in the range 3-6 mm. Periodic modulation of the curvature of the deformable mirror with a frequency of 250 Hz produced quick switching between stable and unstable resonator configurations, which resulted in pulse-period Q -switched generation with average power in the range 50-200 W, modulation depth from 95% to 10%, and an M(2) parameter of 6.5 to 30.

  15. Investigative study of a diode-pumped continuous-wave Tm:YAP laser as an efficient 1.94 μm pump source

    Science.gov (United States)

    Kwiatkowski, Jacek; Zendzian, Waldemar; Jabczynski, Jan K.

    2016-12-01

    A detailed study of a Tm:YAP laser in continuous-wave (CW), single-pass end-pumped by a 793 nm diode laser is presented. The laser based on c-cut 3 at. % Tm:YAP crystal was experimentally examined and presented in the dependence on transmittance and radius of curvature of output coupling mirrors. A detailed spectral analysis was presented. The influence of a heat-sink cooling water temperature on the laser performance was studied. At room temperature, for an output coupling transmission of 19.5%, the maximum CW output power of 4.53 W was achieved, corresponding to a slope efficiency of 41.5% and an optical-to-optical conversion efficiency of 25.7% with respect to the incident pump power, respectively. We have shown that the output spectrum at a certain wavelength (e.g. 1940 nm) for a given pump power can be realized via the change of resonator parameters (OC transmittance, mode size).

  16. Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.

    Science.gov (United States)

    Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

    2015-04-01

    We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated.

  17. Photobiomodulation with Pulsed and Continuous Wave Near-Infrared Laser (810 nm, Al-Ga-As) Augments Dermal Wound Healing in Immunosuppressed Rats.

    Science.gov (United States)

    Keshri, Gaurav K; Gupta, Asheesh; Yadav, Anju; Sharma, Sanjeev K; Singh, Shashi Bala

    2016-01-01

    Chronic non-healing cutaneous wounds are often vulnerable in one or more repair phases that prevent normal healing and pose challenges to the use of conventional wound care modalities. In immunosuppressed subject, the sequential stages of healing get hampered, which may be the consequences of dysregulated or stagnant wound inflammation. Photobiomodulation (PBM) or low-level laser (light) therapy (LLLT) emerges as a promising drug-free, non-invasive biophysical approach for promoting wound healing, reduction of inflammation, pain and restoration of functions. The present study was therefore undertaken to evaluate the photobiomodulatory effects of 810 nm diode laser (40 mW/cm2; 22.6 J/cm2) with pulsed (10 and 100 Hz, 50% duty cycle) and continuous wave on full-thickness excision-type dermal wound healing in hydrocortisone-induced immunosuppressed rats. Results clearly delineated that 810 nm PBM at 10 Hz was more effective over continuous and 100 Hz frequency in accelerating wound healing by attenuating the pro-inflammatory markers (NF-kB, TNF-α), augmenting wound contraction (α-SM actin), enhancing cellular proliferation, ECM deposition, neovascularization (HIF-1α, VEGF), re-epithelialization along with up-regulated protein expression of FGFR-1, Fibronectin, HSP-90 and TGF-β2 as compared to the non-irradiated controls. Additionally, 810 nm laser irradiation significantly increased CCO activity and cellular ATP contents. Overall, the findings from this study might broaden the current biological mechanism that could be responsible for photobiomodulatory effect mediated through pulsed NIR 810 nm laser (10 Hz) for promoting dermal wound healing in immunosuppressed subjects.

  18. Nonadiabatic dynamics in intense continuous wave laser fields and real-time observation of the associated wavepacket bifurcation in terms of spectrogram of induced photon emission

    Science.gov (United States)

    Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo

    2016-11-01

    We propose a theoretical principle to directly monitor the bifurcation of quantum wavepackets passing through nonadiabatic regions of a molecule that is placed in intense continuous wave (CW) laser fields. This idea makes use of the phenomenon of laser-driven photon emission from molecules that can undergo nonadiabatic transitions between ionic and covalent potential energy surfaces like Li+ F- and LiF. The resultant photon emission spectra are of anomalous yet characteristic frequency and intensity, if pumped to an energy level in which the nonadiabatic region is accessible and placed in a CW laser field. The proposed method is designed to take the time-frequency spectrogram with an appropriate time-window from this photon emission to detect the time evolution of the frequency and intensity, which depends on the dynamics and location of the relevant nuclear wavepackets. This method is specifically designed for the study of dynamics in intense CW laser fields and is rather limited in scope than other techniques for femtosecond chemical dynamics in vacuum. The following characteristic features of dynamics can be mapped onto the spectrogram: (1) the period of driven vibrational motion (temporally confined vibrational states in otherwise dissociative channels, the period and other states of which dramatically vary depending on the CW driving lasers applied), (2) the existence of multiple nuclear wavepackets running individually on the field-dressed potential energy surfaces, (3) the time scale of coherent interaction between the nuclear wavepackets running on ionic and covalent electronic states after their branching (the so-called coherence time in the terminology of the theory of nonadiabatic interaction), and so on.

  19. [Comparative study on software demodulation for continuous wave and quasi-continuous wave wavelength modulation spectroscopy].

    Science.gov (United States)

    Shao, Xin; Liu, Fu-Gui; Chen, Wen-Liang

    2013-12-01

    According to the modulation signal applied on laser diodes, wavelength modulation spectroscopy (WMS) can be divided into continuous wave (CW) WMS and quasi-continuous wave (QCW) WMS. In order to deeply compare CW-WMS and QCW-WMS, we used a specific software-realized lock-in amplifier for continuous and quasi-continuous modulation signal demodulation. The invalid signal in quasi-continuous modulation spectrum was filtered off, and then the effective detection signal was demodulated to obtain the second harmonic signal (WMS-2f). It was compared with the 2f signal demodulated continuous laser modulation spectrum with software. The results show that while the same system parameters are set, the signal-to-noise of the quasi-continuous modulation spectrum is 5% higher than the continuous modulation spectrum with software demodulation measurements, and the detection limit is 11.3% lower. And without the invalid signal in quasi-continuous modulation spectrum, the standard WMS-2f signal can be demodulated, which has potential to be used for the investigation of gas absorption profile. This work has provided accurate reference for selections of the laser modulation spectroscopy.

  20. High-temperature continuous wave operation (up to 100°C) of InAs/InGaAs quantum dot electrically injected microdisk lasers

    Science.gov (United States)

    Kryzhanovskaya, N. V.; Moiseev, E. I.; Kudashova, Yu. V.; Zubov, F. I.; Kulagina, M. M.; Troshkov, S. I.; Zadiranov, Yu. M.; Livshits, D. A.; Maximov, M. V.; Zhukov, A. E.

    2016-03-01

    In this work, electrically-injected microdisk lasers with diameter varied from 15 to 31μm based on an InAs/InGaAs QD active region have been fabricated and tested in continuous wave regime. At room temperature, lasing is achieved at wavelength around 1.26…1.27 μm with threshold current density about 900 A/cm2. Specific series resistance is estimated to be about 10-4 Ohm•cm2. The lasers were tested at elevated temperatures. Lasing is achieved up to 100°C with threshold current of 13.8mA and lasing wavelength of 1304nm in device with 31μm diameter. To the best of our knowledge, this is the highest CW lasing temperature and the longest lasing wavelength ever reported for injection QD microdisk/microring lasers on GaAs substrates. Emission spectrum demonstrates single-mode lasing with side mode suppression ration of 24dB and dominant mode linewidth of 35pm. The far field radiation pattern demonstrates two narrow maxima off the disk plane. A combination of device characteristics achieved (low threshold, long wavelength, operation at elevated temperatures) makes them suitable for application in future optoelectronic circuits for optical interconnect systems.

  1. Analytical model of transient temperature and thermal stress in continuous wave double-end-pumped laser rod: Thermal stress minimization study

    Indian Academy of Sciences (India)

    Khalid S Shibib; Mayada M Tahir; Haqi I Qatta

    2012-08-01

    A time-dependent analytical thermal model of the temperature and the corresponding induced thermal stresses in continuous wave double-end-pumped laser rod are derived from the first principle using the integral transform method. The aim of the paper is to study the effect of increasing the pumping powers while the laser crystals are still in the safe zone (i.e. far away from failure stress) and to suitably choose a crystal that achieves this task. The result of this work is compared with a well-verified finite element solution and a good agreement has been found. Some conclusions are obtained: Tm:YAP crystal, which has high thermal conductivity, low expansion coefficient, low absorption coefficient, low thermal factor and low product of /(1−), is the best choice to reduce induced stress although it is responded and brought to thermal equilibrium faster than the other types of crystal usually used in the end-pumped solid-state laser.

  2. Reliable and well-controlled synthesis of noble metal nanoparticles by continuous wave laser ablation in different liquids for deposition of thin films with variable optical properties

    Science.gov (United States)

    Arakelyan, S. M.; Veiko, V. P.; Kutrovskaya, S. V.; Kucherik, A. O.; Osipov, A. V.; Vartanyan, T. A.; Itina, T. E.

    2016-06-01

    We report the results of continuous wave laser interactions with both gold and silver targets in the presence of different liquids (deionized water, ethanol, and glycerol). Upon moderate laser irradiation at wavelength of 1.06 nm during 30 min, nanoparticle colloids are shown to be formed with surprisingly narrow size distributions and average dispersion as small as 15-20 nm. The average particle sizes range between 8 and 52 nm for gold and between 20 and 107 nm for silver. This parameter is shown to be stable and well-controlled by such laser parameters as intensity and effective irradiation time, as well as by the choice of the liquid phase. The possibilities of an efficient control over the proposed synthesis techniques are discussed, and the results of a bimetallic Au-Ag structure deposition from the obtained colloids are presented. The formation of the extended arrays of gold and silver nanoparticles with controlled morphology is examined. The changes in the optical properties of the obtained thin films are found to depend on their morphology, in particular, on the particle size, and distance between them.

  3. High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd:YVO4 Laser at 671 nm with a Compact Three-Element Cavity

    Institute of Scientific and Technical Information of China (English)

    ZHOU Rui; DING Xin; WEN Wu-Qi; CAI Zhi-Qiang; WANG Peng; YAO Jian-Quan

    2006-01-01

    @@ We report a high-power high-effcient continuous-wave (cw) diode-end-pumped Nd:YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope efficiency of 37.3%. By inserting a type-I critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd:YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.

  4. Continuous-wave 1.55 $\\mu$m diode-pumped surface emitting semiconductor laser for broadband multiplex spectroscopy

    CERN Document Server

    Jacquemet, M; Guelachvili, G; Picqué, N; Sagnes, I; Strassner, M; Symonds, C; Garnache, Arnaud; Guelachvili, Guy; Jacquemet, Mathieu; Picqu\\'{e}, Nathalie; Sagnes, Isabelle; Strassner, Martin; Symonds, Cl\\'{e}mentine

    2007-01-01

    A room temperature operating Vertical External Cavity Surface Emitting Laser is applied around 1550 nm to intracavity laser absorption spectroscopy analyzed by time-resolved Fourier transform interferometry. At an equivalent pathlength of 15 km, the high resolution spectrum of the semiconductor disk laser emission covers 17 nm simultaneously. A noise equivalent absorption coefficient at one second averaging equal to 1.5 10^{-10} cm^{-1}.Hz^{-1/2} per spectral element is reported for the 65 km longest path length employed.

  5. Phase locking of a seven-channel continuous wave fibre laser system by a stochastic parallel gradient algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, M V; Garanin, S G; Dolgopolov, Yu V; Kopalkin, A V; Kulikov, S M; Sinyavin, D N; Starikov, F A; Sukharev, S A; Tyutin, S V; Khokhlov, S V; Chaparin, D A [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation)

    2014-11-30

    A seven-channel fibre laser system operated by the master oscillator – multichannel power amplifier scheme is the phase locked using a stochastic parallel gradient algorithm. The phase modulators on lithium niobate crystals are controlled by a multichannel electronic unit with the microcontroller processing signals in real time. The dynamic phase locking of the laser system with the bandwidth of 14 kHz is demonstrated, the time of phasing is 3 – 4 ms. (fibre and integrated-optical structures)

  6. Coded continuous wave meteor radar

    Science.gov (United States)

    Vierinen, Juha; Chau, Jorge L.; Pfeffer, Nico; Clahsen, Matthias; Stober, Gunter

    2016-03-01

    The concept of a coded continuous wave specular meteor radar (SMR) is described. The radar uses a continuously transmitted pseudorandom phase-modulated waveform, which has several advantages compared to conventional pulsed SMRs. The coding avoids range and Doppler aliasing, which are in some cases problematic with pulsed radars. Continuous transmissions maximize pulse compression gain, allowing operation at lower peak power than a pulsed system. With continuous coding, the temporal and spectral resolution are not dependent on the transmit waveform and they can be fairly flexibly changed after performing a measurement. The low signal-to-noise ratio before pulse compression, combined with independent pseudorandom transmit waveforms, allows multiple geographically separated transmitters to be used in the same frequency band simultaneously without significantly interfering with each other. Because the same frequency band can be used by multiple transmitters, the same interferometric receiver antennas can be used to receive multiple transmitters at the same time. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large-scale multi-static network of meteor radar transmitters and receivers. Such a system would be useful for increasing the number of meteor detections to obtain improved meteor radar data products.

  7. Coded continuous wave meteor radar

    Directory of Open Access Journals (Sweden)

    J. Vierinen

    2015-07-01

    Full Text Available The concept of coded continuous wave meteor radar is introduced. The radar uses a continuously transmitted pseudo-random waveform, which has several advantages: coding avoids range aliased echoes, which are often seen with commonly used pulsed specular meteor radars (SMRs; continuous transmissions maximize pulse compression gain, allowing operation with significantly lower peak transmit power; the temporal resolution can be changed after performing a measurement, as it does not depend on pulse spacing; and the low signal to noise ratio allows multiple geographically separated transmitters to be used in the same frequency band without significantly interfering with each other. The latter allows the same receiver antennas to be used to receive multiple transmitters. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large scale multi-static network of meteor radar transmitters and receivers. This would, for example, provide higher spatio-temporal resolution for mesospheric wind field measurements.

  8. Coded continuous wave meteor radar

    Science.gov (United States)

    Vierinen, J.; Chau, J. L.; Pfeffer, N.; Clahsen, M.; Stober, G.

    2015-07-01

    The concept of coded continuous wave meteor radar is introduced. The radar uses a continuously transmitted pseudo-random waveform, which has several advantages: coding avoids range aliased echoes, which are often seen with commonly used pulsed specular meteor radars (SMRs); continuous transmissions maximize pulse compression gain, allowing operation with significantly lower peak transmit power; the temporal resolution can be changed after performing a measurement, as it does not depend on pulse spacing; and the low signal to noise ratio allows multiple geographically separated transmitters to be used in the same frequency band without significantly interfering with each other. The latter allows the same receiver antennas to be used to receive multiple transmitters. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large scale multi-static network of meteor radar transmitters and receivers. This would, for example, provide higher spatio-temporal resolution for mesospheric wind field measurements.

  9. 175-W continuous-wave master oscillator power amplifier structure ytterbium-doped all-fiber laser

    Institute of Scientific and Technical Information of China (English)

    Ping Yan; Shupeng Yin; Mali Gong

    2008-01-01

    We report on hundred watts range ytterbium-doped all-fiber laser assembly based on the master oscillator power amplifier structure. It consisted of an oscillator and an amplifier with all-fiber components. And fiber fusion splice made the laser be an integrated fiber system. It generated up to 175.5 W of continuouswave (CW) output power at 1085 nm with more than 75% extraction efficiency in the amplifier when the total coupled pump power into the double clad fiber was 270 W.

  10. Influence of normal and inverse upconversion processes on the continuous wave operation of the Er3+ 3 µm crystal laser

    NARCIS (Netherlands)

    Pollnau, M.; Lüthy, W.; Weber, H.P.; Chai, Bruce H.T.; Fan, Tso Yee

    1994-01-01

    A computer simulation of the dynamics of the Er3+ 3 µm cw crystal laser considering the full rate-equation scheme up to the 4F7/2 level has been performed. The influence of the important system parameters on lasing and the interaction of these parameters has been clarified with multiple-parameter va

  11. Growth of micro-crystals in solution by in-situ heating via continuous wave infrared laser light and an absorber

    Science.gov (United States)

    Pathak, Shashank; Dharmadhikari, Jayashree A.; Thamizhavel, A.; Mathur, Deepak; Dharmadhikari, Aditya K.

    2016-01-01

    We report on growth of micro-crystals such as sodium chloride (NaCl), copper sulphate (CuSO4), potassium di-hydrogen phosphate (KDP) and glycine (NH2CH2COOH) in solution by in-situ heating using continuous wave Nd:YVO4 laser light. Crystals are grown by adding single walled carbon nanotubes (SWNT). The SWNTs absorb 1064 nm light and act as an in-situ heat source that vaporizes the solvent producing microcrystals. The temporal dynamics of micro-crystal growth is investigated by varying experimental parameters such as SWNT bundle size and incident laser power. We also report crystal growth without SWNT in an absorbing medium: copper sulphate in water. Even though the growth dynamics with SWNT and copper sulphate are significantly different, our results indicate that bubble formation is necessary for nucleation. Our simple method may open up new vistas for rapid growth of seed crystals especially for examining the crystallizability of inorganic and organic materials.

  12. Reduced dimer production in solar-simulator-pumped continuous wave iodine lasers based on model simulations and scaling and pumping studies

    Science.gov (United States)

    Costen, Robert C.; Heinbockel, John H.; Miner, Gilda A.; Meador, Willard E., Jr.; Tabibi, Bagher M.; Lee, Ja H.; Williams, Michael D.

    1995-01-01

    A numerical rate equation model for a continuous wave iodine laser with longitudinally flowing gaseous lasant is validated by approximating two experiments that compare the perfluoroalkyl iodine lasants n-C3F7I and t-C4F9I. The salient feature of the simulations is that the production rate of the dimer (C4F9)2 is reduced by one order of magnitude relative to the dimer (C3F7)2. The model is then used to investigate the kinetic effects of this reduced dimer production, especially how it improves output power. Related parametric and scaling studies are also presented. When dimer production is reduced, more monomer radicals (t-C4F9) are available to combine with iodine ions, thus enhancing depletion of the laser lower level and reducing buildup of the principal quencher, molecular iodine. Fewer iodine molecules result in fewer downward transitions from quenching and more transitions from stimulated emission of lasing photons. Enhanced depletion of the lower level reduces the absorption of lasing photons. The combined result is more lasing photons and proportionally increased output power.

  13. The physics of transverse mode instability-induced nonlinear phase distortions in large area optical fiber amplifiers and their mitigation with applications in scaling of pulsed and continuous wave high-energy lasers

    Science.gov (United States)

    2016-12-13

    their mitigation with applications in scaling of pulsed and continuous- wave high- energy lasers Balaji Srinivasan INDIAN INSTITUTE OF TECHNOLOGY...high- energy lasers 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-15-1-5044 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Balaji Srinivasan 5d...use of vortex beams to mitigate thermal mode instability in high energy fiber amplifiers. The investigation is carried out through (1) the

  14. Azobenzene liquid crystalline materials for efficient optical switching with pulsed and/or continuous wave laser beams.

    Science.gov (United States)

    Hrozhyk, Uladzimir A; Serak, Svetlana V; Tabiryan, Nelson V; Hoke, Landa; Steeves, Diane M; Kimball, Brian R

    2010-04-12

    This study compares optical switching capabilities of liquid crystal (LC) materials based on different classes of azobenzene dyes. LCs based on molecules containing benzene rings with nearly symmetrical pi-pi conjugation respond more efficiently to a cw beam than to a nanosecond laser pulse and maintain the changes induced by the beam for tens of hours. Using azo dye molecules containing two benzene rings with push-pull pi-pi conjugation we demonstrate high photosensitivity to both a cw beam as well as nanosecond laser pulse with only 1 s relaxation of light-induced changes in material properties. Even faster, 1 ms restoration time is obtained for azo dye molecules containing hetaryl (benzothiazole) ring with enhanced push-pull pi-pi conjugation. These materials respond most efficiently to pulsed excitation while discriminating cw radiation.

  15. Coded continuous wave meteor radar

    Science.gov (United States)

    Chau, J. L.; Vierinen, J.; Pfeffer, N.; Clahsen, M.; Stober, G.

    2016-12-01

    The concept of a coded continuous wave specular meteor radar (SMR) is described. The radar uses a continuously transmitted pseudorandom phase-modulated waveform, which has several advantages compared to conventional pulsed SMRs. The coding avoids range and Doppler aliasing, which are in some cases problematic with pulsed radars. Continuous transmissions maximize pulse compression gain, allowing operation at lower peak power than a pulsed system. With continuous coding, the temporal and spectral resolution are not dependent on the transmit waveform and they can be fairly flexibly changed after performing a measurement. The low signal-to-noise ratio before pulse compression, combined with independent pseudorandom transmit waveforms, allows multiple geographically separated transmitters to be used in the same frequency band simultaneously without significantly interfering with each other. Because the same frequency band can be used by multiple transmitters, the same interferometric receiver antennas can be used to receive multiple transmitters at the same time. The principles of the signal processing are discussed, in addition to discussion of several practical ways to increase computation speed, and how to optimally detect meteor echoes. Measurements from a campaign performed with a coded continuous wave SMR are shown and compared with two standard pulsed SMR measurements. The type of meteor radar described in this paper would be suited for use in a large-scale multi-static network of meteor radar transmitters and receivers. Such a system would be useful for increasing the number of meteor detections to obtain improved meteor radar data products, such as wind fields. This type of a radar would also be useful for over-the-horizon radar, ionosondes, and observations of field-aligned-irregularities.

  16. Fabrication of advanced fiber Bragg gratings by use of sequential writing with a continuous-wave ultraviolet laser source.

    Science.gov (United States)

    Petermann, Ingemar; Sahlgren, Bengt; Helmfrid, Sten; Friberg, Ari T; Fonjallaz, Pierre-Yves

    2002-02-20

    We present a novel scheme based on sequential writing for fabrication of advanced fiber Bragg gratings. As opposed to earlier sequential methods this technique uses a cw UV laser source and allows for very precise control and repetitivity of the formation of the gratings. Furthermore it is possible to use high average irradiances without destroying the fiber, resulting in considerable reduction in fabrication time for complex gratings. The method has been applied to several test gratings, which proved its versatility and quality.

  17. Comparison of Monolithic Optical Frequency Comb Generators Based on Passively Mode-Locked Lasers for Continuous Wave mm-Wave and Sub-THz Generation

    DEFF Research Database (Denmark)

    Criado, A. R.; de Dios, C.; Acedo, P.;

    2012-01-01

    In this paper, two different Passive Mode-Locked Laser Diodes (PMLLD) structures, a Fabry–Perot cavity and a ring cavity laser are characterized and evaluated as monolithic Optical Frequency Comb Generators (OFCG) for CW sub-THz generation. An extensive characterization of the devices under study...

  18. 840 mW Continuous-Wave Fe:ZnSe Laser Operating at 4140 nm (Postprint)

    Science.gov (United States)

    2012-11-30

    lasing has been demonstrated in the 2–3 μm region from Cr2 ions doped into various II–VI crystal hosts [1], most notably ZnSe [2] and ZnS [3]. These...in ZnSe is 370 ns [6], making it difficult to maintain popula- tion inversion. The radiative lifetime of Fe2 in ZnSe is a maximum of 105 μs near 120 K...Fe:ZnSe laser with high beam quality. We employed a polycrystalline ZnSe sample diffusion- dopedwith Fe2 ions to a concentration of approximately 9 × 1018

  19. A compact, continuous-wave terahertz source based on a quantum-cascade laser and a miniature cryocooler

    OpenAIRE

    Richter, Heiko; Greiner-Bär, Michael; Pavlov, Sergey; Semenov, Alexei D.; Wienold, Martin; Schrottke, Lutz; Giehler, M.; Hey, R.; Grahn, H.T.; Huebers, H. -W.

    2010-01-01

    We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum cascade laser (QCL) operating at 3.1 THz with a compact, low input-power Stirling cooler. The QCL, which is based on a two miniband design, has been developed for high output and low electrical pump power. The amount of generated heat complies with the nominal cooling capacity of the Stirling cooler of 7 W at 65 K with 240 W of electrical input power. Special care has been taken to achi...

  20. A compact, continuous-wave terahertz source based on a quantum-cascade laser and a miniature cryocooler.

    Science.gov (United States)

    Richter, H; Greiner-Bär, M; Pavlov, S G; Semenov, A D; Wienold, M; Schrottke, L; Giehler, M; Hey, R; Grahn, H T; Hübers, H-W

    2010-05-10

    We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum-cascade laser (QCL) operating at 3.1 THz with a compact, low-input-power Stirling cooler. The QCL, which is based on a two-miniband design, has been developed for high output and low electrical pump power. The amount of generated heat complies with the nominal cooling capacity of the Stirling cooler of 7 W at 65 K with 240 W of electrical input power. Special care has been taken to achieve a good thermal coupling between the QCL and the cold finger of the cooler. The whole system weighs less than 15 kg including the cooler and power supplies. The maximum output power is 8 mW at 3.1 THz. With an appropriate optical beam shaping, the emission profile of the laser is fundamental Gaussian. The applicability of the system is demonstrated by imaging and molecular-spectroscopy experiments.

  1. Deceleration of a continuous-wave(CW)molecular beam with a single quasi-CW semi-Gaussian laser beam

    Institute of Scientific and Technical Information of China (English)

    Yin Ya-Ling; Xia Yong; Yin Jian-Ping

    2008-01-01

    We propose a promising scheme to decelerate a CW molecular beam by using a red-detuned quasi-cw semi-Gaussian laser beam(SGB).We study the dynamical process of the deceleration for a CW deuterated ammonia(ND3)molecular beam by Monte-Carlo simulation method.Our study shows that we can obtain a ND3 molecular beam with a relative average kinetic energy loss of about 10% and a relative output molecular number of more than 90% by using a single quasi-cw SGB with a power of 1.5kW and a maximum optical well depth of 7.33mK.

  2. Simple way for achieving passive all-optical switching of continuous waves lasers using pure nematic liquid crystal.

    Science.gov (United States)

    Sheng, C; Chen, Q; Norwood, R A; Wang, J; Thomas, J; Peyghambarian, N

    2011-10-20

    We have examined pure nematic liquid crystal (LC), 4'-pentyl-4-biphenylcarbonitrile (5-CB), with a 90° twisted alignment within a cell made of two cross-polarized absorptive plastic polarizers, and investigated the nonlinear transmission properties using cw (532 nm) lasers. We observed optically self-activated polarization switching with a factor of three lower switching power than a dye-doped LC cell with similar linear transmittance using glass substrates. We also studied the dynamics of the switching processes and observed millisecond switching time. These studies have demonstrated a simpler but more efficient way for fabricating broadband, low switching power, millisecond time scale switching, and optical limiting devices. © 2011 Optical Society of America

  3. Compact Continuous-Wave Nd:YVO4 Laser with Self-Raman Conversion and Sum Frequency Generation

    Institute of Scientific and Technical Information of China (English)

    ZHU Hai-Yong; ZHANG Ge; DUAN Yan-Min; HUANG Cheng-Hui; WEI Yong

    2011-01-01

    @@ Low threshold and compact cw Nd:YVO4 self-Raman lasers at 1176 nm and sum-frequency mixing of fundamental and first-Stokes wavelengths are demonstrated.A 20-mm Nd:YVO4 crystal is adopted in a compact plane-concave resonator.The results show that the cw Raman conversion is sensitive to cavity length.At an incident pump power of 22.5 W,output power of 1.53 W at 1175.6 nm is achieved,corresponding to the threshold of only 0.8 W and the slop efficiency of 8.1%.Intra-cavity sum-frequency generation is realized in a type-Ⅱ phase-matching cut KTP crystal,480 m W at 558.6 nm is obtained at incident pump power of 12 W.%Low threshold and compact cw Nd:YVO4 self-Ranman lasers at 11 76 nm and sum-frequency mixing of fundamental and first-Stokes wavelengths are demonstrated. A 20-mm Nd:YVO4 crystal is adopted in a compact plane-concave resonator. The results show that the cw Raman conversion is sensitive to cavity length. At an incident pump power of 22.5 W, output power of 153 W at 1175.6nm is achieved, corresponding to the threshold of only 0.8 W and the slop effciency of 8. 1% Intra-cavity sum- frequency generation is realized in a type-Ⅱ phase-matching cut KTP Crystal, 480mW at 558.6nm is obtained at incident pump power of 12 W.

  4. Continuous-Wave Green Laser of 9.9W by Intracavity Frequency Doubling in Laser Diode Single-End-Pumped Nd:YVO4/LBO

    Institute of Scientific and Technical Information of China (English)

    BAI Yang; LI Long; CHEN Hao-Wei; YANG Zhi; BAI Jin-Tao

    2004-01-01

    @@ A maximum of 9.9 W cw TEM00 output at 532nm laser has been obtained by intracavity frequency doubling with LBO in laser-diode single-end-pumped Nd:YVO4. The Nd:YVO4/LBO green laser has a simple three mirror V-fold cavity structure. The optical-optical conversion efficiency was 34.8%. Based on the equation of thermal conduction, a general solution for the laser-crystal interior temperature distribution is obtained by the semi-analytical thermal analysis method.

  5. Signature of Wave Chaos in Spectral Characteristics of Microcavity Lasers

    CERN Document Server

    Sunada, Satoshi; Fukushima, Takehiro; Harayama, Takahisa

    2016-01-01

    We report the spectral characteristics of fully chaotic and non-chaotic microcavity lasers under continuous-wave operating conditions. It is found that fully chaotic microcavity lasers operate in single mode, whereas non-chaotic microcavity lasers operate in multimode. The suppression of multimode lasing for fully chaotic microcavity lasers is explained by large spatial overlaps of the resonance wave functions that spread throughout the two-dimensional cavity due to the ergodicity of chaotic ray orbits.

  6. Long-term frequency and amplitude stability of a solid-nitrogen-cooled, continuous wave THz quantum cascade laser

    Science.gov (United States)

    Danylov, Andriy A.; Waldman, Jerry; Light, Alexander R.; Goyette, Thomas M.; Giles, Robert H.; Qian, Xifeng; Chandrayan, Neelima; Goodhue, William D.; Nixon, William E.

    2012-02-01

    Operational temperature increase of CW THz QCLs to 77 K has enabled us to employ solid nitrogen (SN2) as the cryogen. A roughing pump was used to solidify liquid nitrogen and when the residual vapor pressure in the nitrogen reservoir reached the pumping system's minimum pressure the temperature equilibrated and remained constant until all the nitrogen sublimated. The hold time compared to liquid helium has thereby increased approximately 70-fold, and at a greatly reduced cost. The milliwatt CW QCL was at a temperature of approximately 60 K, dissipating 5 W of electrical power. To measure the long-term frequency, current, and temperature stability, we heterodyned the free-running 2.31 THz QCL with a CO2 pumped far-infrared gas laser line in methanol (2.314 THz) in a corner-cube Schottky diode and recorded the IF frequency, current and temperature. Under these conditions the performance characteristics of the QCL, which will be reported, exceeded that of a device mounted in a mechanical cryocooler.

  7. BeZnCdSe quantum-well ridge-waveguide laser diodes under low threshold room-temperature continuous-wave operation

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Jijun [Shanghai Key Laboratory of Modern Optical System, Engineering Research Center of Optical Instrument and System (Ministry of Education), School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093 (China); Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Akimoto, Ryoichi, E-mail: r-akimoto@aist.go.jp [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan)

    2015-10-19

    Low threshold current ridge-waveguide BeZnCdSe quantum-well laser diodes (LDs) have been developed by completely etching away the top p-type BeMgZnSe/ZnSe:N short-period superlattice cladding layer, which can suppress the leakage current that flows laterally outside of the electrode. The waveguide LDs are covered with a thick SiO{sub 2} layer and planarized with chemical-mechanical polishing and a reactive ion etching process. Room-temperature lasing under continuous-wave condition is achieved with the laser cavity formed by the cleaved waveguide facets coated with high-reflectivity dielectric films. For a 4 μm-wide green LD lasing around a wavelength of 535 nm, threshold current and voltage of 7.07 mA and 7.89 V are achieved for a cavity length of 300 μm, and the internal differential quantum efficiency, internal absorption loss, gain constant, and nominal transparency current density are estimated to be 27%, 4.09 cm{sup −1}, 29.92 (cm × μm)/kA and 6.35 kA/(cm{sup 2 }× μm), respectively. This compact device can realize a significantly improved performance with much lower threshold power consumption, which would benefit the potential application for ZnSe-based green LDs as light sources in full-color display and projector devices installed in consumer products such as pocket projectors.

  8. Ppb-level mid-infrared ethane detection based on three measurement schemes using a 3.34-μm continuous-wave interband cascade laser

    Science.gov (United States)

    Li, Chunguang; Zheng, Chuantao; Dong, Lei; Ye, Weilin; Tittel, Frank K.; Wang, Yiding

    2016-07-01

    A ppb-level mid-infrared ethane (C2H6) sensor was developed using a continuous-wave, thermoelectrically cooled, distributed feedback interband cascade laser emitting at 3.34 μm and a miniature dense patterned multipass gas cell with a 54.6-m optical path length. The performance of the sensor was investigated using two different techniques based on the tunable interband cascade laser: direct absorption spectroscopy (DAS) and second-harmonic wavelength modulation spectroscopy (2 f-WMS). Three measurement schemes, DAS, WMS and quasi-simultaneous DAS and WMS, were realized based on the same optical sensor core. A detection limit of ~7.92 ppbv with a precision of ±30 ppbv for the separate DAS scheme with an averaging time of 1 s and a detection limit of ~1.19 ppbv with a precision of about ±4 ppbv for the separate WMS scheme with a 4-s averaging time were achieved. An Allan-Werle variance analysis indicated that the precisions can be further improved to 777 pptv @ 166 s for the separate DAS scheme and 269 pptv @ 108 s for the WMS scheme, respectively. For the quasi-simultaneous DAS and WMS scheme, both the 2 f signal and the direct absorption signal were simultaneously extracted using a LabVIEW platform, and four C2H6 samples (0, 30, 60 and 90 ppbv with nitrogen as the balance gas) were used as the target gases to assess the sensor performance. A detailed comparison of the three measurement schemes is reported. Atmospheric C2H6 measurements on the Rice University campus and a field test at a compressed natural gas station in Houston, TX, were conducted to evaluate the performance of the sensor system as a robust and reliable field-deployable sensor system.

  9. Atmospheric CO2 Column Measurements with an Airborne Intensity-Modulated Continuous-Wave 1.57-micron Fiber Laser Lidar

    Science.gov (United States)

    Dobler, Jeremy T.; Harrison, F. Wallace; Browell, Edward V.; Lin, Bing; McGregor, Doug; Kooi, Susan; Choi, Yonghoon; Ismail, Syed

    2013-01-01

    The 2007 National Research Council (NRC) Decadal Survey on Earth Science and Applications from Space recommended Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) as a mid-term, Tier II, NASA space mission. ITT Exelis, formerly ITT Corp., and NASA Langley Research Center have been working together since 2004 to develop and demonstrate a prototype Laser Absorption Spectrometer for making high-precision, column CO2 mixing ratio measurements needed for the ASCENDS mission. This instrument, called the Multifunctional Fiber Laser Lidar (MFLL), operates in an intensity-modulated, continuous-wave mode in the 1.57- micron CO2 absorption band. Flight experiments have been conducted with the MFLL on a Lear-25, UC-12, and DC-8 aircraft over a variety of different surfaces and under a wide range of atmospheric conditions. Very high-precision CO2 column measurements resulting from high signal-to-noise (great than 1300) column optical depth measurements for a 10-s (approximately 1 km) averaging interval have been achieved. In situ measurements of atmospheric CO2 profiles were used to derive the expected CO2 column values, and when compared to the MFLL measurements over desert and vegetated surfaces, the MFLL measurements were found to agree with the in situ-derived CO2 columns to within an average of 0.17% or approximately 0.65 ppmv with a standard deviation of 0.44% or approximately 1.7 ppmv. Initial results demonstrating ranging capability using a swept modulation technique are also presented.

  10. Continuous-wave simultaneous dual-wavelength and power-ratio-tunable operation at 1064 and 1342 nm in an Nd:LuVO4 laser

    Science.gov (United States)

    Hsu, C.-C.; Wu, S.-S.; Chou, C.-C.; Wei, M.-D.

    2011-11-01

    This study demonstrates continuous-wave simultaneous dual-wavelength emission at 1064 and 1342 nm in an Nd:LuVO4 laser by using a T-type cavity configuration. The output powers indicating a function of pump power had two evolutions depending on the strength of the completion of two wavelength emissions. One is that the output power increased linearly with the pump power in weak competition, and the output power and slope efficiency of 1064 and 1342 nm were 1.17 W and 13%, and 0.213 W and 2.8%, respectively. The other is that the extracting-energy capabilities of two wavelength emissions were close, and the evolution was not linear and the variations demonstrated multiple stages depending on the pump power. Moreover, the ratio of output power, defined as the output power at 1064 nm divided by that at 1342 nm, is tuned from 0 to 5.5 by varying the 1064 nm cavity, and equal output powers of 1064 and 1342 nm can be obtained at each pump power.

  11. Arrayed Continuous-wave THz Photomixers

    CERN Document Server

    Bauerschmidt, S T; Döhler, G H; Lu, H; Gossard, A C; Preu, S

    2013-01-01

    We present both chip-scale and free space coherent arrays of continuous-wave THz photomixers. By altering the relative phases of the exciting laser signals, the relative THz phase between the array elements can be tuned, allowing for beam steering. The constructive interference of the emission of N elements leads to an increase of the focal intensity by a factor of NxN while reducing the beam width by ~1/N, below the diffraction limit of a single source. Such array architectures strongly improve the THz power distribution for stand-off spectroscopy and imaging systems while providing a huge bandwidth at the same time. We demonstrate this by beam profiles generated by a free space 2x2 and a 4x1 array for a transmission distance of 4.2 meters. Spectra between 70 GHz and 1.1 THz have been recorded with these arrays.

  12. Continuous-terahertz-wave molecular imaging system for biomedical applications

    Science.gov (United States)

    Zhang, Rui; Zhang, Liangliang; Wu, Tong; Wang, Ruixue; Zuo, Shasha; Wu, Dong; Zhang, Cunlin; Zhang, Jue; Fang, Jing

    2016-07-01

    Molecular imaging techniques are becoming increasingly important in biomedical research and potentially in clinical practice. We present a continuous-terahertz (THz)-wave molecular imaging system for biomedical applications, in which an infrared (IR) laser is integrated into a 0.2-THz reflection-mode continuous-THz-wave imaging system to induce surface plasmon polaritons on the nanoparticles and further improve the intensity of the reflected signal from the water around the nanoparticles. A strong and rapid increment of the reflected THz signal in the nanoparticle solution upon the IR laser irradiation is demonstrated, using either gold or silver nanoparticles. This low-cost, simple, and stable continuous-THz-wave molecular imaging system is suitable for miniaturization and practical imaging applications; in particular, it shows great promise for cancer diagnosis and nanoparticle drug-delivery monitoring.

  13. Continuous wave carbon dioxide treatment of balanitis xerotica obliterans.

    Science.gov (United States)

    Rosemberg, S K; Jacobs, H

    1982-05-01

    Herein is presented the first case of balanitis xerotica obliterans treated successfully by carbon dioxide-continuous wave (CW-CO2) laser vaporization. This method appears to be a safe addition to other well-known treatment modalities, offering minimal postoperative discomfort, preservation of anatomic landmarks and function, and excellent cosmetic results.

  14. K403合金连续CO2激光熔覆层质量控制%Quality Controlling of Laser Cladding Layer on K403 Superalloy by Continuous Wave CO2 Laser

    Institute of Scientific and Technical Information of China (English)

    张乔斌; 熊征; 曾晓雁

    2011-01-01

    在K403高温合金的基体上,采用连续CO2激光器熔覆商用司太立合金,分析了激光熔覆层的组织特征和熔覆层熔合质量.结果表明,熔覆层组织由柱状树枝晶和细小等轴晶等构成;良好的熔覆质量与激光熔覆线能量有关,当线能量为200~320 J/mm时可以获得熔合界面良好,无裂纹的熔覆层;熔覆层裂纹与K403合金中沿晶分布的低熔点共晶及碳化物有关.%Laser cladding process of K403 superalloy with a commercial manual stallite alloy was conducted by continuous wave(CW) CO2 laser. The microstructure and melting quality of the cladding layer were analyzed. The results show that the microstructure of the cladding consists of columnar branch grain and fine equiaxed grain. A good cladding quality without cracking and unmelted boundary is obtained when line energy is 200~320 J/mm. The eutectic phase with low melting point and carbide existed along the grain boundary of K403 superalloy is the main factors causing the cladding cracking.

  15. Passive coherent discriminator using phase diversity for the simultaneous measurement of frequency noise and intensity noise of a continuous-wave laser

    Science.gov (United States)

    Michaud-Belleau, V.; Bergeron, H.; Light, P. S.; Hébert, N. B.; Deschênes, J. D.; Luiten, A. N.; Genest, J.

    2016-10-01

    The frequency noise and intensity noise of a laser set the performance limits in many modern photonics applications and, consequently, must often be characterized. As lasers continue to improve, the measurement of these noises however becomes increasingly challenging. Current approaches for the characterization of very high-performance lasers often call for a second laser with equal or higher performance to the one that is to be measured, an incoherent interferometer having an extremely long delay-arm, or an interferometer that relies on an active device. These instrumental features can be impractical or problematic under certain experimental conditions. As an alternative, this paper presents an entirely passive coherent interferometer that employs an optical 90° hybrid coupler to perform in-phase and quadrature detection. We demonstrate the technique by measuring the frequency noise power spectral density of a highly-stable 192 THz (1560 nm) fiber laser over five frequency decades. Simultaneously, we are able to measure its relative intensity noise power spectral density and characterize the correlation between its amplitude noise and phase noise. We correct some common misconceptions through a detailed theoretical analysis and demonstrate the necessity to account for normal imperfections of the optical 90° hybrid coupler. We finally conclude that this passive coherent discriminator is suitable for reliable and simple noise characterization of highly-stable lasers, with bandwidth and dynamic range benefits but susceptibility to additive noise contamination.

  16. Effects of different doses of low power continuous wave he-ne laser radiation on some seed thermodynamic and germination parameters, and potential enzymes involved in seed germination of sunflower (Helianthus annuus L.).

    Science.gov (United States)

    Perveen, Rashida; Ali, Qasim; Ashraf, Muhammad; Al-Qurainy, Fahad; Jamil, Yasir; Raza Ahmad, Muhammad

    2010-01-01

    In this study, water-soaked seeds of sunflower were exposed to He-Ne laser irradiation of different energies to determine whether or not He-Ne laser irradiation caused changes to seed thermodynamic and germination parameters as well as effects on the activities of germination enzymes. The experiment comprised four energy levels: 0 (control), 100, 300 and 500mJ of laser energy and each treatment replicated four times arranged in a completely randomized design. The experimentation was performed under the greenhouse conditions in the net-house of the Department of Botany, University of Agriculture, Faisalabad. The seed thermodynamic parameters were calculated according to seed germination thermograms determined with a calorimeter at 25.8°C for 72h. Various thermodynamic parameters of seed (ΔH, (ΔS)(e), (ΔS)(c), (ΔS)(e) /Δt and (ΔS)(c) /Δt) were affected significantly due to presowing laser treatment. Significant changes in seed germination parameters and enzyme activities were observed in seeds treated with He-Ne laser. The He-Ne laser seed treatment resulted in increased activities of amylase and protease. These results indicate that the low power continuous wave He-Ne laser light seed treatment has considerable biological effects on seed metabolism. This seed treatment technique can be potentially employed to enhance agricultural productivity.

  17. Continuous-wave operation up to 20 °C of deep-ridge npn-InGaAsP/InP multiple quantum well transistor laser emitting at 1.5-μm wavelength.

    Science.gov (United States)

    Qiao, L J; Liang, S; Han, L S; Xu, J J; Zhu, H L; Wang, W

    2015-05-04

    We report continuous-wave (CW) operation up to 20 °C of 1.5-μm wavelength npn-InGaAsP/InP multiple quantum well (MQW) transistor laser (TL) with a deep-ridge structure. With CW laser emission, the common emitter current gain of the device can be over 3.5, which is significantly larger than those of the previously reported long wavelength TLs. It is found that at low base current, the laser operation occurs on the first excited state of the MQWs. At high base current, however, the device shows stimulated emissions on the ground state transition. The trend is contrary to what has been observed in the GaAs based TLs and is explained by the change of carrier flow at different base currents.

  18. Continuing Higher Education: The Coming Wave.

    Science.gov (United States)

    Lerner, Allan W., Ed.; King, B. Kay, Ed.

    This book, containing seven chapters and an epilogue, describes how continuing education--as a structure and a function--can become a unique tool for reorienting major universities toward confronting new societal challenges. "The Coming Wave" (Lerner) discusses relevant organizational theory to explain the special role of continuing education in…

  19. Polarization decoherence differential frequency-modulated continuous-wave gyroscope.

    Science.gov (United States)

    Zheng, Chao; Zheng, Gang; Han, Liwei; Luo, Jianhua; Teng, Fei; Wang, Bing; Song, Ping; Gao, Kun; Hou, Zhiqing

    2014-12-01

    A polarization decoherence differential frequency-modulated continuous-wave (FMCW) gyroscope is presented. The impact of coherent polarization crosstalk noise on the differential FMCW gyro is analyzed. In order to suppress coherent polarization crosstalk noise, a novel method was proposed to produce two incoherent orthogonal polarization narrow band beams from laser diode. In this way, the random drift has been reduced about one order.

  20. Compact CH{sub 4} sensor system based on a continuous-wave, low power consumption, room temperature interband cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Lei, E-mail: donglei@sxu.edu.cn [Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005 (United States); State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006 (China); Li, Chunguang; Gluszek, Aleksander K.; Tittel, Frank K. [Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005 (United States); Sanchez, Nancy P.; Griffin, Robert J. [Department of Civil and Environmental Engineering, Rice University, Houston, Texas 77005 (United States)

    2016-01-04

    A tunable diode laser absorption spectroscopy-based methane sensor, employing a dense-pattern multi-pass gas cell and a 3.3 μm, CW, DFB, room temperature interband cascade laser (ICL), is reported. The optical integration based on an advanced folded optical path design and an efficient ICL control system with appropriate electrical power management resulted in a CH{sub 4} sensor with a small footprint (32 × 20 × 17 cm{sup 3}) and low-power consumption (6 W). Polynomial and least-squares fit algorithms are employed to remove the baseline of the spectral scan and retrieve CH{sub 4} concentrations, respectively. An Allan-Werle deviation analysis shows that the measurement precision can reach 1.4 ppb for a 60 s averaging time. Continuous measurements covering a seven-day period were performed to demonstrate the stability and robustness of the reported CH{sub 4} sensor system.

  1. Photonic-integrated circuit for continuous-wave THz generation.

    Science.gov (United States)

    Theurer, Michael; Göbel, Thorsten; Stanze, Dennis; Troppenz, Ute; Soares, Francisco; Grote, Norbert; Schell, Martin

    2013-10-01

    We demonstrate a photonic-integrated circuit for continuous-wave (cw) terahertz (THz) generation. By comprising two lasers and an optical phase modulator on a single chip, the full control of the THz signal is enabled via a unique bidirectional operation technique. Integrated heaters allow for continuous tuning of the THz frequency over 570 GHz. Applied to a coherent cw THz photomixing system operated at 1.5 μm optical wavelength, we reach a signal-to-noise ratio of 44 dB at 1.25 THz, which is identical to the performance of a standard system based on discrete components.

  2. Continuous Observations and the Wave Function Collapse

    CERN Document Server

    Marchewka, A

    2011-01-01

    We propose to modify the collapse axiom of quantum measurement theory by replacing the instantaneous with a continuous collapse of the wave function in finite time $\\tau$. We apply it to coordinate measurement of a free quantum particle that is initially confined to a domain $D\\subset\\rR^d$ and is observed continuously by illuminating $\\rR^d-D$. The continuous collapse axiom (CCA) defines the post-measurement wave function (PMWF)in $D$ after a negative measurement as the solution of Schr\\"odinger's equation at time $\\tau$ with instantaneously collapsed initial condition and homogeneous Dirichlet condition on the boundary of $D$. The CCA applies to all cases that exhibit the Zeno effect. It rids quantum mechanics of the unphysical artifacts caused by instantaneous collapse and introduces no new artifacts.

  3. Manufacturing laser glass by continuous melting

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, J H; Suratwala, T; krenitsky, S; Takeuchi, K

    2000-07-01

    A novel, continuous melting process is being used to manufacture meter-sized plates of laser glass at a rate 20-times faster, 5-times cheaper, and with 2-3 times better optical quality than with previous one-at-a-time, ''discontinuous'' technology processes. This new technology for manufacturing laser glass, which is arguably the most difficult continuously-melted optical material ever produced, comes as a result of a $60 million, six-year joint R&D program between government and industry. The glasses manufactured by the new continuous melting process are Nd-doped phosphate-based glasses and are marketed under the product names LG-770 (Schott Glass Technologies) and LHG-8 (Hoya Corporation USA). With this advance in glass manufacturing technology, it is now possible to construct high-energy, high-peak-power lasers for use in fusion energy development, national defense, and basic physics research that would have been impractical to build using the old melting technology. The development of continuously melted laser glass required technological advances that have lead to improvements in the manufacture of other optical glass products as well. For example, advances in forming, annealing, and conditioning steps of the laser glass continuous melting process are now being used in manufacture of other large-size optical glasses.

  4. Measurement and analysis of internal loss and injection efficiency for continuous-wave blue semipolar ( 20 2 ¯ 1 ¯ ) III-nitride laser diodes with chemically assisted ion beam etched facets

    Science.gov (United States)

    Becerra, Daniel L.; Kuritzky, Leah Y.; Nedy, Joseph; Saud Abbas, Arwa; Pourhashemi, Arash; Farrell, Robert M.; Cohen, Daniel A.; DenBaars, Steven P.; Speck, James S.; Nakamura, Shuji

    2016-02-01

    Continuous-wave blue semipolar ( 20 2 ¯ 1 ¯ ) III-nitride laser diodes were fabricated with highly vertical, smooth, and uniform mirror facets produced by chemically assisted ion beam etching. Uniform mirror facets are a requirement for accurate experimental determination of internal laser parameters, including internal loss and injection efficiency, which were determined to be 9 cm-1 and 73%, respectively, using the cavity length dependent method. The cavity length of the uncoated devices was varied from 900 μm to 1800 μm, with threshold current densities ranging from 3 kA/cm2 to 9 kA/cm2 and threshold voltages ranging from 5.5 V to 7 V. The experimentally determined internal loss was found to be in good agreement with a calculated value of 9.5 cm-1 using a 1D mode solver. The loss in each layer was calculated and in light of the analysis several modifications to the laser design are proposed.

  5. Surface oxidation of porous ZrB{sub 2}-SiC ceramic composites by continuous-wave ytterbium fibre laser

    Energy Technology Data Exchange (ETDEWEB)

    Mahmod, Dayang Salyani Abang, E-mail: dygsalyani@gmail.com [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak (Malaysia); Glandut, Nicolas [SPCTS, UMR 7315, CNRS, University of Limoges, European Ceramic Center, 12 Rue Atlantis, 87068 Limoges (France); Khan, Amir Azam [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak (Malaysia); Labbe, Jean-Claude [SPCTS, UMR 7315, CNRS, University of Limoges, European Ceramic Center, 12 Rue Atlantis, 87068 Limoges (France)

    2015-12-01

    Highlights: • Surface oxidation of ZrB{sub 2}-SiC ceramic composites by Yb-fibre laser. • Round spiral laser pattern created for the surface oxidation. • Presence of laser-formed oxide scale and unaffected beneath regions. • Crazed but uncracked surface oxide. • A dense glassy SiO{sub 2}-rich layer exhibited enhances oxidation resistance. - Abstract: Surface treatment of ceramic substrates by a laser beam can allow to incorporate interesting properties to these ceramics. In the present work, surface oxidation of ca. 30% porous ZrB{sub 2}-SiC ceramic composites by using an ytterbium fibre laser was conducted. Oxidation of ceramic substrates through this process under ambient conditions has certain advantages compared to the classical oxidation method. A particular spiral laser pattern was created in order to produce an oxidized structure on ZrB{sub 2}-SiC porous substrates. The laser parameters were as follows i.e., laser power of 50, 60 and 70 W, a beam diameter of 1.25 mm, velocity of 2 mm/s, acceleration and deceleration of 1 mm/s{sup 2}. The microstructural and morphological changes in the laser-treated region was examined using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. At laser power of 70 W, the sample exhibits uniform oxidation. It revealed that the very porous bulk beneath remained unaffected and unoxidized because this laser-formed oxide scale protects the substrate from oxidation. The presence of oxidized and unaffected regions indicated a high degree of heat localization. The dense glassy SiO{sub 2}-rich layer prevents the inward oxygen diffusion into the inner bulk hence enhances the oxidation resistance.

  6. Continuous reversal of Hanle resonances of counter-propagating pulse and continuous-wave field

    CERN Document Server

    Dimitrijević, Jelena; Jelenković, Branislav M

    2013-01-01

    In this work we study propagation dynamics of the two counter-propagating lasers, the continuous-wave (CW) laser and the pulse of another laser, when both lasers are tuned to the $F_{g}=2 \\rightarrow F_{e}=1$ transition in $^{87}$Rb, and therefore can develop Hanle electromagnetically induced transparency (EIT) in Rb vapor. We calculate transmission of both lasers as a function of applied magnetic field, and investigate how the propagation of the pulse affects the transmission of the CW laser. And vice versa, we have found conditions when the Gaussian pulse can either pass unchanged, or be significantly absorbed in the vacuum Rb cell. This configuration is therefore suitable for the convenient control of the pulse propagation and the system is of interest for optically switching of the laser pulses. In terms of the corresponding shapes of the coherent Hanle resonances, this is equivalent to turning the coherent resonance from Hanle EIT into electromagnetically induced absorption (EIA) peak. There is the range...

  7. Demonstration of long-term reliability of a 266-nm, continuous-wave, frequency-quadrupled solid-state laser using beta-BaB(2)O(4).

    Science.gov (United States)

    Kondo, K; Oka, M; Wada, H; Fukui, T; Umezu, N; Tatsuki, K; Kubota, S

    1998-02-01

    We report what we believe to be the first operation of more than 1000 h of a 266-nm (cw) frequency-quadrupled solid-state laser with a 100-mW output. We used beta-BaB(2)O(4)(BBO) crystal grown by the Czochralski method to double the green-light (532-nm) wavelength, using an external resonant cavity. The green light was generated with an intracavity frequency-doubled Nd:YVO(4)laser pumped by a 4-W laser diode. When the incident 532-nm power on the external resonant doubler was 500 mW, we generated 100 mW of cw 266-nm radiation with the BBO crystal. The degradation rate seems to be proportional to the strength of the UV optical electric field. We also obtained a relative intensity noise of -130dB/Hz at frequencies of 2 to 10 MHz for 266-nm laser light.

  8. 5.5 W continuous-wave TEM00-mode Nd:YAG solar laser by a light-guide/2V-shaped pump cavity

    Science.gov (United States)

    Almeida, J.; Liang, D.; Vistas, C. R.; Bouadjemine, R.; Guillot, E.

    2015-12-01

    A significant progress in TEM00-mode solar laser power and efficiency with heliostat-parabolic mirror system is reported here. A double-stage light-guide/2V-shaped pump cavity is used to efficiently couple and redistribute the concentrated pump light from a 2-m-diameter parabolic mirror to a 4-mm-diameter, 30-mm-length, 1.1 at.% Nd:YAG single-crystal rod. The light guide with large rectangular cross section enables a stable uniform pumping profile along the laser rod, resulting also in an enhanced tracking error compensation capacity. 5.5 W cw TEM00-mode solar laser power was measured at the output of a thermally near unstable asymmetric resonator. 150 and 157 % improvement in TEM00-mode solar laser collection efficiency and slope efficiency were obtained, respectively.

  9. Stable High Power and High Beam Quality Diode-Side-Pumped Continuous-Wave Intracavity Frequency-Doubled Nd:YAG Laser

    Institute of Scientific and Technical Information of China (English)

    CHENG Xian-Kun; ZHOU Yong; CUI Qian-Jin; YANG Feng; BO Yong; PENG Qin-Jun; CUI Da-Fu; XU Zu-Yan

    2009-01-01

    We report a stable high power and high beam quality diode-side-pumped cw green laser from intracavity frequency-doubled Nd:YAG laser with KTP.By using a L-shaped concave-convex resonator,designed with two Nd:YAG rods birefringence compensation,a large fundamental mode size in the laser crystal arid a tight focus in the nonlinear crystal could be obtained simultaneously.The green laser delivers a maximum 532nm output power of 23.2 W.Under 532 nm output power of 20.9 W,the beam quality factor is measured to be 4.1,and the fluctuation of the output power is less than 1.4% in an hour.

  10. Terahertz Transmission Imaging with 2.52 THz Continuous Wave

    Institute of Scientific and Technical Information of China (English)

    Xiao-Tong Guan; De-Wei Zheng; Min Hu; Wen-Jie Fu; Yu-Meng Cui; Xiang Fan; Liang Zhang; Ye Yuan; Jing-Yuan Xu; Yuan Li

    2013-01-01

    In this article, two terahertz transmission imaging systems are built with a 2.52 THz continuous wave laser and two types of sensors. One is array scanning system using a 124×124 pyro-electric array camera as the detector; the other is a point-wise scanning system utilizing a Golay cell as the detector. The imaging speed and quality is briefly analyzed. Terahertz (THz) imaging results demonstrate that the array scanning system has higher imaging speed with lower resolution. The point-wise scanning system has higher imaging quality with lower speed.

  11. Enhanced efficiency of a continuous-wave mode-locked Nd:YAG laser by compensation of the thermally induced, polarization-dependent bifocal lens.

    Science.gov (United States)

    Wetter, N U; Maldonado, E P; Vieira, N D

    1993-09-20

    Measurements of the bifocal, thermally induced lenses of a cw Nd:YAG laser were obtained. We observed four different focal lengths that are polarization and direction dependent. The focal lengths were used to design stable resonators with large fundamental mode filling in the laser gain medium. The beam is totally polarized in the desired direction even without an intracavity Brewster window. We developed a general approach for the optimization of single-lamp, cw-pumped Nd:YAG lasers. Up to 22 W of cw output power in the vertically polarized TEM(00) mode and 15 W in the horizontal polarization are obtained for moderate lamp currents. Also, we demonstrate mode locking with 56-ps pulse duration at 33 A of lamp current and up to 13 W of average output power.

  12. One-Watt level mid-IR output, singly resonant, continuous-wave optical parametric oscillator pumped by a monolithic diode laser

    NARCIS (Netherlands)

    Nieuwenhuis, Albert F.; Lee, Christopher James; Sumpf, Bernd; van der Slot, Petrus J.M.; Erbert, Götz; Boller, Klaus J.

    2010-01-01

    We report more than 1.1 Watt of idler power at 3373 nm in a singly resonant optical parametric oscillator (SRO), directly pumped by a single-frequency monolithic tapered diode laser. The SRO is based on a periodically poled MgO:LiNbO3 crystal in a four mirror cavity and is excited by 8.05 W of 1062

  13. Continuous-wave operation of a $(20\\bar{2}\\bar{1})$ InGaN laser diode with a photoelectrochemically etched current aperture

    KAUST Repository

    Megalini, Ludovico

    2015-03-06

    © 2015 The Japan Society of Applied Physics. We demonstrated selective and controllable undercut etching of the InGaN/GaN multiple quantum well (MQW) active region of a (2021) laser diode (LD) structure by photoelectrochemical etching. This technique was used to fabricate current aperture edge-emitting blue laser diodes (CALDs), whose performance was compared with that of shallow-etched ridge LDs with a nominally identical epitaxial structure. The threshold current density, threshold voltage, peak output power, and series resistance for the CA-LD (shallow-etched LD) with a 2.5-μm-wide active region were 4.4 (8.1) kA/cm2, 6.1 (7.7) V, 96.5 (63.5)mW, and 4.7 (6.0)Ω under pulsed conditions and before facet coating, respectively.

  14. High Power Continuous-Wave Diode-End-Pumped 1.34-μm Nd:GdVO4 Laser

    Institute of Scientific and Technical Information of China (English)

    ZHOU Rui; RUAN Shuang-Chen; DU Chen-Lin; YAO Jian-Quan

    2008-01-01

    @@ A high power cw all-solid-state 1.34-μm Nd:GdVO4 laser is experimentally demonstrated. With a diode-doubleend-pumped configuration and a simple plane-parallel cavity, a maximum output power of 27.9 W is obtained at incident pump power of 96 W, introducing a slope efficiency of 35.4%. To the best of our knowledge, this is the highest output power of diode-end-pumped 1.3-gin laser. With the experimental data, the thermal-stress-resistance figure of merit of Nd:GdVO4 crystal with 0.3at% Nd3+ doped level is calculated to be larger than 9.94 W/cm.

  15. Note: Optical and electronic design of an amplitude-modulated continuous-wave laser scanner for high-accuracy distance measurement.

    Science.gov (United States)

    Jang, Junhwan; Hwang, Sungui; Park, Kyihwan

    2015-04-01

    To utilize a time-of-flight-based laser scanner as a distance measurement sensor, the measurable distance and accuracy are the most important performance parameters to consider. For these purposes, the optical system and electronic signal processing of the laser scanner should be optimally designed in order to reduce a distance error caused by the optical crosstalk and wide dynamic range input. Optical system design for removing optical crosstalk problem is proposed in this work. Intensity control is also considered to solve the problem of a phase-shift variation in the signal processing circuit caused by object reflectivity. The experimental results for optical system and signal processing design are performed using 3D measurements.

  16. Note: Optical and electronic design of an amplitude-modulated continuous-wave laser scanner for high-accuracy distance measurement

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Junhwan; Hwang, Sungui; Park, Kyihwan, E-mail: khpark@gist.ac.kr [School of Mechatronics, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju (Korea, Republic of)

    2015-04-15

    To utilize a time-of-flight-based laser scanner as a distance measurement sensor, the measurable distance and accuracy are the most important performance parameters to consider. For these purposes, the optical system and electronic signal processing of the laser scanner should be optimally designed in order to reduce a distance error caused by the optical crosstalk and wide dynamic range input. Optical system design for removing optical crosstalk problem is proposed in this work. Intensity control is also considered to solve the problem of a phase-shift variation in the signal processing circuit caused by object reflectivity. The experimental results for optical system and signal processing design are performed using 3D measurements.

  17. Generation of 2.1 W Continuous Wave Blue Light by Intracavity Doubling of a Diode-End-Pumped Nd:YAG Laser in a 30 mm LBO

    Institute of Scientific and Technical Information of China (English)

    CHEN Ya-Hui; HOU Wei; PENG Hai-Bo; GENG Ai-Cong; ZHOU Yong; GUI Da-Fu; XU Zu-Yan

    2006-01-01

    A folded four-mirror cavity with a composite Nd:YAG rod is optimized to obtain high efficient cw 473nm blue output. The laser could operate stably in the region of the thermal-lens focal length from 20mm to 70 ram. LBO is used for intracavity frequency doubling of the 946nm transition of Nd:YAG and the optimum LBO length is investigated. A maximum output power of 2.1 W in the blue spectral range at 473 nm is achieved with 30-mm-long LBO, corresponding to an optical conversion efficiency of 9.1%.

  18. LDRD final report on continuous wave intersubband terahertz sources.

    Energy Technology Data Exchange (ETDEWEB)

    Samora, Sally; Mangan, Michael A.; Foltynowicz, Robert J.; Young, Erik W.; Fuller, Charles T.; Stephenson, Larry L.; Reno, John Louis; Wanke, Michael Clement; Hudgens, James J.

    2005-02-01

    There is a general lack of compact electromagnetic radiation sources between 1 and 10 terahertz (THz). This a challenging spectral region lying between optical devices at high frequencies and electronic devices at low frequencies. While technologically very underdeveloped the THz region has the promise to be of significant technological importance, yet demonstrating its relevance has proven difficult due to the immaturity of the area. While the last decade has seen much experimental work in ultra-short pulsed terahertz sources, many applications will require continuous wave (cw) sources, which are just beginning to demonstrate adequate performance for application use. In this project, we proposed examination of two potential THz sources based on intersubband semiconductor transitions, which were as yet unproven. In particular we wished to explore quantum cascade lasers based sources and electronic based harmonic generators. Shortly after the beginning of the project, we shifted our emphasis to the quantum cascade lasers due to two events; the publication of the first THz quantum cascade laser by another group thereby proving feasibility, and the temporary shut down of the UC Santa Barbara free-electron lasers which were to be used as the pump source for the harmonic generation. The development efforts focused on two separate cascade laser thrusts. The ultimate goal of the first thrust was for a quantum cascade laser to simultaneously emit two mid-infrared frequencies differing by a few THz and to use these to pump a non-linear optical material to generate THz radiation via parametric interactions in a specifically engineered intersubband transition. While the final goal was not realized by the end of the project, many of the completed steps leading to the goal will be described in the report. The second thrust was to develop direct THz QC lasers operating at terahertz frequencies. This is simpler than a mixing approach, and has now been demonstrated by a few groups

  19. Optimal directed searches for continuous gravitational waves

    CERN Document Server

    Ming, Jing; Papa, Maria Alessandra; Aulbert, Carsten; Fehrmann, Henning

    2015-01-01

    Wide parameter space searches for long lived continuous gravitational wave signals are computationally limited. It is therefore critically important that available computational resources are used rationally. In this paper we consider directed searches, i.e. targets for which the sky position is known accurately but the frequency and spindown parameters are completely unknown. Given a list of such potential astrophysical targets, we therefore need to prioritize. On which target(s) should we spend scarce computing resources? What parameter space region in frequency and spindown should we search? Finally, what is the optimal search set-up that we should use? In this paper we present a general framework that allows to solve all three of these problems. This framework is based on maximizing the probability of making a detection subject to a constraint on the maximum available computational cost. We illustrate the method for a simplified problem.

  20. Continuous wave terahertz spectroscopy system with stably tunable beat source using optical switch

    Science.gov (United States)

    Eom, Joo Beom; Kim, Chihoon; Ahn, Jaesung

    2017-01-01

    A tunable beat source has been made using an optical switch module. A stably-tunable beat source for continuous wave terahertz spectroscopy system was implemented by simply connecting 16 coaxial distributed feedback laser diodes to an optical switch. The terahertz frequency was rapidly changed without frequency drifts by changing the optical path. The continuous wave terahertz frequency was tuned from 0.05 to 0.8 THz in steps of 50 GHz or 0.4 nm. We measured continuous wave terahertz waveforms emitted from the photomixers using the switched optical beat source. We also calculated the terahertz frequency peaks by taking fast Fourier transforms of the measured terahertz waveforms. By equipping the implemented tunable beat source with an optical switch, a continuous wave terahertz spectroscopy system was constructed and used to demonstrate the feasibility of continuous wave terahertz spectroscopy for nondestructive tests using the spectra of two type of Si wafers with different resistivity.

  1. Stochastic generation of continuous wave spectra

    DEFF Research Database (Denmark)

    Trulsen, J.; Dysthe, K. B.; Pécseli, Hans

    1983-01-01

    Wave packets of electromagnetic or Langmuir waves trapped in a well between oscillating reflectors are considered. An equation for the temporal evolution of the probability distribution for the carrier wave number is derived, and solved analytically in terms of moments in the limits of long...

  2. Temperature measurement using ultraviolet laser absorption of carbon dioxide behind shock waves.

    Science.gov (United States)

    Oehlschlaeger, Matthew A; Davidson, David F; Jeffries, Jay B

    2005-11-01

    A diagnostic for microsecond time-resolved temperature measurements behind shock waves, using ultraviolet laser absorption of vibrationally hot carbon dioxide, is demonstrated. Continuous-wave laser radiation at 244 and 266 nm was employed to probe the spectrally smooth CO2 ultraviolet absorption, and an absorbance ratio technique was used to determine temperature. Measurements behind shock waves in both nonreacting and reacting (ignition) systems were made, and comparisons with isentropic and constant-volume calculations are reported.

  3. Continuous wave MRI of heterogeneous materials

    Science.gov (United States)

    Fagan, Andrew J.; Davies, Gareth R.; Hutchison, James M. S.; Lurie, David J.

    2003-08-01

    A prototype continuous wave MRI system operating at 7 T has been used successfully to study a variety of heterogeneous materials exhibiting T 2 relaxation values ranging from 10 μs to 50 ms. Two-dimensional images of a poly(methly methacrylate) (PMMA) resolution phantom (T 2=38 μs) exhibited a spatial resolution of approximately 1 mm at a magnetic field gradient strength of 200 mT/m. The technique was used to study the hydration, drying, and subsequent water penetration properties of cement samples made from ordinary Portland cement, and revealed inhomogeneities arising from the cure conditions. Sandstone samples from an oil reservoir in the North Sea were also studied; structure within these materials, arising from the sedimentary bed layering in the reservoir, was found to have an effect on their water transport properties. A section from a confectionery bar (T 2* approximately 50-60 ms) was also imaged, and its internal structure could be clearly discerned.

  4. Frequency modulated continuous wave lidar performance model for target detection

    Science.gov (United States)

    Du Bosq, Todd W.; Preece, Bradley L.

    2017-05-01

    The desire to provide the warfighter both ranging and reflected intensity information is increasing to meet expanding operational needs. LIDAR imaging systems can provide the user with intensity, range, and even velocity information of a scene. The ability to predict the performance of LIDAR systems is critical for the development of future designs without the need to conduct time consuming and costly field studies. Performance modeling of a frequency modulated continuous wave (FMCW) LIDAR system is challenging due to the addition of the chirped laser source and waveform mixing. The FMCW LIDAR model is implemented in the NV-IPM framework using the custom component generation tool. This paper presents an overview of the FMCW Lidar, the customized LIDAR components, and a series of trade studies using the LIDAR model.

  5. Extracting Information from the Atom-Laser Wave Function UsingInterferometric Measurement with a Laser Standing-Wave Grating

    Institute of Scientific and Technical Information of China (English)

    刘正东; 武强; 曾亮; 林宇; 朱诗尧

    2001-01-01

    The reconstruction of the atom-laser wave function is performed using an interferometric measurement with a standing-wave grating, and the results of this scheme are studied. The relations between the measurement data and the atomic wave function are also presented. This scheme is quite applicable and effectively avoids the initial random phase problem of the method that employs the laser running wave. The information which is encoded in the atom-laser wave is extracted.

  6. Gas lasers with wave-chaotic resonators

    CERN Document Server

    Zaitsev, Oleg

    2010-01-01

    Semiclassical multimode laser theory is extended to gas lasers with open two-dimensional resonators of arbitrary shape. The Doppler frequency shift of the linear-gain coefficient leads to an additional linear coupling between the modes, which, however, is shown to be negligible. The nonlinear laser equations simplify in the special case of wave-chaotic resonators. In the single-mode regime, the intensity of a chaotic laser, as a function of the mode frequency, displays a local minimum at the frequency of the atomic transition. The width of the minimum scales with the inhomogeneous linewidth, in contrast to the Lamb dip in uniaxial resonators whose width is given by the homogeneous linewidth.

  7. A Continuous-Wave Ho:YAlO3 Laser with Output 8.5 W Pumped by a 1.91 μm Laser at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    YAO Bao-Quan; YANG Xiao-Tao; DUAN Xiao-Ming; WANG Tian-Heng; JU You-Lun; WANG Yue-Zhu

    2009-01-01

    @@ A cw high efficient Ho:YAlO3 laser pumped by 1.91 μm diode-pumped Tm:YLF laser at room temperature is realized. The maximum output power reaches 8.5 W when the incident pump power is 15.6 W. The slope efficiency is 63.7%, and the Tm:YLF to Ho:YAP optical conversion efficiency is 54.5%. The laser wavelength is 2118.3nm when the transmission of output coupler is 30%. The beam quality factor is M2~1.39 measured by the traveling knife-edge method.

  8. Optical frequency combs generated by four-wave mixing in a dual wavelength Brillouin laser cavity

    Directory of Open Access Journals (Sweden)

    Qing Li

    2017-07-01

    Full Text Available We propose and demonstrate the generation of optical frequency combs via four-wave mixing in a dual wavelength Brillouin laser cavity. When pumped by two continuous-wave lasers with a varied frequency separation, dual wavelength Brillouin lasers with reduced linewidth and improved optical signal to noise ratios are generated in a direction opposite to the pump laser. Simultaneously, cavity-enhanced cascaded four-wave mixing between dual wavelength Brillouin lasers occurs in the laser cavity, causing the generation of broadband optical frequency combs with step tunable mode spacing from 40 to 1300 GHz. Compared to the cavity-less case, the number of the comb lines generated in the dual wavelength Brillouin laser cavity is increased by ∼38 times.

  9. Diode-pumped intracavity optical parametric oscillator in pulsed and continuous-wave operation

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Skettrup, Torben; Petersen, O.B.;

    2002-01-01

    An intracavity optical parametric oscillator is investigated in pulsed and continuous-wave operation. The intracavity optical parametric oscillator is based on Yb:YAG as the laser material and a periodically poled lithium niobate crystal as the nonlinear material. Tuneable idler output powers above...

  10. Continuous-wave Optically Pumped Lasing of Hybrid Perovskite VCSEL at Green Wavelength

    KAUST Repository

    Alias, Mohd Sharizal

    2017-05-08

    We demonstrate the lasing of a perovskite vertical-cavity surface-emitting laser at green wavelengths, which operates under continuous-wave optical pumping at room-temperature by embedding hybrid perovskite between dielectric mirrors deposited at low-temperature.

  11. Searches for Continuous Gravitational Waves from Nine Young Supernova Remnants

    Science.gov (United States)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Ain, A.; Ajith, P.; Alemic, A.; Allen, B.; Allocca, A.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J. S.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barbet, M.; Barclay, S.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Bartlett, J.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bauer, Th. S.; Baune, C.; Bavigadda, V.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Bell, C.; Benacquista, M.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackburn, L.; Blair, C. D.; Blair, D.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bojtos, P.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, Sukanta; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchman, S.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C.; Colombini, M.; Cominsky, L.; Constancio, M., Jr.; Conte, A.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, C.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dartez, L.; Dattilo, V.; Dave, I.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Dominguez, E.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S.; Eberle, T.; Edo, T.; Edwards, M.; Edwards, M.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Essick, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fuentes-Tapia, S.; Fulda, P.; Fyffe, M.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S.; Garufi, F.; Gatto, A.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Gossler, S.; Gouaty, R.; Gräf, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C. J.; Guo, X.; Gushwa, K.; Gustafson, E. K.; Gustafson, R.; Hacker, J.; Hall, E. D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M.; Heinzel, G.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E.; Howell, E. J.; Hu, Y. M.

    2015-11-01

    We describe directed searches for continuous gravitational waves (GWs) in data from the sixth Laser Interferometer Gravitational-wave Observatory (LIGO) science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the remnants are associated with non-pulsing suspected neutron stars. One target's parameters are uncertain enough to warrant two searches, for a total of 10. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering {F}-statistic. We found no evidence of GW signals. We set 95% confidence upper limits as strong (low) as 4 × 10-25 on intrinsic strain, 2 × 10-7 on fiducial ellipticity, and 4 × 10-5 on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes.

  12. Tunable Plasma-Wave Laser Amplifier

    Science.gov (United States)

    Bromage, J.; Haberberger, D.; Davies, A.; Bucht, S.; Zuegel, J. D.; Froula, D. H.; Trines, R.; Bingham, R.; Sadler, J.; Norreys, P. A.

    2016-10-01

    Raman amplification is a process by which a long energetic pump pulse transfers its energy to a counter-propagating short seed pulse through a resonant electron plasma wave. Since its conception, theory and simulations have shown exciting results with up to tens of percent of energy transfer from the pump to the seed pulse. However, experiments have yet to surpass transfer efficiencies of a few percent. A review of past literature shows that largely chirped pump pulses and finite temperature wave breaking could have been the two most detrimental effects. A Raman amplification platform is being developed at the Laboratory for Laser Energetics where a combination of a high-intensity tunable seed laser with sophisticated plasma diagnostics (dynamic Thomson scattering) will make it possible to find the optimal parameter space for high-energy transfer. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  13. Evaluation of ground stiffness parameters using continuous surface wave geophysics

    DEFF Research Database (Denmark)

    Gordon, Anne; Foged, Niels

    2000-01-01

    -small-strain stiffness of the ground Gmax. Continuous surface wave geophysics offers a quick, non-intrusive and economical way of making such measurements. This paper reviews the continuous surface wave techniques and evaluates, in engineering terms, the applicability of the method to the site investigation industry....

  14. Evaluation of ground stiffness parameters using continuous surface wave geophysics

    DEFF Research Database (Denmark)

    Gordon, Anne; Foged, Niels

    2000-01-01

    -small-strain stiffness of the ground Gmax. Continuous surface wave geophysics offers a quick, non-intrusive and economical way of making such measurements. This paper reviews the continuous surface wave techniques and evaluates, in engineering terms, the applicability of the method to the site investigation industry....

  15. Solitary Wave Generation from Constant Continuous Wave in Asymmetric Oppositely Directed Waveguide Coupler

    Directory of Open Access Journals (Sweden)

    Kazantseva E.V.

    2015-01-01

    Full Text Available In a model which describes asymmetric oppositely directed nonlinear coupler it was observed in numerical simulations a phenomenon of solitary wave generation from the input constant continuous wave set at the entrance of a waveguide with negative refraction. The period of solitary wave formation decreases with increase of the continuum wave amplitude.

  16. Dynamics of laser interferometric gravitational wave detectors

    Science.gov (United States)

    Rakhmanov, Malik

    2000-11-01

    Dynamics of fields and mirrors in the new laser interferometric gravitational wave detectors is described. The dynamics of fields is formulated in terms of difference equations, which take into account the large delay due to the light transit time in the interferometer arm cavities. Solutions of these field equations are found in both transient and steady-state regimes. The solutions for fields in the transient regime can be used for the measurement of the parameters of Fabry-Perot cavities. The solutions for fields in the steady-state regime can be used for the analysis of noise performance of Fabry-Perot cavities. The dynamics of the mirrors is described in terms of two normal coordinates: the cavity length and its center of mass. Such dynamics is strongly affected by the radiation pressure of light circulating in the cavity. The forces of radiation pressure are nonlinear and nonconservative. These two effects introduce instabilities and give rise to a violation of conservation of energy for the motion of the suspended mirrors. Analytical calculations and numerical simulations of the dynamics are done with applications to the Laser Interferometer Gravitational-Wave Observatory (LIGO). The dynamics of signal recycling and power recycling interferometers is analyzed using the field equations. The response of the interferometers to the input laser field and motion of its mirrors is calculated. Several basic transfer functions are found. These correspond to either a single or a nested cavity. A nested cavity appears either in the dynamics of the differential mode in signal recycling interferometers or in the dynamics of the common mode of power recycling interferometers. The poles of transfer functions of these nested cavities are found. The response of the interferometers to gravitational waves is described: the analysis is done in the rest frame of a local observer which is a natural coordinate system of the detector. This response is given by the interferometer

  17. Bandwidth scaling of a phase-modulated continuous-wave comb through four-wave mixing in a silicon nano-waveguide.

    Science.gov (United States)

    Liu, Yang; Metcalf, Andrew J; Company, Victor Torres; Wu, Rui; Fan, Li; Varghese, Leo T; Qi, Minghao; Weiner, Andrew M

    2014-11-15

    We demonstrate an on-chip four-wave mixing (FWM) scheme in a silicon nanowaveguide to scale the bandwidth of a frequency comb generated by phase modulation of continuous-wave (CW) lasers. The FWM process doubles the bandwidth of the initial comb generated by the modulation of a CW laser. For example, a wavelength-tunable frequency comb with >100 comb lines spaced by 10 GHz within a bandwidth of 5 dB is generated.

  18. Bragg-Scattering Four-Wave Mixing in Nonlinear Fibers with Intracavity Frequency-Shifted Laser Pumps

    Directory of Open Access Journals (Sweden)

    Katarzyna Krupa

    2012-01-01

    Full Text Available We experimentally study four-wave mixing in highly nonlinear fibers using two independent and partially coherent laser pumps and a third coherent signal. We focus our attention on the Bragg-scattering frequency conversion. The two pumps were obtained by amplifying two Intracavity frequency-shifted feedback lasers working in a continuous wave regime.

  19. Continuous-wave Raman Lasing in Aluminum Nitride Microresonators

    CERN Document Server

    Liu, Xianwen; Xiong, Bing; Wang, Lai; Wang, Jian; Han, Yanjun; Hao, Zhibiao; Li, Hongtao; Luo, Yi; Yan, Jianchang; Wei, Tongbo; Zhang, Yun; Wang, Junxi

    2016-01-01

    We report the first investigation on continuous-wave Raman lasing in high-quality-factor aluminum nitride (AlN) microring resonators. Although wurtzite AlN is known to exhibit six Raman-active phonons, single-mode Raman lasing with low threshold and high slope efficiency is demonstrated. Selective excitation of A$_1^\\mathrm{TO}$ and E$_2^\\mathrm{high}$ phonons with Raman shifts of $\\sim$612 and 660 cm$^{-1}$ is observed by adjusting the polarization of the pump light. A theoretical analysis of Raman scattering efficiency within ${c}$-plane (0001) of AlN is carried out to help account for the observed lasing behavior. Bidirectional lasing is experimentally confirmed as a result of symmetric Raman gain in micro-scale waveguides. Furthermore, second-order Raman lasing with unparalleled output power of $\\sim$11.3 mW is obtained, which offers the capability to yield higher order Raman lasers for mid-infrared applications.

  20. Continuous optical discharge in a laser cavity

    Science.gov (United States)

    Chivel', Yu. A.

    2016-08-01

    Optical discharge in a laser cavity is experimentally studied. A significant increase in the absorption of laser radiation (up to total absorption) is revealed. Optical schemes for initiation and maintaining of optical discharge in the cavity are proposed for technological applications of the optical discharge.

  1. Generation of magnetosonic waves over a continuous spectrum

    Science.gov (United States)

    Chen, Lunjin; Sun, Jicheng; Lu, Quanming; Gao, Xinliang; Xia, Zhiyang; Zhima, Zeren

    2016-02-01

    Magnetosonic waves, also known as equatorial noise emission, were found to have discrete frequency structures, which is consistent with instability caused by proton ring distribution. Nonetheless, nondiscrete structure, i.e., a broadband spectrum over a continuous frequency range, has been reported. We investigate the question whether proton ring distribution can generate nondiscrete spectra for perpendicularly propagating magnetosonic waves. We propose discrete and nondiscrete characteristics of the local instability for explaining the observation of discrete, continuous, and mixed spectra. The criterion for transition from discrete and continuous instability is given, γ >˜ Ωh/2, where γ is wave growth rate and Ωh is proton cyclotron frequency. The condition is verified by particle-in-cell simulation using more realistic electron-to-proton mass ratio and speed of light than in previous studies. Such criterion of generating a continuous spectrum can be tested against simultaneous in situ measurement of wave and particle. We also find that the modes at low Ωh harmonics, including the fundamental Ωh, can be still excited through nonlinear wave-wave coupling, even when they are neutral modes (γ = 0) according to the linear kinetic theory. Comparison with magnetosonic waves in cold plasma limit and electromagnetic ion Bernstein mode is also discussed.

  2. Directed search for continuous gravitational waves from the Galactic center

    Science.gov (United States)

    Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barker, D.; Barnum, S. H.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Bergmann, G.; Berliner, J. M.; Bertolini, A.; Bessis, D.; Betzwieser, J.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Bose, S.; Bosi, L.; Bowers, J.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brannen, C. A.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Constancio, M., Jr.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Deleeuw, E.; Deléglise, S.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Dmitry, K.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farr, B.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R.; Flaminio, R.; Foley, E.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B.; Hall, E.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Horrom, T.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hua, Z.; Huang, V.; Huerta, E. A.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Iafrate, J.; Ingram, D. R.

    2013-11-01

    We present the results of a directed search for continuous gravitational waves from unknown, isolated neutron stars in the Galactic center region, performed on two years of data from LIGO’s fifth science run from two LIGO detectors. The search uses a semicoherent approach, analyzing coherently 630 segments, each spanning 11.5 hours, and then incoherently combining the results of the single segments. It covers gravitational wave frequencies in a range from 78 to 496 Hz and a frequency-dependent range of first-order spindown values down to -7.86×10-8Hz/s at the highest frequency. No gravitational waves were detected. The 90% confidence upper limits on the gravitational wave amplitude of sources at the Galactic center are ˜3.35×10-25 for frequencies near 150 Hz. These upper limits are the most constraining to date for a large-parameter-space search for continuous gravitational wave signals.

  3. A quasi-continuous superradiant Raman laser with < 1 intracavity photon

    Directory of Open Access Journals (Sweden)

    Bohnet Justin G.

    2013-08-01

    Full Text Available Steady-state collective emission from ensembles of laser cooled atoms has been proposed as a method for generating sub-millihertz linewidth optical lasers, with potential for broad impacts across science and technology. We have built a model system that tests key predictions for such active oscillators using a Raman laser with laser cooled atoms as the gain medium. The laser operates deep in the bad-cavity, or superradiant, regime of laser physics, where the cavity decay rate is much greater than the atomic coherence decay rate. Specifically, we demonstrate that a system of 106 87Rb atoms trapped in a 1D standing wave optical lattice can spontaneously synchronize and collectively emit a quasi-continuous coherent optical output, even when the intracavity field contains on average < 1 photon.

  4. Center crack detection during continuous casting of aluminum by laser ultrasonic measurements

    Science.gov (United States)

    Grün, Hubert; Mitter, Thomas; Roither, Jürgen; Betz, Andreas; Bozorgi, Salar; Burgholzer, Peter

    2014-05-01

    Crack detection during continuous direct chill casting of aluminum is a matter of economics. Determining cracks during production process saves money, energy and raw material. Of course, a non-destructive method is required for this evaluation. Because of temperature concerns conventional ultrasound is not applicable. One non-contact alternative is laser ultrasonics. In laser ultrasonics short laser pulses illuminate the sample. The electromagnetic energy gets absorbed at the surface of the sample and results in local heating followed by expansion. Thereby broadband ultrasonic waves are launched which propagate through the sample and get back reflected or scattered at interfaces (cracks, blowholes,…) like conventional ultrasonic waves. Therefore laser ultrasonics is an alternative thermal infrared technology. By using an interferometer also the detection of the ultrasonic waves at the sample surface is done in a remote manner. During preliminary examinations in the lab by scanning different aluminum studs it was able to distinguish between studs with and without cracks. The prediction of the dimension of the crack by evaluation of the damping of the broadband ultrasonic waves was possible. With simple image reconstruction methods one can localize the crack and give an estimation of its extent and even its shape. Subsequent first measurements using this laser ultrasonic setup during the continuous casting of aluminum were carried out and showed the proof of principle in an industrial environment with elevated temperatures, dust, cooling water and vibrations.

  5. Tunable, continuous-wave single-resonant optical parametric oscillator with output coupling for resonant wave

    Science.gov (United States)

    Xiong-Hua, Zheng; Bao-Fu, Zhang; Zhong-Xing, Jiao; Biao, Wang

    2016-01-01

    We present a continuous-wave singly-resonant optical parametric oscillator with 1.5% output coupling of the resonant signal wave, based on an angle-polished MgO-doped periodically poled lithium niobate (MgO:PPLN), pumped by a commercial Nd:YVO4 laser at 1064 nm. The output-coupled optical parametric oscillator delivers a maximum total output power of 4.19 W with 42.8% extraction efficiency, across a tuning range of 1717 nm in the near- and mid-infrared region. This indicates improvements of 1.87 W in output power, 19.1% in extraction efficiency and 213 nm in tuning range extension in comparison with the optical parametric oscillator with no output coupling, while at the expense of increasing the oscillation threshold by a factor of ˜ 2. Moreover, it is confirmed that the finite output coupling also contributes to the reduction of the thermal effects in crystal. Project supported by the National Natural Science Foundation of China (Grant Nos. 61308056, 11204044, 11232015, and 11072271), the Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20120171110005 and 20130171130003), the Fundamental Research Funds for the Central Universities of China (Grant No. 14lgpy07), and the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory, China (Grant No. ZHD201203).

  6. Influence of acoustic waves on TEA CO2 laser performance

    CSIR Research Space (South Africa)

    Von Bergmann, H

    2007-01-01

    Full Text Available In this paper the author’s present results on the influence of acoustic waves on the output laser beam from high repetition rate TEA CO2 lasers. The authors show that acoustic waves generated inside the cavity lead to deterioration in beam quality...

  7. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Subsonic radiation waves in neon

    Science.gov (United States)

    Loseva, T. V.; Nemchinov, I. V.

    1989-02-01

    Numerical methods are used to investigate the propagation of plane subsonic radiation waves in neon from an obstacle in the direction opposite to the incident radiation of Nd and CO2 lasers. An analysis is made of the influence of the power density of the incident radiation (in the range 10-100 MW/cm2) and of the initial density of neon (beginning from the normal valuep ρ0 up to 10ρ0) on the various characteristics of subsonic radiation waves. It is shown that waves traveling in neon can provide an effective source of radiation with a continuous spectrum and an efficiency of ~ 12-27% in the ultraviolet range (with a characteristic photon energy ~ 5-10 eV).

  8. 周期极化KTiOPO4晶体和频单块非平面环形腔激光产生连续单频589 nm黄光∗%Continuous-wave single-frequency 589 nm yellow laser generated from sum frequency of single-blo ck non-planar ring cavity laser in p erio dically p oled KTiOPO4 crystal

    Institute of Scientific and Technical Information of China (English)

    谢仕永; 张小富; 杨程亮; 乐小云; 薄勇; 崔大复; 许祖彦

    2016-01-01

    Continuous-wave single-frequency 589 nm yellow laser can be used in laser cooling of sodium atoms. Besides, the interaction between 589 nm laser and sodium atoms can be studied by resonance fluorescence, which provides an important basis for the sodium guide star in the adaptive optics. In this paper, single frequency 589 nm yellow light is generated by sum frequency of single-block non-planar ring cavity 1064 nm and 1319 nm laser in periodically poled KTiOPO4 crystal. The geometric parameters of single-block non-planar Nd:YAG crystal and magnetic field intensity are optimally designed by simulation calculation through using Jones matrix. The output powers 1080 mW and 580 mW are obtained for continuous-wave single-frequency 1064 nm and 1319 nm laser in the experiment, respectively The two fundamental beams are expanded to be the same as perfectly as possible in size and are focused into a spot with a size of about 60 µm by an achromatic lens. The sum-frequency generation takes place in a 1 mm×2 mm×20 mm phase-matched type-I periodically poled KTiOPO4 crystal with a matching temperature of 55 ◦C and polarization period of 12.35 µm The crystal is anti-reflection coated for all three wavelengths (1064 nm, 1319 nm and 589 nm). A 14.8 mW output of 589 nm laser is obtained with beam quality factor M 2 =1.14 and the corresponding sum-frequency efficiency is 0.9%. The influence of periodically poled KTiOPO4 temperature on the sum-frequency efficiency is studied and the temperature acceptance bandwidth is measured to be 1.5 degrees The wavelength of 589 nm yellow light can be tuned to the sodium atom D2a absorption line by changing the temperature of 1064 nm Nd:YAG crystal and 0.164 pm of tuning accuracy is reached. The whole laser system is stable and reliable, so it provides a practical and effective technical means to obtain the continuous-wave single-frequency 589 nm laser, for it is relatively simple and easy to implement.

  9. Precision Laser Development for Gravitational Wave Space Mission

    Science.gov (United States)

    Numata, Kenji; Camp, Jordan

    2011-01-01

    Optical fiber and semiconductor laser technologies have evolved dramatically over the last decade due to the increased demands from optical communications. We are developing a laser (master oscillator) and optical amplifier based on those technologies for interferometric space missions, such as the gravitational-wave mission LISA, and GRACE follow-on, by fully utilizing the mature wave-guided optics technologies. In space, where a simple and reliable system is preferred, the wave-guided components are advantageous over bulk, crystal-based, free-space laser, such as NPRO (Non-planar Ring Oscillator) and bulk-crystal amplifier, which are widely used for sensitive laser applications on the ground.

  10. A large aperture reflective wave-plate for high-intensity short-pulse laser experiments

    CERN Document Server

    Aurand, Bastian; Zhao, Huanyu; Kuschel, Stephan; Wünsche, Martin; Jäckel, Oliver; Heyer, Martin; Wunderlich, Frank; Kaluza, Malte C; Paulus, Gerhard G; Kuehl, Thomas

    2012-01-01

    We report on a reflective wave-plate system utilizing phase-shifting mirrors (PSM) for a continuous variation of elliptical polarization without changing the beam position and direction. The scalability of multilayer optics to large apertures and the suitability for high-intensity broad-bandwidth laser beams make reflective wave-plates an ideal tool for experiments on relativistic laser-plasma interaction. Our measurements confirm the preservation of the pulse duration and spectrum when a 30-fs Ti:Sapphire laser beam passes the system.

  11. Real-time, continuous-wave terahertz imaging by a pyroelectric camera

    Institute of Scientific and Technical Information of China (English)

    Jun Yang; Shuangchen Ruan; Min Zhang

    2008-01-01

    Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.

  12. Diode-pumped intracavity optical parametric oscillator in pulsed and continuous-wave operation

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Skettrup, Torben; Petersen, O.B.;

    2002-01-01

    An intracavity optical parametric oscillator is investigated in pulsed and continuous-wave operation. The intracavity optical parametric oscillator is based on Yb:YAG as the laser material and a periodically poled lithium niobate crystal as the nonlinear material. Tuneable idler output powers above...... 200 mW are obtained in both modes of operation with 13.5 W of incident diode pump power. The idler output was tuned in the wavelength range 3820-4570 nm....

  13. 基于重采样技术的调频连续波激光绝对测距高精度及快速测量方法研究∗%High precision and fast metho d for absolute distance measurement based on resampling technique used in FM continuous wave laser ranging

    Institute of Scientific and Technical Information of China (English)

    孟祥松; 张福民; 曲兴华

    2015-01-01

    Frequency modulated continuous wave (FMCW) laser ranging is one of the most interesting techniques for precision distance metrology. It is a promising candidate for absolute distance measurement at large standoff distances (10 to 100 m) with high precision and accuracy, and no cooperation target is needed during the measuring process. How to improve the measurement resolution in practice has been the research focus of the FMCW laser ranging in recent years. FMCW laser ranging system uses the method which may convert the measurement of flight time to the frequency measurement, while the ranging resolution can be determined by the tuning range of the optical frequency sweep in theory. The main impact-factor that reduces the resolution is the tuning nonlinearity of the laser source, which may cause an amount of error points within the sampling signal. So a dual-interferometric FMCW laser ranging system is adopted in this paper. Compared to the traditional Michelson scheme, an assistant interferometer is added. The assistant interferometer has an all-fiber optical Mach-Zehnder configuration, and the delay distance is at least 2 times longer than OPD (optical path difference) of the main interferometer. Because it provides the reference length, the length of the fiber must remain unchanged. The interference signal is obtained on the photodetector. At the time points of every peak and bottom of the auxiliary interferometer signal, the beating signal from the main interferometer is re-sampled. The original signal is not the equal time intervals, while the re-sampled signal is the equal optical frequency intervals. Based on the property of the re-sampled signal, a method by splicing the re-sampled signal to optimize the signal processing is proposed, by which the tuning range of the laser source limitation can be broken and high precision can be easily obtained. Also, a simple high-speed measuring method is proposed. Based on all the above principles, the two-fiber optical

  14. Fast continuous tuning of terahertz quantum-cascade lasers by rear-facet illumination

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Martin, E-mail: hempel@pdi-berlin.de; Röben, Benjamin; Schrottke, Lutz; Grahn, Holger T. [Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5–7, 10117 Berlin (Germany); Hübers, Heinz-Wilhelm [Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstr. 2, 12489 Berlin (Germany); Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany)

    2016-05-09

    GaAs-based terahertz quantum-cascade lasers (QCLs) are continuously tuned in their emission frequency by illuminating the rear facet with a near-infrared, high-power diode laser. For QCLs emitting around 3.1 THz, the maximum tuning range amounts to 2.8 GHz for continuous-wave operation at a heat sink temperature of 55 K, while in pulsed mode 9.1 and 8.0 GHz are achieved at 35 and 55 K, respectively.

  15. Detecting Beyond-Einstein Polarizations of Continuous Gravitational Waves

    OpenAIRE

    Isi, Maximiliano; Weinstein, Alan J.; Mead, Carver; Pitkin, Matthew

    2015-01-01

    The direct detection of gravitational waves with the next-generation detectors, like Advanced LIGO, provides the opportunity to measure deviations from the predictions of general relativity. One such departure would be the existence of alternative polarizations. To measure these, we study a single detector measurement of a continuous gravitational wave from a triaxial pulsar source. We develop methods to detect signals of any polarization content and distinguish between them in a model-indepe...

  16. Continuous Dependence on the Density for Stratified Steady Water Waves

    Science.gov (United States)

    Chen, Robin Ming; Walsh, Samuel

    2016-02-01

    There are two distinct regimes commonly used to model traveling waves in stratified water: continuous stratification, where the density is smooth throughout the fluid, and layer-wise continuous stratification, where the fluid consists of multiple immiscible strata. The former is the more physically accurate description, but the latter is frequently more amenable to analysis and computation. By the conservation of mass, the density is constant along the streamlines of the flow; the stratification can therefore be specified by prescribing the value of the density on each streamline. We call this the streamline density function. Our main result states that, for every smoothly stratified periodic traveling wave in a certain small-amplitude regime, there is an L ∞ neighborhood of its streamline density function such that, for any piecewise smooth streamline density function in that neighborhood, there is a corresponding traveling wave solution. Moreover, the mapping from streamline density function to wave is Lipschitz continuous in a certain function space framework. As this neighborhood includes piecewise smooth densities with arbitrarily many jump discontinues, this theorem provides a rigorous justification for the ubiquitous practice of approximating a smoothly stratified wave by a layered one. We also discuss some applications of this result to the study of the qualitative features of such waves.

  17. Continuity waves in fully resolved simulations of settling particles

    Science.gov (United States)

    Willen, Daniel; Sierakowski, Adam; Prosperetti, Andrea

    2016-11-01

    Fully resolved simulations of 500 to 2,000 particles settling in a fluid have been conducted with the Physalis method. A new approach to the reconstruction of pseudo-continuum fields is described and is used to examine the results with the purpose of identifying concentration waves. The velocity of concentration waves is successfully deduced from the simulations. A comparison of the results with continuity wave theory shows good agreement. Several new insights about the particle microstructure conditionally averaged on volume fraction and velocity are also described. This work is supported by NSF award CBET1335965.

  18. Continuous Variable Quantum Key Distribution with a Noisy Laser

    DEFF Research Database (Denmark)

    Jacobsen, Christian Scheffmann; Gehring, Tobias; Andersen, Ulrik Lund

    2015-01-01

    Existing experimental implementations of continuous-variable quantum key distribution require shot-noise limited operation, achieved with shot-noise limited lasers. However, loosening this requirement on the laser source would allow for cheaper, potentially integrated systems. Here, we implement ...

  19. Continuous 1052, 1064 nm dual-wavelength Nd:YAG laser

    Science.gov (United States)

    Wang, Xiaozhong; Yuan, Haiyang; Wang, Mingshan; Huang, Wencai

    2016-10-01

    Dual-wavelength lasers are usually obtained through balancing the net gain of the two oscillating lines. Competition between transitions 1052 nm, 1061 nm and 1064 nm is utilized to realize a continuous wave 1052 and 1064 nm dual-wavelength Nd:YAG laser firstly in this paper. A specially designed Fabry-Perot band-pass filter is exploited as output coupler to control the thresholds of the oscillating wavelengths. The maximum power of the dual-wavelength laser is 1.6 W and the slope efficiency is about 10%. The power instability of the output dual-wavelength laser is smaller than ±4% in half an hour. The mechanism presented in this paper may provide a new way to obtain dual-wavelength lasers.

  20. Fluorescence excitation by enhanced plasmon upconversion under continuous wave illumination

    Science.gov (United States)

    Tasgin, Mehmet Emre; Salakhutdinov, Ildar; Kendziora, Dania; Abak, Musa Kurtulus; Turkpence, Deniz; Piantanida, Luca; Fruk, Ljiljana; Lazzarino, Marco; Bek, Alpan

    2016-09-01

    We demonstrate effective background-free continuous wave nonlinear optical excitation of molecules that are sandwiched between asymmetrically constructed plasmonic gold nanoparticle clusters. We observe that near infrared photons are converted to visible photons through efficient plasmonic second harmonic generation. Our theoretical model and simulations demonstrate that Fano resonances may be responsible for being able to observe nonlinear conversion using a continuous wave light source. We show that nonlinearity enhancement of plasmonic nanostructures via coupled quantum mechanical oscillators such as molecules can be several orders larger as compared to their classical counterparts.

  1. Continuously tunable wideband semiconductor fiber-ring laser

    Science.gov (United States)

    Mao, Xuefeng; Zhao, Shiwei; Yuan, Suzhen; Wang, Xiaofa; Zheng, Peichao

    2017-08-01

    We demonstrate a wideband tunable semiconductor fiber-ring laser that can be continuously tuned from 1498 nm to 1623 nm. The proposed laser uses a semiconductor optical amplifier (SOA) as a gain medium and a fiber Fabry-Perot tunable filter as a selective wavelength filter. The optimized drive current of the SOA and the output coupling ratio are obtained by experimental research. This laser has a simple configuration, low threshold, flat laser output power and high optical signal-to-noise ratio.

  2. Continuous Variable Quantum Key Distribution with a Noisy Laser

    DEFF Research Database (Denmark)

    Jacobsen, Christian Scheffmann; Gehring, Tobias; Andersen, Ulrik Lund

    2015-01-01

    a theoretically proposed prepare-and-measure continuous-variable protocol and experimentally demonstrate the robustness of it against preparation noise stemming for instance from technical laser noise. Provided that direct reconciliation techniques are used in the post-processing we show that for small distances......Existing experimental implementations of continuous-variable quantum key distribution require shot-noise limited operation, achieved with shot-noise limited lasers. However, loosening this requirement on the laser source would allow for cheaper, potentially integrated systems. Here, we implement...

  3. Laser-driven plasma waves in capillary tubes.

    Science.gov (United States)

    Wojda, F; Cassou, K; Genoud, G; Burza, M; Glinec, Y; Lundh, O; Persson, A; Vieux, G; Brunetti, E; Shanks, R P; Jaroszynski, D; Andreev, N E; Wahlström, C-G; Cros, B

    2009-12-01

    The excitation of plasma waves over a length of up to 8 cm is demonstrated using laser guiding of intense laser pulses through hydrogen-filled glass capillary tubes. The plasma waves are diagnosed by spectral analysis of the transmitted laser radiation. The dependence of the spectral redshift-measured as a function of filling pressure, capillary tube length, and incident laser energy-is in excellent agreement with simulation results. The longitudinal accelerating field inferred from the simulations is in the range of 1-10 GV/m.

  4. Operational experience with room temperature continuous wave accelerator structures

    Science.gov (United States)

    Alimov, A. S.; Ishkhanov, B. S.; Piskarev, I. M.; Shvedunov, V. I.; Tiunov, A. V.

    1993-05-01

    The paper reports the results of the computer simulation of parameters of the on-axis coupled accelerator structure for the continuous wave racetrack microtron. The operational experience with the accelerating sections on the basis of the on-axis coupled structure is described.

  5. Photonic synthesis of continuous‐wave millimeter‐wave signals using a passively mode‐locked laser diode and selective optical filtering

    DEFF Research Database (Denmark)

    Acedo, P.; Carpintero, G.; Criado, A.R.

    2012-01-01

    We report a photonic synthesis scheme for continuous wave millimeter‐wave signal generation using a single passively mode‐locked laser diode (PMLLD), optical filtering and photomixing in a fast photodiode.The phase noise of the photonically synthesized signals is evaluated and inherits...... the characteristics of the PMLLD electrical power spectrum....

  6. Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode.

    Science.gov (United States)

    Klinkhammer, Sönke; Liu, Xin; Huska, Klaus; Shen, Yuxin; Vanderheiden, Sylvia; Valouch, Sebastian; Vannahme, Christoph; Bräse, Stefan; Mappes, Timo; Lemmer, Uli

    2012-03-12

    The fabrication and characterization of continuously tunable, solution-processed distributed feedback (DFB) lasers in the visible regime is reported. Continuous thin film thickness gradients were achieved by means of horizontal dipping of several conjugated polymer and blended small molecule solutions on cm-scale surface gratings of different periods. We report optically pumped continuously tunable laser emission of 13 nm in the blue, 16 nm in the green and 19 nm in the red spectral region on a single chip respectively. Tuning behavior can be described with the Bragg-equation and the measured thickness profile. The laser threshold is low enough that inexpensive laser diodes can be used as pump sources.

  7. Laser-cooled continuous ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Schiffer, J.P.; Hangst, J.S.; Nielsen, J.S. [and others

    1995-08-01

    A collaboration with a group in Arhus, Denmark, using their storage ring ASTRID, brought about better understanding of ion beams cooled to very low temperatures. The longitudinal Schottky fluctuation noise signals from a cooled beam were studied. The fluctuation signals are distorted by the effects of space charge as was observed in earlier measurements at other facilities. However, the signal also exhibits previously unobserved coherent components. The ions` velocity distribution, measured by a laser fluorescence technique suggests that the coherence is due to suppression of Landau damping. The observed behavior has important implications for the eventual attainment of a crystalline ion beam in a storage ring. A significant issue is the transverse temperature of the beam -- where no direct diagnostics are available and where molecular dynamics simulations raise interesting questions about equilibrium.

  8. Saturation of Langmuir waves in laser-produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Baker, K.L.

    1996-04-01

    This dissertation deals with the interaction of an intense laser with a plasma (a quasineutral collection of electrons and ions). During this interaction, the laser drives large-amplitude waves through a class of processes known as parametric instabilities. Several such instabilities drive one type of wave, the Langmuir wave, which involves oscillations of the electrons relative to the nearly-stationary ions. There are a number of mechanisms which limit the amplitude to which Langmuir waves grow. In this dissertation, these mechanisms are examined to identify qualitative features which might be observed in experiments and/or simulations. In addition, a number of experiments are proposed to specifically look for particular saturation mechanisms. In a plasma, a Langmuir wave can decay into an electromagnetic wave and an ion wave. This parametric instability is proposed as a source for electromagnetic emission near half of the incident laser frequency observed from laser-produced plasmas. This interpretation is shown to be consistent with existing experimental data and it is found that one of the previous mechanisms used to explain such emission is not. The scattering version of the electromagnetic decay instability is shown to provide an enhanced noise source of electromagnetic waves near the frequency of the incident laser.

  9. High power continuous-wave GaSb-based superluminescent diodes as gain chips for widely tunable laser spectroscopy in the 1.95-2.45 μm wavelength range

    Science.gov (United States)

    Vizbaras, K.; Dvinelis, E.; ŠimonytÄ--, I.; TrinkÅ«nas, A.; Greibus, M.; Songaila, R.; Žukauskas, T.; Kaušylas, M.; Vizbaras, A.

    2015-07-01

    We present high-power single-spatial mode electrically pumped GaSb-based superluminescent diodes (SLDs) operating in the 1.95 to 2.45 μm wavelength range in continuous-wave (CW). MBE grown GaSb-based heterostructures were fabricated into single-angled facet ridge-waveguide devices that demonstrate more than 40 mW CW output power at 2.05 μm, to >5 mW at 2.40 μm at room-temperature. We integrated these SLDs into an external cavity (Littrow configuration) as gain chips and achieved single-mode CW lasing with maximum output powers exceeding 18 mW. An extremely wide tuning range of 120 nm per chip with side-mode-suppression-ratios >25 dB was demonstrated while maintaining optical output power level above 3 mW across the entire tuning range.

  10. EPILEPTIC ENCEPHALOPATHY WITH CONTINUOUS SPIKES-WAVES ACTIVITY DURING SLEEP

    Directory of Open Access Journals (Sweden)

    E. D. Belousova

    2012-01-01

    Full Text Available The author represents the review and discussion of current scientific literature devoted to epileptic encephalopathy with continuous spikes-waves activity during sleep — the special form of partly reversible age-dependent epileptic encephalopathy, characterized by triad of symptoms: continuous prolonged epileptiform (spike-wave activity on EEG in sleep, epileptic seizures and cognitive disorders. The author describes the aspects of classification, pathogenesis and etiology, prevalence, clinical picture and diagnostics of this disorder, including the peculiar anomalies on EEG. The especial attention is given to approaches to the treatment of epileptic encephalopathy with continuous spikeswaves activity during sleep. Efficacy of valproates, corticosteroid hormones and antiepileptic drugs of other groups is considered. The author represents own experience of treatment this disorder with corticosteroids, scheme of therapy and assessment of efficacy.

  11. Laser Source for Atomic Gravity Wave Detector Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop an Atom Interferometry-based gravity wave detector (vs Optical Interferometry). Characterize a high power laser. Use Goddard Space Flight Center Mission...

  12. Cluster Observations of Non-Time Continuous Magnetosonic Waves

    Science.gov (United States)

    Walker, Simon N.; Demekhov, Andrei G.; Boardsen, Scott A.; Ganushkina, Natalia Y.; Sibeck, David G.; Balikhin, Michael A.

    2016-01-01

    Equatorial magnetosonic waves are normally observed as temporally continuous sets of emissions lasting from minutes to hours. Recent observations, however, have shown that this is not always the case. Using Cluster data, this study identifies two distinct forms of these non temporally continuous use missions. The first, referred to as rising tone emissions, are characterized by the systematic onset of wave activity at increasing proton gyroharmonic frequencies. Sets of harmonic emissions (emission elements)are observed to occur periodically in the region +/- 10 off the geomagnetic equator. The sweep rate of these emissions maximizes at the geomagnetic equator. In addition, the ellipticity and propagation direction also change systematically as Cluster crosses the geomagnetic equator. It is shown that the observed frequency sweep rate is unlikely to result from the sideband instability related to nonlinear trapping of suprathermal protons in the wave field. The second form of emissions is characterized by the simultaneous onset of activity across a range of harmonic frequencies. These waves are observed at irregular intervals. Their occurrence correlates with changes in the spacecraft potential, a measurement that is used as a proxy for electron density. Thus, these waves appear to be trapped within regions of localized enhancement of the electron density.

  13. Enhanced continuous-wave four-wave mixing efficiency in nonlinear AlGaAs waveguides.

    Science.gov (United States)

    Apiratikul, Paveen; Wathen, Jeremiah J; Porkolab, Gyorgy A; Wang, Bohan; He, Lei; Murphy, Thomas E; Richardson, Christopher J K

    2014-11-03

    Enhancements of the continuous-wave four-wave mixing conversion efficiency and bandwidth are accomplished through the application of plasma-assisted photoresist reflow to reduce the sidewall roughness of sub-square-micron-modal area waveguides. Nonlinear AlGaAs optical waveguides with a propagation loss of 0.56 dB/cm demonstrate continuous-wave four-wave mixing conversion efficiency of -7.8 dB. Narrow waveguides that are fabricated with engineered processing produce waveguides with uncoated sidewalls and anti-reflection coatings that show group velocity dispersion of +0.22 ps²/m. Waveguides that are 5-mm long demonstrate broadband four-wave mixing conversion efficiencies with a half-width 3-dB bandwidth of 63.8-nm.

  14. Laser Development for Gravitational-Wave Interferometry in Space

    Science.gov (United States)

    Numata, Kenji; Camp, Jordan

    2012-01-01

    We are reporting on our development work on laser (master oscillator) and optical amplifier systems for gravitational-wave interferometry in space. Our system is based on the mature, wave-guided optics technologies, which have advantages over bulk, crystal-based, free-space optics. We are investing in a new type of compact, low-noise master oscillator, called the planar-waveguide external cavity diode laser. We made measurements, including those of noise, and performed space-qualification tests.

  15. Do laser interferometers absorb energy from gravitational waves ?

    CERN Document Server

    Ma, Yiqiu; Zhao, Chunnong; Kells, William

    2014-01-01

    In this paper we discuss the energy interaction between gravitational waves and laser interferom- eter gravitational wave detectors. We show that the widely held view that the laser interferometer gravitational wave detector absorbs no energy from gravitational waves is only valid under the approximation of a frequency-independent optomechanical coupling strength and a pump laser without detuning with respect to the resonance of the interferometer. For a strongly detuned interferometer, the optical-damping dynamics dissipates gravitational wave energy through the interaction between the test masses and the optical ?eld. For a non-detuned interferometer, the frequency-dependence of the optomechanical coupling strength causes a tiny energy dissipation, which is proved to be equivalent to the Doppler friction raised by Braginsky et.al.

  16. Detecting Beyond-Einstein Polarizations of Continuous Gravitational Waves

    CERN Document Server

    Isi, Maximiliano; Mead, Carver; Pitkin, Matthew

    2015-01-01

    The direct detection of gravitational waves with the next generation detectors, like Advanced LIGO, provides the opportunity to measure deviations from the predictions of General Relativity. One such departure would be the existence of alternative polarizations. To measure these, we study a single detector measurement of a continuous gravitational wave from a triaxial pulsar source. We develop methods to detect signals of any polarization content and distinguish between them in a model independent way. We present LIGO S5 sensitivity estimates for 115 pulsars.

  17. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    Science.gov (United States)

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-05-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency.

  18. Parallel femtosecond laser processing with vector-wave control

    Directory of Open Access Journals (Sweden)

    Hayasaki Yoshio

    2013-11-01

    Full Text Available Parallel femtosecond laser processing with a computer-generated hologram displayed on a spatial light modulator, has the advantages of high throughput and high energy-use efficiency. for further increase of the processing efficiency, we demonstrated parallel femtosecond laser processing with vector-wave control that is based on polarization control using a pair of spatial light modulators.

  19. Density bump formation in a collisionless electrostatic shock wave in a laser-ablated plasma

    CERN Document Server

    Garasev, M A; Kocharovsky, V V; Malkov, Yu A; Murzanev, A A; Nechaev, A A; Stepanov, A N

    2016-01-01

    The emergence of a density bump at the front of a collisionless electrostatic shock wave have been observed experimentally during the ablation of an aluminium foil by a femtosecond laser pulse. We have performed numerical simulations of the dynamics of this phenomena developing alongside the generation of a package of ion-acoustic waves, exposed to a continual flow of energetic electrons, in a collisionless plasma. We present the physical interpretation of the observed effects and show that the bump consists of transit particles, namely, the accelerated ions from the dense plasma layer, and the ions from the diluted background plasma, formed by a nanosecond laser prepulse during the ablation.

  20. Detecting continuous gravitational waves with superfluid $^4$He

    CERN Document Server

    Singh, S; Pikovski, I; Schwab, K C

    2016-01-01

    Direct detection of gravitational waves is opening a new window onto our universe. Here, we study the sensitivity to continuous-wave strain fields of a kg-scale optomechanical system formed by the acoustic motion of superfluid helium-4 parametrically coupled to a superconducting microwave cavity. This narrowband detection scheme can operate at very high $Q$-factors, while the resonant frequency is tunable through pressurization of the helium in the 0.1-1.5 kHz range. The detector can therefore be tuned to a variety of astrophysical sources and can remain sensitive to a particular source over a long period of time. For reasonable experimental parameters, we find that strain fields on the order of $h\\sim 10^{-23} /\\sqrt{\\rm Hz}$ are detectable. We show that the proposed system can significantly improve the limits on gravitational wave strain from nearby pulsars within a few months of integration time.

  1. A full-wave Helmholtz model for continuous-wave ultrasound transmission.

    Science.gov (United States)

    Huttunen, Tomi; Malinen, Matti; Kaipio, Jari P; White, Phillip Jason; Hynynen, Kullervo

    2005-03-01

    A full-wave Helmholtz model of continuous-wave (CW) ultrasound fields may offer several attractive features over widely used partial-wave approximations. For example, many full-wave techniques can be easily adjusted for complex geometries, and multiple reflections of sound are automatically taken into account in the model. To date, however, the full-wave modeling of CW fields in general 3D geometries has been avoided due to the large computational cost associated with the numerical approximation of the Helmholtz equation. Recent developments in computing capacity together with improvements in finite element type modeling techniques are making possible wave simulations in 3D geometries which reach over tens of wavelengths. The aim of this study is to investigate the feasibility of a full-wave solution of the 3D Helmholtz equation for modeling of continuous-wave ultrasound fields in an inhomogeneous medium. The numerical approximation of the Helmholtz equation is computed using the ultraweak variational formulation (UWVF) method. In addition, an inverse problem technique is utilized to reconstruct the velocity distribution on the transducer which is used to model the sound source in the UWVF scheme. The modeling method is verified by comparing simulated and measured fields in the case of transmission of 531 kHz CW fields through layered plastic plates. The comparison shows a reasonable agreement between simulations and measurements at low angles of incidence but, due to mode conversion, the Helmholtz model becomes insufficient for simulating ultrasound fields in plates at large angles of incidence.

  2. Propagation characteristics of ultrasonic guided waves in continuously welded rail

    Science.gov (United States)

    Yao, Wenqing; Sheng, Fuwei; Wei, Xiaoyuan; Zhang, Lei; Yang, Yuan

    2017-07-01

    Rail defects cause numerous railway accidents. Trains are derailed and serious consequences often occur. Compared to traditional bulk wave testing, ultrasonic guided waves (UGWs) can provide larger monitoring ranges and complete coverage of the waveguide cross-section. These advantages are of significant importance for the non-destructive testing (NDT) of the continuously welded rail, and the technique is therefore widely used in high-speed railways. UGWs in continuous welded rail (CWR) and their propagation characteristics have been discussed in this paper. Finite element methods (FEMs) were used to accomplish a vibration modal analysis, which is extended by a subsequent dispersion analysis. Wave structure features were illustrated by displacement profiles. It was concluded that guided waves have the ability to detect defects in the rail via choice of proper mode and frequency. Additionally, thermal conduction that is caused by temperature variation in the rail is added into modeling and simulation. The results indicated that unbalanced thermal distribution may lead to the attenuation of UGWs in the rail.

  3. Spike wave location and density disturb sleep slow waves in patients with CSWS (continuous spike waves during sleep).

    Science.gov (United States)

    Bölsterli Heinzle, Bigna K; Fattinger, Sara; Kurth, Salomé; Lebourgeois, Monique K; Ringli, Maya; Bast, Thomas; Critelli, Hanne; Schmitt, Bernhard; Huber, Reto

    2014-04-01

    In CSWS (continuous spike waves during sleep) activation of spike waves during slow wave sleep has been causally linked to neuropsychological deficits, but the pathophysiologic mechanisms are still unknown. In healthy subjects, the overnight decrease of the slope of slow waves in NREM (non-rapid eye movement) sleep has been linked to brain recovery to regain optimal cognitive performance. Here, we investigated whether the electrophysiologic hallmark of CSWS, the spike waves during sleep, is related to an alteration in the overnight decrease of the slope, and if this alteration is linked to location and density of spike waves. In a retrospective study, the slope of slow waves (0.5-2 Hz) in the first hour and last hour of sleep (19 electroencephalography [EEG] electrodes) of 14 patients with CSWS (3.1-13.5 years) was calculated. The spike wave "focus" was determined as the location of highest spike amplitude and the density of spike waves as spike wave index (SWI). There was no overnight change of the slope of slow waves in the "focus." Instead, in "nonfocal" regions, the slope decreased significantly. This difference in the overnight course resulted in a steeper slope in the "focus" compared to "nonfocal" electrodes during the last hour of sleep. Spike wave density was correlated with the impairment of the overnight slope decrease: The higher the SWI, the more hampered the slope decrease. Location and density of spike waves are related to an alteration of the physiologic overnight decrease of the slow wave slope. This overnight decrease of the slope was shown to be closely related to the recovery function of sleep. Such recovery is necessary for optimal cognitive performance during wakefulness. Therefore we propose the impairment of this process by spike waves as a potential mechanism leading to neuropsychological deficits in CSWS. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here. Wiley Periodicals

  4. Applications of the wave kinetic approach: from laser wakefields to drift wave turbulence

    Science.gov (United States)

    Trines, R. M. G. M.; Bingham, R.; Silva, L. O.; Mendonça, J. T.; Shukla, P. K.; Murphy, C. D.; Dunlop, M. W.; Davies, J. A.; Bamford, R.; Vaivads, A.; Norreys, P. A.

    2010-12-01

    Nonlinear wave-driven processes in plasmas are normally described by either a monochromatic pump wave that couples to other monochromatic waves, or as a random phase wave coupling to other random phase waves. An alternative approach involves a random or broadband pump coupling to monochromatic and/or coherent structures in the plasma. This approach can be implemented through the wave-kinetic model. In this model, the incoming pump wave is described by either a bunch (for coherent waves) or a sea (for random phase waves) of quasi-particles. This approach has been applied to both photon acceleration in laser wakefields and drift wave turbulence in magnetized plasma edge configurations. Numerical simulations have been compared to experiments, varying from photon acceleration to drift mode-zonal flow turbulence, and good qualitative correspondences have been found in all cases.

  5. Laser detection of ultrasonic waves with concave portions of the wave fronts.

    Science.gov (United States)

    Korkh, Yulia; Perov, Dmitry; Rinkevich, Anatoly

    2012-10-01

    Special features of ultrasonic pulse wave field detection with concave regions of the wave fronts are investigated with the use of ultrasonic laser interferometry technique. Experimental proofs of the wave front with concave regions are obtained and it is found that the nonmonotonic wave front profiles are well described by the fourth-order even polynomial. The model proposed is applied to the investigation of the spatiotemporal structure of elastic wave fields on solid surfaces. The results obtained can be used for estimating the local wave front curvature.

  6. Cr:ZnSe guided wave lasers and materials

    Science.gov (United States)

    McDaniel, Sean; Lancaster, Adam; Stites, Ronald; Thorburn, Fiona; Kar, Ajoy; Cook, Gary

    2017-02-01

    We describe a variety of technological advances in the development of efficient, powerful, and continuously tunable Cr:ZnSe lasers operating in the 2.3-2.7 μm spectral region. This includes the development of compact "single chip" waveguide Cr:ZnSe lasers, waveguide mode-locked Cr:ZnSe lasers, and the creation of homogeneously broadened laser material.

  7. Twin mirrors for laser interferometric gravitational-wave detectors.

    Science.gov (United States)

    Sassolas, Benoît; Benoît, Quentin; Flaminio, Raffaele; Forest, Danièle; Franc, Janyce; Galimberti, Massimo; Lacoudre, Aline; Michel, Christophe; Montorio, Jean-Luc; Morgado, Nazario; Pinard, Laurent

    2011-05-01

    Gravitational-wave detectors such as Virgo and the laser interferometric gravitational-wave observatory (LIGO) use a long-baseline Michelson interferometer with Fabry-Perot cavities in the arms to search for gravitational waves. The symmetry between the two Fabry-Perot cavities is crucial to reduce the interferometer's sensitivity to the laser amplitude and frequency noise. To this purpose, the transmittance of the mirrors in both cavities should be as close as possible. This paper describes the realization and the characterization of the first twin large low-loss mirrors with transmissions differing by less than 0.01%.

  8. Bernstein wave aided laser third harmonic generation in a plasma

    Science.gov (United States)

    Tyagi, Yachna; Tripathi, Deepak; Kumar, Ashok

    2016-09-01

    The process of Bernstein wave aided resonant third harmonic generation of laser in a magnetized plasma is investigated. The extra-ordinary mode (X-mode) laser of frequency ω 0 and wave number k → 0 , travelling across the magnetic field in a plasma, exerts a second harmonic ponderomotive force on the electrons imparting them an oscillatory velocity v → 2 ω0 , 2 k → 0 . This velocity beats with the density perturbation due to the Bernstein wave to produce a density perturbation at cyclotron frequency shifted second harmonic. The density perturbation couples with the oscillatory velocity v → ω0 , k → 0 of X-mode of the laser to produce the cyclotron frequency shifted third harmonic current density leading to harmonic radiation. The phase matching condition for the up shifted frequency is satisfied when the Bernstein wave is nearly counter-propagating to the laser. As the transverse wave number of the Bernstein wave is large, it is effective in the phase matched third harmonic generation, when the laser frequency is not too far from the upper hybrid frequency.

  9. Quasi continuous-wave lasing in organic thin-film semiconductors (Conference Presentation)

    Science.gov (United States)

    Sanadanayaka, Atula S. D.; Yoshida, Kou; Ribierre, Jean-Charles; Matsushima, Toshinori; Adachi, Chihaya

    2016-09-01

    Since the discovery of organic solid-state lasers, great efforts have been devoted to the development of continuous-wave (cw) lasing in organic materials. However, the operation of organic solid-state lasers under optical cw excitation or pulse excitation at a very high repetition rate (quasi-cw excitation) is extremely challenging. In this work, we have demonstrated quasi-continuous-wave (quasi-cw) surface-emitting lasing in a distributed feedback device which combines a second-order grating with an organic thin film of a host material 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) blended with an organic laser dye 4,4'-bis[(N-carbazole)styryl]biphenyl (BSBCz). When pumping the device with optical picosecond pulse excitation, the quasi-cw laser operation maintained up to a repetition rate of 8 MHz. The lasing threshold was around 0.25 μJ cm-2 which was almost independent of the repetition rates. For our laser devices, the maximum repetition rate (8 MHz) is the highest ever reported, and the lasing threshold (0.25 μJ cm-2) is the lowest ever reported. These superior quasi-cw lasing characteristics in BSBCz are accomplished by the less generation of triplet excitons via intersystem crossing because a photoluminescence quantum yield of the blend film is nearly 100% and there is no significant spectral overlap between laser and triplet absorption.[1,2] Triplet quenchers, generally used for the fabrication of organic thin-film lasers, were not necessary in our devices because of negligible accumulation of triplet excitons and a small spectral overlap between emission and triplet absorption. Therefore, we believe that BSBCz is the most promising candidate for the first realization of electrically pumped organic laser diodes in terms of optical characteristics. However, electrical characteristics such as charge carrier mobility, charge carrier capture cross section, etc., are also extremely important and will need further investigation and enhancement for realization of

  10. Continuous-wave four-wave mixing in cm-long Chalcogenide microstructured fiber.

    Science.gov (United States)

    Brès, Camille-Sophie; Zlatanovic, Sanja; Wiberg, Andreas O J; Radic, Stojan

    2011-12-12

    We present the experimental demonstration of broadband four-wave mixing in a 2.5 cm-long segment of AsSe Chalcogenide microstructured fiber. The parametric mixing was driven by a continuous-wave pump compatible with data signal wavelength conversion. Four-wave mixing products over more than 70 nm on the anti-stoke side of the pump were measured for 345 mW of pump power and 1.5 dBm of signal power. The ultrafast signal processing capability was verified through wavelength conversion of 1.4 ps pulses at 8 GHz repetition rate. © 2011 Optical Society of America

  11. Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode

    DEFF Research Database (Denmark)

    Klinkhammer, Sönke; Liu, Xin; Huska, Klaus

    2012-01-01

    solutions on cm-scale surface gratings of different periods. We report optically pumped continuously tunable laser emission of 13 nm in the blue, 16 nm in the green and 19 nm in the red spectral region on a single chip respectively. Tuning behavior can be described with the Bragg-equation and the measured...... thickness profile. The laser threshold is low enough that inexpensive laser diodes can be used as pump sources....

  12. Noninvasive continuous monitoring of digital pulse waves during hemodialysis

    DEFF Research Database (Denmark)

    Burkert, Antje; Scholze, Alexandra; Tepel, Martin

    2009-01-01

    Intermittent hemodynamic instability during hemodialysis treatment is a frequent complication in patients with end-stage renal failure. A noninvasive method for continuous hemodynamic monitoring is needed. We used noninvasive digital photoplethysmography and an algorithm for continuous, investiga......Intermittent hemodynamic instability during hemodialysis treatment is a frequent complication in patients with end-stage renal failure. A noninvasive method for continuous hemodynamic monitoring is needed. We used noninvasive digital photoplethysmography and an algorithm for continuous......, investigator-independent, automatic analysis of digital volume pulse in 10 healthy subjects and in 20 patients with end-stage renal failure during the hemodialysis session. The reflective index was defined representing the diastolic component of the digital pulse wave. The properties of the reflective index...... were studied in healthy control subjects (n=10). An increased reflective index was due to increased peripheral pulse wave reflection (e.g., vasoconstriction). During a hemodialysis session, the reflective index increased significantly from 36+/-3 arbitrary units to 41+/-3 arbitrary units (n=20; p...

  13. Specifics of short-wavelength generation in a continuous wave fiber optical parametric oscillator

    Science.gov (United States)

    Zlobina, E. A.; Mishra, V.; Kablukov, S. I.; Singh, S. P.; Varshney, S. K.; Babin, S. A.

    2016-11-01

    We investigate factors limiting short-wavelength generation and therefore tuning range of the continuous wave all-fiber optical parametric oscillator based on birefringent photonic crystal fiber pumped by a tunable linearly polarized ytterbium-doped fiber laser. Influence of the longitudinal dispersion fluctuations in the fiber on the threshold of the fiber optical parametric oscillators is numerically studied. It is shown that even low fluctuations (<0.5 nm) of the zero dispersion wavelength in 18 m-long fiber result in a significant increase of the threshold at large parametric shifts.

  14. Continuous-wave terahertz light from optical parametric oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Sowade, Rosita

    2010-12-15

    Continuous-wave (cw) optical parametric oscillators (OPOs) are working horses for spectroscopy in the near and mid infrared. However, in the terahertz frequency range (0.1 to 10 THz), the pump threshold is more than 100 W due to the high absorption in nonlinear crystals and thus exceeds the power of standard cw single-frequency pump sources. In this thesis the first cw OPO capable of generating terahertz radiation is demonstrated. To overcome the high threshold, the signal wave of a primary infrared process is resonantly enhanced to serve as the pump wave for a cascaded parametric process with one wave being at the terahertz frequency level. A terahertz output power of more than two microwatts is measured and tuning is achieved from 1.3 to 1.7 THz. This terahertz source emits a narrow-band, diffraction-limited beam which remains mode-hop free over more than one hour. Such a device inhibits high potential for applications in areas like astronomy, telecommunications or high-resolution spectroscopy. (orig.)

  15. Searches for Continuous Gravitational Waves in LIGO and Virgo Data

    Science.gov (United States)

    Riles, Keith; LIGO Scientific Collaboration Collaboration; Virgo Collaboration Collaboration

    2017-01-01

    The LIGO Scientific Collaboration and Virgo Collaboration have carried out searches for periodic continuous gravitational waves. These analyses range from targeted searches for gravitational-wave signals from known pulsars, for which precise ephemerides from radio or X-ray observations are available, to all-sky searches for unknown neutron stars, including stars in unknown binary systems. Between these extremes lie directed searches for known stars of unknown spin frequency or for new unknown sources at specific locations. These different types of searches will be presented, including final results from the Initial LIGO and Virgo data runs and, where available, new results from searches of early Advanced LIGO data. This work is supported by the National Science Foundation grant PHY-1505932.

  16. 生物组织中强度调制的连续激光激发的光声信号影响因素研究%Study on Influential Factor of Photoacoustic Signal Excited by Intensity-Modulated Continuous-Wave Laser in Biological Tissue

    Institute of Scientific and Technical Information of China (English)

    张雷洪; 马秀华

    2011-01-01

    分析了强度调制的连续激光激发的光声信号形成过程以及调制脉宽对光声信号强度的影响,发现随着调制方波脉宽的增加,生物组织吸收的光功率增加,光声信号幅值增加.研究了调制脉宽对光声成像技术轴向分辨率的影响,发现随着调制方波脉宽宽度的增加,光声信号的脉宽增加,其轴向分辨率变差.在理论研究的基础上进行了实验验证,通过方波调制的激光二极管的出射激光激发生物组织获取声信号.在激光二极管出射光功率提高受限的条件下,通过增加作用在生物组织上的光功率密度获取高分辨率、高信噪比的光声图像.对强度调制连续激光激发的光声成像技术的研究能够为光声成像技术提供一种低成本、便携式的设备,为进一步研究提供参考.%The forming process of the photoacoustic signal excited by the intensity-modulated continuous-wave laser and the effects of modulation pulse width on photoacoustic signal are researched. It is shown that the power absorbed by the biological tissue increases with the increase of the width of the modulated rectangular pulse and the amplitude of the photoacoustic signal. The effects on the axial resolution of the photoacoustic signal excited by the modulated rectangular pulse are also researched. It is shown that the width of the photoacoustic signal increases with the increase of the width of the modulated rectangular pulse, and the axial resolution of the photoacoustic imaging becomes worse. The modulated rectangular pulse of the continuous-wave laser (laser diode) is used to induce the acoustic signal. The laser power density is raised to obtain photoacoustic imaging with higher signal-to-noise ratio (SNR) and resolution when it is hard to raise the laser power. The research on the influential factor of photoacoustic signal excited by intensity-modulated continuous-wave laser in biological tissue can be used to provide a portable and

  17. Subsurface plasma in beam of continuous CO2-laser

    Science.gov (United States)

    Danytsikov, Y. V.; Dymshakov, V. A.; Lebedev, F. V.; Pismennyy, V. D.; Ryazanov, A. V.

    1986-03-01

    Experiments performed at the Institute of Atomic Energy established the conditions for formation of subsurface plasma in substances by laser radiation and its characteristics. A quasi-continuous CO2 laser emitting square pulses of 0.1 to 1.0 ms duration and 1 to 10 kW power as well as a continuous CO2 laser served as radiation sources. Radiation was focused on spots 0.1 to 0.5 mm in diameter and maintained at levels ensuring constant power density during the interaction time, while the temperature of the target surface was measured continuously. Metals, graphite and dielectric materials were tested with laser action taking place in air N2 + O2 mixtures, Ar or He atmosphere under pressures of 0.01 to 1.0 atm. Data on radiation intensity thresholds for evaporation and plasma formation were obtained. On the basis of these thresholds, combined with data on energy balance and the temperature profile in plasma layers, a universal state diagram was constructed for subsurface plasma with nonquantified surface temperature and radiation intensity coordinates.

  18. High-power pulse trains excited by modulated continuous waves

    CERN Document Server

    Wang, Yan; Li, Lu; Malomed, Boris A

    2015-01-01

    Pulse trains growing from modulated continuous waves (CWs) are considered, using solutions of the Hirota equation for solitons on a finite background. The results demonstrate that pulses extracted from the maximally compressed trains can propagate preserving their shape and forming robust arrays. The dynamics of double high-power pulse trains produced by modulated CWs in a model of optical fibers, including the Raman effect and other higher-order terms, is considered in detail too. It is demonstrated that the double trains propagate in a robust form, with frequencies shifted by the Raman effect.

  19. Optical Frequency-Modulated Continuous-Wave (FMCW) Interferometry

    CERN Document Server

    Zheng, Jesse

    2005-01-01

    This book introduces the optical frequency-modulated continuous-wave (FMCW) interferometry - a new field of optics that is derived from radar. The study of optical FMCW interference not only updates our knowledge about the nature of light, but also creates an advanced technology for precision measurements. The principles, applications and signal processing of optical FMCW interference are systematically discussed. This book is intended for scientists and engineers in both academia and industry. It is especially suited to professionals who are working in the field of measurement instruments.

  20. Challenges in noise removal from Doppler spectra acquired by a continuous-wave lidar

    DEFF Research Database (Denmark)

    Angelou, Nikolas; Foroughi Abari, Farzad; Mann, Jakob;

    2012-01-01

    This paper is focused on the required post processing of Doppler spectra, acquired from a continuous-wave coherent lidar at high sampling rates (400 Hz) and under rapid scanning of the laser beam. In particular, the necessary steps followed for extracting the wind speed from such Doppler spectra...... are presented. A method for determining the background noise spectrum without interrupting the transmission of the laser beam is described. Moreover, the dependency between the determination of the threshold of a Doppler spectrum with low signal-to-noise ratios and the characteristics of the wind flow...... are investigated and a systematic approach for removing the noise is outlined. The suggested post processing procedures are applied to two sample time series acquired by a short-range WindScanner during one second each....

  1. Investigation on laser accelerators. Plasma beat wave accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Akihiko; Miyamoto, Yasuaki; Hagiwara, Masayoshi; Suzuki, Mitsutoshi; Sudo, Osamu [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works

    1998-04-01

    Laser accelerator technology has characteristics of high energy, compact, short pulse and high luminescence{center_dot}low emittance. This means potential many applications in wide ranges of fields as well as high energy and nuclear physics. High power short laser pulses are injected to a plasma in the typical example of laser accelerators. Large electric fields are induced in the plasma. Electrons in the plasma are accelerated with the ponderomotive force of the electric field. The principles of interaction on beat wave, wakefield accelerators, inverse free electron laser and inverse Cherenkov radiation are briefly introduced. The overview of plasma beat wave accelerator study is briefly described on the programs at Chalk River Laboratories(Canada), UCLA(USA), Osaka Univ. (Japan) and Ecole Polytechnique (France). Issues of the plasma beat wave accelerator are discussed from the viewpoint of application. Existing laser technologies of CO{sub 2}, YAG and YFL are available for the present day accelerator technology. An acceleration length of beat wave interaction is limited due to its phase condition. Ideas on multi-staged acceleration using the phasing plasma fiber are introduced. (Y. Tanaka)

  2. Simulation of Chromium Atom Deposition Pattern in a Gaussain Laser Standing Wave with Different Laser Power

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-Tao; ZHU Bao-Hua

    2009-01-01

    One-dimensional deposition of a neutral chromium atomic beam focused by a near-resonant Gaussian standing-laser field is discussed by using a fourth-order Runge-Kutta type algorithm. The deposition pattern of neutral chromium atoms in a laser standing wave with different laser power is discussed and the simulation result shows that the full width at half maximum (FWHM) of a nanometer stripe is 115nm and the contrast is 2.5:1 with laser power 3.93mW; the FWHM is 0.Snm and the contrast is 27:1 with laser power 16mW, the optimal laser power; but with laser power increasing to 50mW, the nanometer structure forms multi-crests and the quality worsens quickly with increasing laser power.

  3. Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode

    DEFF Research Database (Denmark)

    Klinkhammer, Sönke; Liu, Xin; Huska, Klaus

    2012-01-01

    The fabrication and characterization of continuously tunable, solution-processed distributed feedback (DFB) lasers in the visible regime is reported. Continuous thin film thickness gradients were achieved by means of horizontal dipping of several conjugated polymer and blended small molecule...... solutions on cm-scale surface gratings of different periods. We report optically pumped continuously tunable laser emission of 13 nm in the blue, 16 nm in the green and 19 nm in the red spectral region on a single chip respectively. Tuning behavior can be described with the Bragg-equation and the measured...

  4. LASER PLASMA AND LASER APPLICATIONS: Plasma transparency in laser absorption waves in metal capillaries

    Science.gov (United States)

    Anisimov, V. N.; Kozolupenko, A. P.; Sebrant, A. Yu

    1988-12-01

    An experimental investigation was made of the plasma transparency to heating radiation in capillaries when absorption waves propagated in these capillaries as a result of interaction with a CO2 laser pulse of 5-μs duration. When the length of the capillary was in excess of 20 mm, total absorption of the radiation by the plasma was observed at air pressures of 1-100 kPa. When the capillary length was 12 mm, a partial recovery of the transparency took place. A comparison was made with the dynamics and recovery of the plasma transparency when breakdown of air took place near the free surface.

  5. Identification of Laser-induced Lamb waves

    Energy Technology Data Exchange (ETDEWEB)

    Castro C, M.; Lopez, J.A. [Physics Department, U. 1: El Paso, El Paso, TX 79968 (United States); Osegueda, R. [FAST Center, Burgess Hall, U. 1: El Paso, El Paso, TX 79968 (United States)

    2007-07-01

    We studied experimentally the ultrasonic propagating modes produced by a laser pulse of 532 nm while impinging on an aluminum plate. The beam, shaped as a line, induced various Lamb modes whose relative power varied with the laser line length. Identification of their mode was performed by detecting the ultrasonic modes with piezoelectric detectors along a propagation direction orthogonal to the line, and using two dimensional fast Fourier transform. Good agreement is observed between theoretical and experimental dispersion curves for the first fundamental symmetric and anti-symmetric modes. Results are shown for 12 and 24 mm laser line-length at 13.6 and 16.8 ns pulse-width. (Author)

  6. Continuous-wave four-wave mixing with linear growth based on electromagnetically dual induced transparency

    Institute of Scientific and Technical Information of China (English)

    Jiahua Li(李家华); Wenxing Yang(杨文星); Jucun Peng(彭菊村)

    2004-01-01

    Using Schrodinger-Maxwell formalism, we propose and analyze a continuous-wave four-wave mixing (FWM) scheme for the generation of coherent light in a six-level atomic system based on electromagnetically dual induced transparency. We derive the corresponding explicit analytical expressions for the generated mixing field. We find that the scheme greatly enhances FWM production efficiency and is also capable of inhibiting and delaying the onset of the detrimental three-photon destructive interference by choosing the proper decay rate in the second electromagnetically induced transparency (EIT) process.In addition, such an optical process also provides possibilities for producing short-wave-length coherent radiation at low pump intensities.

  7. Continuous-wave non-classical light with GHz squeezing bandwidth

    CERN Document Server

    Ast, Stefan; Mehmet, Moritz; Steinlechner, Sebastian; Eberle, Tobias; Schnabel, Roman

    2012-01-01

    Squeezed states can be employed for entanglement-based continuous-variable quantum key distribution, where the secure key rate is proportional to the bandwidth of the squeezing. We produced a non-classical continuous-wave laser field at the telecommunication wavelength of 1550 nm, which showed squeezing over a bandwidth of more than 2 GHz. The experimental setup used parametric down-conversion via a periodically poled potassium titanyl phosphate crystal (PPKTP). We did not use any resonant enhancement for the funda- mental wavelength, which should in principle allow a production of squeezed light over the full phase-matching bandwidth of several nanometers. We measured the squeezing to be up to 0.3 dB below the vacuum noise from 50 MHz to 2 GHz limited by the measuring bandwidth of the homodyne detector. The squeezing strength was possibly limited by thermal lensing inside the non-linear crystal.

  8. Experimental imaging research on continuous-wave terahertz in-line digital holography

    Science.gov (United States)

    Huang, Haochong; Wang, Dayong; Rong, Lu; Wang, Yunxin

    2014-09-01

    The terahertz (THz) imaging is an advanced technique on the basis of the unique characteristics of terahertz radiation. Due to its noncontact, non-invasive and high-resolution capabilities, it has already shown great application prospects in biomedical observation, sample measurement, and quality control. The continuous-wave terahertz in-line digital holography is a combination of terahertz technology and in-line digital holography of which the source is a continuous-wave terahertz laser. Over the past decade, many researchers used different terahertz sources and detectors to undertake experiments. In this paper, the pre-process of the hologram is accomplished after the holograms' recording process because of the negative pixels in the pyroelectric detector and the air vibration caused by the chopper inside the camera. To improve the quality of images, the phase retrieval algorithm is applied to eliminate the twin images. In the experiment, the pin which terahertz wave can't penetrate and the TPX slice carved letters "THz" are chosen for the samples. The amplitude and phase images of samples are obtained and the twin image and noise in the reconstructed images are suppressed. The results validate the feasibility of the terahertz in-line digital holographic imaging technique. This work also shows the terahertz in-line digital holography technique's prospects in materials science and biological samples' detection.

  9. Hidden Markov model tracking of continuous gravitational waves from a neutron star with wandering spin

    CERN Document Server

    Suvorova, S; Melatos, A; Moran, W; Evans, R J

    2016-01-01

    Gravitational wave searches for continuous-wave signals from neutron stars are especially challenging when the star's spin frequency is unknown a priori from electromagnetic observations and wanders stochastically under the action of internal (e.g. superfluid or magnetospheric) or external (e.g. accretion) torques. It is shown that frequency tracking by hidden Markov model (HMM) methods can be combined with existing maximum likelihood coherent matched filters like the F-statistic to surmount some of the challenges raised by spin wandering. Specifically it is found that, for an isolated, biaxial rotor whose spin frequency walks randomly, HMM tracking of the F-statistic output from coherent segments with duration T_drift = 10d over a total observation time of T_obs = 1yr can detect signals with wave strains h0 > 2e-26 at a noise level characteristic of the Advanced Laser Interferometer Gravitational Wave Observatory (Advanced LIGO). For a biaxial rotor with randomly walking spin in a binary orbit, whose orbital...

  10. Material measurement method based on femtosecond laser plasma shock wave

    Science.gov (United States)

    Zhong, Dong; Li, Zhongming

    2017-03-01

    The acoustic emission signal of laser plasma shock wave, which comes into being when femtosecond laser ablates pure Cu, Fe, and Al target material, has been detected by using the fiber Fabry-Perot (F-P) acoustic emission sensing probe. The spectrum characters of the acoustic emission signals for three kinds of materials have been analyzed and studied by using Fourier transform. The results show that the frequencies of the acoustic emission signals detected from the three kinds of materials are different. Meanwhile, the frequencies are almost identical for the same materials under different ablation energies and detection ranges. Certainly, the amplitudes of the spectral character of the three materials show a fixed pattern. The experimental results and methods suggest a potential application of the plasma shock wave on-line measurement based on the femtosecond laser ablating target by using the fiber F-P acoustic emission sensor probe.

  11. Searches for continuous gravitational waves from nine young supernova remnants

    CERN Document Server

    Aasi, J; Abbott, R; Abbott, T; Abernathy, M R; Acernese, F; Ackley, K; Adams, C; Adams, T; Addesso, P; Adhikari, R X; Adya, V; Affeldt, C; Agathos, M; Agatsuma, K; Aggarwal, N; Aguiar, O D; Ain, A; Ajith, P; Alemic, A; Allen, B; Allocca, A; Amariutei, D; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J S; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Aylott, B E; Babak, S; Baker, P T; Baldaccini, F; Ballardin, G; Ballmer, S W; Barayoga, J C; Barbet, M; Barclay, S; Barish, B C; Barker, D; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Bartlett, J; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J C; Bauer, Th S; Baune, C; Bavigadda, V; Behnke, B; Bejger, M; Belczynski, C; Bell, A S; Bell, C; Benacquista, M; Bergman, J; Bergmann, G; Berry, C P L; Bersanetti, D; Bertolini, A; Betzwieser, J; Bhagwat, S; Bhandare, R; Bilenko, I A; Billingsley, G; Birch, J; Biscans, S; Bitossi, M; Biwer, C; Bizouard, M A; Blackburn, J K; Blackburn, L; Blair, C D; Blair, D; Bloemen, S; Bock, O; Bodiya, T P; Boer, M; Bogaert, G; Bojtos, P; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, Sukanta; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brau, J E; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Brooks, A F; Brown, D A; Brown, D D; Brown, N M; Buchman, S; Buikema, A; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Cadonati, L; Cagnoli, G; Bustillo, J Calderón; Calloni, E; Camp, J B; Cannon, K C; Cao, J; Capano, C D; Carbognani, F; Caride, S; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chamberlin, S J; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Cho, M; Chow, J H; Christensen, N; Chu, Q; Chua, S; Chung, S; Ciani, G; Clara, F; Clark, J A; Cleva, F; Coccia, E; Cohadon, P -F; Colla, A; Collette, C; Colombini, M; Cominsky, L; Constancio,, M; Conte, A; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J -P; Countryman, S; Couvares, P; Coward, D M; Cowart, M J; Coyne, D C; Coyne, R; Craig, K; Creighton, J D E; Creighton, T D; Cripe, J; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Cutler, C; Dahl, K; Canton, T Dal; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dartez, L; Dattilo, V; Dave, I; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; DeBra, D; Debreczeni, G; Degallaix, J; De Laurentis, M; Deléglise, S; Del Pozzo, W; Denker, T; Dent, T; Dereli, H; Dergachev, V; De Rosa, R; DeRosa, R T; DeSalvo, R; Dhurandhar, S; Díaz, M; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Dojcinoski, G; Dolique, V; Dominguez, E; Donovan, F; Dooley, K L; Doravari, S; Douglas, R; Downes, T P; Drago, M; Driggers, J C; Du, Z; Ducrot, M; Dwyer, S; Eberle, T; Edo, T; Edwards, M; Effler, A; Eggenstein, H -B; Ehrens, P; Eichholz, J; Eikenberry, S S; Essick, R; Etzel, T; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fan, X; Fang, Q; Farinon, S; Farr, B; Farr, W M; Favata, M; Fays, M; Fehrmann, H; Fejer, M M; Feldbaum, D; Ferrante, I; Ferreira, E C; Ferrini, F; Fidecaro, F; Fiori, I; Fisher, R P; Flaminio, R; Fournier, J -D; Franco, S; Frasca, S; Frasconi, F; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fuentes-Tapia, S; Fulda, P; Fyffe, M; Gair, J R; Gammaitoni, L; Gaonkar, S; Garufi, F; Gatto, A; Gehrels, N; Gemme, G; Gendre, B; Genin, E; Gennai, A; Gergely, L Á; Ghosh, S; Giaime, J A; Giardina, K D; Giazotto, A; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Gräf, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Groot, P; Grote, H; Grunewald, S; Guidi, G M; Guido, C J; Guo, X; Gushwa, K; Gustafson, E K; Gustafson, R; Hacker, J; Hall, E D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Hardwick, T; Harms, J; Harry, G M; Harry, I W; Hart, M; Hartman, M T; Haster, C -J; Haughian, K; Hee, S; Heidmann, A; Heintze, M; Heinzel, G; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hewitson, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Hollitt, S E; Holt, K; Hopkins, P; Hosken, D J; Hough, J; Houston, E; Howell, E J; Hu, Y M; Huerta, E; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Idrisy, A; Indik, N; Ingram, D R; Inta, R; Islas, G; Isler, J C; Isogai, T; Iyer, B R; Izumi, K; Jacobson, M; Jang, H; Jaranowski, P; Jawahar, S; Ji, Y; Jiménez-Forteza, F; Johnson, W W; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Keiser, G M; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Key, J S; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, C; Kim, K; Kim, N G; Kim, N; Kim, Y -M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kline, J; Koehlenbeck, S; Kokeyama, K; Kondrashov, V; Korobko, M; Korth, W Z; Kowalska, I; Kozak, D B; Kringel, V; Krishnan, B; Królak, A; Krueger, C; Kuehn, G; Kumar, A; Kumar, P; Kuo, L; Kutynia, A; Landry, M; Lantz, B; Larson, S; Lasky, P D; Lazzarini, A; Lazzaro, C; Le, J; Leaci, P; Leavey, S; Lebigot, E; Lebigot, E O; Lee, C H; Lee, H K; Lee, H M; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levin, Y; Levine, B; Lewis, J; Li, T G F; Libbrecht, K; Libson, A; Lin, A C; Littenberg, T B; Lockerbie, N A; Lockett, V; Logue, J; Lombardi, A L; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J; Lubinski, M J; Lück, H; Lundgren, A P; Lynch, R; Ma, Y; Macarthur, J; MacDonald, T; Machenschalk, B; MacInnis, M; Macleod, D M; Magaña-Sandoval, F; Magee, R; Mageswaran, M; Maglione, C; Mailand, K; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Mandel, I; Mandic, V; Mangano, V; Mansell, G L; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A; Maros, E; Martelli, F; Martellini, L; Martin, I W; Martin, R M; Martynov, D; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Matichard, F; Matone, L; Mavalvala, N; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McCormick, S; McGuire, S C; McIntyre, G; McIver, J; McLin, K; McWilliams, S; Meacher, D; Meadors, G D; Meidam, J; Meinders, M; Melatos, A; Mendell, G; Mercer, R A; Meshkov, S; Messenger, C; Meyers, P M; Mezzani, F; Miao, H; Michel, C; Middleton, H; Mikhailov, E E; Milano, L; Miller, A; Miller, J; Millhouse, M; Minenkov, Y; Ming, J; Mirshekari, S; Mishra, C; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moe, B; Moggi, A; Mohan, M; Mohanty, S D; Mohapatra, S R P; Moore, B; Moraru, D; Moreno, G; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D; Murray, P G; Mytidis, A; Nagy, M F; Nardecchia, I; Nash, T; Naticchioni, L; Nayak, R K; Necula, V; Nedkova, K; Nelemans, G; Neri, I; Neri, M; Newton, G; Nguyen, T; Nielsen, A B; Nissanke, S; Nitz, A H; Nocera, F; Nolting, D; Normandin, M E N; Nuttall, L K; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oppermann, P; Oram, R; O'Reilly, B; Ortega, W; O'Shaughnessy, R; Osthelder, C; Ott, C D; Ottaway, D J; Ottens, R S; Overmier, H; Owen, B J; Padilla, C; Pai, A; Pai, S; Palashov, O; Palomba, C; Pal-Singh, A; Pan, H; Pankow, C; Pannarale, F; Pant, B C; Paoletti, F; Papa, M A; Paris, H; Pasqualetti, A; Passaquieti, R; Passuello, D; Patrick, Z; Pedraza, M; Pekowsky, L; Pele, A; Penn, S; Perreca, A; Phelps, M; Pichot, M; Piergiovanni, F; Pierro, V; Pillant, G; Pinard, L; Pinto, I M; Pitkin, M; Poeld, J; Poggiani, R; Post, A; Poteomkin, A; Powell, J; Prasad, J; Predoi, V; Premachandra, S; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Pürrer, M; Qin, J; Quetschke, V; Quintero, E; Quiroga, G; Quitzow-James, R; Raab, F J; Rabeling, D S; Rácz, I; Radkins, H; Raffai, P; Raja, S; Rajalakshmi, G; Rakhmanov, M; Ramirez, K; Rapagnani, P; Raymond, V; Razzano, M; Re, V; Reed, C M; Regimbau, T; Rei, L; Reid, S; Reitze, D H; Reula, O; Ricci, F; Riles, K; Robertson, N A; Robie, R; Robinet, F; Rocchi, A; Rolland, L; Rollins, J G; Roma, V; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Sachdev, S; Sadecki, T; Sadeghian, L; Saleem, M; Salemi, F; Sammut, L; Sandberg, V; Sanders, J R; Sannibale, V; Santiago-Prieto, I; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Savage, R; Sawadsky, A; Scheuer, J; Schilling, R; Schmidt, P; Schnabel, R; Schofield, R M S; Schreiber, E; Schuette, D; Schutz, B F; Scott, J; Scott, S M; Sellers, D; Sengupta, A S; Sentenac, D; Sequino, V; Sergeev, A; Serna, G; Sevigny, A; Shaddock, D A; Shah, S; Shahriar, M S; Shaltev, M; Shao, Z; Shapiro, B; Shawhan, P; Shoemaker, D H; Sidery, T L; Siellez, K; Siemens, X; Sigg, D; Silva, A D; Simakov, D; Singer, A; Singer, L; Singh, R; Sintes, A M; Slagmolen, B J J; Smith, J R; Smith, M R; Smith, R J E; Smith-Lefebvre, N D; Son, E J; Sorazu, B; Souradeep, T; Staley, A; Stebbins, J; Steinke, M; Steinlechner, J; Steinlechner, S; Steinmeyer, D; Stephens, B C; Steplewski, S; Stevenson, S; Stone, R; Strain, K A; Straniero, N; Strigin, S; Sturani, R; Stuver, A L; Summerscales, T Z; Sutton, P J; Swinkels, B; Szczepanczyk, M; Szeifert, G; Tacca, M; Talukder, D; Tanner, D B; Tápai, M; Tarabrin, S P; Taracchini, A; Taylor, R; Tellez, G; Theeg, T; Thirugnanasambandam, M P; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, V; Tomlinson, C; Tonelli, M; Torres, C V; Torrie, C I; Travasso, F; Traylor, G; Tse, M; Tshilumba, D; Ugolini, D; Unnikrishnan, C S; Urban, A L; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; Vallisneri, M; van Bakel, N; van Beuzekom, M; Brand, J F J van den; Broeck, C van den; van der Sluys, M V; van Heijningen, J; van Veggel, A A; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Vetrano, F; Viceré, A; Vincent-Finley, R; Vinet, J -Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vyatchanin, S P; Wade, A R; Wade, L; Wade, M; Walker, M; Wallace, L; Walsh, S; Wang, H; Wang, M; Wang, X; Ward, R L; Warner, J; Was, M; Weaver, B; Wei, L -W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Wessels, P; Westphal, T; Wette, K; Whelan, J T; White, D J; Whiting, B F; Wilkinson, C; Williams, L; Williams, R; Williamson, A R; Willis, J L; Willke, B; Wimmer, M; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Xie, S; Yablon, J; Yakushin, I; Yam, W; Yamamoto, H; Yancey, C C; Yang, Q; Yvert, M; Zadrożny, A; Zanolin, M; Zendri, J -P; Zhang, Fan; Zhang, L; Zhang, M; Zhang, Y; Zhao, C; Zhou, M; Zhu, X J; Zucker, M E; Zuraw, S; Zweizig, J

    2014-01-01

    We describe directed searches for continuous gravitational waves in data from the sixth LIGO science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the remnants are associated with non-pulsing suspected neutron stars. One target's parameters are uncertain enough to warrant two searches, for a total of ten. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering F-statistic. We found no credible gravitational-wave signals. We set 95% confidence upper limits as strong (low) as $4\\times10^{-25}$ on intrinsic strain, $2\\times10^{-7}$ on fiducial ellipticity, and $4\\times10^{-5}$ on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes.

  12. Search for continuous gravitational waves: improving robustness versus instrumental artifacts

    CERN Document Server

    Keitel, David; Papa, Maria Alessandra; Leaci, Paola; Siddiqi, Maham

    2013-01-01

    The standard multi-detector F-statistic for continuous gravitational waves is susceptible to false alarms from instrumental artifacts, for example monochromatic sinusoidal disturbances (lines). This vulnerability to line artifacts arises because the F-statistic compares the signal hypothesis to a Gaussian-noise hypothesis, and hence is triggered by anything that resembles the signal hypothesis more than Gaussian noise. Various ad-hoc veto methods to deal with such line artifacts have been proposed and used in the past. Here we develop a Bayesian framework that includes an explicit alternative hypothesis to model disturbed data. We introduce a simple line model that defines lines as signal candidates appearing only in one detector. This allows us to explicitly compute the odds between the signal hypothesis and an extended noise hypothesis, resulting in a new detection statistic that is more robust to instrumental artifacts. We present and discuss results from Monte-Carlo tests on both simulated data and on det...

  13. Basic gait analysis based on continuous wave radar.

    Science.gov (United States)

    Zhang, Jun

    2012-09-01

    A gait analysis method based on continuous wave (CW) radar is proposed in this paper. Time-frequency analysis is used to analyze the radar micro-Doppler echo from walking humans, and the relationships between the time-frequency spectrogram and human biological gait are discussed. The methods for extracting the gait parameters from the spectrogram are studied in depth and experiments on more than twenty subjects have been performed to acquire the radar gait data. The gait parameters are calculated and compared. The gait difference between men and women are presented based on the experimental data and extracted features. Gait analysis based on CW radar will provide a new method for clinical diagnosis and therapy. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Stability Analysis of Continuous Waves in Nonlocal Random Nonlinear Media

    Directory of Open Access Journals (Sweden)

    Maxim A. Molchan

    2007-08-01

    Full Text Available On the basis of the competing cubic-quintic nonlinearity model, stability (instability of continuous waves in nonlocal random non-Kerr nonlinear media is studied analytically and numerically. Fluctuating media parameters are modeled by the Gaussian white noise. It is shown that for different response functions of a medium nonlocality suppresses, as a rule, both the growth rate peak and bandwidth of instability caused by random parameters. At the same time, for a special form of the response functions there can be an ''anomalous'' subjection of nonlocality to the instability development which leads to further increase of the growth rate. Along with the second-order moments of the modulational amplitude, higher-order moments are taken into account.

  15. Modulated Sine Waves for Differential Absorption Measurements Using a CW Laser System

    Science.gov (United States)

    Campbell, Joel F. (Inventor); Lin, Bing (Inventor); Nehrir, Amin R. (Inventor)

    2015-01-01

    A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

  16. Detection of Laser Generated Ultrasonic Wave Using Michelson Interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Cho; Yamawaki, Hisashi [Japan National Research Institute, Ibaraki (Japan); Jhang, Kyung Young [Hanyang University, Seoul (Korea, Republic of)

    2000-02-15

    In this paper, ultrasonic wave in the thermoelastic regime was generated in a steel disk by illuminating a pulse laser (Q-switched Nd:YAG) on the surface of the sample and was detected on the other side by Michelson interferometer which was stabilized by feed back control. The experimentally detected displacement waveform of the ultrasonic wave showed good agreement with the theoretically expected one. Also it was shown that sound speeds of longitudinal and shear wave were similar to ones measured by pulse-echo method using a contact transducer. As an application of the noncontact ultrasonic measurement by using laser based ultrasonics, the sound speed in the sample was monitored while the sample was heated in a furnace, and the result showed that it decreased according to the increase of sample temperature

  17. Simulations of nonlinear continuous wave pressure fields in FOCUS

    Science.gov (United States)

    Zhao, Xiaofeng; Hamilton, Mark F.; McGough, Robert J.

    2017-03-01

    The Khokhlov - Zabolotskaya - Kuznetsov (KZK) equation is a parabolic approximation to the Westervelt equation that models the effects of diffraction, attenuation, and nonlinearity. Although the KZK equation is only valid in the far field of the paraxial region for mildly focused or unfocused transducers, the KZK equation is widely applied in medical ultrasound simulations. For a continuous wave input, the KZK equation is effectively modeled by the Bergen Code [J. Berntsen, Numerical Calculations of Finite Amplitude Sound Beams, in M. F. Hamilton and D. T. Blackstock, editors, Frontiers of Nonlinear Acoustics: Proceedings of 12th ISNA, Elsevier, 1990], which is a finite difference model that utilizes operator splitting. Similar C++ routines have been developed for FOCUS, the `Fast Object-Oriented C++ Ultrasound Simulator' (http://www.egr.msu.edu/˜fultras-web) to calculate nonlinear pressure fields generated by axisymmetric flat circular and spherically focused ultrasound transducers. This new routine complements an existing FOCUS program that models nonlinear ultrasound propagation with the angular spectrum approach [P. T. Christopher and K. J. Parker, J. Acoust. Soc. Am. 90, 488-499 (1991)]. Results obtained from these two nonlinear ultrasound simulation approaches are evaluated and compared for continuous wave linear simulations. The simulation results match closely in the farfield of the paraxial region, but the results differ in the nearfield. The nonlinear pressure field generated by a spherically focused transducer with a peak surface pressure of 0.2MPa radiating in a lossy medium with β = 3.5 is simulated, and the computation times are also evaluated. The nonlinear simulation results demonstrate acceptable agreement in the focal zone. These two related nonlinear simulation approaches are now included with FOCUS to enable convenient simulations of nonlinear pressure fields on desktop and laptop computers.

  18. Theoretical analysis of one dimensional gas dynamics of total pressure losses for combustion-driven continuous wave DF/HF chemical lasers%燃烧驱动CWDF/HF化学激光器总压损失的一维气体动力学理论分析

    Institute of Scientific and Technical Information of China (English)

    唐力铁; 李艳娜; 赵乐至

    2016-01-01

    The pressure recovery system is one of the key techniques for the high energy chemical lasers. Total pressure losses affect the key specification of lasers, such as the output ability, the size and weight of laser systems. The total pressure losses for combustion-driven continuous wave DF/HF chemical lasers were proposed according to the theory analysis of one dimensional gas exhausting. The analysis of the main factors of total pressure losses in the gain generator of the laser is the foundation of the research of recovering the gain generator with high pressure. Two major factors of total pressure losses caused by viscous friction and the temperature rise caused by chemical reaction in optical cavity were discussed in this paper. The result shows that temperature rise caused by burning has obvious influence on system's performance of pressure recovery.%压力恢复系统是目前高能化学激光器的关键部件,它的总压损失会影响到整个激光器系统的出光能力和全系统的体积重量等关键技术指标。为了研究燃烧驱动CW DF/HF化学激光器总压损失,从一维气体动力学进行了理论分析。分析在激光器增益发生器内引起总压损失的主要因素,是研究高压力恢复激光器增益发生器的基础。主要讨论了引起总压损失的两个主要原因:第一,由于粘性摩擦引起的总压损失;第二,由于光学谐振腔中化学反应放热升温引起的总压损失。计算结果表明,燃烧升温对系统的压力恢复能力有较大的影响。

  19. Real-time continuous-wave imaging with a 1.63THz OPTL and a pyroelectric camera

    Institute of Scientific and Technical Information of China (English)

    YANG Jun; RUAN Shuang-chen; ZHANG Min; ZHANG Wei

    2008-01-01

    Real-time continuous-wave terahertz imaging is demonstrated with a 1.63 THz (184.31 μm) optically-pumped terahertz laser (OPTL) and a 124 × 124 element room-temperature pyroelectric camera. Transmission-mode THz imaging is presented for the samples hidden in various wrapping materials. These experimental results reveal the possibility to construct a simple real-time THz imaging system applied to nondestructive inspection.

  20. Magneto-acoustic imaging by continuous-wave excitation.

    Science.gov (United States)

    Shunqi, Zhang; Zhou, Xiaoqing; Tao, Yin; Zhipeng, Liu

    2016-07-01

    The electrical characteristics of tissue yield valuable information for early diagnosis of pathological changes. Magneto-acoustic imaging is a functional approach for imaging of electrical conductivity. This study proposes a continuous-wave magneto-acoustic imaging method. A kHz-range continuous signal with an amplitude range of several volts is used to excite the magneto-acoustic signal and improve the signal-to-noise ratio. The magneto-acoustic signal amplitude and phase are measured to locate the acoustic source via lock-in technology. An optimisation algorithm incorporating nonlinear equations is used to reconstruct the magneto-acoustic source distribution based on the measured amplitude and phase at various frequencies. Validation simulations and experiments were performed in pork samples. The experimental and simulation results agreed well. While the excitation current was reduced to 10 mA, the acoustic signal magnitude increased up to 10(-7) Pa. Experimental reconstruction of the pork tissue showed that the image resolution reached mm levels when the excitation signal was in the kHz range. The signal-to-noise ratio of the detected magneto-acoustic signal was improved by more than 25 dB at 5 kHz when compared to classical 1 MHz pulse excitation. The results reported here will aid further research into magneto-acoustic generation mechanisms and internal tissue conductivity imaging.

  1. Extended and quasi-continuous tuning of quantum cascade lasers using superstructure gratings and integrated heaters

    Energy Technology Data Exchange (ETDEWEB)

    Bidaux, Yves, E-mail: yves.bidaux@alpeslasers.ch [Alpes Lasers SA, 1-3 Passsage Max Meuron, CH-2001 Neuchâtel (Switzerland); Institute for Quantum Electronics, ETH-Zurich, CH-8093 Zurich (Switzerland); Bismuto, Alfredo, E-mail: alfredo.bismuto@alpeslasers.ch; Tardy, Camille; Terazzi, Romain; Gresch, Tobias; Blaser, Stéphane; Muller, Antoine [Alpes Lasers SA, 1-3 Passsage Max Meuron, CH-2001 Neuchâtel (Switzerland); Faist, Jerome [Institute for Quantum Electronics, ETH-Zurich, CH-8093 Zurich (Switzerland)

    2015-11-30

    In this work, we demonstrate broad electrical tuning of quantum cascade lasers at 9.25 μm, 8.5 μm, and 4.4 μm in continuous wave operation using Vernier-effect distributed Bragg reflectors based on superstructure gratings. Integrated micro-heaters allow to switch from one Vernier channel to the other, while predictable and mode-hop free tuning can be obtained in each channel modulating the laser current with a side mode suppression ratio as high as 30 dB. The resulting device behaves effectively as a switchable multicolour tunable source. Tuning up to 6.5% of the central wavelength is observed. To prove the importance of the developed devices for high resolution molecular spectroscopy, a N{sub 2}O absorption spectrum has been measured.

  2. Influence of laser power on deposition of the chromium atomic beam in laser standing wave

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    One-dimensional deposition of collimated Cr atomic beam focused by a near-resonant Gaussian standing-laser field with wavelength of 425.55 nm is examined from particle-optics approach by using an adaptive step size,fourth-order Runge-Kutta type algorithm.The influence of laser power on deposition of atoms in laser standing wave is discussed and the simulative result shows that the FWHM of nanometer stripe is 102 nm and contrast is 2:1 with laser power equal to 3 mW,the FWHM is 1.2 nm and contrast is 32:1 with laser power equal to 16 mW,but with laser power increase,equal to 50 mW,the nonmeter structure forms the multi-crests and exacerbates.

  3. Influence of laser power on deposition of the chromium atomic beam in laser standing wave

    Institute of Scientific and Technical Information of China (English)

    ZHANG WenTao; ZHU BaoHua; ZHANG BaoWu; LI TongBao

    2009-01-01

    One-dimensional deposition of collimated Cr atomic beam focused by a near-resonant Gaussian standing-laser field with wavelength of 425.55 nm is examined from particle-optics approach by using an adaptive step size, fourth-order Runge-Kutta type algorithm. The influence of laser power on depo-sition of atoms in laser standing wave is discussed and the simulative result shows that the FWHM of nanometer stripe is 102 nm and contrast is 2:1 with laser power equal to 3 mW, the FWHM is 1.2 nm and contrast is 32:1 with laser power equal to 16 mW, but with laser power increase, equal to 50 mW, the nonmeter structure forms the multi-crests and exacerbates.

  4. Ultrarelativistic quasiclassical wave functions in strong laser and atomic fields

    CERN Document Server

    Di Piazza, A

    2014-01-01

    The problem of an ultrarelativistic charge in the presence of an atomic and a plane-wave field is investigated in the quasiclassical regime by including exactly the effects of both background fields. Starting from the quasiclassical Green's function obtained in [Phys. Lett. B \\textbf{717}, 224 (2012)], the corresponding in- and out-wave functions are derived in the experimentally relevant case of the particle initially counterpropagating with respect to the plane wave. The knowledge of these electron wave functions opens the possibility of investigating a variety of problems in strong-field QED, where both the atomic field and the laser field are strong enough to be taken into account exactly from the beginning in the calculations.

  5. Light wave interference during laser drilling of polymer coatings

    Science.gov (United States)

    Pargellis, A. N.; Au, D. T. W.; Kestenbaum, A.

    1988-12-01

    A CO2 laser has been used to drill holes in a 150-μm-thick, UV-curable, modified acrylate, polymer coating a copper substrate. A typical hole is 100-150 μm in diameter. The holes in this study were each made with a single laser pulse of 10.6-μm wavelength, duration 100 or 200 μs, and 4-20 mJ energy. Two superimposed sets of periodic ripples have been observed on the hole walls. The shorter wavelength varies from 4.0 μm at the top of the hole to 5.3 μm at the bottom of the hole. The longer wavelength appears to be 13.2 μm and is attenuated as the wave propagates towards the copper substrate. The experimental data are compared with values calculated using a model that considers the interference of a standing wave inside the hole with radiation propagating through the dielectric surrounding the hole. The amplitude (trough-to-peak distance) of the waves in the hole wall is about half the wavelength of the standing waves. The long-wavelength waves (13.2 μm) yield ripples in the wall of 6.5-μm amplitude. These ripples give 13.0 μm (0.5 mils) as an ultimate lower limit for laser drilling holes using the 10.6-μm wavelengths obtained with a CO2 laser. Chemical etching of the polymer causes all of the holes to have thin rims surrounding the top of the hole. This is due to accelerated etching of the less cured polymer material inside the hole. A chemical etching process etches away some of the ripple pattern, particularly near the top of the hole.

  6. Design of continuous long slot leaky-wave antenna for millimeter wave application

    Institute of Scientific and Technical Information of China (English)

    Lü Shanwei; Zhang Yan; Liu Juan; Zhang Jiangling

    2007-01-01

    A simple and efficient design scheme of the continuous long slot leaky-wave antenna is developed. The key steps involved in the scheme are summarized. First, the cut-off frequencies of slot waveguides with different slot offsets are obtained by 3D finite-difference time-domain (FDTD) method. Second, the attenuation function αra is estimated by the aperture distribution, and the attenuation function αrs is determined by the slot radiation.Finally, the attenuation function αra is combined with the attenuation function αrs by the coefficient K. And an example in Ka band is presented. Moreover, the return loss of the E-plane Tee-junction (ET) and the radiation pattern of leaky-wave antenna are simulated. The scheme is verified by comparing with the experimental result.

  7. Directed searches for continuous gravitational waves from spinning neutron stars in binary systems

    Science.gov (United States)

    Meadors, Grant David

    2014-09-01

    Gravitational wave detectors such as the Laser Interferometer Gravitational-wave Observatory (LIGO) seek to observe ripples in space predicted by General Relativity. Black holes, neutron stars, supernovae, the Big Bang and other sources can radiate gravitational waves. Original contributions to the LIGO effort are presented in this thesis: feedforward filtering, directed binary neutron star searches for continuous waves, and scientific outreach and education, as well as advances in quantum optical squeezing. Feedforward filtering removes extraneous noise from servo-controlled instruments. Filtering of the last science run, S6, improves LIGO's astrophysical range (+4.14% H1, +3.60% L1: +12% volume) after subtracting noise from auxiliary length control channels. This thesis shows how filtering enhances the scientific sensitivity of LIGO's data set during and after S6. Techniques for non-stationarity and verifying calibration and integrity may apply to Advanced LIGO. Squeezing is planned for future interferometers to exceed the standard quantum limit on noise from electromagnetic vacuum fluctuations; this thesis discusses the integration of a prototype squeezer at LIGO Hanford Observatory and impact on astrophysical sensitivity. Continuous gravitational waves may be emitted by neutron stars in low-mass X-ray binary systems such as Scorpius X-1. The TwoSpect directed binary search is designed to detect these waves. TwoSpect is the most sensitive of 4 methods in simulated data, projecting an upper limit of 4.23e-25 in strain, given a year-long data set at an Advanced LIGO design sensitivity of 4e-24 Hz. (-1/2). TwoSpect is also used on real S6 data to set 95% confidence upper limits (40 Hz to 2040 Hz) on strain from Scorpius X-1. A millisecond pulsar, X-ray transient J1751-305, is similarly considered. Search enhancements for Advanced LIGO are proposed. Advanced LIGO and fellow interferometers should detect gravitational waves in the coming decade. Methods in these

  8. Continuous Earth Rotation Monitoring with the large Ring Laser G

    Science.gov (United States)

    Schreiber, K. U.; Klügel, T.; Wells, J. P.; Holdaway, J.; Gebauer, A.

    2010-12-01

    Over the last decade, ring lasers have found their way back into the research laboratories. By scaling them up in size, they have gained several orders of magnitude over their commercial counterparts, both in sensitivity and stability. Unlike the established space geodetic techniques SLR/LLR and VLBI, ring lasers can be operated autonomous and continuously. Furthermore laser gyros reach a resolution of 1 pico-rad/s already after an integration time of less than 2 hours. This opens the door for the research of high frequency variations in Earth rotation. Over the last year we have improved the sensor sensitivity by as much as a factor of 3 in order to reach the shot noise limit at 2.1x10-11 rad/s/sqrt(Hz). So the regime of ΔΩ/Ω ≈ 10-9 of Earth rotation becomes accessible to a local rotation sensor. Recent efforts concentrate on the reduction of scale factor instability by controlling the drift induced by atmospheric pressure variations and the corresponding temperature changes from adiabatic expansion and compression of the local air as well as a new approach to the modeling of the behavior of the sensor location. This talk outlines recent progress in Sagnac interferometry.

  9. Hidden Markov model tracking of continuous gravitational waves from a neutron star with wandering spin

    Science.gov (United States)

    Suvorova, S.; Sun, L.; Melatos, A.; Moran, W.; Evans, R. J.

    2016-06-01

    Gravitational wave searches for continuous-wave signals from neutron stars are especially challenging when the star's spin frequency is unknown a priori from electromagnetic observations and wanders stochastically under the action of internal (e.g., superfluid or magnetospheric) or external (e.g., accretion) torques. It is shown that frequency tracking by hidden Markov model (HMM) methods can be combined with existing maximum likelihood coherent matched filters like the F -statistic to surmount some of the challenges raised by spin wandering. Specifically, it is found that, for an isolated, biaxial rotor whose spin frequency walks randomly, HMM tracking of the F -statistic output from coherent segments with duration Tdrift=10 d over a total observation time of Tobs=1 yr can detect signals with wave strains h0>2 ×10-26 at a noise level characteristic of the Advanced Laser Interferometer Gravitational Wave Observatory (Advanced LIGO). For a biaxial rotor with randomly walking spin in a binary orbit, whose orbital period and semimajor axis are known approximately from electromagnetic observations, HMM tracking of the Bessel-weighted F -statistic output can detect signals with h0>8 ×10-26. An efficient, recursive, HMM solver based on the Viterbi algorithm is demonstrated, which requires ˜103 CPU hours for a typical, broadband (0.5-kHz) search for the low-mass x-ray binary Scorpius X-1, including generation of the relevant F -statistic input. In a "realistic" observational scenario, Viterbi tracking successfully detects 41 out of 50 synthetic signals without spin wandering in stage I of the Scorpius X-1 Mock Data Challenge convened by the LIGO Scientific Collaboration down to a wave strain of h0=1.1 ×10-25, recovering the frequency with a root-mean-square accuracy of ≤4.3 ×10-3 Hz .

  10. A generic travelling wave solution in dissipative laser cavity

    Indian Academy of Sciences (India)

    BALDEEP KAUR; SOUMENDU JANA

    2016-10-01

    A large family of cosh-Gaussian travelling wave solution of a complex Ginzburg–Landau equation (CGLE), that describes dissipative semiconductor laser cavity is derived. Using perturbation method, the stability region is identified. Bifurcation analysis is done by smoothly varying the cavity loss coefficient to provide insight of the system dynamics. He’s variational method is adopted to obtain the standard sech-type and the notso-explored but promising cosh-Gaussian type, travelling wave solutions. For a given set of system parameters, only one sech solution is obtained, whereas several distinct solution points are derived for cosh-Gaussian case. These solutions yield a wide variety of travelling wave profiles, namely Gaussian, near-sech, flat-top and a cosh-Gaussian with variable central dip. A split-step Fourier method and pseudospectral method have been used for direct numerical solution of the CGLE and travelling wave profiles identical to the analytical profiles have been obtained. We also identified the parametric zone that promises an extremely large family of cosh-Gaussian travelling wave solutions with tunable shape. This suggests that the cosh-Gaussian profile is quite generic and would be helpful for further theoretical as well as experimental investigation on pattern formation, pulse dynamics and localization in semiconductor laser cavity.

  11. Multiple structure of a laser-induced underwater shock wave

    CERN Document Server

    Tagawa, Yoshiyuki; Hayasaka, Keisuke; Kameda, Masaharu

    2015-01-01

    The structure of a laser-induced underwater shock wave is examined. Plasma formation, shock-wave expansion, and temporal evolution of shock pressure are observed simultaneously using a combined measurement system that obtains high-resolution nanosecond-order image sequences. In contrast to a well-known spherical-shock model, these detailed measurements reveal a non-spherically-symmteric distribution of pressure peak for a wide range of experimental parameters. The structure is determined to be a collection of multiple spherical shocks originated from elongated plasmas.

  12. Continuous-wave mid-infrared photonic crystal light emitters at room temperature

    Science.gov (United States)

    Weng, Binbin; Qiu, Jijun; Shi, Zhisheng

    2017-01-01

    Mid-infrared photonic crystal enhanced lead-salt light emitters operating under continuous-wave mode at room temperature were investigated in this work. For the device, an active region consisting of 9 pairs of PbSe/Pb0.96Sr0.04Se quantum wells was grown by molecular beam epitaxy method on top of a Si(111) substrate which was initially dry-etched with a two-dimensional photonic crystal structure in a pattern of hexagonal holes. Because of the photonic crystal structure, an optical band gap between 3.49 and 3.58 µm was formed, which matched with the light emission spectrum of the quantum wells at room temperature. As a result, under optical pumping, using a near-infrared continuous-wave semiconductor laser, the device exhibited strong photonic crystal band-edge mode emissions and delivered over 26.5 times higher emission efficiency compared to the one without photonic crystal structure. The output power obtained was up to 7.68 mW (the corresponding power density was 363 mW/cm2), and a maximum quantum efficiency reached to 1.2%. Such photonic crystal emitters can be used as promising light sources for novel miniaturized gas-sensing systems.

  13. Search for continuous gravitational waves: Improving robustness versus instrumental artifacts

    Science.gov (United States)

    Keitel, David; Prix, Reinhard; Papa, Maria Alessandra; Leaci, Paola; Siddiqi, Maham

    2014-03-01

    The standard multidetector F-statistic for continuous gravitational waves is susceptible to false alarms from instrumental artifacts, for example monochromatic sinusoidal disturbances ("lines"). This vulnerability to line artifacts arises because the F-statistic compares the signal hypothesis to a Gaussian-noise hypothesis, and hence is triggered by anything that resembles the signal hypothesis more than Gaussian noise. Various ad-hoc veto methods to deal with such line artifacts have been proposed and used in the past. Here we develop a Bayesian framework that includes an explicit alternative hypothesis to model disturbed data. We introduce a simple line model that defines lines as signal candidates appearing only in one detector. This allows us to explicitly compute the odds between the signal hypothesis and an extended noise hypothesis, resulting in a new detection statistic that is more robust to instrumental artifacts. We present and discuss results from Monte-Carlo tests on both simulated data and on detector data from the fifth LIGO science run. We find that the line-robust statistic retains the detection power of the standard F-statistic in Gaussian noise. In the presence of line artifacts it is more sensitive, even compared to the popular F-statistic consistency veto, over which it improves by as much as a factor of two in detectable signal strength.

  14. Higher Order Mode Coupler Heating in Continuous Wave Operation

    Science.gov (United States)

    Solyak, N.; Awida, M.; Hocker, A.; Khabibobulline, T.; Lunin, A.

    Electromagnetic heating due to higher order modes (HOM) propagation is particularly a concern for continuous wave (CW) particle accelerator machines. Power on the order of several watts could flow out of the cavity's HOM ports in CW operations. The upgrade of the Linac Coherent Light Source (LCLS-II) at SLAC requires a major modification of the design of the higher order mode (HOM) antenna and feed through of the conventional ILC elliptical 9-cell cavity in order to utilize it for LCLS-II. The HOM antenna is required to bear higher RF losses, while relatively maintaining the coupling level of the higher order modes. In this paper, we present a detailed analysis of the heating expected in the HOM coupler with a thorough thermal quench study in comparison with the conventional ILC design. We discuss also how the heat will be removed from the cavity through RF cables with specially designed cooling straps. Finally, we report on the latest experimental results of cavity testing in vertical and horizontal cryostats.

  15. Detection of laser generated ultrasonic wave using Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Cho; Nakano, Hidetoshi [Japan National Research Laboratory of Metrology, Tokyo (Korea, Republic of); Jhang, Kyung Young [School of Mechanical Engineering, Seoul (Korea, Republic of)

    1999-05-15

    A stabilized Michelson Interferometer is proposed in order to detect the laser-generated ultrasonic waves in fee from the external noise such as low frequency mechanical vibration. In order to confirm the performance, theoretically expected waveforms were compared with experimentally detected ones in thermo-elastic region, where we generated ultrasonic wave in steel disk by using a Q-switched Nd:YAG laser. Also sound velocities of longitudinal and shear components were measured and they showed good agreement with the typical values in steel. Finally, the change of sound velocity according to the temperature change was measured to show that the proposed technique could be applied to the characterization of high temperature materials.

  16. Laser-generated acoustic wave studies on tattoo pigment

    Science.gov (United States)

    Paterson, Lorna M.; Dickinson, Mark R.; King, Terence A.

    1996-01-01

    A Q-switched alexandrite laser (180 ns at 755 nm) was used to irradiate samples of agar embedded with red, black and green tattoo dyes. The acoustic waves generated in the samples were detected using a PVDF membrane hydrophone and compared to theoretical expectations. The laser pulses were found to generate acoustic waves in the black and green samples but not in the red pigment. Pressures of up to 1.4 MPa were produced with irradiances of up to 96 MWcm-2 which is comparable to the irradiances used to clear pigment embedded in skin. The pressure gradient generated across pigment particles was approximately 1.09 X 1010 Pam-1 giving a pressure difference of 1.09 +/- 0.17 MPa over a particle with mean diameter 100 micrometers . This is not sufficient to permanently damage skin which has a tensile strength of 7.4 MPa.

  17. Laser ablation method for production of surface acoustic wave sensors

    Science.gov (United States)

    Lukyanov, Dmitry; Shevchenko, Sergey; Kukaev, Alexander; Safronov, Daniil

    2016-10-01

    Nowadays surface acoustic wave (SAW) sensors are produced using a photolithography method. In case of inertial sensors it suffers several disadvantages, such as difficulty in matching topologies produced on opposite sides of the wafer, expensive in small series production, not allowing further topology correction. In this case a laser ablation method seems promising. Details of a proposed technique are described in the paper along with results of its experimental test and discussion.

  18. Generation of Laser Light via Ultrasonic Four-wave Mixing

    Institute of Scientific and Technical Information of China (English)

    OU Fa; WU Fugen; HE Minggao

    2001-01-01

    On the basis of the interaction between phonons in ionic crystals with anharmonic lattice vibration, we present a laser model on acoustic nondegenerate four-wave mixing. Two beams of highfrequency ultrasound, incident on the acoustic cavity fulfilled with the medium of ionic crystal, play the role of pumping and one of the two side-band modes of the pumping frequency as an acoustic signal mode has a strong interaction with the optical cavity mode, the coupling-out of which wiIl be the light (far-infrared) output of a laser. The problem is treated with quantum-mechanics. The theory shows that there is the threshold phenomenon as usual lasers and a so called "phase-matching" condition is derived, which should be satisfied for stability of the system.

  19. Investigation of surface acoustic waves in laser shock peened metals

    Institute of Scientific and Technical Information of China (English)

    Ling Yuan; Gang Yan; Zhonghua Shen; Hangwei Xu; Xiaowu Ni; Jian Lu

    2008-01-01

    Laser shock peening is a well-known method for extending the fatigue life of metal components by introducing near-surface compressive residual stress. The surface acoustic waves (SAWs) are dispersive when the near-surface properties of materials are changed. So the near-surface properties (such as the thickness of hardened layers, elastic properties, residual stresses, etc.) can be analyzed by the phase velocity dispersion. To study the propagation of SAWs in metal samples after peening, a more reasonable experimental method of broadband excitation and reception is introduced. The ultrasonic signals are excited by laser and received by polyvinylindene fluoride (PVDF) transducer. The SAW signals in aluminum alloy materials with different impact times by laser shock peening are detected. Signal spectrum and phase velocity dispersion curves of SAWs are analyzed. Moreover, reasons for dispersion are discussed.

  20. Capillary Waves And Energy Coupling In Laser Materials Processing

    Science.gov (United States)

    Gasser, A.; Herziger, G.; Holtgen, B.; Kreutz, E. W.; Treusch, H. G.

    1987-09-01

    Static and dynamic measurements of the incident laser power, of the diffuse and specular reflected power have been performed in order to determine the absorption behavior of various metals and semiconductors during the interaction with powerful CO2-and Nd:YAG-laser-radiation. The absorptivity of the vapor and laser-induced plasma was probed by high-speed photography and measurements of conductivity transients as a function of intensity, composition, and pressure of the ambient atmosphere. For IIB the intensity-dependent energy coupling is governed by the generation of photon-induced plasma in the surface region in combination with the dynamics of the molten and vaporized material within the interaction zone giving in addition indication for capillary waves.

  1. Long distance high power optical laser fiber break detection and continuity monitoring systems and methods

    Energy Technology Data Exchange (ETDEWEB)

    Rinzler, Charles C.; Gray, William C.; Faircloth, Brian O.; Zediker, Mark S.

    2016-02-23

    A monitoring and detection system for use on high power laser systems, long distance high power laser systems and tools for performing high power laser operations. In particular, the monitoring and detection systems provide break detection and continuity protection for performing high power laser operations on, and in, remote and difficult to access locations.

  2. Long distance high power optical laser fiber break detection and continuity monitoring systems and methods

    Energy Technology Data Exchange (ETDEWEB)

    Rinzler, Charles C.; Gray, William C.; Faircloth, Brian O.; Zediker, Mark S.

    2016-02-23

    A monitoring and detection system for use on high power laser systems, long distance high power laser systems and tools for performing high power laser operations. In particular, the monitoring and detection systems provide break detection and continuity protection for performing high power laser operations on, and in, remote and difficult to access locations.

  3. LIGO: the Laser Interferometer Gravitational-Wave Observatory

    Science.gov (United States)

    Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arain, M. A.; Araya, M.; Armandula, H.; Armor, P.; Aso, Y.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballmer, S.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Behnke, B.; Benacquista, M.; Betzwieser, J.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Biswas, R.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bodiya, T. P.; Bogue, L.; Bork, R.; Boschi, V.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Bridges, D. O.; Brinkmann, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Brunet, G.; Bullington, A.; Buonanno, A.; Burmeister, O.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Cannizzo, J.; Cannon, K. C.; Cao, J.; Cardenas, L.; Caride, S.; Castaldi, G.; Caudill, S.; Cavaglià, M.; Cepeda, C.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Christensen, N.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cokelaer, T.; Colacino, C. N.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Cornish, N.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Danilishin, S. L.; Danzmann, K.; Daudert, B.; Davies, G.; Daw, E. J.; DeBra, D.; Degallaix, J.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Drever, R. W. P.; Dueck, J.; Duke, I.; Dumas, J.-C.; Dwyer, J. G.; Echols, C.; Edgar, M.; Effler, A.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Faltas, Y.; Fan, Y.; Fazi, D.; Fehrmenn, H.; Finn, L. S.; Flasch, K.; Foley, S.; Forrest, C.; Fotopoulos, N.; Franzen, A.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Garofoli, J. A.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Goda, K.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Grimaldi, F.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G. D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Hoyland, D.; Hughey, B.; Huttner, S. H.; Ingram, D. R.; Isogai, T.; Ito, M.; Ivanov, A.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khan, R.; Khazanov, E.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kozak, D.; Krishnan, B.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lei, H.; Lei, M.; Leindecker, N.; Leonor, I.; Li, C.; Lin, H.; Lindquist, P. E.; Littenberg, T. B.; Lockerbie, N. A.; Lodhia, D.; Longo, M.; Lormand, M.; Lu, P.; Lubiński, M.; Lucianetti, A.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Mandel, I.; Mandic, V.; Márka, S.; Márka, Z.; Markosyan, A.; Markowitz, J.; Maros, E.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McIntyre, G.; McKechan, D. J. A.; McKenzie, K.; Mehmet, M.; Melatos, A.; Melissinos, A. C.; Menéndez, D. F.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miller, J.; Minelli, J.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohanty, S. D.; Mohapatra, S. R. P.; Moreno, G.; Morioka, T.; Mors, K.; Mossavi, K.; Mow Lowry, C.; Mueller, G.; Müller-Ebhardt, H.; Muhammad, D.; Mukherjee, S.; Mukhopadhyay, H.; Mullavey, A.; Munch, J.; Murray, P. G.; Myers, E.; Myers, J.; Nash, T.; Nelson, J.; Newton, G.; Nishizawa, A.; Numata, K.; O'Dell, J.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; Ogin, G. H.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pan, Y.; Pankow, C.; Papa, M. A.; Parameshwaraiah, V.; Patel, P.; Pedraza, M.; Penn, S.; Perraca, A.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Postiglione, F.; Principe, M.; Prix, R.; Prokhorov, L.; Punken, O.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raics, Z.; Rainer, N.; Rakhmanov, M.; Raymond, V.; Reed, C. M.; Reed, T.; Rehbein, H.; Reid, S.

    2009-07-01

    The goal of the Laser Interferometric Gravitational-Wave Observatory (LIGO) is to detect and study gravitational waves (GWs) of astrophysical origin. Direct detection of GWs holds the promise of testing general relativity in the strong-field regime, of providing a new probe of exotic objects such as black holes and neutron stars and of uncovering unanticipated new astrophysics. LIGO, a joint Caltech-MIT project supported by the National Science Foundation, operates three multi-kilometer interferometers at two widely separated sites in the United States. These detectors are the result of decades of worldwide technology development, design, construction and commissioning. They are now operating at their design sensitivity, and are sensitive to gravitational wave strains smaller than one part in 1021. With this unprecedented sensitivity, the data are being analyzed to detect or place limits on GWs from a variety of potential astrophysical sources.

  4. LIGO - The Laser Interferometer Gravitational-Wave Observatory

    Science.gov (United States)

    Abramovici, Alex; Althouse, William E.; Drever, Ronald W. P.; Gursel, Yekta; Kawamura, Seiji; Raab, Frederick J.; Shoemaker, David; Sievers, Lisa; Spero, Robert E.; Thorne, Kip S.

    1992-01-01

    The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics for gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGO's gravitational-wave searches will begin in 1998.

  5. LIGO: The Laser Interferometer Gravitational-Wave Observatory.

    Science.gov (United States)

    Abramovici, A; Althouse, W E; Drever, R W; Gürsel, Y; Kawamura, S; Raab, F J; Shoemaker, D; Sievers, L; Spero, R E; Thorne, K S; Vogt, R E; Weiss, R; Whitcomb, S E; Zucker, M E

    1992-04-17

    The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics of gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGO's gravitational-wave searches will begin in 1998.

  6. Radar and Laser Sensors for High Frequency Ocean Wave Measurement.

    Science.gov (United States)

    Kennedy, C. R.

    2016-02-01

    Experimental measurement of air-sea fluxes invariably take place using shipbourne instrumentation and simultaneous measurement of wave height and direction is desired. A number of researchers have shown that range measuring sensors combined with inertial motion compensation can be successful on board stationary or very slowly moving ships. In order to measure wave characteristics from ships moving at moderate to full speed the sensors are required to operate at higher frequency so as to overcome the Doppler shift caused by ship motion. This work presents results from some preliminary testing of laser, radar and ultrasonic range sensors in the laboratory and on board ship. The characteristics of the individual sensors are discussed and comparison of the wave spectra produced by each is presented.

  7. LIGO - The Laser Interferometer Gravitational-Wave Observatory

    Science.gov (United States)

    Abramovici, Alex; Althouse, William E.; Drever, Ronald W. P.; Gursel, Yekta; Kawamura, Seiji; Raab, Frederick J.; Shoemaker, David; Sievers, Lisa; Spero, Robert E.; Thorne, Kip S.

    1992-01-01

    The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics for gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGO's gravitational-wave searches will begin in 1998.

  8. Laser Plasmas : Effect of rippled laser beam on excitation of ion acoustic wave

    Indian Academy of Sciences (India)

    Nareshpal Singh Saini; Tarsem Singh Gill

    2000-11-01

    Growth of a radially symmetrical ripple, superimposed on a Gaussian laser beam in collisional unmagnetised plasma is investigated. From numerical computation, it is observed that self-focusing of main beam as well as ripple determine the growth dynamics of ripple with the distance of propagation. The effect of growing ripple on excitation of ion acoustic wave (IAW) has also been studied

  9. Toward the Extreme Ultra Violet Four Wave Mixing Experiments: From Table Top Lasers to Fourth Generation Light Sources

    Directory of Open Access Journals (Sweden)

    Riccardo Cucini

    2015-01-01

    Full Text Available Three different Transient Grating setups are presented, with pulsed and continuous wave probe at different wavelengths, ranging from infrared to the extreme ultra violet region. Both heterodyne and homodyne detections are considered. Each scheme introduces variations with respect to the previous one, allowing moving from classical table top laser experiments towards a new four wave mixing scheme based on free electron laser radiation. A comparison between the various setups and the first results from extreme ultra violet transient grating experiments is also discussed.

  10. Theory of a ring laser. [electromagnetic field and wave equations

    Science.gov (United States)

    Menegozzi, L. N.; Lamb, W. E., Jr.

    1973-01-01

    Development of a systematic formulation of the theory of a ring laser which is based on first principles and uses a well-known model for laser operation. A simple physical derivation of the electromagnetic field equations for a noninertial reference frame in uniform rotation is presented, and an attempt is made to clarify the nature of the Fox-Li modes for an open polygonal resonator. The polarization of the active medium is obtained by using a Fourier-series method which permits the formulation of a strong-signal theory, and solutions are given in terms of continued fractions. It is shown that when such a continued fraction is expanded to third order in the fields, the familiar small-signal ring-laser theory is obtained.

  11. Statistical reconstruction algorithms for continuous wave electron spin resonance imaging

    Science.gov (United States)

    Kissos, Imry; Levit, Michael; Feuer, Arie; Blank, Aharon

    2013-06-01

    Electron spin resonance imaging (ESRI) is an important branch of ESR that deals with heterogeneous samples ranging from semiconductor materials to small live animals and even humans. ESRI can produce either spatial images (providing information about the spatially dependent radical concentration) or spectral-spatial images, where an extra dimension is added to describe the absorption spectrum of the sample (which can also be spatially dependent). The mapping of oxygen in biological samples, often referred to as oximetry, is a prime example of an ESRI application. ESRI suffers frequently from a low signal-to-noise ratio (SNR), which results in long acquisition times and poor image quality. A broader use of ESRI is hampered by this slow acquisition, which can also be an obstacle for many biological applications where conditions may change relatively quickly over time. The objective of this work is to develop an image reconstruction scheme for continuous wave (CW) ESRI that would make it possible to reduce the data acquisition time without degrading the reconstruction quality. This is achieved by adapting the so-called "statistical reconstruction" method, recently developed for other medical imaging modalities, to the specific case of CW ESRI. Our new algorithm accounts for unique ESRI aspects such as field modulation, spectral-spatial imaging, and possible limitation on the gradient magnitude (the so-called "limited angle" problem). The reconstruction method shows improved SNR and contrast recovery vs. commonly used back-projection-based methods, for a variety of simulated synthetic samples as well as in actual CW ESRI experiments.

  12. Continued advancement of laser damage resistant optically functional microstructures

    Science.gov (United States)

    Hobbs, Douglas S.; MacLeod, Bruce D.; Sabatino, Ernest

    2012-11-01

    Micro- and nano-structured optically functional surface textures continue to exhibit higher performance and longer term survivability than thin-film coatings for an increasing number of materials used within high energy laser (HEL) systems. Anti-reflection (AR) microstructures (ARMs) produce a graded refractive index yielding high transmission over wide spectral ranges along with a chemical, mechanical and laser damage resistance inherited from the bulk optic material. In this study, ARMs were fabricated in the relevant HEL materials sapphire, neodymium-doped YAG, fused silica, BK7 glass, and the magnesium aluminate known as SPINEL. Standardized pulsed laser induced damage threshold (LiDT) measurements were made using commercial testing services to directly compare the damage resistance of ARMs-treated optics to uncoated and thin-film-AR-coated (TFARC) optics at wavelengths of 532nm, 694nm, 800nm, 1064nm, and 1538nm. As found with prior work, the LiDT of ARMs etched in fused silica was typically in the range of 35 J/cm2 at a wavelength of 1064nm and a pulse width of 10ns, a level that is comparable to uncoated samples and 3.5 times greater than the level specified by six prominent TFARC providers. The Army Research Laboratory measured the pulsed LiDT at 532nm (10ns) of ARMs in fused silica to be up to 5 times the level of the ion beam sputtered TFARC previously employed in their HEL system, and 2 times higher than a low performance single layer MgF2 TFARC. This result was repeated and expanded using a commercial LiDT testing service for ARMs in two types of fused silica and for Schott N-BK7 glass. An average damage threshold of 26.5 J/cm2 was recorded for the ARMs-treated glass materials, a level 4 times higher than the commercial IBS TFARCs tested.

  13. Laser light scattering in a laser-induced argon plasma: Investigations of the shock wave

    Energy Technology Data Exchange (ETDEWEB)

    Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI, site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France)

    2012-08-15

    Shock wave produced by a laser induced spark in argon at atmospheric pressure was examined using Rayleigh and Thomson scattering. The spark was generated by focusing a laser pulse from the second harmonic ({lambda} = 532 nm) of a nanosecond Nd:YAG laser using an 80 mm focal length lens, with a fluence of 2 kJ{center_dot}cm{sup -2}. Images of the spark emission were recorded for times between 30 ns and 100 {mu}s after the laser pulse in order to characterize its spatial evolution. The position of the shock wave at several instants of its evolution and for several plasma regions was determined from the Rayleigh-scattered light of another nanosecond Nd:YAG laser (532 nm, 40 J{center_dot}cm{sup -2} fluence). Simultaneously, Thomson scattering technique was applied to determine the electron density and temperature in the hot plasma core. Attempts were made to describe the temporal evolution of the shock wave within a self-similar model, both by the simple Sedov-Taylor formula as well as its extension deduced by de Izarra. The temporal radial evolution of the shock position is similar to that obtained within theory taking into account the counter pressure of the ambient gas. Density profiles just behind the shock front are in qualitative agreement with those obtained by numerically solving the Euler equations for instantaneous explosion at a point with counter pressure. - Highlights: Black-Right-Pointing-Pointer We investigated shock wave evolution by Rayleigh scattering method. Black-Right-Pointing-Pointer 2D map of shockwave position for several times after plasma generation is presented. Black-Right-Pointing-Pointer Shock wave evolution is not satisfactorily described within self-similar models. Black-Right-Pointing-Pointer Evolution of shock position similar to theory taking into account counter pressure. Black-Right-Pointing-Pointer Density profile behind the shock similar to numerical solution of Euler equations.

  14. Corner-Pumped Nd:YAG/YAG Composite Slab Continuous-Wave 1.1μm Multi-Wavelength Laser%角抽运Nd:YAG复合板条1.1μm多波长连续运转激光器

    Institute of Scientific and Technical Information of China (English)

    刘欢; 巩马理

    2011-01-01

    Corner-pumped type is a new pumping type in the laser diode-pumped solid-state lasers, which has the advantages of high pump efficiency and favorable pump uniformity. Using the single corner pumped type, an efficient corner-pumped Nd: YAG/YAG composite slab continuous-wave 1.1 μm multi-wavelength laser is demonstrated in this paper. The compact plano-plane linear cavity configuration is adopted and the cavity length is only 22 mm. When the pump power is 50.3 W, the maximal output power is up to 10.9 W with an optical-to-optical conversion efficiency of 21.7% and a slope efficiency of 22%. The short-term instability of the output power is better than 0.6% when the pump power is 48 W.%报道了一种适合中小功率输出的全固态激光器的角抽运方法,抽运光从板条激光器中板条晶体的角部入射,可获得较高的抽运效率和较好的抽运均匀性.采用单角抽运方式,进行了角抽运Nd:YAG复合板条1.1μm多波长连续运转激光器的实验研究.激光腔采用紧凑型平-平直腔结构,腔长仅为22 mm.当注入抽运功率为50.3 W时,1.1 μm多波长激光连续输出功率最高达10.9 W,光-光转换效率为21.7%,斜率效率为22%.当注入抽运功率为48 W时,1.1μm多波长激光连续输出功率短期不稳定性小于0.6%.

  15. Detailed Characterization of Continuous-Wave and Pulsed-Pump Four-Wave Mixing in Nonlinear Fibers

    DEFF Research Database (Denmark)

    Lillieholm, Mads; Galili, Michael; Grüner-Nielsen, Lars;

    2016-01-01

    We explore the parametric gain differences for continuous-wave and pulse-pumped four-wave mixing, using various highly nonlinear fibers. Detailed simulations support our findings that the dispersion slope determines the experimentally observed differences, limiting the pulsed-pump performance....

  16. Numerical analysis to four-wave mixing induced spectral broadening in high power fiber lasers

    Science.gov (United States)

    Feng, Yujun; Wang, Xiaojun; Ke, Weiwei; Sun, Yinhong; Zhang, Kai; Ma, Yi; Li, Tenglong; Wang, Yanshan; Wu, Juan

    2015-02-01

    For powers exceeding a threshold the spectral broadening in fiber amplifiers becomes a significant challenge for the development of high power narrow bandwidth fiber lasers. In this letter, we show that the spectral broadening can be partly caused by four-wave mixing(FWM) process in which the power of the central wavelength would transfer to the side ones. A practical FWM induced spectral broadening theory has been derived from the early works. A numerical model of fiber amplifier has been established and FWM process has been added to the model. During the simulation process, we find that when a 10 GHz, several watts narrow bandwidth laser is seeded into a few modes fiber laser amplifier, the FWM induced spectral broadening effect might continually increase the FWHM of the spectra of the continuum laser to 100 GHz within the amplification process to several hundred watts which has been convinced by our experiments. Some other results have also been analyzed in this paper to complete the four-wave mixing induced spectral broadening theory in fiber amplifiers.

  17. Externally induced continuous variable entanglement in a correlated emission laser

    Energy Technology Data Exchange (ETDEWEB)

    Tesfa, Sintayehu [Physics Department, Addis Ababa University, PO Box 1176, Addis Ababa (Ethiopia)], E-mail: sint_tesfa@yahoo.com

    2008-07-28

    Analysis of the externally induced quantum features of the cavity radiation of the two-photon correlated emission laser is presented. It turns out that the pumping process induces atomic coherence accountable for observing entanglement in the cavity radiation as well as the nonclassical photon number correlation despite the arising vacuum fluctuations. Even though a significant continuous variable entanglement is obtained near threshold in the strong driving limit, increasing the amplitude of the driving radiation more than required for a fixed value of the linear gain coefficient is found to degrade the degree of entanglement. The two-mode squeezing of the superimposed radiation, entanglement of the cavity radiation and mean number of photon pairs increase with the rate at which the atoms are injected into the cavity, but the nonclassical photon number correlation decreases. Moreover, the mean photon number corresponding to the transition from the upper energy level to the intermediate is found to be greater than the transition from the intermediate to the lower. With conceivable practical challenges, it is in principle possible to generate an intense continuous variable entanglement and quantify it via photon count measurements.

  18. Variational space-time (dis)continuous Galerkin method for nonlinear free surface waves

    OpenAIRE

    Gagarina, E; Vegt, van der, N.F.A.; Ambati, V.R.; Bokhove, O.

    2013-01-01

    A new variational finite element method is developed for nonlinear free surface gravity water waves. This method also handles waves generated by a wave maker. Its formulation stems from Miles' variational principle for water waves together with a space-time finite element discretization that is continuous in space and discontinuous in time. The key features of this formulation are: (i) a discrete variational approach that gives rise to conservation of discrete energy and phase space and prese...

  19. Parametric four-wave mixing using a single cw laser

    CERN Document Server

    Brekke, E

    2013-01-01

    Four-wave mixing can be used to generate coherent output beams, with frequencies difficult to acquire in commercial lasers. Here a single narrow ECDL locked to the two photon 5s-5d transition in rubidium is combined with a tapered amplifier system to produce a high power cw beam at 778 nm and used to generate coherent light at 420 nm through parametric four-wave mixing. This process is analyzed in terms of the the intensity and frequency of the incoming beam as well as the atomic density of the sample. The efficiency of the process is currently limited when on resonance due to the absorption of the 420 nm beam, and modifications should allow a significant increase in output power.

  20. Nonlinear mixing of laser generated narrowband Rayleigh surface waves

    Science.gov (United States)

    Bakre, Chaitanya; Rajagopal, Prabhu; Balasubramaniam, Krishnan

    2017-02-01

    This research presents the nonlinear mixing technique of two co-directionally travelling Rayleigh surface waves generated and detected using laser ultrasonics. The optical generation of Rayleigh waves on the specimen is obtained by shadow mask method. In conventional nonlinear measurements, the inherently small higher harmonics are greatly influenced by the nonlinearities caused by coupling variabilities and surface roughness between the transducer and specimen interface. The proposed technique is completely contactless and it should be possible to eliminate this problem. Moreover, the nonlinear mixing phenomenon yields not only the second harmonics, but also the sum and difference frequency components, which can be used to measure the acoustic nonlinearity of the specimen. In this paper, we will be addressing the experimental configurations for this technique. The proposed technique is validated experimentally on Aluminum 7075 alloy specimen.

  1. Searching for a Stochastic Background of Gravitational Waves with the Laser Interferometer Gravitational-Wave Observatory

    Science.gov (United States)

    Abbott, B.; Abbott, R.; Adhikari, R.; Agresti, J.; Ajith, P.; Allen, B.; Amin, R.; Anderson, S. B.; Anderson, W. G.; Araya, M.; Armandula, H.; Ashley, M.; Aston, S.; Aulbert, C.; Babak, S.; Ballmer, S.; Barish, B. C.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barton, M. A.; Bayer, K.; Belczynski, K.; Betzwieser, J.; Beyersdorf, P.; Bhawal, B.; Bilenko, I. A.; Billingsley, G.; Black, E.; Blackburn, K.; Blackburn, L.; Blair, D.; Bland, B.; Bogue, L.; Bork, R.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Brooks, A.; Brown, D. A.; Bullington, A.; Bunkowski, A.; Buonanno, A.; Burman, R.; Busby, D.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Camp, J. B.; Cannizzo, J.; Cannon, K.; Cantley, C. A.; Cao, J.; Cardenas, L.; Casey, M. M.; Cepeda, C.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Chin, D.; Chin, E.; Chow, J.; Christensen, N.; Cokelaer, T.; Colacino, C. N.; Coldwell, R.; Cook, D.; Corbitt, T.; Coward, D.; Coyne, D.; Creighton, J. D. E.; Creighton, T. D.; Crooks, D. R. M.; Cruise, A. M.; Cumming, A.; Cutler, C.; Dalrymple, J.; D'Ambrosio, E.; Danzmann, K.; Davies, G.; de Vine, G.; DeBra, D.; Degallaix, J.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandar, S.; Di Credico, A.; Díaz, M.; Dickson, J.; Diederichs, G.; Dietz, A.; Doomes, E. E.; Drever, R. W. P.; Dumas, J.-C.; Dupuis, R. J.; Ehrens, P.; Elliffe, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Fan, Y.; Fejer, M. M.; Finn, L. S.; Fotopoulos, N.; Franzen, A.; Franzen, K. Y.; Frey, R. E.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Garofoli, J.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Goda, K.; Goetz, E.; Goggin, L.; González, G.; Gossler, S.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, J.; Gretarsson, A. M.; Grimmett, D.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, R.; Hage, B.; Hanna, C.; Hanson, J.; Hardham, C.; Harms, J.; Harry, G.; Harstad, E.; Hayler, T.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Heurs, M.; Hewitson, M.; Hild, S.; Hindman, N.; Hirose, E.; Hoak, D.; Hoang, P.; Hosken, D.; Hough, J.; Howell, E.; Hoyland, D.; Hua, W.; Huttner, S.; Ingram, D.; Ito, M.; Itoh, Y.; Ivanov, A.; Jackrel, D.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Khalili, F. Ya.; Khan, A.; Kim, C.; King, P.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Kozak, D.; Krishnan, B.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lee, B.; Lei, M.; Leonhardt, V.; Leonor, I.; Libbrecht, K.; Lindquist, P.; Lockerbie, N. A.; Lormand, M.; Lubiński, M.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Malec, M.; Mandic, V.; Márka, S.; Markowitz, J.; Maros, E.; Martin, I.; Marx, J. N.; Mason, K.; Matone, L.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McKenzie, K.; McNabb, J. W. C.; Meier, T.; Melissinos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messaritaki, E.; Messenger, C. J.; Meyers, D.; Mikhailov, E.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Mohanty, S.; Moreno, G.; Mossavi, K.; MowLowry, C.; Moylan, A.; Mudge, D.; Mueller, G.; Müller-Ebhardt, H.; Mukherjee, S.; Munch, J.; Murray, P.; Myers, E.; Myers, J.; Newton, G.; Numata, K.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pan, Y.; Papa, M. A.; Parameshwaraiah, V.; Pedraza, M.; Penn, S.; Pitkin, M.; Plissi, M. V.; Prix, R.; Quetschke, V.; Raab, F.; Rabeling, D.; Radkins, H.; Rahkola, R.; Rakhmanov, M.; Rawlins, K.; Ray-Majumder, S.; Re, V.; Rehbein, H.; Reid, S.; Reitze, D. H.; Ribichini, L.; Riesen, R.; Riles, K.; Rivera, B.; Robertson, D. I.; Robertson, N. A.; Robinson, C.; Roddy, S.; Rodriguez, A.; Rogan, A. M.; Rollins, J.; Romano, J. D.; Romie, J.; Route, R.; Rowan, S.; Rüdiger, A.; Ruet, L.; Russell, P.; Ryan, K.; Sakata, S.; Samidi, M.; de la Jordana, L. Sancho; Sandberg, V.; Sannibale, V.; Saraf, S.; Sarin, P.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R.; Schediwy, S.; Schilling, R.; Schnabel, R.; Schofield, R.; Schutz, B. F.; Schwinberg, P.; Scott, S. M.; Seader, S. E.; Searle, A. C.; Sears, B.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Shawhan, P.; Sheard, B.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Sintes, A. M.; Slagmolen, B.; Slutsky, J.; Smith, J.; Smith, M. R.; Sneddon, P.; Somiya, K.; Speake, C.; Spjeld, O.; Strain, K. A.; Strom, D. M.; Stuver, A.; Summerscales, T.; Sun, K.; Sung, M.; Sutton, P. J.; Tanner, D. B.; Tarallo, M.; Taylor, R.; Taylor, R.; Thacker, J.; Thorne, K. A.; Thorne, K. S.; Thüring, A.; Tokmakov, K. V.; Torres, C.; Torrie, C.; Traylor, G.; Trias, M.; Tyler, W.; Ugolini, D.; Ungarelli, C.; Vahlbruch, H.; Vallisneri, M.; Varvella, M.; Vass, S.; Vecchio, A.; Veitch, J.; Veitch, P.; Vigeland, S.; Villar, A.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Ward, H.; Ward, R.; Watts, K.; Webber, D.; Weidner, A.; Weinstein, A.; Weiss, R.; Wen, S.; Wette, K.; Whelan, J. T.; Whitbeck, D. M.; Whitcomb, S. E.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Willke, B.; Wilmut, I.; Winkler, W.; Wipf, C. C.; Wise, S.; Wiseman, A. G.; Woan, G.; Woods, D.; Wooley, R.; Worden, J.; Wu, W.; Yakushin, I.; Yamamoto, H.; Yan, Z.; Yoshida, S.; Yunes, N.; Zanolin, M.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M.; zur Mühlen, H.; Zweizig, J.; LIGO Scientific Collaboration

    2007-04-01

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new Bayesian 90% upper limit is ΩGW×[H0/(72 km s-1 Mpc-1)2<6.5×10-5. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss the complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.

  2. 经尿道RevoLix2μm激光前列腺切除术对患者性功能的影响%The Impact of Transurethral RevoLix 2 Micron Continuous wave Laser Vaporesection of Prostate on Sexual Functions of the Patients with Benign Prostatic Hyperplasia

    Institute of Scientific and Technical Information of China (English)

    贾永中; 贺兵; 庞栋; 罗敏; 李玉柱; 肖序仁

    2011-01-01

    目的:探讨采用RevoLix 2 μm激光手术系统治疗BPH对患者性功能的影响.方法:对120例BPH患者进行了RevoLix 2μm激光手术治疗,全部病例均行IPSS评分.利用国际勃起功能障碍问卷-5(IIEF-5)和自制统一的射精障碍调查表,分别于术前、术后半年了解患者阴茎勃起功能情况、性欲、射精情况及对性生活满意程度进行调查.结果:全部手术均成功,IPSS有明显改善,从(25.12±3.21)分下降为(6.26±2.12)分,(P<0.05).术后患者均保留性功能.IIEF-5术前评分为(23.50±3.12)分,术后半年为(22.40±4.62)分;术前有性欲者占81.67%,术后半年占85.00%,手术前后比较差异无统计学意义(P>0.05).术前射精异常者占23.33%,术后半年射精异常者占71.67%,术后射精功能较术前明显下降(P<0.05).术前对性生活满意者占65.00%,术后占70.00%,手术前后比较差异无统计学意义(P>0.05).结论:RevoLix 2μm激光手术系统治疗BPH有效安全,术中、术后并发症少,对患者阴茎勃起功能、对性生活满意程度及性欲无明显影响,其影响主要为射精障碍.术中操作仔细,防止损伤影响阴茎勃起的神经血管束,术后处理得当,可减少或避免对患者的性功能影响.%Objective:To evaluate the impact of transurethral RevoLix 2 micron continuous wave laser vapore-section of prostate on sexual functions of the patients with benign prostatic hyperplasia(BPH). Methods: A total of 120 aged patients with BPH who reported normal sexual relation before operation were followed up for 6 months in this study, the International Prostate Symptom Score (IPSS),the International erectile dysfunction questionnaire (IIEF-5) and a self-designed ejaculatory questionnaire were used before operation and 6 months later after operation. The incidence of erectile dysfunction, index of sexual activation including sexual interest, pleasure in sex, sexual climax, satisfaction for sexual intercourse were

  3. Calculation of aerosol backscatter from airborne continuous wave focused CO sub 2 Doppler lidar measurements. 1. Algorithm description

    Energy Technology Data Exchange (ETDEWEB)

    Rothermel, J. (NASA Marshall Space Flight Center, Huntsville, AL (USA)); Bowdle, D.A. (Univ. of Alabama, Huntsville (USA)); Vaughan, J.M.; Brown, D.W. (Royal Signals and Radar Establishment, Worcestershire (England)); Woodfield, A.A. (Royal Aircraft Establishment, Bedfordshire (England))

    1991-03-20

    Since 1981 the Royal Signals and Radar Establishment and the Royal Aircraft Establishment, United Kingdom, have made vertical and horizontal sounding measurements of aerosol backscatter coefficients at 10.6 {mu}m using an airborne continuous wave focused CO{sub 2} Doppler lidar, the Laser True Airspeed System (LATAS). The heterodyne signal from the LATAS detector is spectrally analyzed. Then, in conjunction with aircraft flight parameters, the data are processed in a six-stage computer algorithm: Set search window, search for peak signal, test peak signal, measure total signal, calculate signal-to-noise ratio (SNR), and calculate backscatter coefficient.

  4. Mechanism of laser-induced plasma shock wave evolution in air

    Institute of Scientific and Technical Information of China (English)

    Zhao Rui; Liang Zhong-Cheng; Han Bing; Zhang Hong-Chao; Xu Rong-Qing; Lu Jian; Ni Xiao-Wu

    2009-01-01

    A theoretical model is proposed to describe the mechanism of laser-induced plasma shock wave evolution in air. To verify the validity of the theoretical model, an optical beam deflection technique is employed to track the plasma shock wave evolution process. The theoretical model and the experimental signals are found to be in good agreement with each other. It is shown that the laser-induced plasma shock wave undergoes formation, increase and decay processes; the increase and the decay processes of the laser-induced plasma shock wave result from the overlapping of the compression wave and the rarefaction wave, respectively. In addition, the laser-induced plasma shock wave speed and pressure distributions, both a function of distance, are presented.

  5. Wave Equations about Displacement, Velocity, Stress and Strain in FGM with Constituents Varied Continuously and Smoothly

    Institute of Scientific and Technical Information of China (English)

    ZUO Hongxin; ZHANG Qingjie

    2008-01-01

    The wave equations about displacement, velocity, stress and strain in functionally gradient material (FGM) with constituents varied continuously and smoothly were established. Four kinds of waves are of linear second-order partial differential equation of hyperbolic type and have the same characteristic curve at the plane of X,t. In general, the varying mode of stress is different from that of displacement and velocity at the front of wave. But in a special case that the product of density p and elastic modulus E of the material remains unchanged, the three wave equations have a similar expression and they have a similar varying mode in the front of wave.

  6. Frequency domain laser ultrasonics: Optical transduction of acoustic waves and nanomechanical devices

    Science.gov (United States)

    Bramhavar, Suraj

    The concept of optical excitation and detection of nanoscale mechanical motion has led to a variety of tools for non-destructive materials characterization and remote sensing. These techniques, commonly referred to as laser ultrasonics, offer the benefit of high-bandwidth, highly localized measurements, and also allow for the ability to investigate nanoscale devices. The impact of laser ultrasonic systems has been felt in industries ranging from semiconductor metrology to biological and chemical sensing. In this thesis, we develop a variety of techniques utilizing a frequency domain laser ultrasonic approach, where amplitude modulated continuous wave laser light is used instead of traditional pulsed laser sources, and we apply these systems in free-space, optical fiber based, and integrated on-chip configurations. In doing so, we demonstrate the ability to efficiently transduce various types of mechanical motion including surface and bulk acoustic waves, guided acoustic waves, and resonant motion from nanomechanical systems (NEMS). First, we develop a superheterodyne free-space ultrasonic inspection system in an effort to characterize surface acoustic wave dispersion in thin-film material systems. We utilize a similar system to study negative refraction and focusing behavior of guided elastic waves in a thin metal plate, providing a novel approach for the study of negative index physics. Furthermore, we develop a near-field optical technique using optical fibers to simultaneously transduce the motion of 70 NEMS resonators using a single channel. This multiplexed approach serves as a crucial step in moving NEMS technology out of the research laboratory. Finally, we go on to study opto-mechanical interactions between optical whispering gallery mode (WGM) resonators and integrated NEMS devices on the same chip, using the enhanced interactions to study optical forces acting on the nanoscale mechanical devices. This integrated system provides a very efficient mechanical

  7. Laser-Driven Ultra-Relativistic Plasmas - Nuclear Fusion in Coulomb Shock Waves, Rouge Waves, and Background Matter

    Science.gov (United States)

    2015-05-05

    AND SUBTITLE LASER-DRIVEN ULTRA-RELATIVISTIC PLASMAS - NUCLEAR FUSION IN COULOMB SHOCK WAVES, ROUGE WAVES, AND BACKGROUND MATTER. 5a.  CONTRACT...blackbody radiation on free electrons .........................9 2.vi. Proposal of ultimate test of laser nuclear fusion efficiency in clusters...domain of energies and temperatures, with applications in particular to controlled nuclear fusion . 2. Final technical report on the grant #F49620-11-1

  8. Continuous short-wave (radio-frequency) diathermy.

    OpenAIRE

    1989-01-01

    Continuous shortwave diathermy is the technique of choice when uniform marked elevation of temperature is required in the deep tissues. This heating can be targeted accurately by using an appropriate applicator positioned correctly. SWD also allows superficial structures to be heated selectively, although for this the various methods of surface heating are usually preferable. Sub-acute or chronic conditions respond best to continuous shortwave diathermy which, when used properly, can be as ef...

  9. Generation of fast electrons by breaking of a laser-induced plasma wave

    NARCIS (Netherlands)

    Trines, Rmgm; Goloviznin, V. V.; Kamp, L. P. J.; Schep, T. J.

    2001-01-01

    A one-dimensional model for fast electron generation by an intense, nonevolving laser pulse propagating through an underdense plasma has been developed. Plasma wave breaking is considered to be the dominant mechanism behind this process, and wave breaking both in front of and behind the laser pulse

  10. SQUEEZING PROPERTIES OF A TRAPPED ION IN THE STANDING-WAVE LASER

    Institute of Scientific and Technical Information of China (English)

    FANG MAO-FA; LIU XIANG

    2001-01-01

    We investigate the squeezing properties of a trapped ion in a standing-wave laser. Our results show that the squeezing of a trapped ion in the standing-wave laser is dependent on its position in the latter, the detuning parameter and the initial average phonon number.

  11. Acoustic waves in transversely excited atmospheric CO2 laser discharges: effect on performance and reduction techniques

    CSIR Research Space (South Africa)

    von Bergmann, HM

    2008-08-01

    Full Text Available Results are presented on the influence of acoustic waves on the performance of high-repetition-rate TEA CO2 lasers. It is shown that acoustic waves generated inside the laser cavity lead to nonuniform discharges, resulting in a deterioration...

  12. Continuous Wave Stimulated Raman Spectroscopy Inside a Hollow Core Photonic Crystal Fiber

    Science.gov (United States)

    Domenech, Jose L.; Cueto, Maite

    2013-06-01

    Hollow-core photonic crystal fibers (HCPCF) have raised new opportunities to study light-matter interaction. Dielectric or metallic capillaries are intrinsically lossy, making poor light guides. In contrast, HCPCFs can guide light quite efficiently, due to the band-gap effect produced by an array of smaller channels which surrounds a central hollow core with a few μm diameter. The tight confinement of light inside the core, that can be filled with gases, as well as a long interaction length, enhance multiple nonlinear phenomena, making it possible to devise new ways to do low signal level spectroscopy, as is the case of high resolution stimulated Raman spectroscopy (SRS). A. Owyoung demonstrated high resolution continuous wave SRS in 1978. Shortly afterwards, seeking higher sensitivity, he developed the quasi-continuous SRS technique (a high peak power pump laser, interacting with a low power cw probe laser). That variant remains today the best compromise between resolution and sensitivity for gas-phase Raman spectroscopy. In this work, we show the possibility of fully cw stimulated Raman spectroscopy, using a gas cell built around a HCPCF to overcome the limitations posed by the weakness of the stimulated Raman effect when not using pulsed sources. The interaction length (1.2 m), longer than that of a multiple pass refocusing cell, and the narrow diameter of the core (4.8 μm), can compensate for the much lower laser powers used in the cw set-up. The experimental complexity is considerably reduced and the instrumental resolution is at the 10's of MHz level, limited, with our fiber, by transit time effects. At present, we have demonstrated the feasibility of the experiment, a sensitivity enhancement of ˜ 6000 over the single focus regime, and a spectral resolution better than 0.005 wn in the unresolved Q-branch of the ν_1 component of the Fermi dyad of CO_2 at 1388 wn. Other examples of rotationally resolved spectra will be shown: the Q branch of O_2 at 1555 wn

  13. Broadband Continuous-Wave Multi-Harmonic Optical Comb Based on a Frequency Division-by-Three Optical Parametric Oscillator

    Directory of Open Access Journals (Sweden)

    Yen-Yin Lin

    2014-11-01

    Full Text Available We report a multi-watt broadband continuous-wave multi-harmonic optical comb based on a frequency division-by-three singly-resonant optical parametric oscillator. This cw optical comb is frequency-stabilized with the help of a beat signal derived from the signal and frequency-doubled idler waves. The measured frequency fluctuation in one standard deviation is ~437 kHz. This is comparable to the linewidth of the pump laser which is a master-oscillator seeded Yb:doped fiber amplifier at ~1064 nm. The measured powers of the fundamental wave and the harmonic waves up to the 6th harmonic wave are 1.64 W, 0.77 W, 3.9 W, 0.78 W, 0.17 W, and 0.11 W, respectively. The total spectral width covered by this multi-harmonic comb is ~470 THz. When properly phased, this multi-harmonic optical comb can be expected to produce by Fourier synthesis a light source consisting of periodic optical field waveforms that have an envelope full-width at half-maximum of 1.59 fs in each period.

  14. Continued Optical Sensor Operations in a Laser Environment

    Science.gov (United States)

    2012-10-01

    Russell Callen , and William Rhodes, Introduction to Lasers and Their Applications (Redding, MA: Addison-Wesley Publishing Company, 1977); and Philip...Applications (London: McGraw Hill, 1974). 4. O’Shea, Callen , and Rhodes, Introduction to Lasers. 5. Photons, which are packets of electromagnetic

  15. Enhanced acceleration of injected electrons in a laser-beat-wave-induced plasma channel.

    Science.gov (United States)

    Tochitsky, S Ya; Narang, R; Filip, C V; Musumeci, P; Clayton, C E; Yoder, R B; Marsh, K A; Rosenzweig, J B; Pellegrini, C; Joshi, C

    2004-03-05

    Enhanced energy gain of externally injected electrons by a approximately 3 cm long, high-gradient relativistic plasma wave (RPW) is demonstrated. Using a CO2 laser beat wave of duration longer than the ion motion time across the laser spot size, a laser self-guiding process is initiated in a plasma channel. Guiding compensates for ionization-induced defocusing (IID) creating a longer plasma, which extends the interaction length between electrons and the RPW. In contrast to a maximum energy gain of 10 MeV when IID is dominant, the electrons gain up to 38 MeV energy in a laser-beat-wave-induced plasma channel.

  16. Ramp-wave compression experiment with direct laser illumination on Shen Guang III prototype Laser facility

    Science.gov (United States)

    Wang, Feng; Xu, Tao; Optical Team Collaboration

    2016-10-01

    Ramp-wave compression (RWC) experiment to balance the high compression pressure generation in aluminum and x-ray blanking effect in transparent window was demonstrated on Shen Guang-III prototype laser facility. A new target concept was proposed to develop a laser-driven shocks-RWC technique for studying material behavior under dynamic, high pressure conditions. As the ``little shocks'' in our experiment cannot be avoided, the effort to diminish the shock under a special level has been demonstrated with Al/Au/Al/LiF target. The highest pressure is about 500GPa after using the multilayer target design Al/Au/Al/LiF and about 1013W/cm2 laser pulse incident on the planer Al target, instantaneously affecting ablation layer located 500 μm away. As the x-ray generated by Al layer had been prevented by the Au layer, the width abrupt onset of strong absorption of an optical probe beam (λ = 532 nm) in LiF window may be the limitation for this kind if RWC experiment during the experiment time scale for 30 μm thick step. With the design laser shape and target structure of Al/Au/Al/LiF, 500GPa may be the highest pressure after balance the preheat effect and ablation efficiency for laser direct-drive experiment.

  17. Continuous control of ionization wave chaos by spatially derived feedback signals

    CERN Document Server

    Mausbach, T; Piel, A; Atipo, A; Pierre, T; Bonhomme, G; Mausbach, Th.; Klinger, Th.; Pierre, Th.

    1997-01-01

    In the positive column of a neon glow discharge, two different types of ionization waves occur simultaneously. The low-dimensional chaos arising from the nonlinear interaction between the two waves is controlled by a continuous feedback technique. The control strategy is derived from the time-delayed autosynchronization method. Two spatially displaced points of observation are used to obtain the control information, using the propagation characteristics of the chaotic wave.

  18. Ultrahigh-gradient acceleration of injected eletrons by laser-excited relativistic electron plasma waves

    Science.gov (United States)

    Clayton, C. E.; Marsh, K. A.; Dyson, A.; Everett, M.; Lal, A.; Leemans, W. P.; Williams, R.; Joshi, C.

    1993-01-01

    High-gradient acceleration of externally injected 2.1-MeV electrons by a laser beat wave driven relativistic plasma wave has been demonstrated for the first time. Electrons with energies up to the detection limit of 9.1 MeV were detected when such a plasma wave was resonantly excited using a two-frequency laser. This implies a gradient of 0.7 GeV/m, corresponding to a plasma-wave amplitude of more than 8%. The electron signal was below detection threshold without injection or when the laser was operated on a single frequency.

  19. Continuous short-wave (radio-frequency) diathermy.

    Science.gov (United States)

    Goats, G C

    1989-06-01

    Continuous shortwave diathermy is the technique of choice when uniform marked elevation of temperature is required in the deep tissues. This heating can be targeted accurately by using an appropriate applicator positioned correctly. SWD also allows superficial structures to be heated selectively, although for this the various methods of surface heating are usually preferable. Sub-acute or chronic conditions respond best to continuous shortwave diathermy which, when used properly, can be as effective as ultrasound. Acute lesions are better treated with pulsed shortwave diathermy. Continuous shortwave diathermy can help to relieve pain and muscle spasm, resolve inflammatory states and reduce swelling, promote vasodilation, increase the compliance of connective tissue, increase joint range and decrease joint stiffness.

  20. Continuous-wave wavelength conversion in a photonic crystal fiber with two zero-dispersion wavelengths

    DEFF Research Database (Denmark)

    Andersen, T.V.; Hilligsøe, Karen Marie; Nielsen, C.K.;

    2004-01-01

    We demonstrate continuous-wave wavelength conversion through four-wave mixing in an endlessly single mode photonic crystal fiber. Phasematching is possible at vanishing pump power in the anomalous dispersion regime between the two zero-dispersion wavelengths. By mixing appropriate pump and idler...

  1. A Wave-Optics Approach to Paraxial Geometrical Laws Based on Continuity at Boundaries

    Science.gov (United States)

    Linares, J.; Nistal, M. C.

    2011-01-01

    We present a derivation of the paraxial geometrical laws starting from a wave-optics approach, in particular by using simple continuity conditions of paraxial spherical waves at boundaries (discontinuities) between optical media. Paraxial geometrical imaging and magnification laws, under refraction and reflection at boundaries, are derived for…

  2. Continuity Conditions on Schrodinger Wave Functions at Discontinuities of the Potential.

    Science.gov (United States)

    Branson, David

    1979-01-01

    Several standard arguments which attempt to show that the wave function and its derivative must be continuous across jump discontinuities of the potential are reviewed and their defects discussed. (Author/HM)

  3. The thermoelastic excitation of air-solid interface waves using the pulsed laser

    Institute of Scientific and Technical Information of China (English)

    HU; Wenxiang; QIAN; Menglu

    2004-01-01

    Applying the integral transform to the coupled problem of thermoelastic and heat conduction equations, the integral representation of the normal displacement field for the air-solid interface waves excited by a pulsed laser line source is obtained. The pole residues of the integrand are performed analytically, and the transient displacement field is calculated by using FFT technique. The thermoelastic excitation and detection of the air-solid interface waves is carried out by a laser ultrasonic system, on which the pulsed laser is focused into a line source onto the interface to excite the air-solid interface waves:leaky Rayleigh wave and Scholte wave, and the interface waves displacement signal is detected successfully by a SH130 laser heterodyne interferometer. The theoretic and experimental results are in good agreement.

  4. Analysis and experiment on deformation of sheet metal by laser shock wave

    Institute of Scientific and Technical Information of China (English)

    YANG Chao-jun; ZHANG Yong-kang; ZHOU Jian-zhong; NI Ming-xiong; DU Jian-jun; HUANG Shu; FENG Ai-xin; ZHANG Lei-hong

    2006-01-01

    The mechanism of laser shock deformation and the reason for the production of the shockwave are introduced.An evaluation formula of the detonation wave pressure in the system of laser,energy transferring-medium and sheet metal is built according to the theory of detonation wave and blasting gas-dynamics.The minimal energy of the laser pulse is evaluated on the basis of the formula of the laser shock pressure and evaluation of dynamic yielding strength.The experiment is also validated.The result shows that the quantity of sheet metal deforming is nonlinearly increased with laser energy,i.e.,pressure of the laser shock wave.Under a laser-induced ultra-high pressure and high strain rate,structural steels and composite materials undergo plastic deformation.

  5. Threshold response using modulated continuous wave illumination for multilayer 3D optical data storage

    Science.gov (United States)

    Saini, A.; Christenson, C. W.; Khattab, T. A.; Wang, R.; Twieg, R. J.; Singer, K. D.

    2017-01-01

    In order to achieve a high capacity 3D optical data storage medium, a nonlinear or threshold writing process is necessary to localize data in the axial dimension. To this end, commercial multilayer discs use thermal ablation of metal films or phase change materials to realize such a threshold process. This paper addresses a threshold writing mechanism relevant to recently reported fluorescence-based data storage in dye-doped co-extruded multilayer films. To gain understanding of the essential physics, single layer spun coat films were used so that the data is easily accessible by analytical techniques. Data were written by attenuating the fluorescence using nanosecond-range exposure times from a 488 nm continuous wave laser overlapping with the single photon absorption spectrum. The threshold writing process was studied over a range of exposure times and intensities, and with different fluorescent dyes. It was found that all of the dyes have a common temperature threshold where fluorescence begins to attenuate, and the physical nature of the thermal process was investigated.

  6. Investigation of turbulence measurements with a continuous wave, conically scanning LiDAR

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, R.; Mikkelsen, T.; Courtney, M.

    2009-03-15

    LIDAR systems are getting more and more accurate and reliable. It has been shown many times that the mean horizontal wind speed measured by a lidar over flat terrain compares very well with that measured by a cup anemometer. But can a lidar measure turbulence? Here we investigate the case of a continuous wave, conically scanning Zephir lidar. First, the wind speed standard deviation measured by such a lidar gives on average 80% of the standard deviation measured by a cup anemometer. This difference is due to the spatial averaging inherently made by a cw conically scanning lidar. The spatial averaging is done in two steps: 1) the weighted averaging of the wind speed in the probe volume of the laser beam; 2) the averaging of the wind speeds occurring on the circular path described by the conically scanning lidar. Therefore the standard deviation measured by a lidar resolves only the turbulence structures larger than a length scale depending on the circle diameter and the mean wind speed (range of magnitude: 100m). However, the Zephir lidar gives another turbulence quantity, the so-called turbulence parameter, which can resolve turbulence structures with a smaller length scale. In this paper, we suggest a volumetric filtering of the turbulence to represent the effect of the spatial averaging operated by a lidar when measuring the wind speed. We then evaluate this model by comparing the theoretical results to experimental data obtained with several Zephir systems, for both turbulence quantities. (au)

  7. Analysis and active compensation of microphonics in continuous wave narrow-bandwidth superconducting cavities

    Science.gov (United States)

    Neumann, A.; Anders, W.; Kugeler, O.; Knobloch, J.

    2010-08-01

    Many proposals for next generation light sources based on single pass free electron lasers or energy recovery linac facilities require a continuous wave (cw) driven superconducting linac. The effective beam loading in such machines is very small and in principle the cavities can be operated at a bandwidth of a few Hz and with less than a few kW of rf power. However, a power reserve is required to ensure field stability. A major error source is the mechanical microphonics detuning of the niobium cavities. To understand the influence of cavity detuning on longitudinal beam stability, a measurement program has been started at the horizontal cavity test facility HoBiCaT at HZB to study TESLA-type cavities. The microphonics detuning spectral content, peak detuning values, and the driving terms for these mechanical oscillations have been analyzed. In combination with the characterization of cw-adapted fast tuning systems based on the piezoelectric effect this information has been used to design a detuning compensation algorithm. It has been shown that a compensation factor between 2-7 is achievable, reducing the typical detuning of 2-3 Hz rms to below 0.5 Hz rms. These results were included in rf-control simulations of the cavities, and it was demonstrated that a phase stability below 0.02° can be achieved.

  8. A CO trace gas detection system based on continuous wave DFB-QCL

    Science.gov (United States)

    Dang, Jingmin; Yu, Haiye; Sun, Yujing; Wang, Yiding

    2017-05-01

    A compact and mobile system was demonstrated for the detection of carbon monoxide (CO) at trace level. This system adopted a high-power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at ∼22 °C as excitation source. Wavelength modulation spectroscopy (WMS) as well as second harmonic detection was used to isolate complex, overlapping spectral absorption features typical of ambient pressures and to achieve excellent specificity and high detection sensitivity. For the selected P(11) absorption line of CO molecule, located at 2099.083 cm-1, a limit of detection (LoD) of 26 ppb by volume (ppbv) at atmospheric pressure was achieved with a 1 s acquisition time. Allan deviation analysis was performed to investigate the long term performance of the CO detection system, and a measurement precision of 3.4 ppbv was observed with an optimal integration time of approximate 114 s, which verified the reliable and robust operation of the developed system.

  9. Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements.

    Science.gov (United States)

    Votava, Ondrej; Mašát, Milan; Parker, Alexander E; Jain, Chaithania; Fittschen, Christa

    2012-04-01

    We present in this work a new tracking servoloop electronics for continuous wave cavity-ringdown absorption spectroscopy (cw-CRDS) and its application to time resolved cw-CRDS measurements by coupling the system with a pulsed laser photolysis set-up. The tracking unit significantly increases the repetition rate of the CRDS events and thus improves effective time resolution (and/or the signal-to-noise ratio) in kinetics studies with cw-CRDS in given data acquisition time. The tracking servoloop uses novel strategy to track the cavity resonances that result in a fast relocking (few ms) after the loss of tracking due to an external disturbance. The microcontroller based design is highly flexible and thus advanced tracking strategies are easy to implement by the firmware modification without the need to modify the hardware. We believe that the performance of many existing cw-CRDS experiments, not only time-resolved, can be improved with such tracking unit without any additional modification to the experiment. © 2012 American Institute of Physics

  10. Pump depletion limited evolution of the relativistic plasma wave-front in a forced laser-wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Fang, F; Clayton, C E; Marsh, K A; Pak, A E; Ralph, J E; Joshi, C [Department of Electrical Engineering, University of California, Los Angeles, CA 90095 (United States); Lopes, N C [Grupo de Lasers e Plasmas, Instituto Superior Tecnico, Lisbon (Portugal)], E-mail: cclayton@ucla.edu

    2009-02-15

    In a forced laser-wakefield accelerator experiment (Malka et al 2002 Science 298 1596) where the length of the pump laser pulse is a few plasma periods long, the leading edge of the laser pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake. Therefore, after some propagation distance, the group velocity of the leading edge of the pump pulse-and thus of the driven electron plasma wave-will slow down. This can have implications for the dephasing length of the accelerated electrons and therefore needs to be understood experimentally. We have carried out an experimental investigation where we have measured the velocity v{sub f} of the 'wave-front' of the plasma wave driven by a nominally 50 fs (full width half maximum), intense (a{sub 0} {approx_equal} 1), 0.815 {mu}m laser pulse. To determine the speed of the wave front, time- and space-resolved refractometry, interferometry and Thomson scattering were used. Although a laser pulse propagating through a relatively low-density plasma (n{sub e} = 1.3 x 10{sup 19} cm{sup -3}) showed no measurable changes in v{sub f} over 1.3 mm (and no accelerated electrons), a high-density plasma (n{sub e} = 5 x 10{sup 19} cm{sup -3}) generated accelerated electrons and showed a continuous change in v{sub f} as the laser pulse propagated through the plasma. Possible causes and consequences of the observed v{sub f} evolution are discussed.

  11. Liquid-Solid Interface Waves with Laser Ultrasonic and Mirage Effect

    Institute of Scientific and Technical Information of China (English)

    HAN Qing-Bang; WANG Hao; QIAN Meng-Lu

    2005-01-01

    @@ We experimentally investigate the transparent-liquid/solid (water/aluminum or steel) interface waves generated by laser pulses and detected by the Mirage effect. It is shown that nearly all kinds of liquid/solid interface waves in water are detected, both their measured wave velocities and characteristic of shape are in good agreement with theoretical predictions.

  12. Time reversal of continuous-wave, monochromatic signals in elastic media

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Brian E [Los Alamos National Laboratory; Guyer, Robert A [Los Alamos National Laboratory; Ulrich, Timothy J [Los Alamos National Laboratory; Johnson, Paul A [Los Alamos National Laboratory

    2009-01-01

    Experimental observations of spatial focusing of continuous-wave, steady-state elastic waves in a reverberant elastic cavity using time reversal are reported here. Spatially localized focusing is achieved when multiple channels are employed, while a single channel does not yield such focusing. The amplitude of the energy at the focal location increases as the square of the number of channels used, while the amplitude elsewhere in the medium increases proportionally with the number of channels used. The observation is important in the context of imaging in solid laboratory samples as well as problems involving continuous-wave signals in Earth.

  13. A directed search for continuous Gravitational Waves from the Galactic Center

    CERN Document Server

    Aasi, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Accadia, T; Acernese, F; Adams, C; Adams, T; Adhikari, R X; Affeldt, C; Agathos, M; Aggarwal, N; Aguiar, O D; Ajith, P; Allen, B; Allocca, A; Ceron, E Amador; Amariutei, D; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Austin, L; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barker, D; Barnum, S H; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J; Bauchrowitz, J; Bauer, Th S; Bebronne, M; Behnke, B; Bejger, M; Beker, M G; Bell, A S; Bell, C; Belopolski, I; Bergmann, G; Berliner, J M; Bertolini, A; Bessis, D; Betzwieser, J; Beyersdorf, P T; Bhadbhade, T; Bilenko, I A; Billingsley, G; Birch, J; Bitossi, M; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Blom, M; Bock, O; Bodiya, T P; Boer, M; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Bose, S; Bosi, L; Bowers, J; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brannen, C A; Brau, J E; Breyer, J; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Britzger, M; Brooks, A F; Brown, D A; Brown, D D; Brückner, F; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Byer, R L; Cadonati, L; Cagnoli, G; Bustillo, J Calderón; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castiglia, A; Caudill, S; Cavagliá, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Chow, J; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Cleva, F; Coccia, E; Cohadon, P -F; Colla, A; Colombini, M; Constancio, M; Conte, A; Conte, R; Cook, D; Corbitt, T R; Cordier, M; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J -P; Countryman, S; Couvares, P; Coward, D M; Cowart, M; Coyne, D C; Craig, K; Creighton, J D E; Creighton, T D; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Dahl, K; Canton, T Dal; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dattilo, V; Daudert, B; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; De Rosa, R; Debreczeni, G; Degallaix, J; Del Pozzo, W; Deleeuw, E; Deléglise, S; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Díaz, M; Dietz, A; Dmitry, K; Donovan, F; Dooley, K L; Doravari, S; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Dumas, J -C; Dwyer, S; Eberle, T; Edwards, M; Effler, A; Ehrens, P; Eichholz, J; Eikenberry, S S; Endröczi, G; Essick, R; Etzel, T; Evans, K; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fang, Q; Farr, B; Farr, W; Favata, M; Fazi, D; Fehrmann, H; Feldbaum, D; Ferrante, I; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fisher, R; Flaminio, R; Foley, E; Foley, S; Forsi, E; Forte, L A; Fotopoulos, N; Fournier, J -D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fujimoto, M -K; Fulda, P; Fyffe, M; Gair, J; Gammaitoni, L; Garcia, J; Garufi, F; Gehrels, N; Gemme, G; Genin, E; Gennai, A; Gergely, L; Ghosh, S; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Gil-Casanova, S; Gill, C; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Griffo, C; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C; Gushwa, K E; Gustafson, E K; Gustafson, R; Hall, B; Hall, E; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hartman, M T; Haughian, K; Hayama, K; Heefner, J; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Holt, K; Holtrop, M; Hong, T; Hooper, S; Horrom, T; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Hua, Z; Huang, V; Huerta, E A; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Iafrate, J; Ingram, D R; Inta, R; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; James, E; Jang, H; Jang, Y J; Jaranowski, P; Jiménez-Forteza, F; Johnson, W W; Jones, D; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Kasturi, R; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufman, K; Kawabe, K; Kawamura, S; Kawazoe, F; Kéfélian, F; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, B K; Kim, C; Kim, K; Kim, N; Kim, W; Kim, Y -M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kline, J; Koehlenbeck, S; Kokeyama, K; Kondrashov, V; Koranda, S; Korth, W Z; Kowalska, I; Kozak, D; Kremin, A; Kringel, V; Krishnan, B; Królak, A; Kucharczyk, C; Kudla, S; Kuehn, G; Kumar, A; Kumar, P; Kumar, R; Kurdyumov, R; Kwee, P; Landry, M; Lantz, B; Larson, S; Lasky, P D; Lawrie, C; Lazzarini, A; Roux, A Le; Leaci, P; Lebigot, E O; Lee, C -H; Lee, H K; Lee, H M; Lee, J; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levine, B; Lewis, J B; Lhuillier, V; Li, T G F; Lin, A C; Littenberg, T B; Litvine, V; Liu, F; Liu, H; Liu, Y; Liu, Z; Lloyd, D; Lockerbie, N A; Lockett, V; Lodhia, D; Loew, K; Logue, J; Lombardi, A L; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J; Luan, J; Lubinski, M J; Lück, H; Lundgren, A P; Macarthur, J; Macdonald, E; Machenschalk, B; MacInnis, M; Macleod, D M; Magana-Sandoval, F; Mageswaran, M; Mailand, K; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Manca, G M; Mandel, I; Mandic, V; Mangano, V; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A; Maros, E; Marque, J; Martelli, F; Martin, I W; Martin, R M; Martinelli, L; Martynov, D; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Matichard, F; Matone, L; Matzner, R A; Mavalvala, N; May, G; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McGuire, S C; McIntyre, G; McIver, J; Meacher, D; Meadors, G D; Mehmet, M; Meidam, J; Meier, T; Melatos, A; Mendell, G; Mercer, R A; Meshkov, S; Messenger, C; Meyer, M S; Miao, H; Michel, C; Mikhailov, E E; Milano, L; Miller, J; Minenkov, Y; Mingarelli, C M F; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moe, B; Mohan, M; Mohapatra, S R P; Mokler, F; Moraru, D; Moreno, G; Morgado, N; Mori, T; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D; Murray, P G; Mytidis, A; Nagy, M F; Kumar, D Nanda; Nardecchia, I; Nash, T; Naticchioni, L; Nayak, R; Necula, V; Neri, I; Newton, G; Nguyen, T; Nishida, E; Nishizawa, A; Nitz, A; Nocera, F; Nolting, D; Normandin, M E; Nuttall, L K; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oppermann, P; O'Reilly, B; Larcher, W Ortega; O'Shaughnessy, R; Osthelder, C; Ottaway, D J; Ottens, R S; Ou, J; Overmier, H; Owen, B J; Padilla, C; Pai, A; Palomba, C; Pan, Y; Pankow, C; Paoletti, F; Paoletti, R; Papa, M A; Paris, H; Pasqualetti, A; Passaquieti, R; Passuello, D; Pedraza, M; Peiris, P; Penn, S; Perreca, A; Phelps, M; Pichot, M; Pickenpack, M; Piergiovanni, F; Pierro, V; Pinard, L; Pindor, B; Pinto, I M; Pitkin, M; Pletsch, H; Poeld, J; Poggiani, R; Poole, V; Poux, C; Predoi, V; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Quetschke, V; Quintero, E; Quitzow-James, R; Raab, F J; Rabeling, D S; Rácz, I; Radkins, H; Raffai, P; Raja, S; Rajalakshmi, G; Rakhmanov, M; Ramet, C; Rapagnani, P; Raymond, V; Re, V; Reed, C M; Reed, T; Regimbau, T; Reid, S; Reitze, D H; Ricci, F; Riesen, R; Riles, K; Robertson, N A; Robinet, F; Rocchi, A; Roddy, S; Rodriguez, C; Rodruck, M; Roever, C; Rolland, L; Rollins, J G; Romano, J D; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Salemi, F; Sammut, L; Sandberg, V; Sanders, J; Sannibale, V; Santiago-Prieto, I; Saracco, E; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Savage, R; Schilling, R; Schnabel, R; Schofield, R M S; Schreiber, E; Schuette, D; Schulz, B; Schutz, B F; Schwinberg, P; Scott, J; Scott, S M; Seifert, F; Sellers, D; Sengupta, A S; Sentenac, D; Sergeev, A; Shaddock, D; Shah, S; Shahriar, M S; Shaltev, M; Shapiro, B; Shawhan, P; Shoemaker, D H; Sidery, T L; Siellez, K; Siemens, X; Sigg, D; Simakov, D; Singer, A; Singer, L; Sintes, A M; Skelton, G R; Slagmolen, B J J; Slutsky, J; Smith, J R; Smith, M R; Smith, R J E; Smith-Lefebvre, N D; Soden, K; Son, E J; Sorazu, B; Souradeep, T; Sperandio, L; Staley, A; Steinert, E; Steinlechner, J; Steinlechner, S; Steplewski, S; Stevens, D; Stochino, A; Stone, R; Strain, K A; Strigin, S; Stroeer, A S; Sturani, R; Stuver, A L; Summerscales, T Z; Susmithan, S; Sutton, P J; Swinkels, B; Szeifert, G; Tacca, M; Talukder, D; Tang, L; Tanner, D B; Tarabrin, S P; Taylor, R; ter Braack, A P M; Thirugnanasambandam, M P; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, V; Tokmakov, K V; Tomlinson, C; Toncelli, A; Tonelli, M; Torre, O; Torres, C V; Torrie, C I; Travasso, F; Traylor, G; Tse, M; Ugolini, D; Unnikrishnan, C S; Vahlbruch, H; Vajente, G; Vallisneri, M; Brand, J F J van den; Broeck, C Van Den; van der Putten, S; van der Sluys, M V; van Heijningen, J; van Veggel, A A; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Verma, S; Vetrano, F; Viceré, A; Vincent-Finley, R; Vinet, J -Y; Vitale, S; Vlcek, B; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vrinceanu, D; Vyachanin, S P; Wade, A; Wade, L; Wade, M; Waldman, S J; Walker, M; Wallace, L; Wan, Y; Wang, J; Wang, M; Wang, X; Wanner, A; Ward, R L; Was, M; Weaver, B; Wei, L -W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Wessels, P; West, M; Westphal, T; Wette, K; Whelan, J T; Whitcomb, S E; White, D J; Whiting, B F; Wibowo, S; Wiesner, K; Wilkinson, C; Williams, L; Williams, R; Williams, T; Willis, J L; Willke, B; Wimmer, M; Winkelmann, L; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Yablon, J; Yakushin, I; Yamamoto, H; Yancey, C C; Yang, H; Yeaton-Massey, D; Yoshida, S; Yum, H; Yvert, M; Zadrony, A; Zanolin, M; Zendri, J -P; Zhang, F; Zhang, L; Zhao, C; Zhu, H; Zhu, X J; Zotov, N; Zucker, M E; Zweizig, J

    2013-01-01

    We present the results of a directed search for continuous gravitational waves from unknown, isolated neutron stars in the Galactic Center region, performed on two years of data from LIGO's fifth science run from two LIGO detectors. The search uses a semi-coherent approach, analyzing coherently 630 segments, each spanning 11.5 hours, and then incoherently combining the results of the single segments. It covers gravitational wave frequencies in a range from 78 to 496 Hz and a frequency-dependent range of first order spindown values down to -7.86 x 10^-8 Hz/s at the highest frequency. No gravitational waves were detected. We place 90% confidence upper limits on the gravitational wave amplitude of sources at the Galactic Center. Reaching ~3.35 x 10^-25 at ~150 Hz, those upper limits are the most constraining to date for a large-parameter-space search for continuous gravitational wave signals.

  14. Automatically tunable continuous-wave optical parametric oscillator for high-resolution spectroscopy and sensitive trace-gas detection

    Science.gov (United States)

    Ngai, A. K. Y.; Persijn, S. T.; von Basum, G.; Harren, F. J. M.

    2006-11-01

    We present a high-power (2.75 W), broadly tunable (2.75-3.83 μm) continuous-wave optical parametric oscillator based on MgO-doped periodically poled lithium niobate. Automated tuning of the pump laser, etalon and crystal temperature results in a continuous wavelength coverage up to 450 cm-1 per poling period at water in human breath were measured using photoacoustics. Methane (at 3.2 μm) and ethane (at 3.3 μm) were detected using cavity ring-down spectroscopy with detection limits of 0.16 and 0.07 parts per billion by volume, respectively. A recording of 12CH4 and 13CH4 isotopes of methane shows the ability to detect both species simultaneously at similar sensitivities.

  15. Dynamic analysis and continuous control of semiconductor lasers

    CERN Document Server

    Behnia, Sohrab; Afrang, Saeid

    2011-01-01

    Stability control in laser is still an emerging field of research. In this paper the dynamics of External cavity semiconductor lasers (ECSLs) is widely studied applying the methods of chaos physics. The stability is analyzed through plotting the Lyapunov exponent spectra, bifurcation diagrams and time series. The oscillation of the electric field E has been reported to be either periodic (P1,P2,..) or chaotic. The results of the study show that the rich nonlinear dynamics of the electric field |E|^2 includes saddle node bifurcations, quasi-periodicity and regular pulse packages. The issue of finding the conditions for creating stable domains has been studied. By considering the dynamical pumping current system coupled with laser, a method for the creation of the stable domain has been introduced.

  16. An LDA (Laser-Doppler Anemometry) investigation of three-dimensional normal shock wave boundary-layer interactions

    Science.gov (United States)

    Chriss, R. M.; Hingst, W. R.; Strazisar, A. J.; Keith, T. G., Jr.

    1989-01-01

    Nonintrusive measurements were made of a normal shock wave/boundary layer interaction. Two dimensional measurements were made throughout the interaction region while 3-D measurements were made in the vicinity of the shock wave. The measurements were made in the corner of the test section of a continuous supersonic wind tunnel in which a normal shock wave had been stabilized. Laser Doppler Anemometry, surface pressure measurement and flow visualization techniques were employed for two freestream Mach number test cases: 1.6 and 1.3. The former contained separated flow regions and a system of shock waves. The latter was found to be far less complicated. The results define the flow field structure in detail for each case.

  17. Transcranial direct current stimulation in refractory continuous spikes and waves during slow sleep: a controlled study

    DEFF Research Database (Denmark)

    Varga, Edina T; Terney, Daniella; Atkins, Mary D

    2011-01-01

    Cathodal transcranial direct current stimulation (tDCS) decreases cortical excitability. The purpose of the study was to investigate whether cathodal tDCS could interrupt the continuous epileptiform activity. Five patients with focal, refractory continuous spikes and waves during slow sleep were ...

  18. Neuronal Networks in Children with Continuous Spikes and Waves during Slow Sleep

    Science.gov (United States)

    Siniatchkin, Michael; Groening, Kristina; Moehring, Jan; Moeller, Friederike; Boor, Rainer; Brodbeck, Verena; Michel, Christoph M.; Rodionov, Roman; Lemieux, Louis; Stephani, Ulrich

    2010-01-01

    Epileptic encephalopathy with continuous spikes and waves during slow sleep is an age-related disorder characterized by the presence of interictal epileptiform discharges during at least greater than 85% of sleep and cognitive deficits associated with this electroencephalography pattern. The pathophysiological mechanisms of continuous spikes and…

  19. Continuous 40\\,GW/cm$^2$ laser intensity in a near-concentric optical cavity

    CERN Document Server

    Schwartz, O; Haslinger, P; Glaeser, R M; Mueller, H

    2016-01-01

    Manipulating free-space electron wave functions with laser fields can bring about new electron-optical elements for transmission electron microscopy. In particular, a Zernike phase plate would enable high-contrast imaging of soft matter, leading to new opportunities in structural biology and materials science. A Zernike plate can be implemented using a tight, intense CW laser focus that shifts the phase of the electron wave by the ponderomotive potential. Here, we use a near-concentric cavity to focus 7.5\\,kW of circulating laser power at 1064\\,nm into a $7\\,\\mu$m waist, setting a record for CW laser intensity and establishing a pathway to ponderomotive phase contrast TEM.

  20. Semiconductor lasers with a continuous tuning range above 100 nm in the nearest IR spectral region

    Energy Technology Data Exchange (ETDEWEB)

    Kostin, Yu O; Lobintsov, A A; Shramenko, M V [OOO ' Opton' , Moscow (Russian Federation); Ladugin, M A; Marmalyuk, A A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation); Chamorovsky, A Yu [Superlum Ltd., Unit B3, Fota Point Enterprise Park, Carrigtwohill, Co Cork (Ireland); Yakubovich, S D [Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow (Russian Federation)

    2015-08-31

    We have developed two new types of lasers based on quantum-confined semiconductor optical amplifiers with an acousto-optic tunable filter in an external fibre ring cavity. The lasers offer continuous wavelength tuning ranges from 780 to 885 and from 880 to 1010 nm, 20 mW of cw output power, and a tuning rate up to 10{sup 4} nm s{sup -1} at an instantaneous spectral linewidth less than 0.1 nm. (lasers)

  1. Laser second harmonic generation in a magnetoplasma assisted by an electrostatic wave

    Science.gov (United States)

    Tyagi, Yachna; Tripathi, Deepak; Walia, Keshav

    2017-04-01

    A laser produced plasma, and an electrostatic wave, helps to generate a strong harmonic radiation. The electrostatic wave assists k matching and contributes to non-linear coupling. In the case of the Bernstein wave assisted second harmonic, the frequency of the second harmonic is shifted from the laser second harmonic by electron cyclotron frequency. The lower hybrid wave (LHW) assisted second harmonic has frequency slightly shifted from the laser second harmonic. The upper hybrid wave (UHW) assisted second harmonic has frequency shifted by an amount ω that lies between max( ω c , ω p ) and ω U H . At a 0 = 0.1 and n ω , k → / n0 0 = 0.1, the normalized amplitude value the of electrostatic wave assisted second harmonic is quite high near the upper hybrid resonance. The effect of increasing ω c / ω p increases the max value of normalized amplitude.

  2. Simulation of laser-driven plasma beat-wave propagation in collisional weakly relativistic plasmas

    Science.gov (United States)

    Kaur, Maninder; Nandan Gupta, Devki

    2016-11-01

    The process of interaction of lasers beating in a plasma has been explored by virtue of particle-in-cell (PIC) simulations in the presence of electron-ion collisions. A plasma beat wave is resonantly excited by ponderomotive force by two relatively long laser pulses of different frequencies. The amplitude of the plasma wave become maximum, when the difference in the frequencies is equal to the plasma frequency. We propose to demonstrate the energy transfer between the laser beat wave and the plasma wave in the presence of electron-ion collision in nearly relativistic regime with 2D-PIC simulations. The relativistic effect and electron-ion collision both affect the energy transfer between the interacting waves. The finding of simulation results shows that there is a considerable decay in the plasma wave and the field energy over time in the presence of electron-ion collisions.

  3. Linear Growth of Continuous-Wave Four-Wave Mixing with Dual Induced Transparency

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-Yi; LI Jia-Hua

    2005-01-01

    Using Schrodinger-Maxwell formalism, we propose and analyze an optical four-wave mixing (FWM) scheme for the generation of coherent light in a coherent six-level atomic medium based on dual electromagnetically induced transparency (EIT). We show that the significantly enhanced conversion efficiency enabled by ultraslow propagation of pump waves has no direct relationship with the single-photon detuning, which is different from the FWM with a single EIT. The most important feature is that our scheme is also capable of inhibiting and delaying the onset of the detrimental three-photon destructive interference that looks like a recent scheme [Phys. Rev. Lett. 91 (2003) 243902] andmay be used for generating short-wave-length coherent radiation.

  4. The measurement of capillary waves on a weldpool formed by a Nd:YAG laser

    CERN Document Server

    Deam, R T; Harris, J

    2002-01-01

    Experiments were performed using an on-line pyrometer to measure the capillary waves on a weldpool formed by a Nd: YAG laser. The surface temperature measurements taken from the weldpool revealed strong temporal fluctuations. Fourier transform of the pyrometer data revealed distinct peaks, consistent with calculated resonant frequencies for capillary surface waves on the weldpool formed by the laser. The possibility of using on-line measurement of surface temperature fluctuations to control weldpool depth in laser welds is discussed. The work forms part of an on-going programme to develop closed loop control for laser processing at Swinburne University

  5. Repetition rate continuously tunable 10-GHz picosecond mode-locked fiber ring laser

    Institute of Scientific and Technical Information of China (English)

    Fang Wan; Ziyu Wang

    2006-01-01

    A couple of simple-structure phase modulators were used in active mode-locked fiber laser to implement repetition rate continuous tuning. The laser produces pulse as short as 5.7 ps whose repetition rate tuning can cover the spacing of the adjoining order mode-locking frequencies.

  6. Low-power continuous-wave four-wave mixing wavelength conversion in AlGaAs-nanowaveguide microresonators.

    Science.gov (United States)

    Kultavewuti, Pisek; Pusino, Vincenzo; Sorel, Marc; Stewart Aitchison, J

    2015-07-01

    We experimentally demonstrate enhanced wavelength conversion in a Q∼7500 deeply etched AlGaAs-nanowaveguide microresonator via degenerate continuous-wave four-wave mixing with a pump power of 24 mW. The maximum conversion efficiency is -43  dB and accounts for 12 dB enhancement compared to that of a straight nanowaveguide. The experimental results and theoretical predictions agree very well and show optimized conversion efficiency of -15  dB. This work represents a step toward realizing a fully integrated optical devices for generating new optical frequencies.

  7. Efficient continuous-wave four-wave mixing in bandgap-engineered AlGaAs waveguides.

    Science.gov (United States)

    Wathen, Jeremiah J; Apiratikul, Paveen; Richardson, Christopher J K; Porkolab, Gyorgy A; Carter, Gary M; Murphy, Thomas E

    2014-06-01

    We present a side-by-side comparison of the nonlinear behavior of four passive AlGaAs ridge waveguides where the bandgap energy of the core layers ranges from 1.60 to 1.79 eV. By engineering the bandgap to suppress two-photon absorption, minimizing the linear loss, and minimizing the mode area, we achieve efficient wavelength conversion in the C-band via partially degenerate four-wave mixing with a continuous-wave pump. The observed conversion efficiency [Idler(OUT)/Signal(IN)=-6.8  dB] is among the highest reported in passive semiconductor or glass waveguides.

  8. Low-power continuous-wave four-wave mixing wavelength conversion in AlGaAs-nanowaveguide microresonators

    CERN Document Server

    Kultavewuti, Pisek; Sorel, Marc; Aitchison, J Stewart

    2016-01-01

    We experimentally demonstrate enhanced wavelength conversion in a Q=7500 deeply etched AlGaAs-nanowaveguide microresonator via degenerate continuous-wave four-wave mixing with a pump power of 24 mW. The maximum conversion efficiency is -43 dB and accounts for 12 dB enhancement compared to that of a straight nanowaveguide. The experimental results and theoretical predictions agree very well and show optimized conversion efficiency of -15 dB. This work represents a step toward realizing a fully integrated optical devices for generating new optical frequencies.

  9. Note: Lossless laser beam combiner employing a high-speed rotating half-wave plate

    Science.gov (United States)

    Yatsuka, E.; Yamamoto, T.; Hatae, T.; Torimoto, K.; Itami, K.

    2017-07-01

    We have developed a laser beam combiner employing a high-speed rotating half-wave plate based on the specific requirements of the Thomson scattering measurement systems in the ITER. The polarization extinction ratio of the output beam may exceed 1000 and was maintained for more than 1 h via feedback control of the half-wave plate rotation speed. The pointing fluctuations introduced by rotating the half-wave plate were in the order of microradians. The high-speed rotating half-wave plate provides a lossless means of combining laser beams together with stable beam pointing.

  10. Note: Lossless laser beam combiner employing a high-speed rotating half-wave plate.

    Science.gov (United States)

    Yatsuka, E; Yamamoto, T; Hatae, T; Torimoto, K; Itami, K

    2017-07-01

    We have developed a laser beam combiner employing a high-speed rotating half-wave plate based on the specific requirements of the Thomson scattering measurement systems in the ITER. The polarization extinction ratio of the output beam may exceed 1000 and was maintained for more than 1 h via feedback control of the half-wave plate rotation speed. The pointing fluctuations introduced by rotating the half-wave plate were in the order of microradians. The high-speed rotating half-wave plate provides a lossless means of combining laser beams together with stable beam pointing.

  11. Characteristics of Plasma Shock Waves Generated in the Pulsed Laser Ablation Process

    Institute of Scientific and Technical Information of China (English)

    李智华; 张端明; 郁伯铭; 关丽

    2002-01-01

    We modify the Sedov theory to describe plasma shock waves generated in a pulsed laser ablating process. We also study the propagation characteristics of plasma shock waves during the preparation process of functional thin films deposited by a pulsed laser. In particular, we discuss in detail the temporal behaviour of energy causing the difference of the propagation characteristics between the plasma shock wave and the ideal shock wave in the point explosion model. Under the same experimental conditions, the theoretical results calculated with our modified Sedov theory are in good agreement with the existing experimental data.

  12. Continuous leaky-wave scanning using periodically modulated spoof plasmonic waveguide.

    Science.gov (United States)

    Kong, Gu Sheng; Ma, Hui Feng; Cai, Ben Geng; Cui, Tie Jun

    2016-07-12

    The plasmonic waveguide made of uniform corrugated metallic strip can support and guide spoof surface plasmon polaritons (SSPPs) with high confinements. Here, we propose periodically-modulated plasmonic waveguide composed of non-uniform corrugated metallic strip to convert SSPPs to radiating waves, in which the main beam of radiations can steer continuously as the frequency changes. To increase the radiation efficiency of the periodically-modulated plasmonic waveguide at the broadside, an asymmetrical plasmonic waveguide is further presented to reduce the reflections and realize continuous leaky-wave scanning. Both numerical simulations and experimental results show that the radiation efficiency can be improved greatly and the main beam of leaky-wave radiations can steer from the backward quadrant to the forward quadrant, passing through the broadside direction, which generally is difficult to be realized by the common leaky-wave antennas.

  13. Energy of hydrodynamic and magnetohydrodynamic waves with point and continuous spectra

    Science.gov (United States)

    Hirota, M.; Fukumoto, Y.

    2008-08-01

    Energy of waves (or eigenmodes) in an ideal fluid and plasma is formulated in the noncanonical Hamiltonian context. By imposing the kinematical constraint on perturbations, the linearized Hamiltonian equation provides a formal definition of wave energy not only for eigenmodes corresponding to point spectra but also for singular ones corresponding to a continuous spectrum. The latter becomes dominant when mean fields have inhomogeneity originating from shear or gradient of the fields. The energy of each wave is represented by the eigenfrequency multiplied by the wave action, which is nothing but the action variable and, moreover, is associated with a derivative of a suitably defined dispersion relation. The sign of the action variable is crucial to the occurrence of Hopf bifurcation in Hamiltonian systems of finite degrees of freedom [M. G. Krein, Dokl. Akad. Nauk SSSR, Ser. A 73, 445 (1950)]. Krein's idea is extended to the case of coalescence between point and continuous spectra.

  14. Optoelectronics: Continuously Spatial-Wavelength-Tunable Nanowire Lasers on a Single Chip

    Science.gov (United States)

    2014-01-28

    non peer-reviewed journals: Topic 4.2 Optoelectronics : Continuously spatial-wavelength-tunable nanowire lasers on a single chip Report Title Extensive...Nov-2008 30-Apr-2013 Approved for Public Release; Distribution Unlimited Topic 4.2 Optoelectronics : Continuously spatial-wavelength-tunable nanowire... lasers on a single chip The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued as an official

  15. Four-wave-mixing experiments with seeded free electron lasers.

    Science.gov (United States)

    Bencivenga, F; Calvi, A; Capotondi, F; Cucini, R; Mincigrucci, R; Simoncig, A; Manfredda, M; Pedersoli, E; Principi, E; Dallari, F; Duncan, R A; Izzo, M G; Knopp, G; Maznev, A A; Monaco, G; Di Mitri, S; Gessini, A; Giannessi, L; Mahne, N; Nikolov, I P; Passuello, R; Raimondi, L; Zangrando, M; Masciovecchio, C

    2016-12-16

    The development of free electron laser (FEL) sources has provided an unprecedented bridge between the scientific communities working with ultrafast lasers and extreme ultraviolet (XUV) and X-ray radiation. Indeed, in recent years an increasing number of FEL-based applications have exploited methods and concepts typical of advanced optical approaches. In this context, we recently used a seeded FEL to demonstrate a four-wave-mixing (FWM) process stimulated by coherent XUV radiation, namely the XUV transient grating (X-TG). We hereby report on X-TG measurements carried out on a sample of silicon nitride (Si3N4). The recorded data bears evidence for two distinct signal decay mechanisms: one occurring on a sub-ps timescale and one following slower dynamics extending throughout and beyond the probed timescale range (100 ps). The latter is compatible with a slower relaxation (time decay > ns), that may be interpreted as the signature of thermal diffusion modes. From the peak intensity of the X-TG signal we could estimate a value of the effective third-order susceptibility which is substantially larger than that found in SiO2, so far the only sample with available X-TG data. Furthermore, the intensity of the time-coincidence peak shows a linear dependence on the intensity of the three input beams, indicating that the measurements were performed in the weak field regime. However, the timescale of the ultrafast relaxation exhibits a dependence on the intensity of the XUV radiation. We interpreted the observed behaviour as the generation of a population grating of free-electrons and holes that, on the sub-ps timescale, relaxes to generate lattice excitations. The background free detection inherent to the X-TG approach allowed the determination of FEL-induced electron dynamics with a sensitivity largely exceeding that of transient reflectivity and transmissivity measurements, usually employed for this purpose.

  16. Continuous-wave Terahertz Imaging Applied to Detect Infestations Caused by Insects in Grain

    Directory of Open Access Journals (Sweden)

    Zuojun Tan

    2014-02-01

    Full Text Available Detection infestations caused by insects in grain are important control measures for ensuring storage longevity, seed quality and food safety. The efficiency of the continuous wave terahertz imaging method to detect infestations caused by insects in wheat kernels was determined in this study. A continuous wave terahertz experimental setup was designed for recording of THz images corresponding to different infestations caused by different life stages of insects. The experimental results indicate that the absorbance is generally highest for un-infested wheat kernels and decreased at later growth stages from THz pseudo-color images. Our study intended to demonstrate how the method of continuous wave Terahertz imaging could be applied to detect Infestations Caused by Insects in Grain.

  17. Variational space-time (dis)continuous Galerkin method for nonlinear free surface water waves

    Science.gov (United States)

    Gagarina, E.; Ambati, V. R.; van der Vegt, J. J. W.; Bokhove, O.

    2014-10-01

    A new variational finite element method is developed for nonlinear free surface gravity water waves using the potential flow approximation. This method also handles waves generated by a wave maker. Its formulation stems from Miles' variational principle for water waves together with a finite element discretization that is continuous in space and discontinuous in time. One novel feature of this variational finite element approach is that the free surface evolution is variationally dependent on the mesh deformation vis-à-vis the mesh deformation being geometrically dependent on free surface evolution. Another key feature is the use of a variational (dis)continuous Galerkin finite element discretization in time. Moreover, in the absence of a wave maker, it is shown to be equivalent to the second order symplectic Störmer-Verlet time stepping scheme for the free-surface degrees of freedom. These key features add to the stability of the numerical method. Finally, the resulting numerical scheme is verified against nonlinear analytical solutions with long time simulations and validated against experimental measurements of driven wave solutions in a wave basin of the Maritime Research Institute Netherlands.

  18. Ultra-Low Noise Quad Photoreceiver for Space Based Laser Interferometric Gravity Wave Detection Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Gravity wave detection using space-based long-baseline laser interferometric sensors imposes stringent noise requirements on the system components, including the...

  19. Guided-wave tomography imaging plate defects by laser-based ultrasonic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jun Pil; Lim, Ju Young; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Pusan (Korea, Republic of)

    2014-12-15

    Contact-guided-wave tests are impractical for investigating specimens with limited accessibility and rough surfaces or complex geometric features. A non-contact setup with a laser-ultrasonic transmitter and receiver is quite attractive for guided-wave inspection. In the present work, we developed a non-contact guided-wave tomography technique using the laser-ultrasonic technique in a plate. A method for Lamb-wave generation and detection in an aluminum plate with a pulsed laser-ultrasonic transmitter and Michelson-interferometer receiver was developed. The defect shape and area in the images obtained using laser scanning, showed good agreement with the actual defect. The proposed approach can be used as a non-contact online inspection and monitoring technique.

  20. A study on laser-based ultrasonic technique by the use of guided wave tomographic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junpil, E-mail: jpp@pusan.ac.kr; Lim, Juyoung, E-mail: jpp@pusan.ac.kr [Graduate school, School of Mechanical Engineering, Pusan National University (Korea, Republic of); Cho, Younho [School of Mechanical Engineering, Pusan National University (Korea, Republic of); Krishnaswamy, Sridhar [Center for Quality Engineering and Failure Prevention, Northwestern University, Evanston, IL (United States)

    2015-03-31

    Guided wave tests are impractical for investigating specimens with limited accessibility and coarse surfaces or geometrically complicated features. A non-contact setup with a laser ultrasonic transmitter and receiver is the classic attractive for guided wave inspection. The present work was done to develop a non-contact guided-wave tomography technique by laser ultrasonic technique in a plate-like structure. A method for Lam wave generation and detection in an aluminum plate with a pulse laser ultrasonic transmitter and a Michelson interferometer receiver has been developed. In the images obtained by laser scanning, the defect shape and area showed good agreement with the actual defect. The proposed approach can be used as a non-contact-based online inspection and monitoring technique.

  1. Visualization of Guided Wave Propagation with Laser Doppler Vibrometer Scanning on Curved Surfaces

    Science.gov (United States)

    Hayashi, T.; Kojika, Y.; Kataoka, K.; Takikawa, M.

    2008-02-01

    In guided wave inspection for pipes, defect characterization is performed by echoes from defects. However, since detected signals become very complex due to mode conversion and multiple reflections, wave mechanics in a pipe with defects are not well studied. In this study, therefore, visualization technique for guided waves in a pipe is developed. In order to visualize guided wave propagation in a pipe, we need to scan an ultrasonic probe and measure ultrasonic waves at many points on a surface of a pipe. Position and posture of a laser doppler vibrometer are controlled by a robot arm, and ultrasonic vibration is detected at arbitrary points from arbitrary laser beam direction. Using the laser scanning technique, reflected guided waves from a shallow round defect was observed in the visualization results. From the defect, reflected waves propagated spirally in the oblique direction. From the view point of guided wave, the spiral waves were very high order modes that have not been measured in guided wave inspection. This result shows that such high order guided wave modes should be useful for defect characterization as well as low order modes.

  2. Study of laser-induced plasma shock waves by the probe beam deflection technique

    Institute of Scientific and Technical Information of China (English)

    Yan Qian; Jian Lu; Xiaowu Ni

    2009-01-01

    Laser probe beam deflection technique is used for the analysis of laser-induced plasma shock waves in air and distilled water.The temporal and spatial variations of the parameters on shock fronts are studied as funotions of focal lens position and laser energy.The influences of the characteristics of media are investigated on the well-designed experimental setup.It is found that the shock wave in distilled water attenuates to an acoustic wave faster than in air under the same laser energy.Good agreement is obtained between our experimental results and those attained with other techniques.This technique is versatile,economic,and simple to implement,being a pronmising diagnostic tool for pulsed laser processing.

  3. Time series analysis of continuous-wave coherent Doppler Lidar wind measurements

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Mikkelsen, Torben; Mann, Jakob

    2008-01-01

    The influence of spatial volume averaging of a focused 1.55 mu m continuous-wave coherent Doppler Lidar on observed wind turbulence measured in the atmospheric surface layer over homogeneous terrain is described and analysed. Comparison of Lidar-measured turbulent spectra with spectra simultaneou......The influence of spatial volume averaging of a focused 1.55 mu m continuous-wave coherent Doppler Lidar on observed wind turbulence measured in the atmospheric surface layer over homogeneous terrain is described and analysed. Comparison of Lidar-measured turbulent spectra with spectra...

  4. Athermal Annealing of Semiconductors Using Shock Waves Generated by a Laser-Plasma

    Science.gov (United States)

    Fischer, R. P.; Grun, J.; Mignogna, R.; Donnelly, D. W.; Covington, B.

    2004-07-01

    We are investigating an annealing technique in which shock or sound waves generated by a laser-plasma are used to anneal a semiconductor. The athermal annealing (AA) process occurs very rapidly, which results in almost no diffusion of. dopants. A HeNe laser is used to measure the reflectivity of the silicon as a function of time. Measurements show that the annealing occurs in 1.8 μsec, which is the acoustic time scale for waves to propagate from the focus through the AA region. A knife-edge technique is employed to study acoustic waves in the sample by measuring the deflection of the probe beam. Initial results for aluminum samples irradiated at modest laser intensities (200 mJ, 50 nsec) show well-defined surface acoustic waves. However, both silicon and GaAs have more complicated structure which resemble Lamb (plate) waves.

  5. Cascaded four-wave mixing for broadband tunable laser sideband generation.

    Science.gov (United States)

    Liu, Weimin; Zhu, Liangdong; Wang, Liang; Fang, Chong

    2013-06-01

    We demonstrate the versatile broadband wavelength tunability of frequency upconverted multicolor cascaded four-wave-mixing (CFWM) signals spanning the continuous wavelength range from UV to near IR in a thin type-I BBO crystal using 35 fs, 800 nm fundamental and chirped IR supercontinuum white light pulses. Two sets of spatially dispersed CFWM laser sidebands are concomitantly generated from two incident pulses as well as their second-harmonic-generation and sum-frequency-generation pulses in a crossing geometry. The tunable cascaded signals with ultrabroad bandwidth can be readily achieved via spatially rotating the BBO crystal to different phase-matching conditions and temporally varying the time delay between the two incident near-IR pulses.

  6. Continuously tunable pulsed Ti:Sa laser self-seeded by an extended grating cavity

    CERN Document Server

    Li, Ruohong; Rothe, Sebastian; Teigelhöfer, Andrea; Mostamand, Maryam

    2016-01-01

    A continuously tunable titanium:sapphire (Ti:Sa) laser self-seeded by an extended grating cavity was demonstrated and characterized. By inserting a partially reflecting mirror inside the cavity of a classic single-cavity grating laser, two oscillators are created: a broadband power oscillator, and a narrowband oscillator with a prism beam expander and a diffraction grating in Littrow configuration. By coupling the grating cavity oscillation into the power oscillator, a power-enhanced narrow-linewidth laser oscillation is achieved. Compared to the classic grating laser, this simple modification significantly increases the laser output power without considerably broadening the linewidth. With most of the oscillating laser power confined inside the broadband power cavity and lower power incident onto the grating, the new configuration also allows higher pump power, which is typically limited by the thermal deformation of the grating coating at high oscillation power.

  7. Laser-driven Beat-Wave Current Drive in Dense Plasmas with Demo on CTIX

    Science.gov (United States)

    Liu, Fei; Horton, Robert; Hwang, David; Zhu, Ben; Evans, Russell; Hong, Sean; Hsu, Scott

    2010-11-01

    The ability to remotely generate plasma current in dense plasmas hanging freely in vacuum in voluminous amount without obstruction to diagnostics will greatly enhance our ability to study the physics of high energy density plasmas in strong magnetic fields. Plasma current can be generated through nonlinear beat-wave process by launching two intense electromagnetic waves into unmagnetized plasma. Beat-wave acceleration of electrons has been demonstrated in a low-density plasma using microwaves [1]. The proposed PLX experimental facility presently under construction at Los Alamos offers the opportunity to test the method at a density level scalable to the study of HED plasmas. For PLX beat-wave experiments, CO2 lasers will be used as pump waves due to their high power and tunability. For a typical PLX density ne=10^17cm-3, two CO2 lasers can be separately tuned to 9P(28) and 10P(20) to match the 2.84THz plasma frequency. The beat-wave demo experiment will be conducted on CTIX. The laser arrangement is being converted to two independent single lasers. Frequency-tuning methods, optics focusing system and diagnostics system will be discussed. The laser measurements and results of synchronization of two lasers will be presented, and scaling to PLX experiments will be given. [1] Rogers, J. H. and Hwang, D. Q., PRL. v68 p3877 (1992).

  8. Ultrasensitive standoff chemical sensing based on nonlinear multi-photon laser wave-mixing spectroscopy

    Science.gov (United States)

    Gregerson, Marc; Hetu, Marcel; Iwabuchi, Manna; Jimenez, Jorge; Warren, Ashley; Tong, William G.

    2012-10-01

    Nonlinear multi-photon laser wave mixing is presented as an ultrasensitive optical detection method for chem/bio agents in thin films and gas- and liquid-phase samples. Laser wave mixing is an unusually sensitive optical absorption-based detection method that offers significant inherent advantages including excellent sensitivity, small sample requirements, short optical path lengths, high spatial resolution, high spectral resolution and standoff remote detection capability. Wave mixing can detect trace amounts of chemicals even when using micrometer-thin samples, and hence, it can be conveniently interfaced to fibers, microarrays, microfluidic systems, lab-on-a-chip, capillary electrophoresis and other capillary- or fiber-based chemical separation systems. The wave-mixing signal is generated instantaneously as the two input laser beams intersect inside the analyte of interest. Laser excitation wavelengths can be tuned to detect multiple chemicals in their native form since wave mixing can detect both fluorescing and non-fluorescing samples at parts-pertrillion or better detection sensitivity levels. The wave-mixing signal is a laser-like coherent beam, and hence, it allows reliable and effective remote sensing of chemicals. Sensitive wave-mixing detectors offer many potential applications including sensitive detection of biomarkers, early detection of diseases, sensitive monitoring of environmental samples, and reliable detection of hazardous chem/bio agents with a standoff detection capability.

  9. High-pressure continuously tunable CO2 lasers and molecular laser isotope separation

    Indian Academy of Sciences (India)

    E Ronander; H J Strydom; L R Botha

    2014-01-01

    The acronym MLIS (molecular laser isotope separation) defines the laser process whereby the isotopes of uranium can be separated by mid-infrared laser/s when the molecule employed is UF6. The theoretical and spectroscopical data to configure and enable experiments and demonstrations in the laboratory is adequate. However, the engineering and commercial aspects require innovative technology solutions that are not presently available in the literature on these topics. This paper is an overview of the most salient features of MLIS and its potential utility at an industrial level.

  10. Continuous variable entanglement in a coherently pumped correlated emission laser

    Energy Technology Data Exchange (ETDEWEB)

    Tesfa, Sintayehu [Physics Department, Addis Ababa University, PO Box 1176, Addis Ababa (Ethiopia)], E-mail: sint_tesfa@yahoo.com

    2008-03-14

    Analysis of the effects of external pumping on the quantum features of cavity radiation of the two-photon correlated emission laser is presented. It turns out that the pumping process induces the atomic coherence responsible for the entanglement of the cavity radiation as well as the correlation between the photon numbers belonging to different modes, despite the arising vacuum fluctuations. The photon number correlation is found to be very close to 2 where the entanglement is relatively better. Moreover, the mean number of photon pairs decreases with the amplitude of the driving radiation which is one of the practical limitations associated with the pumping mechanism. It is also shown that the mean photon number of the radiation in mode b is less than one-third of that in mode a.

  11. Transcranial direct current stimulation in refractory continuous spikes and waves during slow sleep: a controlled study

    DEFF Research Database (Denmark)

    Varga, Edina T; Terney, Daniella; Atkins, Mary D;

    2011-01-01

    Cathodal transcranial direct current stimulation (tDCS) decreases cortical excitability. The purpose of the study was to investigate whether cathodal tDCS could interrupt the continuous epileptiform activity. Five patients with focal, refractory continuous spikes and waves during slow sleep were...... recruited. Cathodal tDCS and sham stimulation were applied to the epileptic focus, before sleep (1 mA; 20 min). Cathodal tDCS did not reduce the spike-index in any of the patients....

  12. Omnidirectional Gravitational Wave Detector with a Laser-Interferometric Gravitational Compass

    CERN Document Server

    Maia, M D; Sousa, Claudio M G; Magalhaes, Nadja S; Frajuca, Carlos

    2016-01-01

    Based on the Szekeres-Pirani gravitational compass we suggest the addition of a fourth, non-coplanar mass/mirror to the presently existing laser based gravitational wave observatories, enabling them to operate omnidirectionally, to filter out ambiguous interpretations and to point out the direction of the gravitational wave source.

  13. Acoustic-wave generation in the process of CO2-TEA-laser-radiation interaction with metal targets in air

    Science.gov (United States)

    Apostol, Ileana; Teodorescu, G.; Serbanescu-Oasa, Anca; Dragulinescu, Dumitru; Chis, Ioan; Stoian, Razvan

    1995-03-01

    Laser radiation interaction with materials is a complex process in which creation of acoustic waves or stress waves is a part of it. As a function of the laser radiation energy and intensity incident on steel target surface ultrasound signals were registered and studied. Thermoelastic, ablation and breakdown mechanisms of generation of acoustic waves were analyzed.

  14. Low-power continuous-wave nonlinear optics in doped silica glass integrated waveguide structures

    Science.gov (United States)

    Ferrera, M.; Razzari, L.; Duchesne, D.; Morandotti, R.; Yang, Z.; Liscidini, M.; Sipe, J. E.; Chu, S.; Little, B. E.; Moss, D. J.

    2008-12-01

    Photonic integrated circuits are a key component of future telecommunication networks, where demands for greater bandwidth, network flexibility, and low energy consumption and cost must all be met. The quest for all-optical components has naturally targeted materials with extremely large nonlinearity, including chalcogenide glasses and semiconductors, such as silicon and AlGaAs (ref. 4). However, issues such as immature fabrication technology for chalcogenide glass and high linear and nonlinear losses for semiconductors motivate the search for other materials. Here we present the first demonstration of nonlinear optics in integrated silica-based glass waveguides using continuous-wave light. We demonstrate four-wave mixing, with low (5 mW) continuous-wave pump power at λ = 1,550 nm, in high-index, doped silica glass ring resonators. The low loss, design flexibility and manufacturability of our device are important attributes for low-cost, high-performance, nonlinear all-optical photonic integrated circuits.

  15. Coherently combining short data segments for all-sky semi-coherent continuous gravitational wave searches

    CERN Document Server

    Goetz, Evan

    2015-01-01

    We present a method for coherently combining short data segments from gravitational-wave detectors to improve the sensitivity of semi-coherent searches for continuous gravitational waves. All-sky searches for continuous gravitational waves from unknown sources are computationally limited. The semi-coherent approach reduces the computational cost by dividing the entire observation timespan into short segments to be analyzed coherently, then combined together incoherently. Semi-coherent analyses that attempt to improve sensitivity by coherently combining data from multiple detectors face a computational challenge in accounting for uncertainties in signal parameters. In this article, we lay out a technique to meet this challenge using summed Fourier transform coefficients. Applying this technique to one all-sky search algorithm called TwoSpect, we confirm that the sensitivity of all-sky, semi-coherent searches can be improved by coherently combining the short data segments. For misaligned detectors, however, thi...

  16. Generation of continuous-wave THz radiation by use of quantum interference

    CERN Document Server

    Korsunsky, E A

    1999-01-01

    We propose a scheme for generation of continuous-wave THz radiation. The scheme requires a medium where three discrete states in a $\\Lambda $ configuration can be selected, with the THz-frequency transition between the two lower metastable states. We consider the propagation of three-frequency continuous-wave electromagnetic (e.m.) radiation through a $\\Lambda $ medium. Under resonant excitation, the medium absorption can be strongly reduced due to quantum interference of transitions, while the nonlinear susceptibility is enhanced. This leads to very efficient energy transfer between the e.m. waves providing a possibility for THz generation. We demonstrate that the photon conversion efficiency is approaching unity in this technique.

  17. A wave-optics approach to paraxial geometrical laws based on continuity at boundaries

    Science.gov (United States)

    Liñares, J.; Nistal, M. C.

    2011-09-01

    We present a derivation of the paraxial geometrical laws starting from a wave-optics approach, in particular by using simple continuity conditions of paraxial spherical waves at boundaries (discontinuities) between optical media. Paraxial geometrical imaging and magnification laws, under refraction and reflection at boundaries, are derived for several instructive cases and without using Fresnel diffraction theory. The primary aim is to provide a complementary insight into the standard axiomatic approach of paraxial geometrical optics and likewise to allow the introduction of some wave imaging concepts, such as the transmittance function, with a notable didactic interest for advanced subjects such as Fourier optics. This approach provides a more homogeneous vision of classical optics in which the use of the optical field continuity conditions at a boundary is a usual requirement as is clearly seen, for example, in the case of the derivation of Fresnel formulas. The work is particularly intended for university physics teachers and pregraduate and first year postgraduate students.

  18. A Continuous Millimeter-Wave Imaging Scanner for Art Conservation Science

    Directory of Open Access Journals (Sweden)

    Ayesha Younus

    2011-01-01

    Full Text Available A monochromatic continuous millimeter-wave imaging system coupled with an infrared temperature sensor has been used to investigate artistic objects such as painting artworks or antiquities preserved at the museum of Aquitaine. Especially, 2D and 3D analyses have been performed in order to reveal the internal structure of a nearly 3500-year-old sealed Egyptian jar.

  19. Variational space-time (dis)continuous Galerkin method for linear free surface waves

    NARCIS (Netherlands)

    Ambati, V.R.; Vegt, van der J.J.W.; Bokhove, O.

    2008-01-01

    A new variational (dis)continuous Galerkin finite element method is presented for the linear free surface gravity water wave equations. We formulate the space-time finite element discretization based on a variational formulation analogous to Luke's variational principle. The linear algebraic system

  20. Spatial averaging-effects on turbulence measured by a continuous-wave coherent lidar

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Mikkelsen, Torben; Mann, Jakob;

    2009-01-01

    The influence of spatial volume averaging of a focused continuous-wave coherent Doppler lidar on observed wind turbulence in the atmospheric surface layer is described and analysed. For the first time, comparisons of lidar-measured turbulent spectra with spectra simultaneously obtained from a mast...

  1. Continuous-wave broadband emitter based on a transition-metal-ion-doped waveguide

    NARCIS (Netherlands)

    Pollnau, M.; Salathé, R.P.; Bhutta, T.; Shepherd, D.P.; Eason, R.W.

    2001-01-01

    We demonstrate the suitability of a simple continuous-wave-pumped transition-metal-ion-doped waveguide as a broadband light source in the wavelength region 600–1000 nm for interferometric applications. Spatially coherent (single mode in the confined direction), spectrally broadband (~130-nm FWHM) lu

  2. Determination of hydrocarbon levels in water via laser-induced acoustics wave

    Science.gov (United States)

    Bidin, Noriah; Hossenian, Raheleh; Duralim, Maisarah; Krishnan, Ganesan; Marsin, Faridah Mohd; Nughro, Waskito; Zainal, Jasman

    2016-04-01

    Hydrocarbon contamination in water is a major environmental concern in terms of foreseen collapse of the natural ecosystem. Hydrocarbon level in water was determined by generating acoustic wave via an innovative laser-induced breakdown in conjunction with high-speed photographic coupling with piezoelectric transducer to trace acoustic wave propagation. A Q-switched Nd:YAG (40 mJ) was focused in cuvette-filled hydrocarbon solution at various concentrations (0-2000 ppm) to induce optical breakdown, shock wave generation and later acoustic wave propagation. A nitro-dye (ND) laser (10 mJ) was used as a flash to illuminate and frozen the acoustic wave propagation. Lasers were synchronised using a digital delay generator. The image of acoustic waves was grabbed and recorded via charged couple device (CCD) video camera at the speed of 30 frames/second with the aid of Matrox software version 9. The optical delay (0.8-10.0 μs) between the acoustic wave formation and its frozen time is recorded through photodetectors. A piezo-electric transducer (PZT) was used to trace the acoustic wave (sound signal), which cascades to a digital oscilloscope. The acoustic speed is calculated from the ratio of acoustic wave radius (1-8 mm) and optical time delay. Acoustic wave speed is found to linearly increase with hydrocarbon concentrations. The acoustic signal generation at higher hydrocarbon levels in water is attributed to supplementary mass transfer and impact on the probe. Integrated high-speed photography with transducer detection system authenticated that the signals indeed emerged from the laser-induced acoustic wave instead of photothermal processes. It is established that the acoustic wave speed in water is used as a fingerprint to detect the hydrocarbon levels.

  3. Stabilized high-power laser system for the gravitational wave detector advanced LIGO.

    Science.gov (United States)

    Kwee, P; Bogan, C; Danzmann, K; Frede, M; Kim, H; King, P; Pöld, J; Puncken, O; Savage, R L; Seifert, F; Wessels, P; Winkelmann, L; Willke, B

    2012-05-07

    An ultra-stable, high-power cw Nd:YAG laser system, developed for the ground-based gravitational wave detector Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory), was comprehensively characterized. Laser power, frequency, beam pointing and beam quality were simultaneously stabilized using different active and passive schemes. The output beam, the performance of the stabilization, and the cross-coupling between different stabilization feedback control loops were characterized and found to fulfill most design requirements. The employed stabilization schemes and the achieved performance are of relevance to many high-precision optical experiments.

  4. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses

    CERN Document Server

    Jukna, Vytautas; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-01-01

    Acoustic signals generated by filamentation of ultrashort TW laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.

  5. Wave-front correction of femtosecond terawatt lasers by deformable mirrors.

    Science.gov (United States)

    Druon, F; Chériaux, G; Faure, J; Nees, J; Nantel, M; Maksimchuk, A; Mourou, G; Chanteloup, J C; Vdovin, G

    1998-07-01

    Wave-front correction and focal spot improvement of femtosecond laser beams have been achieved, for the first time to our knowledge, with a deformable mirror with an on-line single-shot three-wave lateral shearing interferometer diagnostic. Wave-front distortions of a 100-fs laser that are due to third-order nonlinear effects have been compensated for. This technique, which permits correction in a straightforward process that requires no feedback loop, is also used on a 10-TW Ti:sapphire-Nd:phosphate glass laser in the subpicosecond regime. We also demonstrate that having a focal spot close to the diffraction limit does not constitute a good criterion for the quality of the laser in terms of peak intensity.

  6. A laterally-coupled distributed feedback laser with equivalent quarter-wave phase shift.

    Science.gov (United States)

    Li, Jingsi; Cheng, Julian

    2013-11-04

    We report the first laterally-coupled distributed feedback (LC-DFB) laser with a quarter-wave equivalent phase shift (EPS) realized by interference lithography (IL) and conventional photolithography. A specially designed sampled grating is fabricated on both sidewalls of a ridge waveguide to provide a quarter-wave EPS at the center of the cavity. The resulting laser exhibits stable single-mode lasing operation over a wide range of injection currents, with a side mode suppression ratio (SMSR) of 41.1 dB. This provides a practical, low-cost method to fabricate quarter-wave phase shifted DFB lasers with high performance without any epitaxial regrowth or the use of electron-beam lithography, thereby simplifying the fabrication of DFB lasers with stable and precise wavelengths, as single devices or as arrays in photonic integrated circuits.

  7. Generation of shear waves by laser in soft media in the ablative and thermoelastic regimes

    Science.gov (United States)

    Grasland-Mongrain, Pol; Lu, Yuankang; Lesage, Frédéric; Catheline, Stefan; Cloutier, Guy

    2016-11-01

    This article describes the generation of elastic shear waves in a soft medium using a laser beam. Our experiments show two different regimes depending on laser energy. Physical modeling of the underlying phenomena reveals a thermoelastic regime caused by a local dilatation resulting from temperature increase and an ablative regime caused by a partial vaporization of the medium by the laser. The computed theoretical displacements are close to the experimental measurements. A numerical study based on the physical modeling gives propagation patterns comparable to those generated experimentally. These results provide a physical basis for the feasibility of a shear wave elastography technique (a technique that measures a soft solid stiffness from shear wave propagation) by using a laser beam.

  8. Development of a US Gravitational Wave Laser System for LISA

    Science.gov (United States)

    Camp, Jordan B.; Numata, Kenji

    2015-01-01

    A highly stable and robust laser system is a key component of the space-based LISA mission architecture.In this talk I will describe our plans to demonstrate a TRL 5 LISA laser system at Goddard Space Flight Center by 2016.The laser system includes a low-noise oscillator followed by a power amplifier. The oscillator is a low-mass, compact 10mW External Cavity Laser, consisting of a semiconductor laser coupled to an optical cavity, built by the laser vendorRedfern Integrated Optics. The amplifier is a diode-pumped Yb fiber with 2W output, built at Goddard. I will show noiseand reliability data for the full laser system, and describe our plans to reach TRL 5 by 2016.

  9. Laser Generation of Surface Waves on Cylinder with a Slow Coating

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shi-Gong; HU Wen-Xiang

    2008-01-01

    @@ An analytical model of acoustic field excited by a pulsed-laser line source on a coated cylinder is presented.Surface wave dispersive behaviours for a cylinder with a slow coating are analysed and compared with that of a bare cylinder.Based on this analysis, the laser-generated transient response of the perturbed Rayleigh wave and the higher modes of steel cylinder with a zinc coating are calculated from the model using residue theory and FFT technique.The theoretical result from the superposed waveform of the perturbed Rayleigh wave and higher modes agree well with the waveform obtained in experiment.The results show that the model and numerical method provide a useful technique for quantitatively characterizing coating parameters of coated cylinder by the laser generated surface waves.

  10. Effect of Heat Treatment on Liquation Cracking in Continuous Fiber and Pulsed Nd:YAG Laser Welding of HASTELLOY X Alloy

    Science.gov (United States)

    Pakniat, M.; Ghaini, F. Malek; Torkamany, M. J.

    2017-09-01

    Laser welding of HASTELLOY X is highly feasible; however, hot cracking can be a matter of concern. The objective of this study is to assess the effect of solution heat treatment on susceptibility to liquation cracking in welding of a 2-mm-thick HASTELLOY X plate. In addition, Nd-YAG pulsed laser (400 W) and continuous wave (CW) fiber laser (600 W) were compared with each other in this respect. Results revealed that performing the prewelding solution heat treatment reduces the tendency for occurrence of liquation cracking. Furthermore, it was established that by increasing pulse frequency, there was a significant reduction in the tendency for liquation cracking. With CW laser welding of HASTELLOY X in the solution-heat-treated condition, the tendency for heat-affected zone (HAZ) cracking was found to be minimized.

  11. Investigating Vaporization of Silica through Laser Driven Shock Wave Experiments

    Science.gov (United States)

    Kraus, R. G.; Swift, D. C.; Stewart, S. T.; Smith, R.; Bolme, C. A.; Spaulding, D. K.; Hicks, D.; Eggert, J.; Collins, G.

    2010-12-01

    Giant impacts melt and vaporize a significant amount of the bolide and target body. However, our ability to determine how much melt or vapor a given impact creates depends strongly on our understanding of the liquid-vapor phase boundary of geologic materials. Our current knowledge of the liquid-vapor equilibrium for one of the most important minerals, SiO2, is rather limited due to the difficulty of performing experiments in this area of phase space. In this study, we investigate the liquid-vapor coexistence region by shocking quartz into a supercritical fluid state and allowing it to adiabatically expand to a state on the liquid-vapor phase boundary. Although shock compression and release has been used to study the liquid-vapor equilibrium of metals [1], few attempts have been made at studying geologic materials by this method [2]. Shock waves were produced by direct ablation of the quartz sample using the Jupiter Laser Facility of Lawrence Livermore National Laboratory. Steady shock pressures of 120-360 GPa were produced in the quartz samples: high enough to force the quartz into a supercritical fluid state. As the shock wave propagates through the sample, we measure the shock velocity using a line imaging velocity interferometer system for any reflector (VISAR) and shock temperature using a streaked optical pyrometer (SOP). When the shock wave reaches the free surface of the sample, the material adiabatically expands. Upon breakout of the shock at the free surface, the SOP records a distinct drop in radiance due to the lower temperature of the expanded material. For a subset of experiments, a LiF window is positioned downrange of the expanding silica. When the expanding silica impacts the LiF window, the velocity at the interface between the expanding silica and LiF window is measured using the VISAR. From the shock velocity measurements, we accurately determine the shocked state in the quartz. The post-shock radiance measurements are used to constrain the

  12. Generation of picosecond laser pulses at 1030 nm with gigahertz range continuously tunable repetition rate.

    Science.gov (United States)

    Aubourg, Adrien; Lhermite, Jérôme; Hocquet, Steve; Cormier, Eric; Santarelli, Giorgio

    2015-12-01

    We report on a watt range laser system generating picosecond pulses using electro-optical modulation of a 1030 nm single frequency low noise laser diode. Its repetition rate is continuously tunable between 11 and 18 GHz. Over this range, output spectra and pulse characteristics are measured and compared with a numerical simulation. Finally, amplitude and residual phase noise measurements of the source are also presented.

  13. Continuous particle focusing in a waved microchannel using negative dc dielectrophoresis

    KAUST Repository

    Li, Ming

    2012-07-26

    We present a waved microchannel for continuous focusing of microparticles and cells using negative direct current (dc) dielectrophoresis. The waved channel is composed of consecutive s-shaped curved channels in series to generate an electric field gradient required for the dielectrophoretic effect. When particles move electrokinetically through the channel, the experienced negative dielectrophoretic forces alternate directions within two adjacent semicircular microchannels, leading to a focused continuous-flow stream along the channel centerline. Both the experimentally observed and numerically simulated results of the focusing performance are reported, which coincide acceptably in proportion to the specified dimensions (i.e. inlet and outlet of the waved channel). How the applied electric field, particle size and medium concentration affect the performance was studied by focusing polystyrene microparticles of varying sizes. As an application in the field of biology, the focusing of yeast cells in the waved mcirochannel was tested. This waved microchannel shows a great potential for microflow cytometry applications and is expected to be widely used before different processing steps in lab-on-A-chip devices with integrated functions. © 2012 IOP Publishing Ltd.

  14. First all-sky search for continuous gravitational waves from unknown sources in binary systems

    Science.gov (United States)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ain, A.; Ajith, P.; Alemic, A.; Allen, B.; Allocca, A.; Amariutei, D.; Andersen, M.; Anderson, R.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barbet, M.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bauchrowitz, J.; Bauer, Th. S.; Behnke, B.; Bejger, M.; Beker, M. G.; Belczynski, C.; Bell, A. S.; Bell, C.; Bergmann, G.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bloemen, S.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, Sukanta; Bosi, L.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Buchman, S.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burman, R.; Buskulic, D.; Buy, C.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Celerier, C.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C.; Colombini, M.; Cominsky, L.; Constancio, M.; Conte, A.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corpuz, A.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coughlin, S.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; Debreczeni, G.; Degallaix, J.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Donath, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dossa, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dwyer, S.; Eberle, T.; Edo, T.; Edwards, M.; Effler, A.; Eggenstein, H.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Feroz, F.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Gaonkar, S.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Gräf, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K.; Gustafson, E. K.; Gustafson, R.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hart, M.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Hooper, S.; Hopkins, P.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Huerta, E.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.

    2014-09-01

    We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ˜2,254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from ˜0.6×10-3 ls to ˜6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3×10-24 at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.

  15. Bright-dark rogue wave in mode-locked fibre laser (Conference Presentation)

    Science.gov (United States)

    Kbashi, Hani; Kolpakov, Stanislav; Martinez, Amós; Mou, Chengbo; Sergeyev, Sergey V.

    2017-05-01

    Bright-Dark Rogue Wave in Mode-Locked Fibre Laser Hani Kbashi1*, Amos Martinez1, S. A. Kolpakov1, Chengbo Mou, Alex Rozhin1, Sergey V. Sergeyev1 1Aston Institute of Photonic Technologies, School of Engineering and Applied Science Aston University, Birmingham, B4 7ET, UK kbashihj@aston.ac.uk , 0044 755 3534 388 Keywords: Optical rogue wave, Bright-Dark rogue wave, rogue wave, mode-locked fiber laser, polarization instability. Abstract: Rogue waves (RWs) are statistically rare localized waves with high amplitude that suddenly appear and disappear in oceans, water tanks, and optical systems [1]. The investigation of these events in optics, optical rogue waves, is of interest for both fundamental research and applied science. Recently, we have shown that the adjustment of the in-cavity birefringence and pump polarization leads to emerge optical RW events [2-4]. Here, we report the first experimental observation of vector bright-dark RWs in an erbium-doped stretched pulse mode-locked fiber laser. The change of induced in-cavity birefringence provides an opportunity to observe RW events at pump power is a little higher than the lasing threshold. Polarization instabilities in the laser cavity result in the coupling between two orthogonal linearly polarized components leading to the emergence of bright-dark RWs. The observed clusters belongs to the class of slow optical RWs because their lifetime is of order of a thousand of laser cavity roundtrip periods. References: 1. D. R. Solli, C. Ropers, P. Koonath,and B. Jalali, Optical rogue waves," Nature, 450, 1054-1057, 2007. 2. S. V. Sergeyev, S. A. Kolpakov, C. Mou, G. Jacobsen, S. Popov, and V. Kalashnikov, "Slow deterministic vector rogue waves," Proc. SPIE 9732, 97320K (2016). 3. S. A. Kolpakov, H. Kbashi, and S. V. Sergeyev, "Dynamics of vector rogue waves in a fiber laser with a ring cavity," Optica, 3, 8, 870, (2016). 5. S. Kolpakov, H. Kbashi, and S. Sergeyev, "Slow optical rogue waves in a unidirectional fiber laser

  16. Analytical model for ring heater thermal compensation in the Advanced Laser Interferometer Gravitational-wave Observatory.

    Science.gov (United States)

    Ramette, Joshua; Kasprzack, Marie; Brooks, Aidan; Blair, Carl; Wang, Haoyu; Heintze, Matthew

    2016-04-01

    Advanced laser interferometer gravitational-wave detectors use high laser power to achieve design sensitivity. A small part of this power is absorbed in the interferometer cavity mirrors where it creates thermal lenses, causing aberrations in the main laser beam that must be minimized by the actuation of "ring heaters," which are additional heater elements that are aimed to reduce the temperature gradients in the mirrors. In this article we derive the first, to the best of our knowledge, analytical model of the temperature field generated by an ideal ring heater. We express the resulting optical aberration contribution to the main laser beam in this axisymmetric case. Used in conjunction with wavefront measurements, our model provides a more complete understanding of the thermal state of the cavity mirrors and will allow a more efficient use of the ring heaters in the Advanced Laser Interferometer Gravitational-wave Observatory.

  17. Highly efficient terahertz wave filter for high-power laser beam separation

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Bo; Cai, Bin, E-mail: bullcai@gmail.com, E-mail: ymzhu@usst.edu.cn; Zhu, YiMing, E-mail: bullcai@gmail.com, E-mail: ymzhu@usst.edu.cn [Engineering Research Center of Optical Instruments and Systems, Ministry of Education, and Shanghai Key Lab of Modern Optical Systems, University of Shanghai for Science and Technology, Shanghai 200093 (China); Tang, Jun [Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China)

    2014-12-01

    In this study, we design and fabricate a two-layer device based on the Rayleigh scattering theory for effectively separating high-energy pump-laser-generated terahertz (THz) waves. The basic layer is comprised of cyclo olefin polymer and silicon nanoparticles, which can obstruct the propagation of the 800-nm, high-energy pump laser through scattering and absorption effects while permitting THz waves to pass through. In order to improve the laser damage threshold of the basic layer, an additional layer, which is composed of hollow silica nanoparticles, is used to diffuse the incident high-energy laser beam. Through this two-layer structure, a high 800-nm laser threshold and highly transparent THz region filter are fabricated.

  18. Continuous resonant four-wave mixing in double- Lambda level configurations of Na2

    Science.gov (United States)

    Babin, S.; Hinze, U.; Tiemann, E.; Wellegehausen, B.

    1996-08-01

    Efficient continuous resonant frequency mixing omega 4= omega 1- omega 2 + omega 3 in Na2 has been realized. A bichromatic field ( lambda 1 =488 nm, lambda 2=525 nm), generated by an Ar+ -laser-pumped Na 2 Raman laser, and radiation at lambda 3=655 nm from a dye laser interact resonantly with corresponding transitions X1 Sigma +g(v=3,J= 43) \\rightarrow B 1 Pi u(6,43) \\rightarrow X 1 Sigma +g(13, 43) \\rightarrow A 1 Sigma +g(24, 44) in a test Na2 heat pipe. For input powers of 200, 25, and 400 mW an output beam of as much as 0.2 mW at lambda 4=599 nm has been observed. Measured parameter dependences indicate an influence of interference effects. This is directly related to the discussion of lasing without inversion.

  19. On the features of the Optical Rogue Waves observed in the Kerr lens mode locked Ti:Sapphire laser

    CERN Document Server

    Hnilo, Alejandro A; Tredicce, Jorge R

    2014-01-01

    Kerr lens-mode-locked Ti:Sapphire lasers are known to display three coexistent modes of operation, that can be described as: continuous wave (CW), transform limited pulses (P1) and positive chirped pulses (P2). Optical rogue waves, in the form of pulses of high energy appearing much often than expected in a Gaussian distribution, are observed in the chaotic regime of the mode P2, but not of P1. These high energy pulses appear in an unpredictable way, but it is observed that their separation (if measured in number of round trips) can take only some definite values, which received the name of "magic numbers". The existence of optical rogue waves in P2 and not in P1, and also of the magic numbers, are correctly reproduced by a numerical simulation based on a five-variables iterative map. But, a successful numerical simulation provides limited insight on the physical causes of the observed phenomena. We present evidence that optical rogue waves in this laser follow a modulational instability, and that an initial ...

  20. Continuous-wave optical parametric oscillation tunable up to 8 μm wavelength

    Science.gov (United States)

    Breunig, Ingo; Fürst, Josef Urban; Hanka, Kevin; Buse, Karsten

    2017-06-01

    We demonstrate the first cw OPO emitting mid-infrared light at wavelengths up to 8 μm. This device is based on a 3.5-mm-diameter whispering gallery resonator made of silver gallium selenide (AgGaSe2) pumped by a compact distributed feedback laser diode emitting light at 1.57 μm wavelength. Phase-matching is achieved for a c-cut resonator disk pumped with extraordinarily polarized light at this wavelength. The oscillation thresholds are in the mW region, while the output power ranges from 10 to 800 μW. Wavelength tuning is achieved via changing the radial mode number of the pump wave and by changing the resonator temperature. Simulations predict that whispering gallery OPOs based on AgGaSe2 with diameters around 2 mm can generate idler waves exceeding 10 μm wavelength.

  1. An Einstein@home search for continuous gravitational waves from Cassiopeia A

    OpenAIRE

    Zhu, Sylvia J.; Papa, Maria Alessandra; Eggenstein, Heinz-Bernd; Prix, Reinhard; Wette, Karl; Allen, Bruce; Bock, Oliver; Keitel, David; Krishnan, Badri; Machenschalk, Bernd; Shaltev, Miroslav; Siemens, Xavier

    2016-01-01

    We report the results of a directed search for continuous gravitational-wave emission in a broad frequency range (between 50 and 1000 Hz) from the central compact object of the supernova remnant Cassiopeia A (Cas A). The data comes from the sixth science run of LIGO and the search is performed on the volunteer distributed computing network Einstein@Home. We find no significant signal candidate, and set the most constraining upper limits to date on the gravitational-wave emission from Cas A, w...

  2. Continuous-Wave Cavity Ring-Down Spectroscopy in a Pulsed Uniform Supersonic Flow

    Science.gov (United States)

    Thawoos, Shameemah; Suas-David, Nicolas; Suits, Arthur

    2017-06-01

    We introduce a new approach that couples a pulsed uniform supersonic flow with high sensitivity continuous wave cavity ringdown spectroscopy (UF-CRDS) operated in the near infrared (NIR). This combination is related to the CRESU technique developed in France and used for many years to study reaction kinetics at low temperature, and to the microwave based chirped-pulse uniform supersonic flow spectrometer (CPUF) developed in our group which has successfully demonstrated the use of pulsed uniform supersonic flow to probe reaction dynamics at temperatures as low as 22 K. CRDS operated with NIR permits access to the first overtones of C-H and O-H stretching/bending which, in combination with its extraordinary sensitivity opens new experiments complementary to the CPUF technique. The UF-CRDS apparatus (Figure) utilizes the pulsed uniform flow produced by means of a piezo-electric stack valve in combination with a Laval nozzle. At present, two machined aluminum Laval nozzles designed for carrier gases Ar and He generate flows with a temperature of approximately 25 K and pressure around 0.15 mbar. This flow is probed by an external cavity diode laser in the NIR (1280-1380 nm). Laval nozzles designed using a newly developed MATLAB-based program will be used in the future. A detailed illustration of the novel UF-CRDS instrumentation and its performance will be presented along with future directions and applications. I. Sims, J. L. Queffelec, A. Defrance, C. Rebrion-Rowe, D. Travers, P. Bocherel, B. Rowe, I. W. Smith, J. Chem. Phys. 100, 4229-4241, (1994). C. Abeysekera, B. Joalland, N. Ariyasingha, L. N. Zack, I. R. Sims, R. W. Field, A. G. Suits, J. Phys. Chem. Lett. 6, 1599-1604, (2015). N. Suas-David, T. Vanfleteren, T. Foldes, S. Kassi, R. Georges, M. Herman, J. Phys. Chem.A, 119, 10022-10034, (2015). C. Abeysekera, B. Joalland, Y. Shi, A. Kamasah, J. M. Oldham, A. G. Suits, Rev. Sci. Instrum. 85, 116107, (2014).

  3. Limitations On The Creation of Continuously Surfable Waves Generated By A Pressure Source Moving In A Circular Path

    NARCIS (Netherlands)

    Schmied, S.A.

    2014-01-01

    The aim of the research presented in this work was to investigate the novel idea to produce continuous breaking waves, whereby a pressure source was rotated within an annular wave pool. The concept was that the pressure source generates non-breaking waves that propagate inward to the inner ring of t

  4. The ''phase velocity'' of nonlinear plasma waves in the laser beat-wave accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Spence, W.L.

    1985-04-01

    A calculational scheme for beat-wave accelerators is introduced that includes all orders in velocity and in plasma density, and additionally accounts for the influence of plasma nonlinearities on the wave's phase velocity. The main assumption is that the laser frequencies are very large compared to the plasma frequency - under which it is possible to sum up all orders of forward Raman scattering. It is found that the nonlinear plasma wave does not have simply a single phase velocity, but that the beat-wave which drives it is usefully described by a non-local ''effective phase velocity'' function. A time-space domain approach is followed. (LEW)

  5. Single step high-speed printing of continuous silver lines by laser-induced forward transfer

    Energy Technology Data Exchange (ETDEWEB)

    Puerto, D., E-mail: puerto@lp3.univ-mrs.fr [Aix-Marseille University, CNRS, LP3 laboratory Campus de Luminy, C.917, Marseille (France); Biver, E. [Aix-Marseille University, CNRS, LP3 laboratory Campus de Luminy, C.917, Marseille (France); Oxford Lasers Ltd., Unit 8, Moorbrook Park, Didcot, OX11 7HP (United Kingdom); Alloncle, A.-P.; Delaporte, Ph. [Aix-Marseille University, CNRS, LP3 laboratory Campus de Luminy, C.917, Marseille (France)

    2016-06-30

    Highlights: • We have performed an experimental study on laser micro-printing of silver nanoparticle inks. • We have achieved the printing of lines in a single pass at velocities of 17 m/s (1 MHz laser). • The ejection dynamics has been investigated by means of a time-resolved imaging technique. • The control of the donor film properties is of prime importance to print lines at high velocities. • Continuous conductive lines of silver inks are laser-printed on PET flexible substrates. - Abstract: The development of high-speed ink printing process by Laser-Induced Forward Transfer (LIFT) is of great interest for the printing community. To address the problems and the limitations of this process that have been previously identified, we have performed an experimental study on laser micro-printing of silver nanoparticle inks by LIFT and demonstrated for the first time the printing of continuous conductive lines in a single pass at velocities of 17 m/s using a 1 MHz repetition rate laser. We investigated the printing process by means of a time-resolved imaging technique to visualize the ejection dynamics of single and adjacent jets. The control of the donor film properties is of prime importance to achieve single step printing of continuous lines at high velocities. We use a 30 ps pulse duration laser with a wavelength of 343 nm and a repetition rate from 0.2 to 1 MHz. A galvanometric mirror head controls the distance between two consecutives jets by scanning the focused beam along an ink-coated donor substrate at different velocities. Droplets and lines of silver inks are laser-printed on glass and PET flexible substrates and we characterized their morphological quality by atomic force microscope (AFM) and optical microscope.

  6. Quenching Plasma Waves in Two Dimensional Electron Gas by a Femtosecond Laser Pulse

    Science.gov (United States)

    Shur, Michael; Rudin, Sergey; Greg Rupper Collaboration; Andrey Muraviev Collaboration

    Plasmonic detectors of terahertz (THz) radiation using the plasma wave excitation in 2D electron gas are capable of detecting ultra short THz pulses. To study the plasma wave propagation and decay, we used femtosecond laser pulses to quench the plasma waves excited by a short THz pulse. The femtosecond laser pulse generates a large concentration of the electron-hole pairs effectively shorting the 2D electron gas channel and dramatically increasing the channel conductance. Immediately after the application of the femtosecond laser pulse, the equivalent circuit of the device reduces to the source and drain contact resistances connected by a short. The total response charge is equal to the integral of the current induced by the THz pulse from the moment of the THz pulse application to the moment of the femtosecond laser pulse application. This current is determined by the plasma wave rectification. Registering the charge as a function of the time delay between the THz and laser pulses allowed us to follow the plasmonic wave decay. We observed the decaying oscillations in a sample with a partially gated channel. The decay depends on the gate bias and reflects the interplay between the gated and ungated plasmons in the device channel. Army Research Office.

  7. Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Li, E-mail: ligan0001@gmail.com; Mousen, Cheng; Xiaokang, Li [College of Aerospace Science and Engineering, National University of Defense Technology, Changsha (China)

    2014-03-15

    In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

  8. Laser-Supported Combustion Wave Ignition in Hydrogen.

    Science.gov (United States)

    1979-10-01

    distribution unlimited. 17. DISTRIBUTION STATEMENT (of the botrac entered In Blek SO, It different firn Report) I8. SeJPPLEMENTARY NOTES IS. KEY WORDS... model of LSC wave propagation based on the analogy of chemical combustion in a long tube. The first stationary plasmatron was observed by Generalov [3...the value predicted from air LSC wave data using Raizer’s model . The LSC waves produced in these experiments radiated strongly in the visible region

  9. A prospective study of levetiracetam efficacy in epileptic syndromes with continuous spikes-waves during slow sleep

    DEFF Research Database (Denmark)

    Atkins, Mary; Nikanorova, Marina

    2011-01-01

    To evaluate the add-on effect of levetiracetam (LEV) treatment on the EEG and clinical status of children with continuous spikes-waves during slow sleep (CSWS).......To evaluate the add-on effect of levetiracetam (LEV) treatment on the EEG and clinical status of children with continuous spikes-waves during slow sleep (CSWS)....

  10. Analysis of S Wave Propagation Through a Nonlinear Joint with the Continuously Yielding Model

    Science.gov (United States)

    Cui, Zhen; Sheng, Qian; Leng, Xianlun

    2017-01-01

    Seismic wave propagation through joints that are embedded in a rock mass is a critical issue for aseismic issues of underground rock engineering. Few studies have investigated nonlinear joints with a continuously yielding model. In this paper, a time-domain recursive method (TDRM) for an S wave across a nonlinear Mohr-Coulomb (MC) slip model is extended to a continuously yielding (CY) model. Verification of the TDRM-based results is conducted by comparison with the simulated results via a built-in model of 3DEC code. Using parametric studies, the effect of normal stress level, amplitude of incident wave, initial joint shear stiffness, and joint spacing is discussed and interpreted for engineering applications because a proper in situ stress level (overburden depth) and acceptable quality of surrounding rock mass are beneficial for seismic stability issues of underground rock excavation. Comparison between the results from the MC model and the CY model is presented both for an idealized impulse excitation and a real ground motion record. Compared with the MC model, complex joint behaviors, such as tangential stiffness degradation, normal stress dependence, and the hysteresis effect, that occurred in the wave propagation can be described with the CY model. The MC model seems to underestimate the joint shear displacement in a high normal stress state and in a real ground motion excitation case.

  11. Helicopter downwash measured by continuous-wave Doppler lidars with agile beam steering

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Angelou, Nikolas; Hansen, Per

    2012-01-01

    A ground-based remote sensing short-range WindScanner with agile beam steering based on a modified ZephIR continuous-wave wind lidar (LIght Detection And Ranging) and a double prism arrangement has recently been developed at the Department of Wind Energy at the DTU Risø campus. The WindScanner me......A ground-based remote sensing short-range WindScanner with agile beam steering based on a modified ZephIR continuous-wave wind lidar (LIght Detection And Ranging) and a double prism arrangement has recently been developed at the Department of Wind Energy at the DTU Risø campus. The Wind...

  12. Generation of pulsed and continuous-wave squeezed light with 87Rb vapor.

    Science.gov (United States)

    Agha, Imad H; Messin, Gaétan; Grangier, Philippe

    2010-03-01

    We present experimental studies on the generation of pulsed and continuous-wave squeezed vacuum via nonlinear rotation of the polarization ellipse in a (87)Rb vapor. Squeezing is observed for a wide range of input powers and pump detunings on the D1 line, while only excess noise is present on the D2 line. The maximum continuous-wave squeezing observed is -1.4 +/- 0.1 dB (-2.0 dB corrected for losses). We measure -1.1 dB squeezing at the resonance frequency of the (85)Rb F = 3 --> F' transition, which may allow the storage of squeezed light generated by (87)Rb in a (85)Rb quantum memory. Using a pulsed pump, pulsed squeezed light with -1 dB of squeezing for 200 ns pulse widths is observed at 1 MHz repetition rate.

  13. A partial reconstruction scheme for continuous wave diffuse optical tomography with reflection geometry.

    Science.gov (United States)

    Patra, Rusha; Dutta, Pranab K

    2015-01-01

    Image quality and photon measurement with good SNR (signal to noise ratio) in continuous wave diffuse optical tomography depend on the source detector density and sensitivity of photo detector. For large volume objects, it is difficult to obtain detectable light intensity with good SNR over the whole boundary. As an alternative, instead of the full boundary, the measurements are taken over a semi circle as in reflection geometry and a partial reconstruction scheme for the same is proposed in this paper. The cross-sectional optical parameters are reconstructed for different half of the sample with modified boundary conditions and finally the average of all the reconstructions are considered as the final reconstructed image. Simulation and experimental results have been illustrated to validate the proposed method. The main advantage of this scheme is to improve signal to noise ratio which controls the quality of reconstruction in actual phantoms. The use of continuous wave measurement makes the system cost effective as well.

  14. Constraints on Individual Supermassive Black Hole Binaries from Pulsar Timing Array Limits on Continuous Gravitational Waves

    CERN Document Server

    Schutz, Katelin

    2015-01-01

    Pulsar timing arrays (PTAs) are placing increasingly stringent constraints on the strain amplitude of continuous gravitational waves emitted by supermassive black hole binaries on subparsec scales. In this paper, we incorporate independent measurements of the dynamical masses $M_{\\rm bh}$ of supermassive black holes in specific galaxies at known distances and leverage this additional information to further constrain whether or not those galaxies could host a detectable supermassive black hole binary. We estimate the strain amplitudes from individual binaries as a function of binary mass ratio for two samples of nearby galaxies: (1) those with direct dynamical measurements of $M_{\\rm bh}$ in the literature, and (2) the 116 most massive early-type galaxies (and thus likely hosts of the most massive black holes) within 108 Mpc from the MASSIVE Survey. Our exploratory analysis shows that the current PTA upper limits on continuous waves can already constrain the mass ratios of hypothetical black hole binaries in a...

  15. Continuous Wave Phase-Sensitive Four-Wave Mixing in Silicon Waveguides With Reverse-Biased p-i-n Junctions

    DEFF Research Database (Denmark)

    Da Ros, Francesco; Vukovic, Dragana; Gajda, A.

    2013-01-01

    Phase-sensitive four-wave mixing is experimentally demonstrated using continuous wave pumps in silicon waveguides with p-i-n junctions. The reverse biasing allows decreasing the free carrier lifetime, enabling a phase-sensitive extinction ratio in excess of 15 dB.......Phase-sensitive four-wave mixing is experimentally demonstrated using continuous wave pumps in silicon waveguides with p-i-n junctions. The reverse biasing allows decreasing the free carrier lifetime, enabling a phase-sensitive extinction ratio in excess of 15 dB....

  16. Suppression of continuous lasing in a carbon nanotube polyimide film mode-locked erbium-doped fiber laser.

    Science.gov (United States)

    Gui, Lili; Yang, Xin; Zhao, Guangzhen; Yang, Xu; Xiao, Xiaosheng; Zhu, Jinsong; Yang, Changxi

    2011-01-01

    We demonstrated an erbium-doped mode-locked fiber laser using a single-walled carbon nanotube-dispersed polyimide (SWNT-PI) film. Different mode-locking operations were compared and analyzed utilizing SWNT-PI films with different concentrations (2, 1, and 0.25 wt.%, respectively). It was found that the continuous single-pulse mode-locking operation was often accompanied by a continuous wave oscillation part for the 1 and 0.25 wt.% SWNT-PI films, whereas the 2 wt.% SWNT-PI film presented the most excellent mode-locking performance, thanks to sufficient modulation depth. Using the 2 wt.% SWNT-PI film, a stable pulse train with a pulse width of 840 fs and a repetition rate of 15.3 MHz was achieved. The average output power was 0.33 mW at the pump power of 155 mW under an output coupling ratio of 10%. Operational performance of the laser cavity when employing the 2 wt.% SWNT-PI film was also demonstrated.

  17. A Feasibility Study for Life Signs Monitoring via a Continuous-Wave Radar

    Directory of Open Access Journals (Sweden)

    Francesco Soldovieri

    2012-01-01

    Full Text Available We present a feasibility study for life signs detection using a continuous-wave radar working in the band around 4 GHz. The data-processing is carried out by using two different data processing approaches, which are compared about the possibility to characterize the frequency behaviour of the breathing and heartbeat activity. The two approaches are used with the main aim to show the possibility of monitoring the vital signs activity in an accurate and reliable way.

  18. Frequency Modulated Continuous Wave RADAR for Objects Mapping in Enclosed Spaces Using Smartphones and Arduino Components

    Science.gov (United States)

    Bar-Magen Numhauser, Jonathan; Zalevsky, Zeev

    2017-06-01

    Based on previous studies and using mobile portable device, we were able to realize a portable system capable of detecting metallic objects in a room surrounded by walls while also extracting the approximate position of such objects. Our hardware included only a smartphone device connected to several Arduino components and we were applying frequency-modulated continuous-wave electronics in each of the Arduino devices.

  19. Improvement of sensitivity in continuous wave near infra-red spectroscopy systems by using silicon photomultipliers.

    Science.gov (United States)

    Pagano, Roberto; Libertino, Sebania; Sanfilippo, Delfo; Fallica, Giorgio; Lombardo, Salvatore

    2016-04-01

    We experimentally analyze the signal-to-noise ratio of continuous wave (CW) near infrared spectroscopy (NIRS) reflectance systems based on light emitting diodes and silicon photomultipliers for high performance low cost NIRS biomedical systems. We show that under suitable experimental conditions such systems exhibit a high SNR, which allows an SDS of 7 cm, to our knowledge the largest ever demonstrated in a CW-NIRs system.

  20. High performance superconducting radio frequency ingot niobium technology for continuous wave applications

    Energy Technology Data Exchange (ETDEWEB)

    Dhakal, Pashupati, E-mail: dhakal@jlab.org; Ciovati, Gianluigi, E-mail: gciovati@jlab.org; Myneni, Ganapati R., E-mail: rao@jlab.org [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)

    2015-12-04

    Future continuous wave (CW) accelerators require the superconducting radio frequency cavities with high quality factor and medium accelerating gradients (≤20 MV/m). Ingot niobium cavities with medium purity fulfill the specifications of both accelerating gradient and high quality factor with simple processing techniques and potential reduction in cost. This contribution reviews the current superconducting radiofrequency research and development and outlines the potential benefits of using ingot niobium technology for CW applications.

  1. Variational space-time (dis)continuous Galerkin method for linear free surface waves

    OpenAIRE

    Ambati, V.R.; Vegt, van der, N.F.A.; Bokhove, O.

    2008-01-01

    A new variational (dis)continuous Galerkin finite element method is presented for the linear free surface gravity water wave equations. We formulate the space-time finite element discretization based on a variational formulation analogous to Luke's variational principle. The linear algebraic system of equations resulting from the finite element discretization is symmetric with a very compact stencil. To build and solve these equations, we have employed PETSc package in which a block sparse ma...

  2. Fourier Deconvolution Methods for Resolution Enhancement in Continuous-Wave EPR Spectroscopy.

    Science.gov (United States)

    Reed, George H; Poyner, Russell R

    2015-01-01

    An overview of resolution enhancement of conventional, field-swept, continuous-wave electron paramagnetic resonance spectra using Fourier transform-based deconvolution methods is presented. Basic steps that are involved in resolution enhancement of calculated spectra using an implementation based on complex discrete Fourier transform algorithms are illustrated. Advantages and limitations of the method are discussed. An application to an experimentally obtained spectrum is provided to illustrate the power of the method for resolving overlapped transitions.

  3. CO2 Laser Beat-Wave Experiment in an Unmagnetized Plasma

    Science.gov (United States)

    Liu, Fei; Hwang, David; Horton, Robert; Hong, Sean; Evans, Russell

    2012-10-01

    The ability to remotely generate plasma current in dense plasmas is a basic yet important investigation in experimental plasma physics and fusion energy research. It is even more advantageous if the wave penetration is independent of the electron acceleration process. Plasma current can be generated through beat-wave mixing process by launching two intense electromagnetic waves (φ>>φpe) into plasma. The beat wave formation process can be efficient if the difference frequency of the two pump waves is matched to a local resonant frequency of the medium, i.e. in this case the local plasma frequency. Beat wave can accelerate plasma electrons via quasi-linear Landau process, which has been demonstrated in a low-density plasma using microwaves.footnotetextRogers, J. H. and Hwang, D. Q., Phys. Rev. Lett. v68 p3877 (1992). The CO2 lasers provide the high tunability for the wave-particle interaction experiment at a variety of plasma densities with plasma frequency in THz range. Two sections of Lumonics TEA CO2 lasers have been modified to serve as the two pump wave sources with peak power over 100MW. The development of the tunable CO2 lasers, a high-density plasma target source and diagnostics system will be presented. The initial results of unbalanced beat-wave experiment using one high-power pulsed and one low-power CW CO2 lasers will be presented and discussed using the independent plasma source to control the φpe of the interaction region. This work is supported by U.S. DOE under Contract No. DE-FG02-10ER55083.

  4. Detailed study of four-wave mixing in Raman DFB fiber lasers.

    Science.gov (United States)

    Shi, Jindan; Horak, Peter; Alam, Shaif-Ul; Ibsen, Morten

    2014-09-22

    We both experimentally and numerically studied the ultra-compact wavelength conversion by using the four-wave mixing (FWM) process in Raman distributed-feedback (R-DFB) fiber lasers. The R-DFB fiber laser is formed in a 30 cm-long commercially available Ge/Si standard optical fiber. The internal generated R-DFB signal acts as the pump wave for the FWM process and is in the normal dispersion range of the fiber. Utilizing a tunable laser source as a probe wave, FWM frequency conversion up to ~40 THz has been demonstrated with conversion efficiency > -40 dB. The principle of such a wide bandwidth and high conversion efficiency in such a short R-DFB cavity has been theoretically analyzed. The simulation results match well with the experimental data.

  5. Four-wave mixing analysis of quantum dot semiconductor lasers for linewidth enhancement factor extraction.

    Science.gov (United States)

    Lin, Chih-Hao; Lin, Hung-Hsin; Lin, Fan-Yi

    2012-01-02

    We apply a four-wave mixing analysis on a quantum dot laser to simultaneously obtain the linewidth enhancement factor α and other intrinsic laser parameters. By fitting the experimentally obtained regenerative signals and power spectra at different detuning frequencies with the respective curves analytically calculated from the rate equations, parameters including the linewidth enhancement factor, the carrier decay rate in the dots, the differential gain, and the photon decay rate can be determined all at once under the same operating conditions. In this paper, a theoretical model for the four-wave mixing analysis of the QD lasers is derived and verified. The sensitivity and accuracy of the parameter extraction using the four-wave mixing method are presented. Moreover, how each each parameters alter the shapes of the regenerative signals and the power spectra are also discussed.

  6. Dynamic acousto-elastic test using continuous probe wave and transient vibration to investigate material nonlinearity.

    Science.gov (United States)

    Eiras, J N; Vu, Q A; Lott, M; Payá, J; Garnier, V; Payan, C

    2016-07-01

    This study demonstrates the feasibility of the dynamic acousto-elastic effect of a continuous high frequency wave for investigating the material nonlinearity upon transient vibration. The approach is demonstrated on a concrete sample measuring 15×15×60cm(3). Two ultrasonic transducers (emitter and receiver) are placed at its middle span. A continuous high frequency wave of 500kHz propagates through the material and is modulated with a hammer blow. The position of the hammer blow on the sample is configured to promote the first bending mode of vibration. The use of a continuous wave allows discrete time extraction of the nonlinear behavior by a short-time Fourier transform approach, through the simultaneous comparison of a reference non-modulated signal and an impact-modulated signal. The hammer blow results in phase shifts and variations of signal amplitude between reference and perturbed signals, which are driven by the resonant frequency of the sample. Finally, a comprehensive analysis of the relaxation mechanisms (modulus and attenuation recovery) is conducted to untangle the coupled fast and slow hysteretic effects. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. A critical test for distorted wave theories: laser-assisted single ionization by ion impact

    Energy Technology Data Exchange (ETDEWEB)

    Ciappina, Marcelo [Max-Planck-Institut fuer Physik Komplexer Systeme, Dresden (Germany); Madsen, Lars Bojer [Department of Physics and Astronomy, Univ. of Aarhus (Denmark)

    2008-07-01

    We study single ionization in laser-assisted high-energy non-relativistic ion-atom collisions and show that the low-energy angular differential electron spectrum may be enhanced significantly by a weak external field. With increasing the strength of the assisting field, the energy spectrum develops a plateau with a characteristic cut-off. In the plateau region we predict distinct multiphoton peaks separated by the photon-energy of the laser field. In the present laser-assisted continuum-distorted-wave eikonal-initial-state (LA-CDW-EIS) theory, this effect may be related to the dynamics in the two-body electron-projectile subsystem. The combined process where an electron is ionized by a heavy ion and subsequently moves in the laser field and under the influence of the Coulomb fields of the projectile and the target represents a stringent test for distorted wave theories.

  8. Atom-interferometric gravitational-wave detection using heterodyne laser links

    Science.gov (United States)

    Hogan, Jason M.; Kasevich, Mark A.

    2016-09-01

    We propose a gravitational-wave detection method based on heterodyne laser links and light-pulse atom interferometry that enables high sensitivity gravitational-wave detection in the 0.1-mHz to 1-Hz frequency band using a single, long (>108 m), detector baseline. The detection baseline in previous atom-based proposals was constrained by the need for a reference laser to remain collimated over the optical propagation path between two satellites. Here we circumvent this requirement by employing a strong local oscillator laser near each atom ensemble that is phase referenced or phase locked to the reference laser beam. Longer baselines offer a number of potential advantages, including enhanced sensitivity, simplified atom optics, and reduced atomic source flux requirements.

  9. Towards PDT with Genetically Encoded Photosensitizer KillerRed: A Comparison of Continuous and Pulsed Laser Regimens in an Animal Tumor Model.

    Directory of Open Access Journals (Sweden)

    Marina Shirmanova

    Full Text Available The strong phototoxicity of the red fluorescent protein KillerRed allows it to be considered as a potential genetically encoded photosensitizer for the photodynamic therapy (PDT of cancer. The advantages of KillerRed over chemical photosensitizers are its expression in tumor cells transduced with the appropriate gene and direct killing of cells through precise damage to any desired cell compartment. The ability of KillerRed to affect cell division and to induce cell death has already been demonstrated in cancer cell lines in vitro and HeLa tumor xenografts in vivo. However, the further development of this approach for PDT requires optimization of the method of treatment. In this study we tested the continuous wave (593 nm and pulsed laser (584 nm, 10 Hz, 18 ns modes to achieve an antitumor effect. The research was implemented on CT26 subcutaneous mouse tumors expressing KillerRed in fusion with histone H2B. The results showed that the pulsed mode provided a higher rate of photobleaching of KillerRed without any temperature increase on the tumor surface. PDT with the continuous wave laser was ineffective against CT26 tumors in mice, whereas the pulsed laser induced pronounced histopathological changes and inhibition of tumor growth. Therefore, we selected an effective regimen for PDT when using the genetically encoded photosensitizer KillerRed and pulsed laser irradiation.

  10. Temperature variation induced by the pulsed-periodic laser pumping under terahertz wave generation

    Science.gov (United States)

    Kitaeva, G. Kh; Moiseenko, E. V.; Shepelev, A. V.

    2017-09-01

    During nonlinear-optical parametric frequency conversion the heat-related effects occur, considerably influencing the conversion process. We develop versatile methods for analytic and numerical calculations of thermo-optical parameters and the temperature distribution inside a non-linear crystal pumped by periodic laser pulses. As an example, numerical results are presented for a number of laser-based schemes actual for the non-linear optical terahertz wave generation and parametric frequency conversion processes.

  11. Vaporization front in the interaction of a high-energy laser with aerosols - A solitary wave

    Science.gov (United States)

    Lee, C. T.; Miller, T. G.

    1982-06-01

    If a high-energy laser beam were to propagate through highly absorbent aerosols, the aerosols might be subject to extinction by evaporation. This could occur, for instance, if a high-energy CO2 laser beam were to propagate through a medium containing a mist of water droplets. The incident energy would evaporate the droplets, thus increasing the transmission with time. In this paper, solitary waves are obtained as the asymptotic solution to the coupled nonlinear equations describing such an interaction.

  12. Phase-delayed laser diode array allows ultrasonic guided wave mode selection and tuning

    Science.gov (United States)

    Karppinen, Pasi; Salmi, Ari; Moilanen, Petro; Karppinen, Timo; Zhao, Zuomin; Myllylä, Risto; Timonen, Jussi; Hæggström, Edward

    2013-04-01

    Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT) since certain modes at various center frequencies are sensitive to specific types of defects. Ideally one should be able to select both the mode and the center frequency of the launched waves. We demonstrated that an affordable laser diode array can selectively launch either the S0 or A0 ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching the selected mode and frequency was employed between the output of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.

  13. Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves.

    Science.gov (United States)

    Schroeder, C B; Esarey, E

    2010-05-01

    A relativistic, warm fluid model of a nonequilibrium, collisionless plasma is developed and applied to examine nonlinear Langmuir waves excited by relativistically intense, short-pulse lasers. Closure of the covariant fluid theory is obtained via an asymptotic expansion assuming a nonrelativistic plasma temperature. The momentum spread is calculated in the presence of an intense laser field and shown to be intrinsically anisotropic. Coupling between the transverse and longitudinal momentum variances is enabled by the laser field. A generalized dispersion relation is derived for Langmuir waves in a thermal plasma in the presence of an intense laser field. Including thermal fluctuations in three-velocity-space dimensions, the properties of the nonlinear electron plasma wave, such as the plasma temperature evolution and nonlinear wavelength, are examined and the maximum amplitude of the nonlinear oscillation is derived. The presence of a relativistically intense laser pulse is shown to strongly influence the maximum plasma wave amplitude for nonrelativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances.

  14. Status of advanced ground-based laser interferometers for gravitational-wave detection

    CERN Document Server

    Dooley, Katherine L; Dwyer, Sheila; Puppo, Paola

    2014-01-01

    Ground-based laser interferometers for gravitational-wave (GW) detection were first constructed starting 20 years ago and as of 2010 collection of several years' worth of science data at initial design sensitivities was completed. Upgrades to the initial detectors together with construction of brand new detectors are ongoing and feature advanced technologies to improve the sensitivity to GWs. This conference proceeding provides an overview of the common design features of ground-based laser interferometric GW detectors and establishes the context for the status updates of each of the four gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo, GEO600 and KAGRA.

  15. Analysis of Nanometer Structure for Chromium Atoms in Gauss Standing Laser Wave

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-Tao; ZHU Bao-Hua; XIONG Xian-Ming

    2010-01-01

    @@ The equation of motion of two-level chromium atoms in Gauss standing laser wave is discussed and the distribution of chromium atoms is given under different transverse velocity conditions.The results show that the focusing position of atoms will be affected by the transverse velocity of atoms.Based on the four-order Runge-Kutta method,the locus of chromium atoms in Gauss standing laser wave is simulated.The three-dimensional characteristics of nanometer structures are stimulated under perfect and emanative conditions.

  16. Quantum dot lasers and integrated guided wave devices on Si

    Science.gov (United States)

    Yang, Jun; Mi, Zetian; Bhattacharya, Pallab

    2007-02-01

    We have studied the growth and characteristics of self-organized InGaAs/GaAs quantum dot lasers and their monolithic integration with waveguides and quantum well electroabsorption modulators on Si. Utilizing multiple layers of InAs quantum dots as effective dislocation filters near the GaAs-Si interface, we have demonstrated high performance quantum dot lasers grown directly on Si that exhibit, for the first time, relatively low threshold current (J th = 900 A/cm2), large characteristic temperature (T 0 = 278 K), and output slope efficiency ( >=0.3 W/A). Focused-ion-beam milling has been used to form high-quality facets for the cavity mirror and coupling groove of an integrated laser/waveguide system on Si. We have also achieved a groove-coupled laser/modulator system on Si that exhibits a coupling coefficient greater than 20% and a modulation depth of ~ 100% at 5 V reverse bias.

  17. Gravitational Wave Detection with Single-Laser Atom Interferometers

    Science.gov (United States)

    Yu, Nan; Tinto, Massimo

    2011-01-01

    A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

  18. Research of the elastic waves generated by a pulse laser. Excitation mechanism of elastic waves and application to nondestructive testing; Pulse laser de reikishita danseiha ni kansuru kenkyu. Danseiha reiki no mechanism to hihakai kensa eno oyo

    Energy Technology Data Exchange (ETDEWEB)

    Cho, H.; Takemoto, M. [Aoyama Gakuin University, Tokyo (Japan). College of Science and Engineering

    1994-07-20

    A bulk wave is generated when a pulse laser is irradiated to the material, and the characteristics of a Young`s modulus and Poisson`s ratio can be nondestructively estimated from the bulk wave. The generation mechanism of laser ultrasonic waves must be first clarified for such application. In this paper, fundamental research was conducted to study the generation mechanism of the elastic waves excited by a Q-switched Nd-YAG laser, and the generation method and characteristics of Rayleigh waves. The following result was obtained. A bulk wave is generated by the disk-like adiabatic expansion near the surface if the laser power is small when a spot-shape pulse laser was irradiated. A bulk wave is generated by the thin disk-like adiabatic expansion beneath the surface due to the thermal diffusion in the depth direction of a base material when the laser power becomes large. Moreover, a bulk wave is generated by the impact force due to abrasion and plasma when the power becomes still larger. The information on the bulk wave characteristics and Rayleigh wave was also obtained. 25 refs., 15 figs., 1 tab.

  19. Experimental and numerical investigation of shock wave propagation through complex geometry, gas continuous, two-phase media

    Energy Technology Data Exchange (ETDEWEB)

    Chien-Chih Liu, James [Univ. of California, Berkeley, CA (United States)

    1993-01-01

    The work presented here investigates the phenomenon of shock wave propagation in gas continuous, two-phase media. The motivation for this work stems from the need to understand blast venting consequences in the HYLIFE inertial confinement fusion (ICF) reactor. The HYLIFE concept utilizes lasers or heavy ion beams to rapidly heat and compress D-T targets injected into the center of a reactor chamber. A segmented blanket of falling molten lithium or Li2BeF4 (Flibe) jets encircles the reactor`s central cavity, shielding the reactor structure from radiation damage, absorbing the fusion energy, and breeding more tritium fuel. X-rays from the fusion microexplosion will ablate a thin layer of blanket material from the surfaces which face toward the fusion site. This generates a highly energetic vapor, which mostly coalesces in the central cavity. The blast expansion from the central cavity generates a shock which propagates through the segmented blanket - a complex geometry, gas-continuous two-phase medium. The impulse that the blast gives to the liquid as it vents past, the gas shock on the chamber wall, and ultimately the liquid impact on the wall are all important quantities to the HYLIFE structural designers.

  20. Invited article: CO2 laser production of fused silica fibers for use in interferometric gravitational wave detector mirror suspensions.

    Science.gov (United States)

    Heptonstall, A; Barton, M A; Bell, A; Cagnoli, G; Cantley, C A; Crooks, D R M; Cumming, A; Grant, A; Hammond, G D; Harry, G M; Hough, J; Jones, R; Kelley, D; Kumar, R; Martin, I W; Robertson, N A; Rowan, S; Strain, K A; Tokmakov, K; van Veggel, M

    2011-01-01

    In 2000 the first mirror suspensions to use a quasi-monolithic final stage were installed at the GEO600 detector site outside Hannover, pioneering the use of fused silica suspension fibers in long baseline interferometric detectors to reduce suspension thermal noise. Since that time, development of the production methods of fused silica fibers has continued. We present here a review of a novel CO(2) laser-based fiber pulling machine developed for the production of fused silica suspensions for the next generation of interferometric gravitational wave detectors and for use in experiments requiring low thermal noise suspensions. We discuss tolerances, strengths, and thermal noise performance requirements for the next generation of gravitational wave detectors. Measurements made on fibers produced using this machine show a 0.8% variation in vertical stiffness and 0.05% tolerance on length, with average strengths exceeding 4 GPa, and mechanical dissipation which meets the requirements for Advanced LIGO thermal noise performance.