WorldWideScience

Sample records for external cavity lasers

  1. Metasurface external cavity laser

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Luyao, E-mail: luyaoxu.ee@ucla.edu; Curwen, Christopher A.; Williams, Benjamin S. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); California NanoSystems Institute, University of California, Los Angeles, California 90095 (United States); Hon, Philip W. C.; Itoh, Tatsuo [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Chen, Qi-Sheng [Northrop Grumman Aerospace Systems, Redondo Beach, California 90278 (United States)

    2015-11-30

    A vertical-external-cavity surface-emitting-laser is demonstrated in the terahertz range, which is based upon an amplifying metasurface reflector composed of a sub-wavelength array of antenna-coupled quantum-cascade sub-cavities. Lasing is possible when the metasurface reflector is placed into a low-loss external cavity such that the external cavity—not the sub-cavities—determines the beam properties. A near-Gaussian beam of 4.3° × 5.1° divergence is observed and an output power level >5 mW is achieved. The polarized response of the metasurface allows the use of a wire-grid polarizer as an output coupler that is continuously tunable.

  2. Vertical external cavity surface emitting semiconductor lasers

    CERN Document Server

    Holm, M

    2001-01-01

    Active stabilisation showed a relative locked linewidth of approx 3 kHz. Coarse tuning over 7 nm was achieved using a 3-plate birefingent filter plate while fine-tuning using cavity length change allowed tuning over 250 MHz. Vertical external cavity semiconductor lasers have emerged as an interesting technology based on current vertical cavity semiconductor laser knowledge. High power output into a single transverse mode has attracted companies requiring good fibre coupling for telecommunications systems. The structure comprises of a grown semiconductor Bragg reflector topped with a multiple quantum well gain region. This is then included in an external cavity. This device is then optically pumped to promote laser action. Theoretical modelling of AIGaAs based VECSEL structures was undertaken, showing the effect of device design on laser characteristics. A simple 3-mirror cavity was constructed to assess the static characteristics of the structure. Up to 153 mW of output power was achieved in a single transver...

  3. External cavity diode laser around 657 nm

    Institute of Scientific and Technical Information of China (English)

    Desheng Lǖ (吕德胜); Kaikai Huang (黄凯凯); Fengzhi Wang (王凤芝); DonghaiYang (杨东海)

    2003-01-01

    Operating a laser diode in an external cavity, which provides frequency-selective feedback, is a very effective method to tune the laser frequency to a range far from its free running frequency. For the Ca atomic Ramsey spectroscopy experiment, we have constructed a 657-nm laser system based on the LittmanMetcalf configuration with a 660-nm commercial laser diode. Continuously 10-GHz tuning range was achieved with about 100-kHz spectral linewidth, measured with beat-note spectrum of two identical laser systems.

  4. Plasmonic external cavity laser refractometric sensor.

    Science.gov (United States)

    Zhang, Meng; Lu, Meng; Ge, Chun; Cunningham, Brian T

    2014-08-25

    Combining the high sensitivity properties of surface plasmon resonance refractive index sensing with a tunable external cavity laser, we demonstrate a plasmonic external cavity laser (ECL) for high resolution refractometric sensing. The plasmonic ECL utilizes a plasmonic crystal with extraordinary optical transmission (EOT) as the wavelength-selective element, and achieves single mode lasing at the transmission peak of the EOT resonance. The plasmonic ECL refractometric sensor maintains the high sensitivity of a plasmonic crystal sensor, while simultaneously providing a narrow spectral linewidth through lasing emission, resulting in a record high figure of merit for refractometric sensing with an active or passive optical resonator. We demonstrate single-mode and continuous-wave operation of the electrically-pumped laser system, and show the ability to measure refractive index changes with a 3σ detection limit of 1.79 × 10(-6) RIU. The demonstrated approach is a promising path towards label-free optical biosensing with enhanced signal-to-noise ratios for challenging applications in small molecule drug discovery and pathogen sensing.

  5. Porous photonic crystal external cavity laser biosensor

    Science.gov (United States)

    Huang, Qinglan; Peh, Jessie; Hergenrother, Paul J.; Cunningham, Brian T.

    2016-08-01

    We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO2 dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions with much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.

  6. Porous photonic crystal external cavity laser biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qinglan [Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Peh, Jessie; Hergenrother, Paul J. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Cunningham, Brian T. [Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2016-08-15

    We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO{sub 2} dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions with much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.

  7. Optical complexity in external cavity semiconductor laser

    Science.gov (United States)

    Rondoni, Lamberto; Ariffin, M. R. K.; Varatharajoo, Renuganth; Mukherjee, Sayan; Palit, Sanjay K.; Banerjee, Santo

    2017-03-01

    In this article, the window based complexity and output modulation of a time delayed chaotic semiconductor laser (SL) model has been investigated. The window based optical complexity (OC), is measured by introducing the recurrence sample entropy (SampEn). The analysis has been done without and in the presence of external noise. The significant changes in the dynamics can be observed under induced noise with weak strength. It has also been found that there is a strong positive correlation between the output power and the complexity of the system with various sets of parameters. The laser intensity, as well as the OC can be increased with the incremental noise strength and the associated system parameters. Thus, optical complexity quantifies the system dynamics and its instabilities, since is strongly correlated with the laser outputs. This analysis can be applied to measure the laser instabilities and modulation of output power.

  8. Silicon reflectors for external cavity lasers based on ring resonators

    Science.gov (United States)

    Wang, Chao; Li, Xia; Jin, Hao; Yu, Hui; Yang, Jianyi; Jiang, Xiaoqing

    2017-01-01

    We propose and experimentally investigate types of silicon ring reflectors on Silicon-On-Insulator (SOI) platform. These reflectors are used for realizing the silicon hybrid external cavity lasers. A suspended edge coupler is used to connect the reflective semiconductor optical amplifier (RSOA) chip and the reflectors. The properties of the reflectors and the hybrid external cavity lasers with these reflectors are illustrated. The experimental results show that all of those reflectors have a high reflectivity and the highest reflectivity can up to be 95%. The lowest insertion loss can be as low as 0.4 dB. The output power of the hybrid external cavity lasers with these reflectors can reach mW magnitude and the highest output power is 6.1 mW. Over 30 dB side mode suppression ratio is obtained.

  9. Commercial mode-locked vertical external cavity surface emitting lasers

    Science.gov (United States)

    Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

    2017-02-01

    In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

  10. External cavity beam combining of 21 semiconductor lasers using SPGD.

    Science.gov (United States)

    Montoya, Juan; Augst, Steven J; Creedon, Kevin; Kansky, Jan; Fan, Tso Yee; Sanchez-Rubio, Antonio

    2012-04-10

    Active coherent beam combining of laser oscillators is an attractive way to achieve high output power in a diffraction limited beam. Here we describe an active beam combining system used to coherently combine 21 semiconductor laser elements with an 81% beam combining efficiency in an external cavity configuration compared with an upper limit of 90% efficiency in the particular configuration of the experiment. Our beam combining system utilizes a stochastic parallel gradient descent (SPGD) algorithm for active phase control. This work demonstrates that active beam combining is not subject to the scaling limits imposed on passive-phasing systems.

  11. External cavity diode laser with very-low frequency drift

    Science.gov (United States)

    Takamizawa, Akifumi; Yanagimachi, Shinya; Ikegami, Takeshi

    2016-03-01

    An external cavity diode laser with significant mechanical robustness was installed in a housing that was sealed from outside for eliminating variations in the refractive index of air. Using the feedback signal for a frequency lock, it was found that the variation in the laser frequency under free running was suppressed to 275 MHz over one month and depended on the room temperature. Moreover, the upper limit of the linear frequency drift rate was evaluated as intrinsically 40 Hz/s. The frequency lock is expected to be sustainable for more than 110 days with temperature-controlled housing.

  12. Variation of Lasing Wavelength of Fiber Grating Semiconductor Laser with Temperature for Different External Cavity Lengths

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    For different external cavity lengths, lasing wavelength variation of fiber grating external cavity semiconductor laser (FGECSL) with ambient temperature has been investigated theoretically, and the theoretical results are in agreement with reported experimental observations.

  13. Pulse properties of external cavity mode locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Kroh, Marcel; Mørk, Jesper

    2006-01-01

    The performance of an external-cavity mode-locked semiconductor laser is investigated both theoretically and experimentally. The optimization analysis focuses on the regimes of stable mode locking and the generation of sub-picosecond optical pulses. We demonstrate stable output pulses down to one...... picosecond duration with more than 30 dB trailing pulse suppression. The limiting factors to the device performance are investigated on the basis of a fully-distributed time-domain model.We find that ultrafast gain dynamics effectively reduce the pulse-shaping strength and inhibit the generation...

  14. Intensity Tuning in Single Mode Microchip Nd:YAG Laser with External Cavity

    Institute of Scientific and Technical Information of China (English)

    TAN Yi-Dong; ZHANG Shu-Lian

    2006-01-01

    We investigate the characteristics of intensity tuning in a single mode microchip Nd:YAG laser with an external cavity. The undulation of laser intensity in a period of λ/2 change of the internal cavity length is observed.Two different optical feedback cases are performed. One is an external cavity reflector perfectly aligned and the other is an external cavity reflector tilted. However, the fluctuation frequency of laser intensity in a period of λ/2 change of the internal cavity length in these two cases is found to be determined by the ratio of external cavity length to internal cavity length. Meanwhile, for the tilted external cavity, the fluctuation frequency is also related to multiple feedbacks in the tilted external cavity.

  15. Tunable external cavity laser employing uncooled superluminescent diode.

    Science.gov (United States)

    Oh, Su Hwan; Kim, Ki Soo; Ju, Jung Jin; Kim, Min-Su; Yoon, Ki-Hong; Oh, Dae Kon; Noh, Young-Ouk; Lee, Hyung-Jong

    2009-06-08

    We have fabricated a tunable external cavity laser (T-ECL) based on a superluminescent diode and a polymeric waveguide Bragg reflector, providing a cost-effective solution for wavelength division multiplexing-passive optical network (WDM-PON) systems. The wavelength of the T-ECL is tuned through 100 GHz-spacing 16 channels by the thermo-optic tuning of the refractive index of the polymer waveguide at a low input power of 70 mW. The maximum output power and the slope efficiency of the uncooled diode at 20 (75) degrees C are 8.83 (3.80) mW and 0.107 (0.061) W/A, respectively. The T-ECL operated successfully in the direct modulation for 1.25 Gbit/s transmissions over 20 km.

  16. Tunable high-power blue external cavity semiconductor laser

    Science.gov (United States)

    Ding, Ding; Lv, Xueqin; Chen, Xinyi; Wang, Fei; Zhang, Jiangyong; Che, Kaijun

    2017-09-01

    A commercially available high-power GaN-based blue laser diode has been operated in a simple Littrow-type external cavity (EC). Two kinds of EC configurations with the grating lines perpendicular (A configuration) and parallel (B configuration) to the p-n junction are evaluated. Good performance has been demonstrated for the EC laser with B configuration due to the better mode selection effect induced by the narrow feedback wavelength range from the grating. Under an injection current of 1100 mA, the spectral linewidth is narrowed significantly down to ∼0.1 nm from ∼1 nm (the free-running width), with a good wavelength-locking behavior and a higher than 35 dB-amplified spontaneous emission suppression ratio. Moreover, a tuning bandwidth of 3.6 nm from 443.9 nm to 447.5 nm is realized with output power of 1.24 W and EC coupling efficiency of 80% at the central wavelength. The grating-coupled blue EC laser with narrow spectral linewidth, flexible wavelength tunability, and high output power shows potential applications in atom cooling and trapping, high-resolution spectroscopy, second harmonic generation, and high-capacity holographic data storage.

  17. Facet Reflection Coefficient of Phase-locked Diode Laser Array in an External Cavity

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A diode laser array(DLA)positioned in an external cavity can receive the radiations emitted from its neighboring elements (C1) and that of itself (S) after being reflected at the DLA facet as well as from the external mirror (C0). Considering the fact that|C0/S| should be larger than unity if the external cavity is effective,and|C1/S| should be larger than unity if the phase locking may be established in the external cavity.The requirements on the reflection at the facet of the diode laser array have been specified in terms of the cavity length and reflection coefficient of the external mirror.

  18. A Step Tunable External Cavity Semiconductor Laser for WDM Network Deployment

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We put forward a kind of tunable external cavity semiconductor laser with feedback on both chip facets. It outputs the single-frequency laser with high side-mode suppression ratio and the frequency could be step tuned.

  19. External-cavity solid-state organic lasers: Design rules and application perspectives (Conference Presentation)

    Science.gov (United States)

    Chénais, Sébastien; Gallinelli, Thomas; Mhibik, Oussama; Blanchard, Cédric; Forget, Sébastien

    2016-09-01

    Among various laser architectures currently used to make lasers out of organic materials (distributed feedback lasers or organic vertical cavity surface-emitting lasers, ....), vertical EXTERNAL cavities have several distinctive features that enable making lasers with a high brightness, resulting from a combination of high efficiency and good beam quality, and also offer a superior flexibility to monitor the laser spectrum. In this talk I will highlight a few recent results on external-cavity organic lasers and reveal their potential through the example of a single mode organic laser device with an ultranarrow linewidth (art). From the material point of view, I will also show how ink-jet printing can be successfully used in vertical external-cavity organic lasers to make thick and optical-quality films that have the potential to be easily produced with a high throughput.

  20. All-solid-state ultraviolet laser based on frequency doubling in an external ring cavity

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An all-solid-state ultraviolet laser based on frequency doubling in an external ring cavity with low input pump power is reported. Both second harmonic generation (SHG) and fourth harmonic generation (FHG) occurred in an external threemirrors ring cavity. The need for impedance matching of this cavity to the input radiation was eliminated and the cavity adaptation was simplified, because the mirrors were not highly reflecting at 1064 nm and the cavity resonates only at 532 nm. Experiment results demonstrate that the conversion efficiency of this external cavity is higher than that of the singlepass condition.

  1. Green high-power tunable external-cavity GaN diode laser at 515 nm

    DEFF Research Database (Denmark)

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

    2016-01-01

    A 480 mW green tunable diode laser system is demonstrated for the first time to our knowledge. The laser system is based on a GaN broad-area diode laser and Littrow external-cavity feedback. The green laser system is operated in two modes by switching the polarization direction of the laser beam ...

  2. A compact chaotic laser device with a two-dimensional external cavity structure

    Energy Technology Data Exchange (ETDEWEB)

    Sunada, Satoshi, E-mail: sunada@se.kanazawa-u.ac.jp; Adachi, Masaaki [Faculty of Mechanical Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192 (Japan); Fukushima, Takehiro [Department of Information and Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); Shinohara, Susumu; Arai, Kenichi [NTT Communication Science Laboratories, NTT Corporation, 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan); Harayama, Takahisa [NTT Communication Science Laboratories, NTT Corporation, 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan); Department of Mechanical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)

    2014-06-16

    We propose a compact chaotic laser device, which consists of a semiconductor laser and a two-dimensional (2D) external cavity for delayed optical feedback. The overall size of the device is within 230 μm × 1 mm. A long time delay sufficient for chaos generation can be achieved with the small area by the multiple reflections at the 2D cavity boundary, and the feedback strength is controlled by the injection current to the external cavity. We experimentally demonstrate that a variety of output properties, including chaotic output, can be selectively generated by controlling the injection current to the external cavity.

  3. Mode-locked Pr3+-doped silica fiber laser with an external cavity

    DEFF Research Database (Denmark)

    Shi, Yuan; Poulsen, Christian; Sejka, Milan

    1994-01-01

    We present a Pr3+-doped silica-based fiber laser mode-locked by using a linear external cavity with a vibrating mirror. Stable laser pulses with a FWHM of less than 44 ps, peak power greater than 9 W, and repetition rate up to 100 MHz are obtained. The pulse width versus cavity mismatch ΔL and pump...

  4. Mode-locking external-cavity laser-diode sensor for displacement measurements of technical surfaces

    Science.gov (United States)

    Czarske, Jürgen; Möbius, Jasper; Moldenhauer, Karsten

    2005-09-01

    A novel laser sensor for position measurements of technical solid-state surfaces is proposed. An external Fabry-Perot laser cavity is assembled by use of an antireflection-coated laser diode together with the technical surface. Mode locking results from pumping the laser diode synchronously to the mode spacing of the cavity. The laser cavity length, i.e., the distance to the measurement object, is determined by evaluation of the modulation transfer function of the cavity by means of a phase-locked loop. The mode-locking external-cavity laser sensor incorporates a resonance effect that results in highly resolving position and displacement measurements. More than a factor-of-10 higher resolution than with conventional nonresonant sensing principles is achieved. Results of the displacement measurements of various technical surfaces are reported. Experimental and theoretical investigations are in good agreement.

  5. Analysis of Trace Gas Mixtures Using an External Cavity Quantum Cascade Laser Sensor

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.; Brumfield, Brian E.; Kriesel, Jason M.

    2015-07-01

    We measure and analyze mixtures of trace gases at ppb-ppm levels using an external cavity quantum cascade laser sensor with a 1-second response time. Accurate spectral fits are obtained in the presence of overlapping spectra.

  6. Rapid Swept-Wavelength External Cavity Quantum Cascade Laser for Open Path Sensing

    Energy Technology Data Exchange (ETDEWEB)

    Brumfield, Brian E.; Phillips, Mark C.

    2015-07-01

    A rapidly tunable external cavity quantum cascade laser system is used for open path sensing. The system permits acquisition of transient absorption spectra over a 125 cm-1 tuning range in less than 0.01 s.

  7. Intracavity frequency-doubled green vertical external cavity surface emitting laser

    Institute of Scientific and Technical Information of China (English)

    Yanrong Song; Peng Zhang; Xinping Zhang; Boxia Yan; Yi Zhou; Yong Bi; Zhigang Zhang

    2008-01-01

    @@ An intracavity frequency-doubled vertical external cavity surface emitting laser (VECSEL) with green light is demonstrated. The fundamental frequency laser cavity consists of a distributed Bragg reflector (DBR) of the gain chip and an external mirror. A 12-mW frequency-doubled output has been reached at 540 nm with a nonlinear crystal LBO when the fundamental frequency output is 44 mW at 1080 nm. The frequency doubling efficiency is about 30%.

  8. Laser absorption spectroscopy based on a broadband external cavity quantum cascade laser

    Science.gov (United States)

    Sun, Juan; Liu, Ningwu; Deng, Hao; Ding, Junya; Sun, Jiancha; Zhang, Lei; Li, Jingsong

    2017-02-01

    A tunable diode laser absorption spectroscopy (TDLAS) system based on a broad band external cavity quantum cascade laser (ECQCL) near 7.78 μm was used to study volatile organic compounds (VOCs) measurements. Instead of using a standard infrared mercury cadmium telluride (MCT) detector, a quartz crystal tuning fork (QCTF) as a light detector was successfully used for laser signal detection. Fast Fourier transform (FFT) was used to extract vibration intensity information of QCTF. Primary results indicate that the new developed system has a good reproducibility, and a good agreement was obtained by comparing with data taken from standard spectroscopic database.

  9. High finesse external cavity VCSELs: from very low noise lasers to dual frequency lasers

    Science.gov (United States)

    Baili, Ghaya; Alouini, Medhi; Morvan, Loic; Bretenaker, Fabien; Sagnes, Isabelle; Garnache, Arnaud; Dolfi, Daniel

    2011-01-01

    Low noise-level optical sources are required for numerous applications such as microwave photonics, fiber-optic sensing and time/frequency references distribution. In this paper, we demonstrate how inserting a SC active medium into a centimetric high-Q external cavity is a simple way to obtain a shot-noise-limited laser source over a very wide frequency bandwidth. This approach ensures, with a compact design, a sufficiently long photon lifetime to reach the oscillation-relaxation- free class-A regime. This concept has been illustrated by inserting a 1/2-VCSEL in an external cavity including an etalon filter. A -156dB/Hz relative intensity noise level is obtained over the 100 MHz to 18 GHz bandwidth of interest. This is several orders of magnitude better than the noise, previously observed in VCSELs, belonging to the class-B regime. The optimization, in terms of noise, is shown to be a trade-off between the cavity length and the laser mode filtering. The transition between the class-B and class-A dynamical behaviors is directly observed by continuously controlling the photon lifetime is a sub-millimetric to a centimetric cavity length. It's proven that the transition occurs progressively, without any discontinuity. Based on the same laser architecture, tunable dual-frequency oscillation is demonstrated by reducing the polarized eigenstates overlap in the gain medium. The class-A dynamics of such a laser, free of relaxation oscillations, enables to suppress the electrical phase noise in excess, usually observed in the vicinity of the beat note. An original technique for jitter reduction in mode-locked VECSELs is also investigated. Such lasers are needed for photonic analog to digital converters.

  10. Tunable single and dual mode operation of an external cavity quantum-dot injection laser

    Energy Technology Data Exchange (ETDEWEB)

    Biebersdorf, A [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Lingk, C [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); De Giorgi, M [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Feldmann, J [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Sacher, J [Sacher Lasertechnik GmbH, Hannah Arendt Strasse 3-7, D-35037 Marburg (Germany); Arzberger, M [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Ulbrich, C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Boehm, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Amann, M-C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Abstreiter, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany)

    2003-08-21

    We investigate quantum-dot (QD) lasers in an external cavity using Littrow and Littman configurations. Here, we report on a continuously tunable QD laser with a broad tuning range from 1047 to 1130 nm with high stability and efficient side mode suppression. The full-width at half-maximum of the laser line is 0.85 nm determined mainly by the quality of the external grating. This laser can be operated in a dual-mode modus, where the mode-spacing can be tuned continuously between 1.1 and 34 nm. Simultaneous emission of the two laser modes is shown by sum frequency generation experiments.

  11. Construction and characterization of external cavity diode lasers for atomic physics.

    Science.gov (United States)

    Hardman, Kyle S; Bennetts, Shayne; Debs, John E; Kuhn, Carlos C N; McDonald, Gordon D; Robins, Nick

    2014-04-24

    Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

  12. Power-efficient III-V/silicon external cavity DBR lasers.

    Science.gov (United States)

    Zilkie, A J; Seddighian, P; Bijlani, B J; Qian, W; Lee, D C; Fathololoumi, S; Fong, J; Shafiiha, R; Feng, D; Luff, B J; Zheng, X; Cunningham, J E; Krishnamoorthy, A V; Asghari, M

    2012-10-08

    We report the design and characterization of external-cavity DBR lasers built with a III-V-semiconductor reflective-SOA with spot-size converter edge-coupled to SOI waveguides containing Bragg grating mirrors. The un-cooled lasers have wall-plug-efficiencies of up to 9.5% at powers of 6 mW. The lasers are suitable for making power efficient, hybrid WDM transmitters in a CMOS-compatible SOI optical platform.

  13. Actively controlled tuning of an external cavity diode laser by polarization spectroscopy.

    Science.gov (United States)

    Führer, Thorsten; Stang, Denise; Walther, Thomas

    2009-03-30

    We report on an universal method to achieve and sustain a large mode-hop free tuning range of an external cavity diode laser. By locking one of the resonators using a closed loop control based on polarization spectroscopy while tuning the laser we achieved mode-hop free tuning of up to 130 GHz with a non AR-coated, off-the-shelf laser diode.

  14. Tunable mode-locked semiconductor laser with Bragg mirror external cavity

    DEFF Research Database (Denmark)

    Yvind, Kresten; Jørgensen, T.; Birkedal, Dan

    2002-01-01

    We present a simplified design for a wavelength tunable external cavity mode-locked laser by employing a wedged GaAs/AlGaAs Bragg mirror. The device emits 4-6 ps pulses at 10 GHz and is tunable over 15 nm. Although, in the present configuration, tunability is limited to 15 nm, however, we have...

  15. Performance of external cavity mode-locked semiconductor lasers employing reverse biased saturable absorbers

    DEFF Research Database (Denmark)

    Yvind, Kresten; Skovgaard, P.M.W.; Mørk, Jesper;

    2002-01-01

    We have experimentally investigated the performance of external cavity mode-locked semiconductor lasers employing reverse biased saturable absorbers. We have measured the magnitude of trailing pulses when varying the chip length and studied the pulse quality when changing the driving conditions...

  16. Spectrally narrowed external-cavity high-power stack of laser diode arrays.

    Science.gov (United States)

    Zhu, H; Ruset, I C; Hersman, F W

    2005-06-01

    We describe an effective external cavity for narrowing the spectral linewidth of a multiarray stack of laser diode arrays. For a commercially available 279-W free-running five-array laser diode array operating at 60 A, we narrow the spectral linewidth to 0.40 nm at FWHM with 115 W of cw power output. This technique leads to the possibility of higher-efficiency, lower-cost production of hyperpolarized noble gases for magnetic resonance imaging.

  17. Control of light polarization using optically spin-injected vertical external cavity surface emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Frougier, J., E-mail: julien.frougier@thalesgroup.com; Jaffrès, H.; Deranlot, C.; George, J.-M. [Unité Mixte de Physique CNRS-Thales and Université Paris Sud 11, 1 av. Fresnel, 91767 Palaiseau (France); Baili, G.; Dolfi, D. [Thales Research and Technology, 1 av. Fresnel, 91767 Palaiseau (France); Alouini, M. [Institut de Physique de Rennes, 263 Avenue Général Leclerc, 35042 Rennes (France); Sagnes, I. [Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis (France); Garnache, A. [Institut d' électronique du Sud CNRS UMR5214, Université Montpellier 2 Place Eugene Bataillon, 34095 Montpellier (France)

    2013-12-16

    We fabricated and characterized an optically pumped (100)-oriented InGaAs/GaAsP multiple quantum well Vertical External Cavity Surface Emitting Laser (VECSEL). The structure is designed to allow the integration of a Metal-Tunnel-Junction ferromagnetic spin-injector for future electrical injection. We report here the control at room temperature of the electromagnetic field polarization using optical spin injection in the active medium of the VECSEL. The switching between two highly circular polarization states had been demonstrated using an M-shaped extended cavity in multi-modes lasing. This result witnesses an efficient spin-injection in the active medium of the LASER.

  18. Piezo activated mode tracking system for widely tunable mode-hop-free external cavity mid-IR semiconductor lasers

    Science.gov (United States)

    Wysocki, Gerard (Inventor); Tittel, Frank K. (Inventor); Curl, Robert F. (Inventor)

    2010-01-01

    A widely tunable, mode-hop-free semiconductor laser operating in the mid-IR comprises a QCL laser chip having an effective QCL cavity length, a diffraction grating defining a grating angle and an external cavity length with respect to said chip, and means for controlling the QCL cavity length, the external cavity length, and the grating angle. The laser of claim 1 wherein said chip may be tuned over a range of frequencies even in the absence of an anti-reflective coating. The diffraction grating is controllably pivotable and translatable relative to said chip and the effective QCL cavity length can be adjusted by varying the injection current to the chip. The laser can be used for high resolution spectroscopic applications and multi species trace-gas detection. Mode-hopping is avoided by controlling the effective QCL cavity length, the external cavity length, and the grating angle so as to replicate a virtual pivot point.

  19. Active mode locking of quantum cascade lasers operating in external ring cavity

    CERN Document Server

    Revin, D G; Wang, Y; Cockburn, J W; Belyanin, A

    2015-01-01

    Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode locked operation remains a challenge despite dedicated effort. Here we report the first demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents of a standard commercial laser chip.

  20. 25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity

    NARCIS (Netherlands)

    Oldenbeuving, R. M.; Klein, E. J.; Offerhaus, H. L.; Lee, C. J.; Song, H.; Boller, K. J.

    2013-01-01

    We report on the spectral properties of a diode laser with a tunable external cavity mirror, realized as an integrated optics waveguide circuit. Even though the external cavity is short compared to that of other narrow bandwidth external cavity lasers, the spectral bandwidth of this tunable laser is

  1. Intensity modulation in single-mode microchip Nd:YAG lasers with asymmetric external cavity

    Institute of Scientific and Technical Information of China (English)

    Tan Yi-Dong; Zhang Shu-Lian; Liu Wei-Xin; Mao Wei

    2007-01-01

    Intensity modulation induced by the asymmetric external cavity in single-mode microchip Nd:YAG lasers is presented. Two kinds of experimental results are discussed based on multiple feedback effects. In one case, the intensity modulation curve is a normal sine wave, whose fringe frequency is four times higher than that of a conventional optical feedback system, caused by multiple feedback effects. In the other case, the intensity modulation curve is the overlapping of the above quadruple-frequency signal and conventional optical feedback signal, which is determined by the additional phase difference induced by the asymmetric external cavity. The theoretical analyses are in good agreement with the experimental results. The quadruple-frequency modulation of the laser output intensity can greatly increase the resolution of displacement measurement of an optical feedback system.

  2. The Complex Way to Laser Diode Spectra: Example of an External Cavity Laser With Strong Optical Feedback

    DEFF Research Database (Denmark)

    Detoma, Enrico; Tromborg, Bjarne; Montrosset, Ivo

    2005-01-01

    An external cavity laser with strong grating-filtered feedback to an antireflection-coated facet is studied with a time-domain integral equation for the electric field, which reproduces the modes of the oscillation condition as steady-state solutions. For each mode, the stability and spectral...

  3. A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA

    Science.gov (United States)

    Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao

    2015-10-01

    Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

  4. Narrow-line external cavity diode laser micro-packaging in the NIR and MIR spectral range

    Science.gov (United States)

    Jiménez, A.; Milde, T.; Staacke, N.; Aßmann, C.; Carpintero, G.; Sacher, J.

    2017-07-01

    Narrow-linewidth tunable diode lasers are an important tool for spectroscopic instrumentation. Conventional external cavity diode lasers offer high output power and narrow linewidth. However, most external cavity diode lasers are designed as laboratory instrument and do not allow portability. In comparison, other commonly used lasers, like distributed feedback lasers (DFB) that are capable of driving a handheld device, are limited in power and show linewidths which are not sufficiently narrow for certain applications. We present new miniaturized types of tunable external cavity diode laser which overcome the drawbacks of conventional external cavity diode lasers and which preserve the advantages of this laser concept. Three different configurations are discussed in this article. The three types of miniaturized external cavity diode laser systems achieve power values of more than 50 mW within the 1.4 μm water vapor absorption band with excellent side-mode suppression and linewidth below 100 kHz. Typical features outstand with respect to other type of laser systems which are of extended use such as DFB laser diodes. The higher output power and the lower linewidth will enable a higher sensitivity and resolution for a wide range of applications.

  5. Fluctuations in the intensity of a single-frequency injection laser with an external dispersion cavity

    Energy Technology Data Exchange (ETDEWEB)

    Bogatov, A.P.; Eliseev, P.G.; Kobildzhanov, O.A.; Madgazin, V.R.; Okhotnikov, O.G.

    1986-12-01

    Studies of the intensity fluctuations of a single-frequency injection laser have revealed that they are caused by beats between the coherent field and superluminescent spontaneous radiation. A drop in the fluctuation level with an increase in the laser output power in the region of developed laser generation is observed experimentally as well as a relative shift in the frequencies of the superluminescent modes of the external cavity; this shift is a function of lasing power. This behavior is explained by a mechanism of nonlinear interaction of fields in the active region of the laser diode. With significant laser output power (about 6 mW), the fluctuation level exceeds the shot noise level by no more than 4 dB. 12 references.

  6. A Digital Phase Lock Loop for an External Cavity Diode Laser

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Long; TAO Tian-Jiong; CHENG Bing; WU Bin; XU Yun-Fei; WANG Zhao-Ying; LIN Qiang

    2011-01-01

    @@ A digital optical phase lock loop (OPLL) is implemented to synchronize the frequency and phase between two external cavity diode lasers (ECDL), generating Raman pulses for atom interferometry.The setup involves alldigital phase detection and a programmable digital proportional-integral-derivative (PID) loop in locking.The lock generates a narrow beat-note linewidth below 1 Hz and low phase-noise of 0.03rad2 between the master and slave ECDLs.The lock proves to be stable and robust, and all the locking parameters can be set and optimized on a computer interface with convenience, making the lock adaptable to various setups of laser systems.

  7. A Digital Phase Lock Loop for an External Cavity Diode Laser

    Science.gov (United States)

    Wang, Xiao-Long; Tao, Tian-Jiong; Cheng, Bing; Wu, Bin; Xu, Yun-Fei; Wang, Zhao-Ying; Lin, Qiang

    2011-08-01

    A digital optical phase lock loop (OPLL) is implemented to synchronize the frequency and phase between two external cavity diode lasers (ECDL), generating Raman pulses for atom interferometry. The setup involves all-digital phase detection and a programmable digital proportional-integral-derivative (PID) loop in locking. The lock generates a narrow beat-note linewidth below 1 Hz and low phase-noise of 0.03rad2 between the master and slave ECDLs. The lock proves to be stable and robust, and all the locking parameters can be set and optimized on a computer interface with convenience, making the lock adaptable to various setups of laser systems.

  8. 10-Gb/s direct modulation of polymer-based tunable external cavity lasers.

    Science.gov (United States)

    Choi, Byung-Seok; Oh, Su Hwan; Kim, Ki Soo; Yoon, Ki-Hong; Kim, Hyun Soo; Park, Mi-Ran; Jeong, Jong Sool; Kwon, O-Kyun; Seo, Jun-Kyu; Lee, Hak-Kyu; Chung, Yun C

    2012-08-27

    We demonstrate a directly-modulated 10-Gb/s tunable external cavity laser (ECL) fabricated by using a polymer Bragg reflector and a high-speed superluminescent diode (SLD). The tuning range and output power of this ECL are measured to be >11 nm and 2.6 mW (@ 100 mA), respectively. We directly modulate this laser at 10 Gb/s and transmit the modulated signal over 20 km of standard single-mode fiber. The power penalty is measured to be <2.8 dB at the bit-error rate (BER) of 10(-10).

  9. External-cavity diode lasers with different devices and collimating optics.

    Science.gov (United States)

    Kane, D M; Willis, A P

    1995-07-20

    Comparative operating characteristics of external-cavity diode lasers (ECDL's) with either a channel substrate planar device or a multi-quantum-well (MQW) device are presented. These include the output beam profile, which is significantly altered depending on the collimating lens used (either multielement or graded index), power versus injection-current characteristics, and the optical frequency and the rf spectra. The coherence lengths of the different laser diode-collimating-lens combinations in the ECDL are measured, and a new method for calculating the coupling coefficient and the coupled values of the internal quantum efficiency and the internal lumped loss is demonstrated for the MQW device.

  10. Frequency stabilization in FBG external cavity semiconductor laser based on acetylene absorption method

    Institute of Scientific and Technical Information of China (English)

    Li Zhi-quan; Su Feng-yan; Kang Li-li

    2008-01-01

    A frequency-stabilized 1.53 μm FBG external-cavity semiconductor laser by using acetylene absorption is presented and its basic principles are introduced. Graded refractive index fiber and pigtailed fiber are used in the absorption air chamber to enhance the coupling stability. The impact of the background power is eliminated by using the third-harmonic modelocking technique. A lock-in amplifier is utilized to ensure that the output laser wavelength is locked at the C2H2 absorption line of 1530.37 nm. The frequency stability reaches 10-8 within 24 h.

  11. Standoff Hyperspectral Imaging of Explosives Residues Using Broadly Tunable External Cavity Quantum Cascade Laser Illumination

    Energy Technology Data Exchange (ETDEWEB)

    Bernacki, Bruce E.; Phillips, Mark C.

    2010-05-01

    We describe experimental results on the detection of explosives residues using active hyperspectral imaging by illumination of the target surface using an external cavity quantum cascade laser (ECQCL) and imaging using a room temperature microbolometer camera. The active hyperspectral imaging technique forms an image hypercube by recording one image for each tuning step of the ECQCL. The resulting hyperspectral image contains the full absorption spectrum produced by the illumination laser at each pixel in the image which can then be used to identify the explosive type and relative quantity using spectral identification approaches developed initially in the remote sensing community.

  12. High power external cavity laser diode arrays for the generation of hyperpolarized noble gases

    Science.gov (United States)

    Blasche, Gregory Paul

    Hyperpolarized noble gas magnetic resonance imaging promises to be a useful medical diagnostic tool due to its ability to image airways and brain function. A current limitation to widespread use is the time needed to generate gas quantities large enough for clinical patient imaging. Here I investigate line-narrowing of laser diode arrays in order to optimize the generation of hyperpolarized noble gases. Hyperpolarized noble gases are nuclear spin-½ isotopes that are polarized externally to have a large excess population of metastable spin up nuclei. When inhaled and imaged, they provide a novel tool for scientific studies and medical diagnosis in the human body. The gases are generated through a spin-exchange process via the spin-conserving hyperfine interaction of noble gas nuclei and optically pumped alkali metals. The net amount of polarized gas is limited by the optical power which is absorbed by the alkali metals as this is the first stage in the spin-exchange process. Laser diode arrays are typically used because they have a high available power for relatively low cost. Unfortunately, they are optically inefficient due to the factor of twenty larger inherent linewidth relative to the pressure broadened absorption linewidth of the alkali metal. In order to increase the efficiency of the system, I have designed and built an external cavity around the laser diode array consisting of a diffraction grating which acts as a wavelength dependent mirror tuned to the alkali metal rubidium absorption frequency. This causes the laser to operate solely at the desired wavelength, reducing the linewidth. External cavities have long been used for single element laser diodes. I extend this technique to laser diode arrays by imaging the diodes onto the grating using a set of imaging lenses forming individual cavities. I discuss the limitations on the power and linewidth achievable due to the optics of the cavity, as well as limitations caused by non-uniform heating effects

  13. Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array.

    Science.gov (United States)

    Lin, Shiyun; Zheng, Xuezhe; Yao, Jin; Djordjevic, Stevan S; Cunningham, John E; Lee, Jin-Hyoung; Shubin, Ivan; Luo, Ying; Bovington, Jock; Lee, Daniel Y; Thacker, Hiren D; Raj, Kannan; Krishnamoorthy, Ashok V

    2016-09-19

    We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits.

  14. Quantum modeling of semiconductor gain materials and vertical-external-cavity surface-emitting laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Bueckers, Christina; Kuehn, Eckhard; Schlichenmaier, Christoph; Koch, Stephan W. [Department of Physics and Material Sciences Center, Philipps-University Marburg (Germany); Imhof, Sebastian; Thraenhardt, Angela [Faculty of Natural Sciences, Chemnitz University of Technology, Chemnitz (Germany); Hader, Joerg; Moloney, Jerome V. [Nonlinear Control Strategies, Inc., Tucson, AZ (United States); College of Optical Sciences, University of Arizona, Tucson, AZ (United States); Rubel, Oleg [Thunder Bay Regional Research Institute, Thunder Bay, ON (Canada); Department of Physics, Lakehead University, Thunder Bay, ON (Canada); Zhang, Wei [Centre for Biophotonics, SIPBS, University of Strathclyde, Glasgow, Scotland (United Kingdom); Ackemann, Thorsten [SUPA and Department of Physics, University of Strathclyde, Glasgow, Scotland (United Kingdom)

    2010-04-15

    This article gives an overview of the microscopic theory used to quantitatively model a wide range of semiconductor laser gain materials. As a snapshot of the current state of research, applications to a variety of actual quantum-well systems are presented. Detailed theory-experiment comparisons are shown and it is analyzed how the theory can be used to extract poorly known material parameters. The intrinsic laser loss processes due to radiative and nonradiative Auger recombination are evaluated microscopically. The results are used for realistic simulations of vertical-external-cavity surface-emitting laser systems. To account for nonequilibrium effects, a simplified model is presented using pre-computed microscopic scattering and dephasing rates. Prominent deviations from quasi-equilibrium carrier distributions are obtained under strong in-well pumping conditions. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  15. Note: Demonstration of an external-cavity diode laser system immune to current and temperature fluctuations.

    Science.gov (United States)

    Miao, Xinyu; Yin, Longfei; Zhuang, Wei; Luo, Bin; Dang, Anhong; Chen, Jingbiao; Guo, Hong

    2011-08-01

    We demonstrate an external-cavity laser system using an anti-reflection coated laser diode as gain medium with about 60 nm fluorescence spectrum, and a Rb Faraday anomalous dispersion optical filter (FADOF) as frequency-selecting element with a transmission bandwidth of 1.3 GHz. With 6.4% optical feedback, a single stable longitudinal mode is obtained with a linewidth of 69 kHz. The wavelength of this laser is operating within the center of the highest transmission peak of FADOF over a diode current range from 55 mA to 142 mA and a diode temperature range from 15 °C to 35 °C, thus it is immune to the fluctuations of current and temperature.

  16. Littrow-type external-cavity blue laser for holographic data storage

    Science.gov (United States)

    Tanaka, Tomiji; Takahashi, Kazuo; Sako, Kageyasu; Kasegawa, Ryo; Toishi, Mitsuru; Watanabe, Kenjiro; Samuels, David; Takeya, Motonobu

    2007-06-01

    An external-cavity laser with a wavelength of 405 nm and an output of 80 mW has been developed for holographic data storage. The laser has three states: the first is a perfect single mode, whose coherent length is 14 m; the second is a three-mode state with a coherent length of 3 mm; and the third is a six-mode state with a coherent length of 0.3 mm. The first and second states are available for angular-multiplexing recording; all states are available for coaxial multiplexing recording. Due to its short wavelength, the recording density is higher than that of a 532 nm laser.

  17. Mid-infrared gas absorption sensor based on a broadband external cavity quantum cascade laser

    Science.gov (United States)

    Sun, Juan; Deng, Hao; Liu, Ningwu; Wang, Hongliang; Yu, Benli; Li, Jingsong

    2016-12-01

    We developed a laser absorption sensor based on a pulsed, broadband tunable external cavity quantum cascade laser (ECQCL) centered at 1285 cm-1. Unlike traditional infrared spectroscopy system, a quartz crystal tuning fork (QCTF) as a light detector was used for laser signal detection. Fast Fourier transform was applied to extract vibration intensity information of QCTF. The sensor system is successfully tested on nitrous oxide (N2O) spectroscopy measurements and compared with a standard infrared detector. The wide wavelength tunability of ECQCL will allow us to access the fundamental vibrational bands of many chemical agents, which are well-suited for trace explosive, chemical warfare agent, and toxic industrial chemical detection and spectroscopic analysis.

  18. Trace-gas sensing using the compliance voltage of an external cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.

    2013-06-04

    Quantum cascade lasers (QCLs) are increasingly being used to detect, identify, and measure levels of trace gases in the air. External cavity QCLs (ECQCLs) provide a broadly-tunable infrared source to measure absorption spectra of chemicals and provide high detection sensitivity and identification confidence. Applications include detecting chemical warfare agents and toxic industrial chemicals, monitoring building air quality, measuring greenhouse gases for atmospheric research, monitoring and controlling industrial processes, analyzing chemicals in exhaled breath for medical diagnostics, and many more. Compact, portable trace gas sensors enable in-field operation in a wide range of platforms, including handheld units for use by first responders, fixed installations for monitoring air quality, and lightweight sensors for deployment in unmanned aerial vehicles (UAVs). We present experimental demonstration of a new chemical sensing technique based on intracavity absorption in an external cavity quantum cascade laser (ECQCL). This new technique eliminates the need for an infrared photodetector and gas cell by detecting the intracavity absorption spectrum in the compliance voltage of the laser device itself. To demonstrate and characterize the technique, we measure infrared absorption spectra of chemicals including water vapor and Freon-134a. Sub-ppm detection limits in one second are achieved, with the potential for increased sensitivity after further optimization. The technique enables development of handheld, high-sensitivity, and high-accuracy trace gas sensors for in-field use.

  19. Liquid detection with InGaAsP semiconductor lasers having multiple short external cavities.

    Science.gov (United States)

    Zhu, X; Cassidy, D T

    1996-08-20

    A liquid detection system consisting of a diode laser with multiple short external cavities (MSXC's) is reported. The MSXC diode laser operates single mode on one of 18 distinct modes that span a range of 72 nm. We selected the modes by setting the length of one of the external cavities using a piezoelectric positioner. One can measure the transmission through cells by modulating the injection current at audio frequencies and using phase-sensitive detection to reject the ambient light and reduce 1/f noise. A method to determine regions of single-mode operation by the rms of the output of the laser is described. The transmission data were processed by multivariate calibration techniques, i.e., partial least squares and principal component regression. Water concentration in acetone was used to demonstrate the performance of the system. A correlation coefficient of R(2) = 0.997 and 0.29% root-mean-square error of prediction are found for water concentration over the range of 2-19%.

  20. Frequency and time domain analysis of an external cavity laser with strong filtered optical feedback

    DEFF Research Database (Denmark)

    Detoma, Enrico; Tromborg, Bjarne; Montrosset, Ivo

    -signal analysis in the frequency domain allows a calculation of the range of operation without mode hopping around the grating reflectivity peak. This region should be as large as possible for proper operation of the tunable laser source. The analysis shows this stabilizing effect of mode coupling and gain......The stability properties of an external cavity laser with strong grating-filtered optical feedback to an anti-reflection coated facet are studied with a general frequency domain model. The model takes into account non-linear effects like four wave mixing and gain compression. A small...... copression in the lasing mode. An integral equation for the electrical field is derived from the frequency domain model and used for time domain simulations of large-signal behavior....

  1. Long-term frequency stabilization system for external cavity diode laser based on mode boundary detection.

    Science.gov (United States)

    Xu, Zhouxiang; Huang, Kaikai; Jiang, Yunfeng; Lu, Xuanhui

    2011-12-01

    We have realized a long-term frequency stabilization system for external cavity diode laser (ECDL) based on mode boundary detection method. In this system, the saturated absorption spectroscopy was used. The current and the grating of the ECDL were controlled by a computer-based feedback control system. By checking if there are mode boundaries in the spectrum, the control system determined how to adjust current to avoid mode hopping. This procedure was executed periodically to ensure the long-term stabilization of ECDL in the absence of mode hops. This diode laser system with non-antireflection coating had operated in the condition of long-term mode-hop-free stabilization for almost 400 h, which is a significant improvement of ECDL frequency stabilization system.

  2. Scaling the spectral beam combining channel by multiple diode laser stacks in an external cavity

    Science.gov (United States)

    Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao; Lei, Fuchuan; Yu, Junhong; Tan, Hao

    2017-04-01

    Spectral beam combining of a broad area diode laser is a promising technique for direct diode laser applications. We present an experimental study of three mini-bar stacks in an external cavity on spectral beam combining in conjunction with spatial beam combining. At the pump current of 70 A, a CW output power of 579 W, spectral bandwidth of 18.8 nm and electro-optical conversion efficiency of 47% are achieved. The measured M 2 values of spectral beam combining are 18.4 and 14.7 for the fast and the slow axis, respectively. The brightness of the spectral beam combining output is 232 MW · cm‑2 · sr‑1.

  3. Coupled resonator vertical cavity laser

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

    1998-01-01

    The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

  4. A low-temperature external cavity diode laser for broad wavelength tuning

    Science.gov (United States)

    Tobias, William G.; Rosenberg, Jason S.; Hutzler, Nicholas R.; Ni, Kang-Kuen

    2016-11-01

    We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to the spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64 °C, more than 85 °C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation is achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers and extending the wavelength coverage of commercial laser diodes.

  5. A low-temperature external cavity diode laser for broad wavelength tuning

    CERN Document Server

    Tobias, William G; Hutzler, Nicholas R; Ni, Kang-Kuen

    2016-01-01

    We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64{\\deg}C, more than 85{\\deg}C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation was achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers ...

  6. A grating-coupled external cavity InAs/InP quantum dot laser with 85-nm tuning range

    Science.gov (United States)

    Wei, Heng; Jin, Peng; Luo, Shuai; Ji, Hai-Ming; Yang, Tao; Li, Xin-Kun; Wu, Jian; An, Qi; Wu, Yan-Hua; Chen, Hong-Mei; Wang, Fei-Fei; Wu, Ju; Wang, Zhan-Guo

    2013-09-01

    The optical performance of a grating-coupled external cavity laser based on InAs/InP quantum dots is investigated. Continuous tuning from 1391 nm to 1468 nm is realized at an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented.

  7. Wideband digitally tunable lasers based on fiber Bragg grating external cavity array and 1×N optical switch

    Institute of Scientific and Technical Information of China (English)

    Haiwen Cai(蔡海文); Jianxin Geng(耿建新); Zuoren Dong(董作人); Gaoting Chen(陈高庭); Zujie Fang(方祖捷)

    2003-01-01

    A novel wideband digitally tunable laser based on fiber Bragg grating external cavities and 1 × N optical switch provides 5 ms fast tuning time with output power more than 1 dBm over whole C-band that is only limited by the laser emission bandwidth. Less than 50 pm wavelength drift over -10 to 55℃ temperature range make that the wavelength locker and monitor are not necessary in this tunable laser.

  8. Study of an electrodynamic system consisting of a laser cavity and an external weakly reflecting element

    Science.gov (United States)

    Shatrov, A. D.; Dubrov, M. N.; Aleksandrov, D. V.

    2016-12-01

    The behaviour of the electromagnetic field in a three-mirror laser cavity is described using the method of integral equations. The results of numerical calculations and experimental studies for particular examples implementing the considered configuration are presented. The conditions for optimal tuning of a laser interferometer-deformograph with a three-mirror cavity are determined. The contribution of the reflected and scattered light and arising additional seismic noises to the resulting error of laser gravitational wave detectors is studied.

  9. External cavity-quantum cascade laser (EC-QCL) spectroscopy for protein analysis in bovine milk.

    Science.gov (United States)

    Kuligowski, Julia; Schwaighofer, Andreas; Alcaráz, Mirta Raquel; Quintás, Guillermo; Mayer, Helmut; Vento, Máximo; Lendl, Bernhard

    2017-04-22

    The analytical determination of bovine milk proteins is important in food and non-food industrial applications and yet, rather labour-intensive wet-chemical, low-throughput methods have been employed since decades. This work proposes the use of external cavity-quantum cascade laser (EC-QCL) spectroscopy for the simultaneous quantification of the most abundant bovine milk proteins and the total protein content based on the chemical information contained in mid-infrared (IR) spectral features of the amide I band. Mid-IR spectra of protein standard mixtures were used for building partial least squares (PLS) regression models. Protein concentrations in commercial bovine milk samples were calculated after chemometric compensation of the matrix contribution employing science-based calibration (SBC) without sample pre-processing. The use of EC-QCL spectroscopy together with advanced multivariate data analysis allowed the determination of casein, α-lactalbumin, β-lactoglobulin and total protein content within several minutes.

  10. Wavelength beam combining of a 980-nm tapered diode laser bar in an external cavity

    Science.gov (United States)

    Vijayakumar, Deepak; Jensen, Ole Bjarlin; Thestrup, Birgitte

    2010-04-01

    High power diode lasers are used in a large number of applications. A limiting factor for more widespread use of broad area lasers is the poor beam quality. Gain guided tapered diode lasers are ideal candidates for industrial applications that demands watt level output power with good beam quality. By adapting a bar geometry, the output power could be scaled even up to several tens of watts. Unfortunately, the high divergence which is a characteristic feature of the bar geometry could lead to a degradation of the overall beam quality of the laser bar. However, spectral beam combining is an effective solution for preserving the beam quality of the bar in the range of that of a single emitter and at the same time, enabling the power scaling. We report spectral beam combining applied to a 12 emitter tapered laser bar at 980 nm. The external cavity has been designed for a wavelength separation of 4.0 nm between the emitters. An output power of 9 W has been achieved at an operating current of 30 A. The combined beam had an M2 value (1/e2) of 5.3 along the slow axis which is comparable to that of a single tapered emitter on the laser bar. The overall beam combining efficiency was measured to be 63%. The output spectrum of the individual emitters was narrowed considerably. In the free running mode, the individual emitters displayed a broad spectrum of the order of 0.5-1.0 nm while the spectral width has been reduced to 30-100 pm in the spectral beam combining mode.

  11. Coherent beam combination of broad-area laser diode array using off-axis external cavity with double feedback

    Institute of Scientific and Technical Information of China (English)

    Zhouping Su; Zhicheng Ji; Lizhi Que; Zhuowei Zhu

    2012-01-01

    In this letter,we demonstrate coherent beam combination of laser diode array using the external Talbot cavity with double feedback.The double feedback elements consist of grating and high-reflection plane mirror.Compared with single high-reflection plane mirror feedback,the external Talbot cavity with double feedback reduce the number of interference strips in the far-field pattern and narrow spectral line-width of the laser diode array.The results indicate that the application of the external Talbot cavity with double feedback produces a clear far-field interference pattern.In addition,line-width is reduced to 0.15 nm full-width at half-maximum (FWHM).

  12. Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason M.

    2015-02-08

    We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 µm) at a 10 Hz repetition rate.

  13. 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.

  14. Broadband spectroscopy with external cavity quantum cascade lasers beyond conventional absorption measurements.

    Science.gov (United States)

    Lambrecht, Armin; Pfeifer, Marcel; Konz, Werner; Herbst, Johannes; Axtmann, Felix

    2014-05-07

    Laser spectroscopy is a powerful tool for analyzing small molecules, i.e. in the gas phase. In the mid-infrared spectral region quantum cascade lasers (QCLs) have been established as the most frequently used laser radiation source. Spectroscopy of larger molecules in the gas phase, of complex mixtures, and analysis in the liquid phase requires a broader tuning range and is thus still the domain of Fourier transform infrared (FTIR) spectroscopy. However, the development of tunable external cavity (EC) QCLs is starting to change this situation. The main advantage of QCLs is their high spectral emission power that is enhanced by a factor of 10(4) compared with thermal light sources. Obviously, transmission measurements with EC-QCLs in strongly absorbing samples are feasible, which can hardly be measured by FTIR due to detector noise limitations. We show that the high power of EC-QCLs facilitates spectroscopy beyond simple absorption measurements. Starting from QCL experiments with liquid samples, we show results of fiber evanescent field analysis (FEFA) to detect pesticides in drinking water. FEFA is a special case of attenuated total reflection spectroscopy. Furthermore, powerful CW EC-QCLs enable fast vibrational circular dichroism (VCD) spectroscopy of chiral molecules in the liquid phase - a technique which is very time consuming with standard FTIR equipment. We present results obtained for the chiral compound 1,1'-bi-2-naphthol (BINOL). Finally, powerful CW EC-QCLs enable the application of laser photothermal emission spectroscopy (LPTES). We demonstrate this for a narrowband and broadband absorber in the gas phase. All three techniques have great potential for MIR process analytical applications.

  15. Highly-efficient, diffraction-limited laser emission from a Vertical External Cavity Surface-emitting Organic Laser

    CERN Document Server

    Rabbani-Haghighi, Hadi; Chenais, Sebastien; Siove, Alain

    2010-01-01

    We report on a solid-state laser structure being the organic counterpart of the Vertical External-Cavity Surface-Emitting Laser (VECSEL) design. The gain medium is a poly (methyl methacrylate) film doped with Rhodamine 640, spin-casted onto the High-Reflectivity mirror of a plano-concave resonator. Upon pumping by 7-ns pulses at 532 nm, a diffraction-limited beam (M^2=1) was obtained, with a conversion efficiency of 43%; higher peak powers (2kW) could be attained when resorting to shorter (0.5 ns) pump pulses. The spectrum was controlled by the thickness of the active layer playing the role of an intracavity etalon; tunability is demonstrated over up to 20 nm.

  16. Efficient second harmonic generation of a diode-laser-pumped CW Nd:YAG laser using monolithic MgO:LiNbO3 external resonant cavities

    Science.gov (United States)

    Kozlovsky, William J.; Nabors, C. D.; Byer, Robert L.

    1988-01-01

    56-percent efficient external-cavity-resonant second-harmonic generation of a diode-laser pumped, CW single-axial-mode Nd:YAG laser is reported. A theory of external doubling with a resonant fundamental is presented and compared to experimental results for three monolithic cavities of nonlinear MgO:LiNbO3. The best conversion efficiency was obtained with a 12.5-mm-long monolithic ring cavity doubler, which produced 29.7 mW of CW, single-axial model 532-nm radiation from an input of 52.5 mW.

  17. Planar-waveguide external cavity laser stabilization for an optical link with 10(-19) frequency stability.

    Science.gov (United States)

    Clivati, Cecilia; Mura, Alberto; Calonico, Davide; Levi, Filippo; Costanzo, Giovanni A; Calosso, Claudio E; Godone, Aldo

    2011-12-01

    We stabilized the frequency of a compact planar-waveguide external cavity laser (ECL) on a Fabry-Perot cavity (FPC) through a Pound-Drever-Hall scheme. The residual frequency stability of the ECL is 10(-14), comparable to the stability achievable with a fiber laser (FL) locked to an FPC through the same scheme. We set up an optical link of 100 km, based on fiber spools, that reaches 10(-19) relative stability, and we show that its performances using the ECL or FL are comparable. Thus ECLs could serve as an excellent replacement for FLs in optical links where cost-effectiveness and robustness are important considerations.

  18. 25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity

    CERN Document Server

    Oldenbeuving, R M; Offerhaus, H L; Lee, C J; Song, H; Boller, K -J

    2012-01-01

    We report on the spectral properties of a diode laser with a tunable external cavity in integrated optics. Even though the external cavity is short compared to other small-bandwidth external cavity lasers, the spectral bandwidth of this tunable laser is as small as 25 kHz (FWHM), at a side-mode suppression ratio (SMSR) of 50 dB. Our laser is also able to access preset wavelengths in as little as 200 us and able to tune over the full telecom C-band (1530 nm - 1565 nm).

  19. External cavity tunable quantum cascade lasers and their applications to trace gas monitoring.

    Science.gov (United States)

    Rao, Gottipaty N; Karpf, Andreas

    2011-02-01

    Since the first quantum cascade laser (QCL) was demonstrated approximately 16 years ago, we have witnessed an explosion of interesting developments in QCL technology and QCL-based trace gas sensors. QCLs operate in the mid-IR region (3-24 μm) and can directly access the rotational vibrational bands of most molecular species and, therefore, are ideally suited for trace gas detection with high specificity and sensitivity. These sensors have applications in a wide range of fields, including environmental monitoring, atmospheric chemistry, medical diagnostics, homeland security, detection of explosive compounds, and industrial process control, to name a few. Tunable external cavity (EC)-QCLs in particular offer narrow linewidths, wide ranges of tunability, and stable power outputs, which open up new possibilities for sensor development. These features allow for the simultaneous detection of multiple species and the study of large molecules, free radicals, ions, and reaction kinetics. In this article, we review the current status of EC-QCLs and sensor developments based on them and speculate on possible future developments.

  20. Standoff detection of turbulent chemical mixture plumes using a swept external cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C. [Pacific Northwest National Laboratory, Richland, Washington; Brumfield, Brian E. [Pacific Northwest National Laboratory, Richland, Washington

    2017-08-21

    We demonstrate standoff detection of turbulent mixed-chemical plumes using a broadly-tunable external cavity quantum cascade laser (ECQCL). The ECQCL was directed through plumes of mixed methanol/ethanol vapor to a partially-reflective surface located 10 m away. The reflected power was measured as the ECQCL was swept over its tuning range of 930-1065 cm-1 (9.4-10.8 µm) at rates up to 200 Hz. Analysis of the transmission spectra though the plume was performed to determine chemical concentrations with time resolution of 0.005 s. Comparison of multiple spectral sweep rates of 2 Hz, 20 Hz, and 200 Hz shows that higher sweep rates reduce effects of atmospheric and source turbulence, resulting in lower detection noise and more accurate measurement of the rapidly-changing chemical concentrations. Detection sensitivities of 0.13 ppm*m for MeOH and 1.2 ppm*m for EtOH are demonstrated for a 200 Hz spectral sweep rate, normalized to 1 s detection time.

  1. Achieving single-lobed far-field patterns of broad area laser diode with external cavity feedback

    Institute of Scientific and Technical Information of China (English)

    Jianhong Ge(葛剑虹); Jun Chen(陈军); Andreas Hermerschmidt; H.J.Eichler

    2003-01-01

    We demonstrate a technique for single transverse mode operation of high-power broad area laser diode(BAL). In the experiment, the HR mirror is used as an external cavity mirror and the grating is used as a wavelength selective component. By tiling the HR mirror and the grating, the number of transverse modes oscillating in the cavity can be limited and the spectral bandwidth of the laser diode can be reduced. A single-lobed near diffraction-limited laser beam with the beam divergence (FWHM) of 0.43°, the spectral line-width of 0.7 nm and the output power of 350 mW are obtained. With the feedback, the power density of the output laser beam is increased 6 times in comparison with the free running.

  2. Stabilization and Shift of Frequency in an External Cavity Diode Laser with Solenoid-Assisted Saturated Absorption

    Institute of Scientific and Technical Information of China (English)

    HAN Shun-Li; CHENG Bing; ZHANG Jing-Fang; XU Yun-Fei; WANG Zhao-Ying; LIN Qiang

    2009-01-01

    A simple method to realize both stabilization and shift of the frequency in an external cavity diode laser (ECDL) is reported.Due to the Zeeman effect,the saturated absorption spectrum of Rb atoms in a magnetic field is shifted.This shift can be used to detune the frequency of the ECDL,which is locked to the saturated absorption spectrum.The frequency shift amount can be controlled by changing the magnetic field for a specific polarization state of the laser beam.The advantages of this tunable frequency lock include low laser power requirement,without additional power loss,cheapness,and so on.

  3. Broadband and high-speed swept external-cavity laser using a quantum-dot superluminescent diode as gain device

    Institute of Scientific and Technical Information of China (English)

    胡发杰; 金鹏; 吴艳华; 王飞飞; 魏恒; 王占国

    2015-01-01

    A wide wavelength tuning range swept external-cavity laser using an InAs/GaAs quantum-dot superluminescent diode as a gain device is demonstrated. The tunable filter consists of a polygon scanner and a grating in Littrow telescope-less configuration. The swept laser generates greater than 54-mW peak output power and up to 33-kHz sweep rate with a sweep range of 150 nm centered at 1155 nm. The effects of injection current and sweep rate on the sweep performance of the swept laser are studied.

  4. Broadband tunable external cavity laser using a bent-waveguide quantum-dot superluminescent diode as gain device

    Institute of Scientific and Technical Information of China (English)

    Wu Jian; Lü Xue-Qin; Jin Peng; Meng Xian-Quan; Wang Zhan-Guo

    2011-01-01

    A broadband tunable grating-coupled external cavity laser is realized by employing a self-assembled InAs/GaAs quantum-dot (QD) superluminescent diode (SLD) as the gain device. The SLD device is processed with a bent-waveguide structure and facet antireflection (AR) coating. Tuning bandwidths of 106 nm and 117 nm are achieved under 3-A and 3.5-A injection currents, respectively. The large tuning range originates essentially from the broad gain spectrum of self-assembled QDs. The bent waveguide structure combined with the facet AR coating plays a role in suppressing the inner-cavity lasing under a large injection current.

  5. Demonstration of a rapidly-swept external cavity quantum cascade laser for atmospheric sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.; Suter, Jonathan D.

    2016-07-01

    The application of quantum cascade lasers (QCLs) in atmospheric science for trace detection of gases has been demonstrated using sensors in point or remote sensing configurations. Many of these systems utilize single narrowly-tunable (~10 cm-1) distributed feedback (DFB-) QCLs that limit simultaneous detection to a restricted number of small chemical species like H2O or N2O. The narrow wavelength range of DFB-QCLs precludes accurate quantification of large chemical species with broad rotationally-unresolved vibrational spectra, such as volatile organic compounds, that play an important role in the chemistry of the atmosphere. External-cavity (EC-) QCL systems are available that offer tuning ranges >100 cm-1, making them excellent IR sources for measuring multiple small and large chemical species in the atmosphere. While the broad wavelength coverage afforded by an EC system enables measurements of large chemical species, most commercial systems can only be swept over their entire wavelength range at less than 10 Hz. This prohibits broadband simultaneous measurements of multiple chemicals in plumes from natural or industrial sources where turbulence and/or chemical reactivity are resulting in rapid changes in chemical composition on sub-1s timescales. At Pacific Northwest National Laboratory we have developed rapidly-swept EC-QCL technology that acquires broadband absorption spectra (~100 cm-1) on ms timescales. The spectral resolution of this system has enabled simultaneous measurement of narrow rotationally-resolved atmospherically-broadened lines from small chemical species, while offering the broad tuning range needed to measure broadband spectral features from multiple large chemical species. In this talk the application of this technology for open-path atmospheric measurements will be discussed based on results from laboratory measurements with simulated plumes of chemicals. The performance offered by the system for simultaneous detection of multiple chemical

  6. Composite resonator vertical cavity laser diode

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Hou, H.Q.; Chow, W.W.; Geib, K.M.; Hammons, B.E.

    1998-05-01

    The use of two coupled laser cavities has been employed in edge emitting semiconductor lasers for mode suppression and frequency stabilization. The incorporation of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. Composite resonators can be utilized to control spectral and temporal properties within the laser; previous studies of coupled cavity vertical cavity lasers have employed photopumped structures. The authors report the first composite resonator vertical cavity laser diode consisting of two optical cavities and three monolithic distributed Bragg reflectors. Cavity coupling effects and two techniques for external modulation of the laser are described.

  7. Tunable External Cavity Quantum Cascade Lasers (EC-QCL): an application field for MOEMS based scanning gratings

    Science.gov (United States)

    Grahmann, Jan; Merten, André; Ostendorf, Ralf; Fontenot, Michael; Bleh, Daniela; Schenk, Harald; Wagner, Hans-Joachim

    2014-03-01

    In situ process information in the chemical, pharmaceutical or food industry as well as emission monitoring, sensitive trace detection and biological sensing applications would increasingly rely on MIR-spectroscopic anal­ysis in the 3 μm - 12 μm wavelength range. However, cost effective, portable, low power consuming and fast spectrometers with a wide tuning range are not available so far. To provide these MIR-spectrometer properties, the combination of quantum cascade lasers with a MOEMS scanning grating as wavelength selective element in the external cavity is addressed to provide a very compact and fast tunable laser source for spectroscopic analysis.

  8. Ultra-Stable Rubidium-Stabilized External-Cavity Diode Laser Based on the Modulation Transfer Spectroscopy Technique

    Institute of Scientific and Technical Information of China (English)

    QI Xiang-Hui; CHEN Wen-Lan; YI Lin; ZHOU Da-Wei; ZHOU Tong; XIAO Qin; DUAN Jun; ZHOU Xiao-Ji; CHEN Xu-Zong

    2009-01-01

    @@ We construct an ultra-stable external-cavity diode laser via modulation transfer spectroscopy referencing on a hyperfine component of the 87Rb D2 lines at 780 hm. The Doppler-free dispersion-like modulation transfer signal is obtained with high signal-to-noise-ratio. The instability of the laser frequency is measured by beating with an optical frequency comb which is phase-locked to an ultra-stable oven controlled crystal oscillator. The Allan deviation is 3.9×10-13 at 1s averaging time and 9.8×10-14 at 90s averaging time.

  9. High-Power Hybrid Mode-Locked External Cavity Semiconductor Laser Using Tapered Amplifier with Large Tunability

    Directory of Open Access Journals (Sweden)

    Andreas Schmitt-Sody

    2008-01-01

    Full Text Available We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature.

  10. Packaged, High-Power, Narrow-Linewidth Slab-Coupled Optical Waveguide External Cavity Laser (SCOWECL)

    Science.gov (United States)

    2010-12-01

    efficiency. With the 20% reflecli vity FBG, the laser ex hibi ts a threshold of 0.9 A and reaches a CW peak power of 0.37 W aI 4 A. The peak effic ...twice the photon energy . The SCOWECL is expected to find applications in free space coherent optical communications and in microwave photollic...Dai , " High effic ient and narrow linewidlh fiber laser based on fiber grat ing Fabry- Perot cavity," Frolltiers of Oploeieclrollics il/ Chinll, vol

  11. 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.

  12. Tuning range and output power optimization of an external-cavity GaN diode laser at 455  nm.

    Science.gov (United States)

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

    2016-03-20

    In this paper we discuss how different feedback gratings affect the tuning range and the output power of external feedback diode laser systems. A tunable high-power narrow-spectrum external-cavity diode laser system around 455 nm is investigated. The laser system is based on a high-power GaN diode laser in a Littrow external-cavity. Both a holographic diffraction grating and a ruled diffraction grating are used as feedback elements in the external cavity. The output power, spectral bandwidth, and tunable range of the external cavity diode laser system are measured and compared with the two gratings at different injected currents. When the holographic grating is used, the laser system can be tuned over a range of 1.4 nm with an output power around 530 mW. When the ruled grating is used, the laser system can be tuned over a range of 6.0 nm with an output power around 80 mW. The results can be used as a guide for selecting gratings for external-cavity diode lasers for different requirements.

  13. Optical Fiber Link with 1E-19 frequency stability using a Planar-Waveguide External Cavity Laser Diode

    CERN Document Server

    Clivati, Cecilia; Calonico, Davide; Levi, Filippo; Costanzo, Giovanni A; Calosso, Claudio E; Godone, Aldo

    2011-01-01

    We compare the performances of a compact planar-waveguide external cavity laser (ECL) and a traditional fiber laser (FL) frequency locked to a Fabry-P\\'erot cavity and demonstrate the possibility to use such ECL in an optical link for ultra stable frequency dissemination. A relative stability of the ECL of 1E-14 is obtained and an optical link of 100 km based on fiber spools has been realized, that reaches 2E-19 relative stability, limited by the system noise floor. The performances of ECL and FL are shown to be comparable. Thus, ECLs could be a better choice than FLs in longer optical links with amplification and regenerating stations, thanks to their cost-effectiveness, robustness and small size.

  14. Eavesdropping in chaotic optical communication using the feedback length of an external-cavity laser as a key.

    Science.gov (United States)

    Zhao, Qingchun; Wang, Yuncai; Wang, Anbang

    2009-06-20

    An external-cavity laser (ECL) operating in a chaotic state is usually used in a chaotic optical secure communication system and its feedback length (FL) is often regarded as an additional key. Our analyses show that an eavesdropper's (Eve) laser can synchronize with a transmitter (Alice) without any knowledge of the FL by simply increasing the injection strength. A sequence of a 1 Gbit/s nonreturn-to-zero message encoded by the FL as the key is successfully eavesdropped. The reason for the synchronization deviation between Alice's and Eve's lasers is given. Our results indicate that the FL as a key cannot enhance the security of chaotic optical communication using long-ECLs.

  15. Broadband and high-speed swept external-cavity laser using a quantum-dot superluminescent diode as gain device

    Science.gov (United States)

    Hu, Fa-Jie; Jin, Peng; Wu, Yan-Hua; Wang, Fei-Fei; Wei, Heng; Wang, Zhan-Guo

    2015-10-01

    A wide wavelength tuning range swept external-cavity laser using an InAs/GaAs quantum-dot superluminescent diode as a gain device is demonstrated. The tunable filter consists of a polygon scanner and a grating in Littrow telescope-less configuration. The swept laser generates greater than 54-mW peak output power and up to 33-kHz sweep rate with a sweep range of 150 nm centered at 1155 nm. The effects of injection current and sweep rate on the sweep performance of the swept laser are studied. Project supported by the National Natural Science Foundation of China (Grant No. 61274072) and the National High Technology Research and Development Program of China (Grant No. 2013AA014201).

  16. 1300 nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Orchard, J. [Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Clarke, E. [EPSRC National Centre for III-V Technologies, University of Sheffield, Mappin Street, S1 3JD Sheffield (United Kingdom)

    2015-10-12

    We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3 μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11 mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization.

  17. Efficient quasi-three-level Nd:YAG laser at 946 nm pumped by a tunable external cavity tapered diode laser

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter;

    2010-01-01

    Using a tunable external cavity tapered diode laser (ECDL) pumped quasi-three-level Nd:YAG laser, a fivefold reduction in threshold and twofold increase in slope efficiency is demonstrated when compared to a traditional broad area diode laser pump source. A TEM00 power of 800 mW with 65% slope...... efficiency is obtained, the highest reported TEM00 power from any 946 nm Nd:YAG laser pumped by a single emitter diode laser pump source. A quantum efficiency of 0.85 has been estimated from experimental data using a simple quasi-three-level model. The reported value is in good agreement with published...... values, suggesting that the model is adequate. Improvement of the 946 nm laser due to the ECDL's narrow spectrum proves to be less significant when compared to its spatial quality, inferring a broad spectrum tapered diode laser pump source may be most practical. Experimental confirmation of such setup...

  18. The Study on the Performance of the Wavelength Conversion Based on a Tunable External Cavity Semiconductor Laser

    Institute of Scientific and Technical Information of China (English)

    YE Yabin; ZHANG Hanyi; ZHENG Xiaoping

    2001-01-01

    In this paper, the performance of the wavelength conversion based on a tunable external cavity semiconductor laser (ECL) was studied. The static wavelength conversion was achieved in the tunable wavelength range of the ECL. The dynamic wavelength conversions of 155 Mb/s and 622 Mb/s nonreturn to zero (NRZ) signals were realized. The simulation of the ECL output characteristics using modified compound cavity rate equation shows that the higher bit rate wavelength conversion can be realized by increasing the relaxation oscillation frequency of the ECL. When the modulated bit rate is much lower than the relaxation oscillation frequency, under a fixed input signal power, there is an optimal bias current for the wavelength converter based on ECL.

  19. Widely tunable, narrow linewidth external-cavity gain chip laser for spectroscopy between 1.0 - 1.1 um

    CERN Document Server

    Shin, Dong K; Khakimov, Roman I; Ross, Jacob A; Dedman, Colin J; Hodgman, Sean S; Baldwin, Kenneth G H; Truscott, Andrew G

    2016-01-01

    We have developed and characterised a stable, narrow linewidth external-cavity laser (ECL) tunable over 100 nm around 1080 nm, using a single-angled-facet gain chip. We propose the ECL as a low-cost, high-performance alternative to fibre and diode lasers in this wavelength range and demonstrate its capability through the spectroscopy of metastable helium. Within the coarse tuning range, the wavelength can be continuously tuned over 30 pm (7.8 GHz) without mode-hopping and modulated with bandwidths up to 3 kHz (piezo) and 37(3) kHz (current). The spectral linewidth of the free-running ECL was measured to be 22(2) kHz (Gaussian) and 4.2(3) kHz (Lorentzian) over 22.5 ms, while a long-term frequency stability better than 40(20) kHz over 11 hours was observed when locked to an atomic reference.

  20. Sensitive Raman gas analysis using a 500 mW external cavity diode laser at 410 nm

    Science.gov (United States)

    Li, Bin; Luo, Shiwen; Yu, Anlan; Gao, Jun; Sun, Pengfei; Wang, Xinbing; Zuo, Duluo

    2017-09-01

    Sensitive Raman gas analysis based on a home-made high power 410 nm Littrow-arranged external cavity diode laser (ECDL) and a parabolic sample cell is presented. Using a commercially available violet laser diode and a reflective holographic grating, the ECDL achieves a maximum output power of 505 mW with line-width about 50 pm. Spontaneous Raman scattering of ambient air is acquired with this ECDL, in which an imaging Raman spectrometer is applied. Strong Raman signals of O2, N2 and H2O are observed with 1 s exposure time; a limit of detection (LOD) of CO2 about 210 ppm is achieved with an exposure time of 100 s and a 3.5-fold enhancement to the signal level is also demonstrated compared with a 532 nm green laser with the same exciting power. The results show that violet diode laser can be an attractive excitation source for Raman gas analysis.

  1. Lead-chalcogenide mid-infrared vertical external cavity surface emitting lasers with improved threshold: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Fill, Matthias [ETH Zurich, Laser Spectroscopy and Sensing Lab, 8093 Zurich (Switzerland); Phocone AG, 8005 Zurich (Switzerland); Debernardi, Pierluigi [IEIIT-CNR, Torino 10129 (Italy); Felder, Ferdinand [Phocone AG, 8005 Zurich (Switzerland); Zogg, Hans [ETH Zurich (Switzerland)

    2013-11-11

    Mid-infrared Vertical External Cavity Surface Emitting Lasers (VECSEL) based on narrow gap lead-chalcogenide (IV-VI) semiconductors exhibit strongly reduced threshold powers if the active layers are structured laterally for improved optical confinement. This is predicted by 3-d optical calculations; they show that lateral optical confinement is needed to counteract the anti-guiding features of IV-VIs due to their negative temperature dependence of the refractive index. An experimental proof is performed with PbSe quantum well based VECSEL grown on a Si-substrate by molecular beam epitaxy and emitting around 3.3 μm. With proper mesa-etching, the threshold intensity is about 8-times reduced.

  2. Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

    2016-02-13

    A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

  3. Wavelength beam combining of a 980-nm tapered diode laser bar in an external cavity

    DEFF Research Database (Denmark)

    Vijayakumar, Deepak; Jensen, Ole Bjarlin; Thestrup Nielsen, Birgitte

    2010-01-01

    High power diode lasers are used in a large number of applications. A limiting factor for more widespread use of broad area lasers is the poor beam quality. Gain guided tapered diode lasers are ideal candidates for industrial applications that demands watt level output power with good beam quality...

  4. Dual-wavelength high-power diode laser system based on an external-cavity tapered amplifier with tunable frequency difference

    DEFF Research Database (Denmark)

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

    2012-01-01

    A dual-wavelength high-power semiconductor laser system based on a tapered amplifier with double-Littrow external cavity is demonstrated around 800 nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 10.0 THz. To our knowle...

  5. Monolithic integration of MQW wavelength tunable DBR lasers with external cavity electroabsorption modulators by selective-area MOCVD

    Science.gov (United States)

    Lammert, Robert M.; Smith, Gary M.; Hughes, J. S.; Osowski, Mark L.; Jones, A. M.; Coleman, James J.

    1997-01-01

    The design and operation of multiple-quantum well (MQW) wavelength tunable distributed Bragg reflector (DBR) lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area metal-organic chemical vapor deposition (MOCVD) are presented. Uncoated devices exhibit cw threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet and 0.06 W/A from the modulator facet. After the application of facet coatings, slope efficiencies from the modulator facet increase to 0.14 W/A. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibit high extinction ratios of 40 dB at a modulator bias of 1.25 V. Photo-generated current versus optical power plots indicate that the extinction ratios are not limited by carrier build- up in the modulator quantum wells.

  6. Theory modeling and experimental research of external-cavity frequency doubling technology of short pulse laser

    Science.gov (United States)

    Duan, Cun-li; Zhang, Su-juan; He, Jiang-long

    2011-06-01

    Q-switched Short pulse laser has been widely applied in many fields, such as optical ranging, remote sensing, communications, nonlinear optics and spectroscopy etc. Q-switched Nd3+: YAG laser, with its high thermal conductivity and resistance to damage threshold, longer energy levels were generally used especially. Second harmonics generation was usually obtained through optical nonlinear effects in crystal. To the frequency doubling technology, poor conversion efficiency and multi-output frequency are the main problems. Researchers focus more on phase and group velocity matching induced by nonlinear effects, but pays less attention on theoretical modeling and numerical calculation of factors affecting frequency doubling of pulsed laser. In this article, nonlinear effects of double frequency crystals in Q-switched Nd3+: YAG laser was first analyzed in theory, then we deduced the relation expressions between factors affecting the efficiency of frequency doubling( thickness of frequency doubling crystal, cross section area of incident beam, power of the fundamental field, phase matching of incidence light)and double frequency efficiency. Secondly, taken KTP Crystal for example; numerical results and theirs' corresponding curves on these relation expressions was calculated and drawn with MATLAB software. These findings can be used for processing the specific requests of frequency doubling crystal. Finally, Theory modeling and numerical calculation were tested in experiment. The experiment results are in good agreement with those obtained in theory.

  7. Recent Vertical External Cavity Surface Emitting Lasers (VECSELs) Developments for Sensor Applications (POSTPRINT)

    Science.gov (United States)

    2013-02-01

    and Nanotechnology Sensors, Systems, and Applications III, SPIE, ed., Proc. SPIE 8031(1), p. 803126, SPIE, 2011. [7] S. Masui, Y. Matsuyama, T...Tuning and brightness optimization of high-performance GaSb-based semiconductor disk lasers from 1.86 to 2.80 μm,” CLEO Europe 09, p. 1, june 2009

  8. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Zaugg, C. A., E-mail: zauggc@phys.ethz.ch; Mangold, M.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U. [Department of Physics, Institute for Quantum Electronics, ETH Zürich, 8093 Zürich (Switzerland); Gronenborn, S.; Moench, H.; Weichmann, U. [Philips Technologie GmbH Photonics Aachen, Steinbachstrasse 15, 52074 Aachen (Germany); Miller, M. [Philips Technologie GmbH U-L-M Photonics, Lise-Meitner-Strasse 13, 89081 Ulm (Germany)

    2014-03-24

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM{sub 00} mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiN{sub x} and SiO{sub 2}) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm{sup 2} to 1.1 μJ/cm{sup 2}, respectively.

  9. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    Science.gov (United States)

    Zaugg, C. A.; Gronenborn, S.; Moench, H.; Mangold, M.; Miller, M.; Weichmann, U.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U.

    2014-03-01

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM00 mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiNx and SiO2) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm2 to 1.1 μJ/cm2, respectively.

  10. Rapid and Sensitive Quantification of Isotopic Mixtures Using a Rapidly-Swept External Cavity Quantum Cascade Laser

    Energy Technology Data Exchange (ETDEWEB)

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

    2016-05-23

    A rapidly-swept external-cavity quantum cascade laser with an open-path Herriott cell is used to quantify gas-phase chemical mixtures of D2O and HDO at an update rate of 40 Hz (25 ms measurement time). The chemical mixtures were generated by evaporating D2O liquid near the open-path Herriott cell, allowing the H/D exchange reaction with ambient H2O to produce HDO. Fluctuations in the ratio of D2O and HDO on timescales of < 1 s due to the combined effects of plume transport and the H/D exchange chemical reaction are observed. Noise equivalent concentrations (1σ) (NEC) of 147.0 ppbv and 151.6 ppbv in a 25 ms measurement time are estimated for D2O and HDO respectively with a 127 m optical path. These NECs are reduced to 23.0 and 24.0 ppbv with a 1 s averaging time for D2O and HDO respectively. NECs < 200 ppbv are also estimated for N2O, F134A, CH4, Acetone, and SO2 for a 25 ms measurement time. Based on the NECs obtained for D2O and HDO, the isotopic precision for measurement of the [D2O]/[HDO] concentration ratio was studied. An isotopic precision of 33‰ and 5‰ was calculated for the current experimental conditions for measurement times of 25 ms and 1 s, respectively.

  11. External cavity based single mode Fabry-Pérot laser diode and its application towards all-optical digital circuits

    Science.gov (United States)

    Nakarmi, Bikash; Zhang, Xuping; Won, Yong Hyub

    2012-11-01

    We have proposed a novel approach of realizing all-optical logic gates and combinational circuit using external cavity based single mode Fabry-Pérot laser diodes (SMFP-LDs). Different techniques and critical parameters for injection locking the any one of the modes of SMFP-LDs are discussed. Taking consideration of wavelength detuning and input injected power, we have proposed and demonstrated multi-input injection locking, supporting beam injection locking with the conventional injection locking which are used for demonstrating different logic gates (NAND, AND, XNOR, XOR, NOT, NOR) and digital circuits (Half adder and Comparator). Since we have used SMFP-LDs, there is no requirement of additional probe beam and associated components as required by other optical technologies making the realization simple in configuration, cost effective and power efficient. Clear output waveforms, eye diagrams, risingfalling times and BER are presented to verify the proposed method. All-optical logic units and digital circuit are demonstrated at the data rate of 10 Gbps with the waveform of NRZ signal waveform and measured eye diagram and BER of the PRBS of 231-1 signal. The maximum power penalty among all demonstrated units is below 1.4 dB at the BER of 10-9.

  12. Analysis of timing jitter in external-cavity mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mørk, Jesper

    2006-01-01

    processes, self-phase modulation, and spontaneous emission noise. Fluctuations of the mode-locked pulses are characterized from the fully distributed model using direct integration of noise-skirts in the phase-noise spectrum and the soliton perturbations introduced by Haus. We implement the model in order...... to investigate the performance of a MQW buried heterostructure laser. Results from numerical simulations show that the optimum driving conditions for achieving the shortest pulses with minimum timing jitter occur for large reverse bias in the absorber section at an optimum optical bandwidth limited by Gordon...

  13. Hybrid vertical cavity laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2010-01-01

    A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.......A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide....

  14. Self-Seeded RSOA-Fiber Cavity Lasers vs. ASE Spectrum-Sliced or Externally Seeded Transmitters—A Comparative Study

    OpenAIRE

    Simon A. Gebrewold; Romain Bonjour; Sophie Barbet; Anaelle Maho; Romain Brenot; Philippe Chanclou; Marco Brunero; Lucia Marazzi; Paola Parolari; Angelina Totovic; Dejan Gvozdic; David Hillerkuss; Christian Hafner; Juerg Leuthold

    2015-01-01

    Reflective semiconductor optical amplifier fiber cavity lasers (RSOA-FCLs) are appealing, colorless, self-seeded, self-tuning and cost-efficient upstream transmitters. They are of interest for wavelength division multiplexed passive optical networks (WDM-PONs) based links. In this paper, we compare RSOA-FCLs with alternative colorless sources, namely the amplified spontaneous emission (ASE) spectrum-sliced and the externally seeded RSOAs. We compare the differences in output power, signal-to-...

  15. Coupled external cavity photonic crystal enhanced fluorescence.

    Science.gov (United States)

    Pokhriyal, Anusha; Lu, Meng; Ge, Chun; Cunningham, Brian T

    2014-05-01

    We report a fundamentally new approach to enhance fluorescence in which surface adsorbed fluorophore-tagged biomolecules are excited on a photonic crystal surface that functions as a narrow bandwidth and tunable mirror of an external cavity laser. This scheme leads to ∼10× increase in the electromagnetic enhancement factor compared to ordinary photonic crystal enhanced fluorescence. In our experiments, the cavity automatically tunes its lasing wavelength to the resonance wavelength of the photonic crystal, ensuring optimal on-resonance coupling even in the presence of variable device parameters and variations in the density of surface-adsorbed capture molecules. We achieve ∼10(5) × improvement in the limit of detection of a fluorophore-tagged protein compared to its detection on an unpatterned glass substrate. The enhanced fluorescence signal and easy optical alignment make cavity-coupled photonic crystals a viable approach for further reducing detection limits of optically-excited light emitters that are used in biological assays.

  16. Low frequency fluctuation with two external cavity reflectors

    Institute of Scientific and Technical Information of China (English)

    王春林; 伍剑; 林金桐

    2003-01-01

    The dynamics of a semiconductor laser with two optical feedbacks is studied in this paper. A new set of nonlinear rate equations that can describe external cavity semiconductor lasers with any amount of two optical feedbacks is proposed. It is found that when the laser is biased above the threshold and subjected to one feedback, the other feedback can induce low-frequency fluctuations.

  17. Dynamics of 1.55 μm Wavelength Single-Mode Vertical-Cavity Surface-Emitting Laser Output under External Optical Injection

    Directory of Open Access Journals (Sweden)

    Kyong Hon Kim

    2012-01-01

    Full Text Available We review the temporal dynamics of the laser output spectrum and polarization state of 1.55 μm wavelength single-mode (SM vertical-cavity surface-emitting lasers (VCSELs induced by external optical beam injection. Injection of an external continuous-wave laser beam to a gain-switched SM VCSEL near the resonance wavelength corresponding to its main polarization-mode output was critical for improvement of its laser pulse generation characteristics, such as pulse timing-jitter reduction, linewidth narrowing, pulse amplitude enhancement, and pulse width shortening. Pulse injection of pulse width shorter than the cavity photon lifetime into the SM VCSEL in the orthogonal polarization direction with respect to its main polarization mode caused temporal delay of the polarization recovery after polarization switching (PS, and its delay was found to be the minimum at an optimized bias current. Polarization-mode bistability was observed even in the laser output of an SM VCSEL of a standard circularly cylindrical shape and used for all-optical flip-flop operations with set and reset injection pulses of very low pulse energy of order of the 3.5~4.5 fJ.

  18. Single-pass UV generation at 222.5 nm based on high-power GaN external cavity diode laser.

    Science.gov (United States)

    Ruhnke, N; Müller, A; Eppich, B; Güther, R; Maiwald, M; Sumpf, B; Erbert, G; Tränkle, G

    2015-05-01

    We demonstrate a compact system for single-pass frequency doubling of high-power GaN diode laser radiation. The deep UV laser light at 222.5 nm is generated in a β-BaB2O4 (BBO) crystal. A high-power GaN external cavity diode laser (ECDL) system in Littrow configuration with narrowband emission at 445 nm is used as pump source. At a pump power of 680 mW, a maximum UV power of 16 μW in continuous-wave operation at 222.5 nm is achieved. This concept enables a compact diode laser-based system emitting in the deep ultraviolet spectral range.

  19. Vertical cavity laser

    DEFF Research Database (Denmark)

    2016-01-01

    The present invention provides a vertical cavity laser comprising a grating layer comprising an in-plane grating, the grating layer having a first side and having a second side opposite the first side and comprising a contiguous core grating region having a grating structure, wherein an index...

  20. Intensity- and phase-noise correlations in a dual-frequency vertical-external-cavity surface-emitting laser operating at telecom wavelength

    Science.gov (United States)

    De, Syamsundar; Baili, Ghaya; Bouchoule, Sophie; Alouini, Mehdi; Bretenaker, Fabien

    2015-05-01

    The amplitude and phase noises of a dual-frequency vertical-external-cavity surface-emitting laser (DF-VECSEL) operating at telecom wavelength are theoretically and experimentally investigated in detail. In particular, the spectral behavior of the correlation between the intensity noises of the two modes of the DF-VECSEL is measured. Moreover, the correlation between the phase noise of the radio-frequency beat note generated by optical mixing of the two laser modes with the intensity noises of the two modes is investigated. All these spectral behaviors of noise correlations are analyzed for two different values of the nonlinear coupling between the laser modes. We find that to describe the spectral behavior of noise correlations between the laser modes, it is of utmost importance to have precise knowledge about the spectral behavior of the pump noise, which is the dominant source of noise in the frequency range of interest (10 kHz to 35 MHz). Moreover, it is found that the noise correlation also depends on how the spatially separated laser modes of the DF-VECSEL intercept the noise from a multimode fiber-coupled laser diode used for pumping both the laser modes. To this aim, a specific experiment is reported which aims at measuring the correlations between different spatial regions of the pump beam. The experimental results are in excellent agreement with a theoretical model based on modified rate equations.

  1. Atmospheric ammonia measurements in Houston, TX using an external cavity-quantum cascade laser-based sensor

    Science.gov (United States)

    Gong, L.; Lewicki, R.; Griffin, R. J.; Flynn, J. H.; Lefer, B. L.; Tittel, F. K.

    2010-12-01

    Ammonia (NH3) plays a significant role in atmospheric chemistry. It has many anthropogenic (e.g., agricultural crops and mineral fertilizers) and natural sources (e.g., animals, oceans, and vegetation) in the environment. In certain areas, industrial and motor vehicle activities also can contribute to increases in atmospheric NH3 levels. From a perspective of environmental concern, NH3 is a precursor of particulate matter (PM) because it can lead to production of ammonium salts (e.g., (NH4)2SO4 and NH4NO3) through chemical reactions with sulfuric and nitric acid. As a result, the abundance of NH3 in the atmosphere has a great impact on aerosol nucleation and composition. Despite this, NH3 is not regulated. It is crucial, however, to improve our understanding of the dynamics of NH3 in an industrial and urban area such as Greater Houston where atmospheric NH3 data are limited. In this study, a 10.4 µm external cavity quantum cascade laser (EC-QCL)-based sensor was developed and utilized. To monitor atmospheric NH3 at trace gas concentration levels, an amplitude modulated photo-acoustic spectroscopy (AM-PAS) technique was employed. The minimum detection limit obtained from the sensor is ~1.5 ppb for a 5-second data acquisition time. After averaging data over 300 seconds a sub-ppb NH3 concentration level can be achieved. The NH3 sensor has been deployed on the roof of a ~60-meter-high building (North Moody Tower) located on the University of Houston campus since November 2009. Several episodes of high NH3 concentrations were observed. For example, the sensor recorded a significant and lasting increase in NH3 concentrations (~21 ppb) on August 14, 2010, when a major accident occurred during the same time period on the Gulf Freeway (I-45) in Houston only 2 miles from the sampling site. The elevated concentration levels are assumed to be associated with NH3 generation from a chemical fire resulting from the collision involving two 18-wheelers, one carrying fertilizer

  2. A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth <400 kHz and long-term stability of <1 MHz

    Science.gov (United States)

    Keaveney, James; Hamlyn, William J.; Adams, Charles S.; Hughes, Ifan G.

    2016-09-01

    We report on the development of a diode laser system - the "Faraday laser" - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Faraday filter. Our system has both short-term and long-term stability of less than 1 MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a "turn-key" solution for laser-cooling experiments.

  3. A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth $<400$ kHz and long-term stability of $<1$ MHz

    CERN Document Server

    Keaveney, James; Adams, Charles S; Hughes, Ifan G

    2016-01-01

    We report on the development of a diode laser system - the `Faraday laser' - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Farady filter. Our system has both short-term and long-term stability of less than 1~MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a `turn-key' solution for laser cooling experiments.

  4. A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth <400 kHz and long-term stability of <1 MHz.

    Science.gov (United States)

    Keaveney, James; Hamlyn, William J; Adams, Charles S; Hughes, Ifan G

    2016-09-01

    We report on the development of a diode laser system - the "Faraday laser" - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Faraday filter. Our system has both short-term and long-term stability of less than 1 MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a "turn-key" solution for laser-cooling experiments.

  5. An off Axis Cavity Enhanced Absorption Spectrometer and a Rapid Scan Spectrometer with a Room-Temperature External Cavity Quantum Cascade Laser

    Science.gov (United States)

    Liu, Xunchen; Kang, Cheolhwa; Xu, Yunjie

    2009-06-01

    Quantum cascade laser (QCL) is a new type of mid-infrared tunable diode lasers with superior output power and mode quality. Recent developments, such as room temperature operation, wide frequency tunability, and narrow line width, make QCLs an ideal light source for high resolution spectroscopy. Two slit jet infrared spectrometers, namely an off-axis cavity enhanced absorption (CEA) spectrometer and a rapid scan spectrometer with an astigmatic multi-pass cell assembly, have been coupled with a newly purchased room temperature tunable mod-hop-free QCL with a frequency coverage from 1592 cm^{-1} to 1698 cm^{-1} and a scan rate of 0.1 cm^{-1}/ms. Our aim is to utilize these two sensitive spectrometers, that are equipped with a molecular jet expansion, to investigate the chiral molecules-(water)_n clusters. To demonstrate the resolution and sensitivity achieved, the rovibrational transitions of the static N_2O gas and the bending rovibrational transitions of the Ar-water complex, a test system, at 1634 cm^{-1} have been measured. D. Hofstetter and J. Faist in High performance quantum cascade lasers and their applications, Vol.89 Springer-Verlag Berlin & Heidelberg, 2003, pp. 61-98. Y. Xu, X. Liu, Z. Su, R. M. Kulkarni, W. S. Tam, C. Kang, I. Leonov and L. D'Agostino, Proc. Spie, 2009, 722208 (1-11). M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 1997, 106, 3078-3089.

  6. Control of chaos in an external-cavity multi-quantum-well laser subjected to dual-wedges and optical dual-feedback

    Institute of Scientific and Technical Information of China (English)

    YAN SenLin

    2009-01-01

    A multi-parameter chaos-control method used to control chaos in an external cavity multi-quantum-well (MQW) laser via the dual-wedges and external delayed optical dual-feedback is presented. The physical model of the laser dynamic is established under the conditions of the dual-wedges and dual-feedback light control. The frequency detuning and stable ranges of the control system are theoretically demon-strated. The optical-length of the feedback light may be adjusted by shifting horizontally or sliding the dual-wedges relatively in the external optical road, which will alter the delaying time and feedback in-tensity of the dual-feedback light. Accordingly, the multi-parameter chaos-control of the optical dual-feedback may be achieved physically. The numerical simulations approve that the chaotic laser may be controlled into a stable state, a single-periodic state and multi-periodic states, and the con-trolled periodic pulse power may be increased.

  7. Implementation of electro-optic amplitude modulator in the external cavity of semiconductor laser for generation of periodic sates and chaos control

    Directory of Open Access Journals (Sweden)

    Kh Mabhouti

    2016-12-01

    Full Text Available In this paper, by placing the electro optical modulator (EOM into the external cavity of the semiconductor laser (SL and amplitude modulation of the optical feedback, the dynamical variation of the output intensity  of the laser has been studied. This is analyzed numerically via bifurcation and time series diagrams with respect to the applied amplitude modulation index, and modulation voltage frequency of the EOM. It has been shown that, by modulating the amplitude of the optical feedback beam, various changes in the types of the dynamics of  can be observed, and various periodic states can be generated. This makes it possible to receive the desired dynamics without any variations in the main parameters of the SL. Also, in present study, a method of chaos control in the SL has been presented based on EOM in the external cavity. The obtained results confirm that based on this method the chaotic dynamics can be controlled single-periodic dynamics

  8. 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.

  9. 2.5-Gb/s hybridly-integrated tunable external cavity laser using a superluminescent diode and a polymer Bragg reflector.

    Science.gov (United States)

    Yoon, Ki-Hong; Oh, Su Hwan; Kim, Ki Soo; Kwon, O-Kyun; Oh, Dae Kon; Noh, Young-Ouk; Lee, Hyung-Jong

    2010-03-15

    We presented a hybridly-integrated tunable external cavity laser with 0.8 nm mode spacing 16 channels operating in the direct modulation of 2.5-Gbps for a low-cost source of a WDM-PON system. The tunable laser was fabricated by using a superluminescent diode (SLD) and a polymer Bragg reflector. The maximum output power and the power slope efficiency of the tunable laser were 10.3 mW and 0.132 mW/mA, respectively, at the SLD current of 100 mA and the temperature of 25 degrees C. The directly-modulated tunable laser successfully provided 2.5-Gbps transmissions through 20-km standard single mode fiber. The power penalty of the tunable laser was less than 0.8 dB for 16 channels after a 20-km transmission. The power penalty variation was less than 1.4 dB during the blue-shifted wavelength tuning.

  10. L-band tunable external cavity laser based on 1.58 μm superluminescent diode integrated with spot-size converter.

    Science.gov (United States)

    Oh, Su Hwan; Yoon, Ki-Hong; Kim, Ki Soo; Kim, Jongbae; Kwon, O-Kyun; Oh, Dae Kon; Noh, Young-Ouk; Lee, Hyung-Jong

    2010-09-13

    We report a 1.58 μm superluminescent diode (SLD) with a spot-size converter (SSC) designed and fabricated as a light source for a tunable external cavity laser (T-ECL). The active section of the SLD is fabricated by using a planar buried heterostructure (PBH) for low-threshold current and high-output power operation at a low injection current. The SSC structure of the SLD is designed to possess a buried deep-ridge waveguide (BD-RWG) and show a beam of less divergence. The full-width at half maximum (FWHM) of the horizontal and vertical far-field patterns (FFPs), due to the beam of the less divergence, are 14° and 13°, respectively. We also confirm that an L-band T-ECL employing the SSC SLD operates well enough to prove the characteristics of high performance.

  11. Ultrafast and widely tuneable vertical-external-cavity surface-emitting laser, mode-locked by a graphene-integrated distributed Bragg reflector.

    Science.gov (United States)

    Zaugg, C A; Sun, Z; Wittwer, V J; Popa, D; Milana, S; Kulmala, T S; Sundaram, R S; Mangold, M; Sieber, O D; Golling, M; Lee, Y; Ahn, J H; Ferrari, A C; Keller, U

    2013-12-16

    We report a versatile way of controlling the unsaturated loss, modulation depth and saturation fluence of graphene-based saturable absorbers (GSAs), by changing the thickness of a spacer between a single layer graphene (SLG) and a high-reflection mirror. This allows us to modulate the electric field intensity enhancement at the GSA from 0 up to 400%, due to the interference of incident and reflected light at the mirror. The unsaturated loss of the SLG-mirror-assembly can be reduced to ∼0. We use this to mode-lock a vertical-external-cavity surface-emitting laser (VECSEL) from 935 to 981 nm. This approach can be applied to integrate SLG into various optical components, such as output coupler mirrors, dispersive mirrors or dielectric coatings on gain materials. Conversely, it can also be used to increase the absorption (up to 10%) in various graphene based photonics and optoelectronics devices, such as photodetectors.

  12. Generation of more than 300 mW diffraction-limited light at 405 nm by second-harmonic generation of a tapered diode laser with external cavity feedback

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Holm, J.; Sumpf, B.;

    2007-01-01

    We have constructed a blue laser source consisting of a single-frequency tapered diode laser with external cavity feedback that is frequency doubled by a quasi-phase matched KTP (PPKTP) in a bowtie ring cavity and extract more than 360 mW of power at 405 nm. The conversion efficiency from fundame...... fundamental laser power to second harmonic power is 35 %, while it is 64 % from coupled fundamental power to extracted blue light. Thermal effects and gray tracking set an upper limit on the amount of generated blue light....

  13. Applications of external cavity diode laser-based technique to noninvasive clinical diagnosis using expired breath ammonia analysis: chronic kidney disease, epilepsy

    Science.gov (United States)

    Bayrakli, Ismail; Turkmen, Aysenur; Akman, Hatice; Sezer, M. Tugrul; Kutluhan, Suleyman

    2016-08-01

    An external cavity laser (ECL)-based off-axis cavity-enhanced absorption spectroscopy was applied to noninvasive clinical diagnosis using expired breath ammonia analysis: (1) the correlation between breath ammonia levels and blood parameters related to chronic kidney disease (CKD) was investigated and (2) the relationship between breath ammonia levels and blood concentrations of valproic acid (VAP) was studied. The concentrations of breath ammonia in 15 healthy volunteers, 10 epilepsy patients (before and after taking VAP), and 27 patients with different stages of CKD were examined. The range of breath ammonia levels was 120 to 530 ppb for healthy subjects and 710 to 10,400 ppb for patients with CKD. There was a statistically significant positive correlation between breath ammonia concentrations and urea, blood urea nitrogen, creatinine, or estimated glomerular filtration rate in 27 patients. It was demonstrated that taking VAP gave rise to increasing breath ammonia levels. A statistically significant difference was found between the levels of exhaled ammonia (NH3) in healthy subjects and in patients with epilepsy before and after taking VAP. The results suggest that our breath ammonia measurement system has great potential as an easy, noninvasive, real-time, and continuous monitor of the clinical parameters related to epilepsy and CKD.

  14. Self-Seeded RSOA-Fiber Cavity Lasers vs. ASE Spectrum-Sliced or Externally Seeded Transmitters—A Comparative Study

    Directory of Open Access Journals (Sweden)

    Simon A. Gebrewold

    2015-12-01

    Full Text Available Reflective semiconductor optical amplifier fiber cavity lasers (RSOA-FCLs are appealing, colorless, self-seeded, self-tuning and cost-efficient upstream transmitters. They are of interest for wavelength division multiplexed passive optical networks (WDM-PONs based links. In this paper, we compare RSOA-FCLs with alternative colorless sources, namely the amplified spontaneous emission (ASE spectrum-sliced and the externally seeded RSOAs. We compare the differences in output power, signal-to-noise ratio (SNR, relative intensity noise (RIN, frequency response and transmission characteristics of these three sources. It is shown that an RSOA-FCL offers a higher output power over an ASE spectrum-sliced source with SNR, RIN and frequency response characteristics halfway between an ASE spectrum-sliced and a more expensive externally seeded RSOA. The results show that the RSOA-FCL is a cost-efficient WDM-PON upstream source, borrowing simplicity and cost-efficiency from ASE spectrum slicing with characteristics that are, in many instances, good enough to perform short-haul transmission. To substantiate our statement and to quantitatively compare the potential of the three schemes, we perform data transmission experiments at 5 and 10 Gbit/s.

  15. Measurement of air-refractive-index fluctuation from frequency change using a phase modulation homodyne interferometer and an external cavity laser diode

    Science.gov (United States)

    Ishige, Masashi; Aketagawa, Masato; Banh Quoc, Tuan; Hoshino, Yuta

    2009-08-01

    We present a method for air-refractive-index (nair) fluctuation measurement using a laser interferometer. The method is based on a combination of a phase modulation homodyne interferometer (PMHI), an external cavity laser diode (ECLD) and an ultralow thermal expansion material (ULTEM). The PMHI utilizes a Michelson interferometer which is constructed on the ULTEM plate under the condition of an air temperature fluctuation of less than 10 mK, so that the optical path change or the air-refractive-index fluctuation (Δnair) caused by the thermal disturbance can be neglected. Meanwhile, the ECLD is controlled by adjusting its frequency to track some of the dark fringes of the interferometer, so that Δnair can be derived from the ECLD frequency change. The uncertainty of the Δnair measurement in the experiment is of 10-8 order. However, it will be possible to decrease the uncertainty to 10-9 or less if the signal-to-noise ratio (SNR) of the control system is improved.

  16. Performance of a quantum-dot external-cavity laser based on digital micro-mirror device%基于DMD的外腔量子点激光器性能研究

    Institute of Scientific and Technical Information of China (English)

    成若海; 王海龙; 龚谦; 严进一; 汪洋; 柳庆博; 曹春芳; 岳丽

    2013-01-01

    In order to obtain more complete test data of quantum-dot external-cavity lasers,the InAs/InP quantum-dot external-cavity lasers using digital micro-mirror device (DMD) are successfully built up and their spectrum characteristics and the tuning range are measured.We also measure its tuning range and the corresponding change in the mode based on DMD quantum external cavity laser dots.The spectrum characteristics of InAs/InP quantum-dot external-cavity laser based on the grating and the DMD are compared theoretically and experimentally,and the differences between the reflection spectrum and angular dispersion are obtained.And a new method based on DMD will be applied to the external-cavity quantum-dot lasers.%为了取得更加完善的外腔量子点激光器(QDL)测试数据,构建了基于数字微镜器件(DMD,digital micro-mirror device)的InAs/InP量子点外腔QDL.测量了其光谱特性以及调谐范围,得到了基于DMD的外腔QDL调谐范围和相应的模式变化.在理论和实验上与基于光栅的外腔QDL性能进行了比较,得到了在角色散和反射光谱中与光栅的区别,实现了将DMD应用于外腔QDL中而获得的一种新方法.

  17. Short-lived species detection of nitrous acid by external-cavity quantum cascade laser based quartz-enhanced photoacoustic absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Hongming [Laboratoire de Physicochimie de l' Atmosphère, Université du Littoral Côte d' Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque (France); Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 1125, 350 Shushanhu Road, Hefei, Anhui 230031 (China); Maamary, Rabih; Fertein, Eric; Chen, Weidong, E-mail: chen@univ-littoral.fr [Laboratoire de Physicochimie de l' Atmosphère, Université du Littoral Côte d' Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque (France); Gao, Xiaoming [Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 1125, 350 Shushanhu Road, Hefei, Anhui 230031 (China); Sigrist, Markus W. [ETH Zurich, Institute for Quantum Electronics, HPT H4.1, Auguste-Piccard-Hof 1, CH-8093 Zürich (Switzerland)

    2015-03-09

    Spectroscopic detection of short-lived gaseous nitrous acid (HONO) at 1254.85 cm{sup −1} was realized by off-beam coupled quartz-enhanced photoacoustic spectroscopy (QEPAS) in conjunction with an external cavity quantum cascade lasers (EC-QCL). High sensitivity monitoring of HONO was performed within a very small gas-sample volume (of ∼40 mm{sup 3}) allowing a significant reduction (of about 4 orders of magnitude) of air sampling residence time which is highly desired for accurate quantification of chemically reactive short-lived species. Calibration of the developed QEPAS-based HONO sensor was carried out by means of lab-generated HONO samples whose concentrations were determined by direct absorption spectroscopy involving a ∼109.5 m multipass cell and a distributed feedback QCL. A minimum detection limit (MDL) of 66 ppbv (1 σ) HONO was achieved at 70 mbar using a laser output power of 50 mW and 1 s integration time, which corresponded to a normalized noise equivalent absorption coefficient of 3.6 × 10{sup −8 }cm{sup −1} W/Hz{sup 1/2}. This MDL was down to 7 ppbv at the optimal integration time of 150 s. The corresponding 1σ minimum detected absorption coefficient is ∼1.1 × 10{sup −7 }cm{sup −1} (MDL ∼ 3 ppbv) in 1 s and ∼1.1 × 10{sup −8 }cm{sup −1} (MDL ∼ 330 pptv) in 150 s, respectively, with 1 W laser power.

  18. Investigation of double-mode operation and fast fine tuning properties of a grating-coupled external cavity diode laser configuration

    Science.gov (United States)

    Bayrakli, Ismail

    2017-01-01

    Double-mode operation and fast piezo fine tuning properties of a gain chip on a thermoelectric cooler in an external cavity are investigated. A widely course double-mode tuning range of 120 nm for the spectral range between 1470 and 1590 nm is achieved by rotating the diffraction gratings forming a double Littrow-type configuration. A fast piezo fine tuning range over 7cm-1 (1.5 nm, 210 GHz) in a single-mode operation is obtained by scanning the external cavity length with scan rates up to 0.5 kHz.

  19. Stability analysis for bad cavity lasers with inhomogeneously broadened gain

    CERN Document Server

    Kazakov, Georgy A

    2016-01-01

    Bad cavity lasers are experiencing renewed interest in the context of active optical frequency standards, due to their enhanced robustness against fluctuations of the laser cavity. The gain medium would consist of narrow-linewidth atoms, either trapped inside the cavity or intersecting the cavity mode dynamically. A finite velocity distribution, atomic interactions, or interactions of realistic multilevel atoms with external field leads to an inhomogeneous broadening of the atomic gain profile. This can bring the bad cavity laser to operate in unstable regimes characterized by complex temporal patterns of the field amplitude. We present a new and efficient method for the stability analysis of bad cavity lasers with inhomogeneously broadened gain. We apply this method to identify the steady-state solutions for the metrology-relevant case of spin-1/2 atoms interacting with an external magnetic field.

  20. DFB laser with attached external intensity modulator

    Energy Technology Data Exchange (ETDEWEB)

    Marcuse, D. (AT and T Bell Labs. Holmdel, NJ (US))

    1990-02-01

    This paper presents a theoretical study of the frequency pulling effect exerted on a DFB laser by an external amplitude modulator that is directly attached to it. The modulator consists of a piece of waveguide whose loss is modulated by means of an externally applied voltage. The modulator affects the laser due to residual reflections from its far end which appear as a variable effective reflectivity to the output end of the DFB laser. Modulation affects the magnitude as well as the phase of the effective reflection coefficient presented to the laser due to the coupling of the real and imaginary parts of the effective refractive index of the modulator waveguide. The tuning problem is formulated as an eigenvalue equation for the DFB laser in the presence of an externally attached lossy cavity.

  1. External cavity-quantum cascade laser infrared spectroscopy for secondary structure analysis of proteins at low concentrations

    Science.gov (United States)

    Schwaighofer, Andreas; Alcaráz, Mirta R.; Araman, Can; Goicoechea, Héctor; Lendl, Bernhard

    2016-09-01

    Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy are analytical techniques employed for the analysis of protein secondary structure. The use of CD spectroscopy is limited to low protein concentrations (5 mg ml-1). Here we introduce a quantum cascade laser (QCL)-based IR transmission setup for analysis of protein and polypeptide secondary structure at concentrations as low as 0.25 mg ml-1 in deuterated buffer solution. We present dynamic QCL-IR spectra of the temperature-induced α-helix to β-sheet transition of poly-L-lysine. The concentration dependence of the α-β transition temperature between 0.25 and 10 mg ml-1 was investigated by QCL-IR, FTIR and CD spectroscopy. By using QCL-IR spectroscopy it is possible to perform IR spectroscopic analysis in the same concentration range as CD spectroscopy, thus enabling a combined analysis of biomolecules secondary structure by CD and IR spectroscopy.

  2. High peak-power picosecond pulse generation at 1.26 µm using a quantum-dot-based external-cavity mode-locked laser and tapered optical amplifier.

    Science.gov (United States)

    Ding, Y; Aviles-Espinosa, R; Cataluna, M A; Nikitichev, D; Ruiz, M; Tran, M; Robert, Y; Kapsalis, A; Simos, H; Mesaritakis, C; Xu, T; Bardella, P; Rossetti, M; Krestnikov, I; Livshits, D; Montrosset, Ivo; Syvridis, D; Krakowski, M; Loza-Alvarez, P; Rafailov, E

    2012-06-18

    In this paper, we present the generation of high peak-power picosecond optical pulses in the 1.26 μm spectral band from a repetition-rate-tunable quantum-dot external-cavity passively mode-locked laser (QD-ECMLL), amplified by a tapered quantum-dot semiconductor optical amplifier (QD-SOA). The laser emission wavelength was controlled through a chirped volume Bragg grating which was used as an external cavity output coupler. An average power of 208.2 mW, pulse energy of 321 pJ, and peak power of 30.3 W were achieved. Preliminary nonlinear imaging investigations indicate that this system is promising as a high peak-power pulsed light source for nonlinear bio-imaging applications across the 1.0 μm - 1.3 μm spectral range.

  3. High Power Diode Lasers with External Feedback: Overview and Prospects

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael

    2012-01-01

    In summary, different external-cavity feedback techniques to improve the spatial beam quality and narrow the linewidth of the output beam from both BALs and TDLs are presented. Broad-area diode laser system with external-cavity feedback around 800 nm can produce several Watts of output power...

  4. Hybrid Vertical-Cavity Laser

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention provides a light source (2) for light circuits on a silicon platform (3). A vertical laser cavity is formed by a gain region (101) arranged between a top mirror (4) and a bottom grating-mirror (12) in a grating region (11) in a silicon layer (10) on a substrate. A waveguide...

  5. 1.38 W tunable high-power narrow-linewidth external-cavity tapered amplifier at 670 nm

    DEFF Research Database (Denmark)

    Chi, Mingjun; Erbert, G.; Sumpf, B.;

    2010-01-01

    A diffraction-limited narrow-linewidth diode laser system based on a tapered amplifier in external cavity is demonstrated. 1.38 W output power is obtained. The laser system is tunable from 659 to 675 nm.......A diffraction-limited narrow-linewidth diode laser system based on a tapered amplifier in external cavity is demonstrated. 1.38 W output power is obtained. The laser system is tunable from 659 to 675 nm....

  6. 5-W Yellow Laser by Intracavity Frequency Doubling of High-Power Vertical-External-Cavity Surface-Emitting Laser (POSTPRINT)

    Science.gov (United States)

    2008-10-15

    to: The University of Arizona. Downloaded on October 16, 2008 at 14:27 from IEEE Xplore . Restrictions apply. 1 FALLAHI et al.: 5-W YELLOW LASER BY...Authorized licensed use limited to: The University of Arizona. Downloaded on October 16, 2008 at 14:27 from IEEE Xplore . Restrictions apply. 2 1702 IEEE...Theory and Practice, 2nd ed. San Diego, CA: Academic, 1999. Authorized licensed use limited to: The University of Arizona. Downloaded on October 16, 2008 at 14:27 from IEEE Xplore . Restrictions apply. 3

  7. 浅析元件参数对外腔半导体激光器输出谱宽影响%Influencing factors on spectral linewidth of external cavity diode laser

    Institute of Scientific and Technical Information of China (English)

    李元栋; 武永福; 胡猛; 孙瑞

    2014-01-01

    High power narrowed linewidth pump source is needed with diode pumped alkali laser developed. But the linewidth of the commercial diode laser is far exceed the absorption linewidth of the alkali atom. So the Littrow external cavity is used to narrowed the spectrum of high power diode laser array. The linewidth of high power diode laser array is directly affected by the parameters of elements in Littrow external cavity. In this paper, the model of external cavity diode laser was set up by using ray tracing method. By replacing cylindrical lens with sphere lens, the influence of micro-cylindrical lens array, beam shaping optics and grating were analysed. The resutls show that, to obtain narrower output laser linewidth, the focal length of micro-cylindrical lens array should be smaller, the grating grooves is denser, and the focal of spherical lens is larger. And the theoretical conclusions is demonstrated by experimental results.%半导体抽运碱金属蒸气激光器(DPAL)需大功率窄线宽泵浦源,但市售半导体激光器输出线宽远远大于碱金属原子吸收谱宽,难以实现有效泵浦,因此需采用Littrow外腔法压窄半导体激光器输出谱宽。 Littrow外腔系统中元件参数的选择直接影响大功率半导体激光器输出谱宽。为此文中沿入射光线方向构建外腔压窄模型,利用球面镜替代柱面镜,分析了微柱透镜阵列、光学系统和光栅元件对外腔输出谱宽的影响,模拟结果为微柱透镜阵列焦距越小、光栅刻线越密、球面镜焦距越大,外腔输出谱宽越窄,实验结果符合理论模型。

  8. 基于组合模理论设计的激光二极管阵列外腔%External Cavity Design for Laser Diode Bar Based on Calculation of Combined Array Mode

    Institute of Scientific and Technical Information of China (English)

    苏宙平; 朱焯炜; 阙立志

    2012-01-01

    针对激光二极管阵列提出了“组合模”慨念,计算了组合模的远场分布,每个组合模在远场的空间分布呈双瓣结构,基于激光二极管阵列组合模的远场分布特征,设计了离轴外腔反馈的激光二极管阵列,运用此装置所获得激光二极管阵列的远场分布有了明显变化,与自由运转的激光二极管阵列相比,离轴外腔反馈的激光二极管阵列远场宽度减少了4.3倍,在抽运电流为16 A时,测得输出激光的功率1.82W,这相当于相同电流下自由运转激光器输出功率的79%.组合模理论不仅可以用来指导设计一维离轴外腔反馈激光二极管阵列,而且也可以用于设计二维离轴外腔反馈激光二极管阵列.二维离轴外腔反馈激光二极管阵列可以产生高功率,高光束质量输出的激光.%In this paper,the concept of "combined array mode" for laser diode bar is proposcd.and the far-field profile of "combined array mode" is calculated.The far-field of each combined array mode exhibits a two-lobe profile with different angular position. On the basis of the characteristic of far-field profile of combined array mode,an off-axis external cavity feedback laser diode bar is designed. By employing the setup,the far-field profile of laser diode bar is narrowed by 4.3 times compared with the free- running laser diode bar. The output power of external cavity feedback laser diode bar is about 1.82 W at the drive current of 16 A.or 79% of the radiated power of the free-running state.The theory of combined array mode cannot only be applied to design the external cavity feedback laser diode har but also can be designed the external cavity feeedback laser diode stack.

  9. Coupled Resonator Vertical Cavity Laser Diode

    Energy Technology Data Exchange (ETDEWEB)

    CHOQUETTE, KENT D.; CHOW, WENG W.; FISCHER, ARTHUR J.; GEIB, KENT M.; HOU, HONG Q.

    1999-09-16

    We report the operation of an electrically injected monolithic coupled resonator vertical cavity laser which consists of an active cavity containing In{sub x}Ga{sub 1{minus}x}As quantum wells optically coupled to a passive GaAs cavity. This device demonstrates novel modulation characteristics arising from dynamic changes in the coupling between the active and passive cavities. A composite mode theory is used to model the output modulation of the coupled resonator vertical cavity laser. It is shown that the laser intensity can be modulated by either forward or reverse biasing the passive cavity. Under forward biasing, the modulation is due to carrier induced changes in the refractive index, while for reverse bias operation the modulation is caused by field dependent cavity enhanced absorption.

  10. 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.

  11. Coupled Resonator Vertical Cavity Laser Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Chow, W.W.; Fischer, A.J.; Allerman, A.A.; Hou, H.Q.; Geib, K.M.

    1999-07-22

    For many applications, the device performance of edge emitting semiconductor lasers can be significantly improved through the use of multiple section devices. For example, cleaved coupled cavity (C3) lasers have been shown to provide single mode operation, wavelength tuning, high speed switching, as well as the generation of short pulses via mode-locking and Q-switching [1]. Using composite resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the coupling between the monolithic cavities, incorporate passive or active resonators which are spectrally degenerate or detuned, and to fabricate these devices in 2-dimensional arrays. Composite resonator vertical cavity lasers (CRVCL) have been examined using optical pumping and electrical injection [2-5]. We report on CRVCL diodes and show that efficient modulation of the laser emission can be achieved by either forward or reverse biasing the passive cavity within a CRVCL.

  12. Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Wilmsen, Carl W.; Temkin, Henryk; Coldren, Larry A.

    2002-01-01

    1. Introduction to VCSELs L. A. Coldren, C. W. Wilmsen and H. Temkin; 2. Fundamental issues in VCSEL design L. A. Coldren and Eric R. Hegblom; 3. Enhancement of spontaneous emission in microcavities E. F. Schubert and N. E. J. Hunt; 4. Epitaxy of vertical-cavity lasers R. P. Schneider Jr and Y. H. Young; 5. Fabrication and performance of vertical-cavity surface-emitting lasers Kent D. Choquette and Kent Geib; 6. Polarization related properties of vertical cavity lasers Dmitri Kuksenkov and Henryk Temkin; 7. Visible light emitting vertical cavity lasers Robert L. Thornton; 8. Long-wavelength vertical-cavity lasers Dubrakovo I. Babic, Joachim Piprek and John E. Bowers; 9. Overview of VCSEL applications Richard C. Williamson; 10. Optical interconnection applications and required characteristics Kenichi Kasahara; 11. VCSEL-based fiber-optic data communications Kenneth Hahn and Kirk Giboney; 12. VCSEL-based smart pixels for free space optoelectronic processing C. W. Wilmsen.

  13. Laser frequency modulator for modulating a laser cavity

    Science.gov (United States)

    Erbert, Gaylen V.

    1992-01-01

    The present invention relates to a laser frequency modulator for modulating a laser cavity. It is known in the prior art to utilize a PZT (piezoelectric transducer) element in combination with a mirror to change the cavity length of a laser cavity (which changes the laser frequency). Using a PZT element to drive the mirror directly is adequate at frequencies below 10 kHz. However, in high frequency applications (100 kHz and higher) PZT elements alone do not provide a sufficient change in the cavity length. The present invention utilizes an ultrasonic concentrator with a PZT element and mirror to provide modulation of the laser cavity. With an ultrasonic concentrator, the mirror element at the end of a laser cavity can move at larger amplitudes and higher frequencies.

  14. Extracavity and external cavity second-harmonic generation in a periodically poled silica fibre

    Science.gov (United States)

    Dontsova, E. I.; Kablukov, S. I.; Lobach, I. A.; Dostovalov, A. V.; Babin, S. A.; Gladyshev, A. V.; Dianov, E. M.; Corbary, C.; Ibsen, M.; Kazansky, P. G.

    2016-11-01

    We have studied second-harmonic generation (SHG) of a cw single-frequency ytterbium-doped fibre laser, using a periodically poled silica fibre as a nonlinear medium for frequency conversion. All-fibre external cavity SHG has been investigated for the first time. A twofold increase in second-harmonic power in a fibre ring cavity has been demonstrated and possibilities of further optimising the fibre scheme have been analysed.

  15. Nanobeam photonic crystal cavity quantum dot laser

    CERN Document Server

    Gong, Yiyang; Shambat, Gary; Sarmiento, Tomas; Harris, James S; Vuckovic, Jelena

    2010-01-01

    The lasing behavior of one dimensional GaAs nanobeam cavities with embedded InAs quantum dots is studied at room temperature. Lasing is observed throughout the quantum dot PL spectrum, and the wavelength dependence of the threshold is calculated. We study the cavity lasers under both 780 nm and 980 nm pump, finding thresholds as low as 0.3 uW and 19 uW for the two pump wavelengths, respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to 7 nm by employing a fiber taper in near proximity to the cavities. The fiber taper is used both to efficiently pump the cavity and collect the cavity emission.

  16. 3D cavity detection technique and its application based on cavity auto scanning laser system

    Institute of Scientific and Technical Information of China (English)

    LIU Xi-ling; LI Xi-bing; LI Fa-ben; ZHAO Guo-yan; QIN Yu-hui

    2008-01-01

    Ground constructions and mines are severely threatened by underground cavities especially those unsafe or inaccessible ones. Safe and precise cavity detection is vital for reasonable cavity evaluation and disposal. The conventional cavity detection methods and their limitation were analyzed. Those methods cannot form 3D model of underground cavity which is used for instructing the cavity disposal; and their precisions in detection are always greatly affected by the geological circumstance. The importance of 3D cavity detection in metal mine for safe exploitation was pointed out; and the 3D cavity laser detection method and its principle were introduced. A cavity auto scanning laser system was recommended to actualize the cavity 3D detection after comparing with the other laser detection systems. Four boreholes were chosen to verify the validity of the cavity auto scanning laser system. The results show that the cavity auto scanning laser system is very suitable for underground 3D cavity detection, especially for those inaccessible ones.

  17. Femtosecond SESAM lasers with shortlength cavity

    Science.gov (United States)

    Trunov, V. I.; Pestryakov, Efim V.; Petrov, V. V.; Kirpichnikov, A. V.; Bordzilovskii, A. S.; Preobrazhenskii, V. V.; Putyato, M. A.; Semyagin, B. R.

    2003-10-01

    Femtosecond pulse generation in Al2O3:Ti3+ laser with some types of laser cavity configuration with semiconductor saturable absorber mirror (SESAM), based on semiconductor quantum well low temperature (LT) GaAs/AlAs, GaxIn1-xAs/AlyGa1-yAs saturated absorbers and metal mirrors have been investigated.

  18. Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene

    Science.gov (United States)

    2015-07-16

    disperse the graphene by physical adsorption on its surface. The dispersions are mixed with poly vinyl alcohol (PVA) in a polymer mixer. The...is a more bring color . The bottom structure shows the image of the structure after the incorporation of the GSAM in the VECSEL cavity. The single

  19. Green pulsed lidar-radar emitter based on a multipass frequency-shifting external cavity.

    Science.gov (United States)

    Zhang, Haiyang; Brunel, Marc; Romanelli, Marco; Vallet, Marc

    2016-04-01

    This paper investigates the radio frequency (RF) up-conversion properties of a frequency-shifting external cavity on a laser beam. We consider an infrared passively Q-switched pulsed laser whose intensity modulation results from the multiple round-trips in the external cavity, which contains a frequency shifter. The output beam undergoes optical second-harmonic generation necessary to reach the green wavelength. We model the pulse train using a rate-equation model to simulate the laser pulses, together with a time-delayed interference calculation taking both the diffraction efficiency and the Gaussian beam propagation into account. The predictions are verified experimentally using a diode-pumped Nd:YAG laser passively Q-switched by Cr4+:YAG whose pulse train makes multiple round-trips in a mode-matched external cavity containing an acousto-optic frequency shifter driven at 85 MHz. Second-harmonic generation is realized in a KTP crystal, yielding RF-modulated pulses at 532 nm with a modulation contrast of almost 100%. RF harmonics up to the 6th order (1.020 GHz) are observed in the green output pulses. Such a RF-modulated green laser may find applications in underwater detection and ranging.

  20. Substrate-etched high power external-cavity surface-emitting lasers%基质刻蚀的高功率外腔面发射激光器

    Institute of Scientific and Technical Information of China (English)

    伍瑜; 倪演海; 戴特力; 周勇; 秦莉; 梁一平; 范嗣强; 张鹏

    2012-01-01

    为了降低光抽运外腔面发射激光器的热效应,提高激光器的输出功率,采用液体毛细键合方法将逆序生长的半导体外延片与高热导率的碳化硅散热窗口键合,并用化学刻蚀方法去除外延片的基质.实验研究了用基质刻蚀的外延片搭建的外腔面发射激光器的性能.当增益介质的有源区为InGaAs/AlGaAs多量子阱、抽运源为808nm的光纤耦合输出半导体激光器,输出镜对激光波长透过率为3%时,在室温下获得TEM00模的最大输出功率0.52W,激光波长1018nm,光谱线宽2nm(半峰全宽),激光器的光光转换效率约为20%.测得x方向与y方向的M2因子分别为1.01和1.00,说明输出光束为质量优良的近衍射极限高斯光束.结果表明,基质刻蚀技术可明显改善外腔面发射激光器的热性能,获得高功率、高光束质量的激光输出.%To decrease the thermal effect of a vertical-external-cavity surface-emitting laser and increase its output power, a high thermal conductivity SiC heatspreader was bond on the reverse-order semiconductor wafer with the capillary method, and then the substrate was removed by means of chemical etch. The characteristics of the laser formed by the substrate-etched wafer were experimentally studied. When the active region in the gain structure is InGaAs/AlGaAs multiple quantum wells, the pump source is a fiber-coupled 808nm diode laser, and the transmission of the output coupler is 3% at laser wavelength, the TEM00 mode output power of 0. 52W and the optical-to-optical conversion efficiency of 20% are obtained at room temperature. The laser wavelength is 1018nm, and the spectrum width is 2nm(full width half maximum) . The measured M2 factor in x and y direction of 1. 01 and 1. 00 demonstrate the near diffraction-limited Gaussian beam of the laser. It can be concluded that the substrate-etching technology can significantly improve the thermal property of vertical-external-cavity surface

  1. Rugged, Tunable Extended-Cavity Diode Laser

    Science.gov (United States)

    Moore, Donald; Brinza, David; Seidel, David; Klipstein, William; Choi, Dong Ho; Le, Lam; Zhang, Guangzhi; Iniguez, Roberto; Tang, Wade

    2007-01-01

    A rugged, tunable extended-cavity diode laser (ECDL) has been developed to satisfy stringent requirements for frequency stability, notably including low sensitivity to vibration. This laser is designed specifically for use in an atomic-clock experiment to be performed aboard the International Space Station (ISS). Lasers of similar design would be suitable for use in terrestrial laboratories engaged in atomic-clock and atomic-physics research.

  2. Tunable high-power narrow-spectrum external-cavity diode laser at 675 nm as a pump source for UV generation

    DEFF Research Database (Denmark)

    Chi, Mingjun; Jensen, Ole Bjarlin; Erbert, Gotz;

    2011-01-01

    of 1.0 W. The laser system B based on device B is tunable from 666 to 685 nm. As high as 1.05 W output power is obtained around 675.67 nm. The emission spectral bandwidth is less than 0.07 nm throughout the tuning range, and the beam quality factor M2 is 1.13 at an output power of 0.93 W. The laser...

  3. Compact and highly efficient laser pump cavity

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Jim J. (Dublin, CA); Bass, Isaac L. (Castro Valley, CA); Zapata, Luis E. (Livermore, CA)

    1999-01-01

    A new, compact, side-pumped laser pump cavity design which uses non-conventional optics for injection of laser-diode light into a laser pump chamber includes a plurality of elongated light concentration channels. In one embodiment, the light concentration channels are compound parabolic concentrators (CPC) which have very small exit apertures so that light will not escape from the pumping chamber and will be multiply reflected through the laser rod. This new design effectively traps the pump radiation inside the pump chamber that encloses the laser rod. It enables more uniform laser pumping and highly effective recycle of pump radiation, leading to significantly improved laser performance. This new design also effectively widens the acceptable radiation wavelength of the diodes, resulting in a more reliable laser performance with lower cost.

  4. Electrostatically tunable optomechanical "zipper" cavity laser

    CERN Document Server

    Perahia, Raviv; Meenehan, Sean; Alegre, Thiago P Mayer; Painter, Oskar

    2010-01-01

    A tunable nanoscale "zipper" laser cavity, formed from two doubly clamped photonic crystal nanobeams, is demonstrated. Pulsed, room temperature, optically pumped lasing action at a wavelength of 1.3 micron is observed for cavities formed in a thin membrane containing InAsP/GaInAsP quantum-wells. Metal electrodes are deposited on the ends of the nanobeams to allow for micro-electro-mechanical actuation. Electrostatic tuning and modulation of the laser wavelength is demonstrated at a rate of 0.25nm/V^2 and a frequency as high as 6.7MHz, respectively.

  5. Droplet based cavities and lasers

    DEFF Research Database (Denmark)

    Mølhave, Kristian; Kristensen, Anders; Mortensen, Asger

    2009-01-01

    The self-organized and molecularly smooth surface on liquid microdroplets makes them attractive as optical cavities with very high quality factors. This chapter describes the basic theory of optical modes in spherical droplets. The mechanical properties including vibrational excitation are also d...

  6. Gratings' rotation angle tolerance for diode lasers with external cavity formed by volume Bragg grating%体布拉格光栅外腔半导体激光器的光栅旋转角度容差

    Institute of Scientific and Technical Information of China (English)

    李志永; 谭荣清; 徐程; 李琳; 刘世明; 赵志龙; 黄伟

    2013-01-01

    采用步进电机控制光栅角度,对φ200 μm和φ600 μm圆柱透镜准直的体布拉格光栅(VBG)外腔单管C封装半导体激光器进行了系统研究.实验结果表明:激光二极管(LD)驱动电流越大,准直效果越好,VBG的角度调整容差越小;快轴方向的准直效果越好,慢轴方向的光栅调节角度容差越大;对于衍射效率28%、厚1.4 mm的光栅,LD快轴发散角为7.3 mrad时,快轴方向的角度容差不大于3.2 mrad,慢轴方向的角度容差较快轴大约一个数量级.%For high power linewidth-narrowed diode lasers, it's important to study rotation angle tolerance of the volume Bragg grating (VBG) for narrowing the spectral linewidth of two dimensional diode laser stacks. The diode laser with the VBG' s external cavity and C-mounted modules is collimated by Φ200 μm and Φ600μm cylindrical lens separately in the paper. The VBG's angle tolerance is acquired by two stepper motors. According to the research, more accuracy is needed for the VBG's adjustment with higher driving current and better beam collimation. If the laser diode is collimated better in fast axis direction, rotation angle tolerance in slow axis direction will be bigger. When a VBG with a diffraction efficiency of 28% and thickness of 1. 4 mm is used to lock the wavelength of a laser diode with a fast axis divergence angle of 7. 3 mrad, the grating's rotation angle tolerance is no more than 3. 2 mrad in the fast axis direction and that for the slow axis direction is one order of magnitude bigger.

  7. High efficiency SHG of orbital angular momentum light in an external cavity

    CERN Document Server

    Zhou, Zhi-Yuan; Ding, Dong-Sheng; Jiang, Yun-Kun; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can

    2014-01-01

    Traditional methods for generating orbital angular momentum (OAM) light include holographic diffraction gratings, vortex phase plate and spatial light modulator. In this article, we report a new method for high efficient OAM light generation. By pumping an external cavity contains a quasi phase matching nonlinear crystal with a fundamental OAM carrying light and properly aligning the cavity, mode matching between the pump light and the cavitys higher order Laguerre-Gaussian (LG) mode is achieved, conversion efficiency up to 10.3 percentage have been obtained. We have demonstrated that the cavity can stably operate at its higher order LG mode just as Gaussian mode for the first time. The SHG light possesses a doubled OAM value with respect to the pump light. The parameters that affect the beam quality and conversion efficiency are discussed in detail. Our work opens a brand new field in laser optics, and makes the first step toward high efficiency OAM light processing.

  8. Micro-Cavity Fluidic Dye Laser

    DEFF Research Database (Denmark)

    Helbo, Bjarne; Kristensen, Anders; Menon, Aric Kumaran

    2003-01-01

    We have successfully designed, fabricated and characterized a micro-cavity fluidic dye laser with metallic mirrors, which can be integrated with polymer based lab-on-a-chip microsystems without further processing steps. A simple rate-equation model is used to predict the average pumping power...

  9. Coupling coefficients for coupled-cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lang, R.J.; Yariv, A.

    1987-03-01

    The authors derive simple, analytic formulas for the field coupling coefficients in a two-section coupled-cavity laser using a local field rate equation treatment. They show that there is a correction to the heuristic formulas based on power flow calculated by Marcuse; the correction is in agreement with numerical calculations from a coupled-mode approach.

  10. Observing mode propagation inside a laser cavity

    CSIR Research Space (South Africa)

    Naidoo, Darryl

    2012-05-01

    Full Text Available The mode inside a laser cavity may be understood as the interference of two counter-propagating waves, referred to as the forward and backward waves, respectively. We outline a simple experimental procedure, which does not require any additional...

  11. Dynamics of a broad-area diode laser with lateral-mode-selected long-cavity feedback

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael

    2014-01-01

    of the cases, the output of the laser shows a periodic oscillation corresponding to a single roundtrip external-cavity loop, but the dynamic behavior disappears in some case; when the zero-order lateral-mode is selected, periodic oscillation corresponding to a double roundtrip external-cavity loop is observed....... When the feedback mirror is aligned non-perfectly, pulse-package oscillation is observed, for the first time to our knowledge, in a diode laser with long-cavity feedback....

  12. Spectrum Characteristics of 1.5 mm InAs/InP Quantum-dot-laser Modulated by Mirror External-cavity%1.5mm腔长InAs/InP量子点激光器镜面外腔光谱特性研究

    Institute of Scientific and Technical Information of China (English)

    柳庆博; 龚谦; 曹春芳; 汪洋; 岳丽; 严进一; 成若海

    2012-01-01

    Based on self-made 1.5 mm InAs/InP QD laser,its spectrum characteristics modulated by mirror external-cavity are studied.The periodicity,the multimode lasing and the mode change of the spectrum versus current are explained.Contrast to short coupling-cavity quantum-well lasers used for single mode,long cavity-length InAs/InP QD lasers show smaller mode-compression and much easier multimode-lasing under the modulation of mirror external-cavity.%基于研制的1.5mm腔长InAs/InP共面条状量子点激光器,搭建了其镜面外腔结构,并对其光谱特性进行了测试,获得了镜面外腔周期性调制光谱,并在周期性的产生、多模激射和模式随电流的变化等方面对其光谱特性进行了分析研究。相比以前为获得单模使用的超短腔长超短外腔量子阱激光器,长腔长InAs/InP量子点激光器表现出较小的模式压缩比,更容易发生多模激射。

  13. Long wavelength vertical cavity surface emitting laser

    Science.gov (United States)

    Choquette, Kent D.; Klem, John F.

    2005-08-16

    Selectively oxidized vertical cavity lasers emitting near 1300 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave below, 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 active region, 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.degree. C.

  14. Laser in-cavity Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, C.M.

    1978-09-01

    A new laser interferometer is proposed which can be regarded as an in-cavity Michelson interferometer. It utilizes a polarizing beam splitter in conjunction with two quarter-wave plates to produce oscillations between three mirrors. It would measure a change in length of 10/sup -3/ A that, if used for plasma diagnostics, is equivalent to measuring an electron density of 10/sup 9/ cm/sup -3/ over a plasma length of 1 cm.

  15. Engineering high-performance vertical cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lear, K.L.; Hou, H.Q.; Hietala, V.M.; Choquette, K.D.; Schneider, R.P. Jr.

    1996-12-31

    The cw and high-speed performance of vertical cavity surface emitting laser diodes (VCSELs) are affected by both electrical and optical issues arising from the geometry and fabrication of these devices. Structures with low resistance semiconductor mirrors and Al-oxide confinement layers address these issues and have produced record performance including 50% power conversion efficiency and modulation bandwidths up to 20 GHz at small bias currents.

  16. 光纤光栅外腔半导体激光器频率调谐技术研究%Study on frequency tuning technology of fiber Bragg grating external cavity semiconductor laser

    Institute of Scientific and Technical Information of China (English)

    高源

    2016-01-01

    Based on the analysis of the basic characteristics of fiber Bragg grating external cavity semiconductor laser (FBG -ECL),the frequency tuning methods for this type of lasers are investigated,including temperature tuning method and stress tuning method.The center wavelength of fiber Bragg grating is changed by the axial stress tuning method to realize the frequency tuning.The piezoelectric ceramic(PZT)was used to exert an axial stress on the grat-ing,and the amount of change in the center wavelength of the fiber Bragg grating was controlled by adjusting PZT drive voltage.The experimental results show that,for the FBG -ECL with wavelength 1550 nm,when the PZT drive voltage adds up to 126 V,tuning range can reach 100 GHz and tuning speed can reach 2 ms per cycle.%在分析了光纤光栅外腔半导体激光器(FBG -ECL)基本特性的基础上,调研了适用于该类型激光器的频率调谐方法,包括温度调谐法和应力调谐法,选取轴向应力调谐法改变光纤光栅的布拉格中心波长,进而实现频率调谐。利用压电陶瓷(PZT)来对光纤光栅施加轴向应力,通过调整 PZT 驱动电压值的大小来控制光纤光栅布拉格中心波长的变化量。实验结果表明,对于波长1550 nm 的光纤光栅激光器,当 PZT 的驱动电压增加到126 V 时,可实现0.8 nm,即100 GHz 的调谐范围以及每周期2 ms 的调谐速度。

  17. Generation of single-frequency tunable green light in a coupled ring tapered diode laser cavity

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Petersen, Paul Michael

    2013-01-01

    We report the realization of a tapered diode laser operated in a coupled ring cavity that significantly improves the coherence properties of the tapered laser and efficiently generates tunable light at the second harmonic frequency. The tapered diode laser is tunable with single-frequency output...... frequency doubling. More than 500 mW green output power is obtained by placing a periodically poled LiNbO3 crystal in the external cavity. The single frequency green output from the laser system is tunable in the 530 nm to 533 nm range limited by the LiNbO3 crystal. The optical to optical conversion...

  18. Modeling of Coupled Nano-Cavity Lasers

    DEFF Research Database (Denmark)

    Skovgård, Troels Suhr

    Modeling of nanocavity light emitting semiconductor devices is done using the semiconductor laser rate equations with spontaneous and stimulated emission terms modified for Purcell enhanced recombination. The modified terms include details about the optical and electronic density......, coupled photonic crystal nanocavity structures are simulated. The resonance frequencies of in-phase and out-of-phase coupled quadrupole modes in rectangular photonic crystal H1 cavities are extracted and are found to vary non-trivially with the intercavity separation. A qualitative explanation is given...... in terms of the in-plane mode profiles. Fareld emission patterns for the structures are calculated based on the finite-dierence time-domain simulations. It is found that only systems with an even number of holes separating the cavities show clear signs of being coupled. This non-trivial coupling behavior...

  19. Optical feedback in dfb quantum cascade laser for mid-infrared cavity ring-down spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Terabayashi, Ryohei, E-mail: terabayashi.ryouhei@h.mbox.nagoya-u.ac.jp; Sonnenschein, Volker, E-mail: volker@nagoya-u.jp; Tomita, Hideki, E-mail: tomita@nagoya-u.jp; Hayashi, Noriyoshi, E-mail: hayashi.noriyoshi@h.mbox.nagoya-u.ac.jp; Kato, Shusuke, E-mail: katou.shuusuke@f.mbox.nagoya-u.ac.jp; Jin, Lei, E-mail: kin@nuee.nagoya-u.ac.jp; Yamanaka, Masahito, E-mail: yamanaka@nuee.nagoya-u.ac.jp; Nishizawa, Norihiko, E-mail: nishizawa@nuee.nagoya-u.ac.jp [Nagoya University, Department of Quantum Engineering, Graduate School of Engineering (Japan); Sato, Atsushi, E-mail: atsushi.sato@sekisui.com; Nozawa, Kohei, E-mail: kohei.nozawa@sekisui.com; Hashizume, Kenta, E-mail: kenta.hashizume@sekisui.com; Oh-hara, Toshinari, E-mail: toshinari.ohara@sekisui.com [Sekisui Medical Co., Ltd., Drug Development Solutions Center (Japan); Iguchi, Tetsuo, E-mail: t-iguchi@nucl.nagoya-u.ac.jp [Nagoya University, Department of Quantum Engineering, Graduate School of Engineering (Japan)

    2017-11-15

    A simple external optical feedback system has been applied to a distributed feedback quantum cascade laser (DFB QCL) for cavity ring-down spectroscopy (CRDS) and a clear effect of feedback was observed. A long external feedback path length of up to 4m can decrease the QCL linewidth to around 50kHz, which is of the order of the transmission linewidth of our high finesse ring-down cavity. The power spectral density of the transmission signal from high finesse cavity reveals that the noise at frequencies above 20kHz is reduced dramatically.

  20. Lambda shifted photonic crystal cavity laser

    DEFF Research Database (Denmark)

    Schubert, Martin; Skovgård, Troels Suhr; Ek, Sara

    2010-01-01

    We propose and demonstrate an alternative type of photonic crystal laser design that shifts all the holes in the lattice by a fixed fraction of the targeted emission wavelength. The structures are realized in InGaAsP =1.15 with InGaAsP quantum wells =1.52 as gain material. Cavities with shifts of 1....../4 and 3/4 of the emission wavelength were fabricated and characterized. Measurements show threshold behavior for several modes at room temperature. Both structures are simulated using a finite difference time domain method to identify the resonances in the spectra and calculate the mode volume...

  1. Cavity solitons in vertical-cavity surface-emitting lasers

    CERN Document Server

    Vladimirov, A G; Gurevich, S V; Panajotov, K; Averlant, E; Tlidi, M

    2014-01-01

    We investigate a control of the motion of localized structures of light by means of delay feedback in the transverse section of a broad area nonlinear optical system. The delayed feedback is found to induce a spontaneous motion of a solitary localized structure that is stationary and stable in the absence of feedback. We focus our analysis on an experimentally relevant system namely the Vertical-Cavity Surface-Emitting Laser (VCSEL). In the absence of the delay feedback we present experimental evidence of stationary localized structures in a 80 $\\mu$m aperture VCSEL. The spontaneous formation of localized structures takes place above the lasing threshold and under optical injection. Then, we consider the effect of the time-delayed optical feedback and investigate analytically the role of the phase of the feedback and the carrier lifetime on the self-mobility properties of the localized structures. We show that these two parameters affect strongly the space time dynamics of two-dimensional localized structures...

  2. Dynamic behaviors of a broad-area diode laser with lateral-mode-selected external feedback

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael

    2014-01-01

    behavior disappears in some case; when the zero-order mode is selected, periodic dynamics corresponding to a double roundtrip external-cavity loop is observed. When the stripe mirror is not aligned perfectly, a dynamic behavior like pulse-package oscillations is observed: a periodic oscillated output...... with a frequency of the single roundtrip external-cavity loop modulated by periodic low-frequency fluctuation. This is the first observation of pulse-package oscillation in a diode laser with long-cavity feedback, to our knowledge....

  3. Self-Mixing Fringes of Vertical-Cavity Surface-Emitting Lasers under Dual Reflector Feedback

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiang; ZHANG Shu-Lian; ZHANG Lian-Qing; TAN Yi-Dong

    2006-01-01

    The self-mixing fringes which shift due to every one-twentieth wavelength displacement of the target are observed.Taking advantage of the dual reflectors in the external cavity of lasers, the resolution of the sensors has been improved by 10 times. The role of the each reflector has been discussed in detail.

  4. 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.

  5. Folded cavity angled-grating broad-area lasers.

    Science.gov (United States)

    Zhao, Yunsong; Zhu, Lin

    2013-10-01

    The angled-grating broad-area laser is a promising candidate for high power, high brightness diode laser source. The key point in the design is the angled gratings which can simultaneously support the unique snake-like zigzag lasing mode and eliminate the direct Fabry-Perot (FP) feedback. Unlike a conventional laser waveguide mode, the phase front of the zigzag mode periodically changes along the propagation direction. By use of the mirror symmetry of the zigzag mode, we propose and demonstrate the folded cavity angled-grating broad-area lasers. One benefit of this design is to reduce the required wafer space compared to a regular angled-grating broad-area laser, especially in a long cavity laser for high power operation. Experimental results show that the folded cavity laser exhibits good beam quality in far field with a slightly larger threshold and smaller slope efficiency due to the additional interface loss.

  6. Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback

    CERN Document Server

    Samutpraphoot, Polnop; Lin, Qian; Gangloff, Dorian; Bylinskii, Alexei; Braverman, Boris; Kawasaki, Akio; Raab, Christoph; Kaenders, Wilhelm; Vuletić, Vladan

    2014-01-01

    We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve a suppression in frequency noise spectral density of 20 dB measured at frequencies around 1 MHz, corresponding to the narrowing of the intrinsic Lorentzian linewidth from 200 kHz to 2 kHz. The system is suitable for experiments requiring a tunable ultraviolet laser with narrow linewidth and low high-frequency noise, such as precision spectroscopy, optical clocks, and quantum information science experiments.

  7. Pulse shape control in a dual cavity laser: numerical modeling

    Science.gov (United States)

    Yashkir, Yuri

    2006-04-01

    We present a numerical model of the laser system for generating a special shape of the pulse: a steep peak at the beginning followed by a long pulse tail. Laser pulses of this nature are required for various applications (laser material processing, optical breakdown spectroscopy, etc.). The laser system consists of two "overlapped" cavities with different round-trip times. The laser crystal, the Q-switching element, the back mirror, and the output coupler are shared. A shorter pulse is generated in a short cavity. A small fraction of this pulse is injected into the long cavity as a seed. It triggers generation of the longer pulse. The output emission from this hybrid laser produces a required pulse shape. Parameters of the laser pulse (ratios of durations and energies of short- and long- pulse components) can be controlled through cavity length and the output coupler reflection. Modelling of the laser system is based on a set of coupled rate equations for dynamic variables of the system: the inverse population in an active laser media and photon densities in coupled cavities. Numerical experiments were provided with typical parameters of a Nd:YAG laser to study the system behaviour for different combinations of parameters.

  8. Cavity-enhanced laser cooling of solid-state materials in a standing-wave cavity

    Institute of Scientific and Technical Information of China (English)

    Youhua Jia; Biao Zhong; Jianping Yin

    2008-01-01

    We propose a new method to cool the Yba+-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique: the pumping power is greatly enhanced and the absorption of the cooling material is greatly increased. We introduce the basic principle of the cavity-enhanced laser cooling and discuss the cooling effect of a solid-state material in a cavity. From the theoretical study, it is found that the laser cooling effect is strongly dependent on the reflectivity of the cavity mirrors, the length of the solid material, the surface scattering of the material, and so on. Some optimal parameters for efficient laser cooling are obtained.

  9. Convective Heat Transfer Between the Wall Surface of a Cavity and the External Main Stream

    Science.gov (United States)

    Yoshiwara, Masahiro; Katto, Yoshiro; Yokoyama, Masanori

    An experimental study has been made under the following conditions for convective heat transfer between the wall surface of a cavity of which both width and depth are 25 mm and the external main stream; the range of Reynolds numbers is from 104 to 105, and the ratio of tripping wire diameter to cavity width is 0.08. The oncoming boundary layer to a cavity is turbulent by the tripping wire with the existing study. Convective heat transfer between a cavity wall surface and the external main stream is treated by the following two phenomena; one is the heat transfer which is related to the temperature difference between the wall surface and the fluid in the cavity, and the other the heat transfer which is related to the temperature difference between the fluid in a cavity and the external mainstream. Experimental data obtained for the foregoing conditions is almost coincide with the existing dimensionless correlations of two of the authors.

  10. Power Enhancement Cavity for Burst-Mode Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun [ORNL

    2015-01-01

    We demonstrate a novel optical cavity scheme and locking method that can realize the power enhancement of picosecond UV laser pulses operating at a burst mode with arbitrary burst (macropulse) lengths and repetition rates.

  11. Piezoelectric deformable mirror for intra-cavity laser adaptive optics.

    CSIR Research Space (South Africa)

    Long, CS

    2008-03-01

    Full Text Available This paper describes the development of a deformable mirror to be used in conjunction with diffractive optical elements inside a laser cavity. A prototype piezoelectric unimorph adaptive mirror was developed to correct for time dependent phase...

  12. Effect of External Optical Feedback for Nano-laser Structures

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2013-01-01

    We theoretically investigated the effect of optical feedback on a photonic crystal nanolaser, comparing with conventional in-plane and vertical-cavity lasers.......We theoretically investigated the effect of optical feedback on a photonic crystal nanolaser, comparing with conventional in-plane and vertical-cavity lasers....

  13. Ultrafast Optics: Vector Cavity Laser - Physics and Technology

    Science.gov (United States)

    2016-06-14

    fiber lasers the effective cavity gain bandwidth could be far broader than the laser emission bandwidth, if the optical field is in resonance with the...periodic modulation on the CW laser field , where fc is the modulation frequency. Fig. 2.1 shows the evolution of the laser emission under existence of...real saturable absorber (SA) mode locking techniques, such as the carbon nanotube mode locking, 2D-nano-materials mode locking, formation of bound

  14. Ultrafast Optics: Vector Cavity Fiber Lasers - Physics and Technology

    Science.gov (United States)

    2016-06-14

    fiber lasers the effective cavity gain bandwidth could be far broader than the laser emission bandwidth, if the optical field is in resonance with the...periodic modulation on the CW laser field , where fc is the modulation frequency. Fig. 2.1 shows the evolution of the laser emission under existence of...real saturable absorber (SA) mode locking techniques, such as the carbon nanotube mode locking, 2D-nano-materials mode locking, formation of bound

  15. Ultrafast Optics - Vector Cavity Lasers: Physics and Technology

    Science.gov (United States)

    2016-06-14

    fiber lasers the effective cavity gain bandwidth could be far broader than the laser emission bandwidth, if the optical field is in resonance with the...periodic modulation on the CW laser field , where fc is the modulation frequency. Fig. 2.1 shows the evolution of the laser emission under existence of...real saturable absorber (SA) mode locking techniques, such as the carbon nanotube mode locking, 2D-nano-materials mode locking, formation of bound

  16. Fiber Ring Laser In-cavity Phase Modulation

    Institute of Scientific and Technical Information of China (English)

    YU Benli; QIAN Jingren; LUO Jiatong; YANG Yinghai

    2001-01-01

    In this paper, experimental results of the in-cavity phase modulation induced by dithering PZT is reported. The dithering PZT can produce strong phase modulation, reshaping the laser output spectrum, but does not affect the laser linewidth, which is measured by homodyne method.

  17. Output characteristics of right angle cone mirror cavity laser

    Institute of Scientific and Technical Information of China (English)

    Hongqi Li; Zuhai Cheng

    2005-01-01

    The anti-misalignment stability and output characteristics of the right angle cone cavity laser are experimentally studied. When the misalignment angle of the cone mirror turns to 46.8 minutes, the single-pulse output energy of the plano-cone cavity laser decreases 24% and the near-field beam patterns have little change; as for the beam directional stability, when the measuring place stands 3.12 m in front of the output mirror, the near-field beam patterns of the plano-cone laser are located at the primary places until the misalignment angle of the cone mirror turns to 18 minutes. These results show that the plano-cone cavity laser has better performances in comparison with the plano-concave cavity laser. The analytical results of the mode instrument are also obtained, which show that the near-field beam intensity distribution of the plano-cone mirror cavity laser is near to the plane wave.

  18. Dynamic behaviors of a broad-area diode laser with lateral-mode-selected external feedback

    DEFF Research Database (Denmark)

    Chi, Mingjun; Petersen, Paul Michael

    2014-01-01

    In this paper, we investigate the dynamics of a BAL with lateral-mode selected external feedback experimentally by measuring the far-field profile, intensity noise spectrum and time series of the output beam. The mode-selection is achieved by adjusting a stripe mirror at the pseudo far-field plan...... with a frequency of the single roundtrip external-cavity loop modulated by periodic low-frequency fluctuation. This is the first observation of pulse-package oscillation in a diode laser with long-cavity feedback, to our knowledge........ Different dynamic behaviors are observed when different lateral modes are selected. When the mirror is aligned correctly and high-order modes are selected, in most of the cases periodic dynamics of the output power corresponding to a single roundtrip external-cavity loop is observed, but the dynamic...

  19. Comparison of Dentin Permeability After Tooth Cavity Preparation with Diamond Bur and Er:YAG Laser

    Directory of Open Access Journals (Sweden)

    Masoumeh Hasani Tabatabaei

    2016-05-01

    Full Text Available Objectives: The aim of this study was to compare the permeability of dentin after using diamond bur and Er:YAG laser.Materials and Methods: Seventy-two recently extracted, intact, and restoration-free human permanent molars were used in this study. The samples were randomly divided into three groups of 24 each and class I cavities were prepared as follows. Group 1: High speed diamond bur with air and water spray. Group 2: Er:YAG laser. Group 3: Er:YAG laser followed by additional sub-ablative laser treatment. Each group consisted of two subgroups with different cavity depths of 2mm and 4mm.  The entire cavity floor was in dentin. Two samples from each subgroup were observed under scanning electron microscope (SEM. The external surfaces of other samples were covered with nail varnish (except the prepared cavity and immersed in 0.5% methylene blue solution for 48 hours.  After irrigation of samples with water, they were sectioned in bucco-lingual direction. Then, the samples were evaluated under a stereomicroscope at ×160 magnification. The data were analyzed using two-way ANOVA and Tukey’s HSD test.Results: Two-way ANOVA showed significant difference in permeability between groups 2 and 3 (laser groups with and without further treatment and group 1 (bur group. The highest permeability was seen in the group 1. There was no significant difference in dentin permeability between groups 2 and 3 and no significant difference was observed between different depths (2mm and 4mm.Conclusion: Cavities prepared by laser have less dentin permeability than cavities prepared by diamond bur.

  20. Single transverse mode selectively oxidized vertical cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    CHOQUETTE,KENT D.

    2000-04-18

    Vertical cavity surface emitting laser (VCSEL) sources have been adopted into Gigabit Ethernet applications in a remarkably short time period. VCSELs are particularly suitable for multimode optical fiber local area networks (LANs), due to their reduced threshold current, circular output beam, and inexpensive and high volume manufacture. Moreover, selectively oxidized VCSELs are nearly ideal LAN sources since the oxide aperture within the laser cavity produces strong electrical and optical confinement which enables high electrical to optical conversion efficiency and minimal modal discrimination allowing emission into multiple transverse optical modes. In addition to the large demand for multimode lasers, VCSELs which emit into a single optical mode are also increasingly sought for emerging applications, which include data communication with single mode optical fiber, bar code scanning, laser printing, optical read/write heads, and modulation spectroscopy. To achieve single mode selectively oxidized VCSELs is a challenging task, since the inherent index confinement within these high performance lasers is very large.

  1. Dynamics of a vertical cavity quantum cascade phonon laser structure

    Science.gov (United States)

    Maryam, W.; Akimov, A. V.; Campion, R. P.; Kent, A. J.

    2013-07-01

    Driven primarily by scientific curiosity, but also by the potential applications of intense sources of coherent sound, researchers have targeted the phonon laser (saser) since the invention of the optical laser over 50 years ago. Here we fabricate a vertical cavity structure designed to operate as a saser oscillator device at a frequency of 325 GHz. It is based on a semiconductor superlattice gain medium, inside a multimode cavity between two acoustic Bragg reflectors. We measure the acoustic output of the device as a function of time after applying electrical pumping. The emission builds in intensity reaching a steady state on a timescale of order 0.1 μs. We show that the results are consistent with a model of the dynamics of a saser cavity exactly analogous to the models used for describing laser dynamics. We also obtain estimates for the gain coefficient, steady-state acoustic power output and efficiency of the device.

  2. Multilayer structures for X-ray laser cavities

    Science.gov (United States)

    Ceglio, N. M.; Stearns, D. G.; Hawryluk, A. M.

    1985-08-01

    Recent demonstrations of the generation of amplified spontaneous emission at soft X-ray wavelenths have spurred interest in normal incidence multilayer structures for use as X-ray laser (XRL) cavity mirrors. Calculations indicate that cavity mirrors can provide significant enhancement of RXL output, and drive the oscillations to the saturation limit. Novel ideas for cavity output coupling may expand the versatility of XRL devices, while encouraging the marriage of lithographic and multilayer technologies to the general benefit of X-ray optics. Preliminary tests of a double pass cavity have already been conducted. These tests point out the importance of detailed cavity design issues such as precision mirror alignment, mirror damage dynamics, and detailed mirror calibration, to the future success of this field.

  3. High-sensitivity time-resolved intracavity laser Fourier transform spectroscopy with vertical cavity surface emitting multiple quantum well lasers

    CERN Document Server

    Picqué, N; Kachanov, A A; Picqu\\'e, Nathalie; Guelachvili, Guy; Kachanov, Alexander A.

    2003-01-01

    Spectra comprised of hundreds of time-components for absorption path lengths up to 130 km have been recorded around 1050 nm by combining two recent techniques, intracavity laser spectroscopy with vertical external cavity surface emitting multiple-quantum-well lasers and time-resolved Fourier transform spectroscopy. A sensitivity of 1 10^{-10} cm^{-1}.Hz^{-1/2} is achieved, for simultaneously acquired 10^4 spectral elements, three orders of magnitude better than the sensitivity obtained in previous similar experiments. Specific advantages of the method, especially for frequency and intensity metrology of weak absorption transitions, are discussed.

  4. Multilongitudinal-mode model for cleaved coupled-cavity lasers

    Science.gov (United States)

    van de Capelle, J. P.; Baets, R.; Lagasse, P. E.

    1987-02-01

    The multilongitudinal-mode model for the analysis of cleaved coupled-cavity lasers proposed by Van de Capelle et al. (1984) is described in full detail. The model includes the optical interactions between the two cavities as well as the noise (spontaneous emission) in each of the resonators. It takes several longitudinal modes into account simultaneously and solves the nonlinear field equations self-consistently, together with a nonlinear resonance condition for each longitudinal mode. These conditions are coupled with each other through the nonlinearity of the laser medium. The results of this model are compared with those from an analytic model based on an effective mirror concept.

  5. Selectively oxidized vertical-cavity laser performance and technology

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

    1998-02-01

    The authors discuss revolutionary performance advances in selectively oxidized vertical-cavity surface emitting lasers (VCSELs), which have enabled low operating power laser diodes appropriate for aerospace applications. Incorporating buried oxide layers converted from AIGaAs layers within the laser cavity produces enhanced optical and electrical confinement enabling superior laser performance, such as high efficiency and modulation bandwidth. VCSELs also shown to be viable over varied environmental conditions such as ambient temperature and ionized radiation. The development of novel VCSEL technologies for advanced system applications is also described. Two dimensional individually addressable VCSEL arrays exhibit uniform threshold and operating characteristics. Bottom emitting 850 nm VCSEL arrays fabricated using wafer fusion are also reported.

  6. Spectral control of diode lasers using external waveguide circuits

    NARCIS (Netherlands)

    Oldenbeuving, Ruud

    2013-01-01

    We investigated spectral control of diode lasers using external waveguide circuits. The purpose of this work is to investigate such external control for providing a new class of diode lasers with technologically interesting properties, such as a narrow spectral bandwidth and spectrally tunable

  7. Spectral control of diode lasers using external waveguide circuits

    NARCIS (Netherlands)

    Oldenbeuving, R.M.

    2013-01-01

    We investigated spectral control of diode lasers using external waveguide circuits. The purpose of this work is to investigate such external control for providing a new class of diode lasers with technologically interesting properties, such as a narrow spectral bandwidth and spectrally tunable outpu

  8. Control of ring lasers by means of coupled cavities

    DEFF Research Database (Denmark)

    Buchhave, Preben; Abitan, Haim; Tidemand-Lichtenberg, Peter

    2000-01-01

    Variable phase coupling to an external ring is used to control a unidirectional ring laser. The observed behavior of the coupled rings is explained theoretically. We have found experimentally that by quickly changing the phase of the feedback from the external ring it is possible to Q-switch the ...

  9. A Moiré Cavity Plasmonic Dye Laser

    Science.gov (United States)

    Karademir, Ertugrul; Balci, Sinan; Kocabas, Coskun; Aydinli, Atilla

    2015-03-01

    From its first conception to its first demonstration, plasmonic lasers have been an intriguing topic of research. In this work, Moiré gratings which manifest a cavity state in the SPP dispersion curve. We used a reverse Kretschmann setup to decouple the amplified light component of SPPs. We employed a Moiré cavity with 250 +256 nm periodicity together with a Styryl 7 laser dye dissolved in ethylene glycol in 5 mM concentration and obtained a lasing at 718 nm. Pumping threshold was 1.5 mJ/cm2 with FWHM of 2.8 nm. Furthermore, periodicities of 242 +248 nm and 260 +266 nm resulted in proportional shift of the lasing peak. We did not observe any lasing action on samples with Au and Ti coatings, although solely Au coated samples showed plasmonic modes in the spectrum. Resulting lasing peak is highly TM polarized. Reflection map measurements confirm that lasing mode is supported with the cavity state of the metallic Moiré cavity and simulations support reflection map measurements. Thus, we demonstrated, to our knowledge, the first plasmonic dye laser on a Moiré cavity. TUBITAK 110T790, 110T589, 112T091.

  10. A Laser Feedback Control Design for Passive Ring Laser Gyros in a Very High Finesse Cavity.

    Science.gov (United States)

    1985-12-01

    14 II. Theory ....................... 16 Optical Cavities ................ 16 Laser Fundamentals ...............24 The Gaussian Beam. ...............28...c 1-(ABC 1h(.8 = (2.18) F = 1 2.19) - (RARCRD) t = = (2.20) C c[i- (RARRc%)] Laser Fundamentals A laser consists of three basic components: a gain

  11. Vertical-cavity surface-emitting lasers for medical diagnosis

    DEFF Research Database (Denmark)

    Ansbæk, Thor

    This thesis deals with the design and fabrication of tunable Vertical-Cavity Surface-Emitting Lasers (VCSELs). The focus has been the application of tunable VCSELs in medical diagnostics, specifically OCT. VCSELs are candidates as light sources for swept-source OCT where their high sweep rate, wide...

  12. Cavity ring down spectroscopy with a free-electron laser

    NARCIS (Netherlands)

    Engeln, R.; van den Berg, E.; Meijer, G.; Lin, L.; Knippels, G.M.H.; van der Meer, A. F. G.

    1997-01-01

    A cavity ring down (CRD) absorption experiment is performed with a free-electron laser (FEL) operating in the 10-11 mu m region. A short infrared pulse of approximately 20 ns, sliced from the much longer FEL pulse, is used to measure CRD spectra of ethylene in two different ways. First, ''

  13. Bifurcation structure of cavity soliton dynamics in a vertical-cavity surface-emitting laser with a saturable absorber and time-delayed feedback

    Science.gov (United States)

    Schelte, Christian; Panajotov, Krassimir; Tlidi, Mustapha; Gurevich, Svetlana V.

    2017-08-01

    We consider a wide-aperture surface-emitting laser with a saturable absorber section subjected to time-delayed feedback. We adopt the mean-field approach assuming a single longitudinal mode operation of the solitary vertical-cavity surface-emitting laser (VCSEL). We investigate cavity soliton dynamics under the effect of time-delayed feedback in a self-imaging configuration where diffraction in the external cavity is negligible. Using bifurcation analysis, direct numerical simulations, and numerical path-continuation methods, we identify the possible bifurcations and map them in a plane of feedback parameters. We show that for both the homogeneous and localized stationary lasing solutions in one spatial dimension, the time-delayed feedback induces complex spatiotemporal dynamics, in particular a period doubling route to chaos, quasiperiodic oscillations, and multistability of the stationary solutions.

  14. A birefringent cavity He-Ne laser and optical feedback

    Institute of Scientific and Technical Information of China (English)

    Liu Gang; Zhang Shu-Lian; Li Yan; Zhu Jun

    2004-01-01

    Strong modes competition makes only one of o-light and e-light oscillate in a birefringent dual-frequency laser when the angle between the crystalline axis and the laser beam is nearly zero. When the oscillated mode is in a different part of the gain curve, the detected intensity curves of o-light and e-light are quite different in the existence of optical feedback. The curves are divided into five cases. Three cases of the experimental results can be used for direction discrimination. The polarization characteristics of the birefringent cavity He-Ne laser are also discussed without optical feedback.

  15. a Numerical Study of a Coupled-Cavity Color Center Laser

    Science.gov (United States)

    Zook, Brian Jay

    The nonlinear effects in a coupled-cavity laser make it difficult to investigate the theory with only analytic methods, though numerical methods can be used. This dissertation discusses the development of computer models of the coupled -cavity laser; portions of FORTRAN code are included. The research goal is to find practical rules of coupled-cavity operation for the laser engineer. The model's foundation is the additive-pulse mode -locking (APM) theory. This theory states that the pulse -shortening mechanism is the coherent superposition of the electric fields of the two cavities at the output coupler of the main cavity. The nonlinearity of the external cavity (only self-phase modulation in the optical fiber is treated) causes a frequency chirp on its pulse. If the phases are correct, the interference of the pulses results in a shorter combined pulse. The first model investigates the nature of the combined pulse, which is reinjected into the main cavity. Although this model is incomplete (it ignores the gain medium), it provides insight into the operation of the laser. This model shows, and experimental results support, that there is an optimum amount of self-phase modulation and that anomalous dispersion in the fiber (which can support soliton propagation) results in longer pulses than normal dispersion. The multi-pass models include the gain medium in order to model the complete laser system. The first of these models uses an iterative method in which the pulses propagate through the simulated system, much as laser pulses propagate through the actual laser. This continues for as many iterations (round trips) as necessary to reach a steady state. The other multi-pass method imposes a steady-state condition to find a closed-form, self-consistent recursion relation which is used to numerically generate the steady-state pulse directly. This latter model generates pulses as short as 500 femtoseconds, which corresponds reasonably to laboratory results. Both simulated

  16. Temporal laser pulse manipulation using multiple optical ring-cavities

    Science.gov (United States)

    Nguyen, Quang-Viet (Inventor); Kojima, Jun (Inventor)

    2010-01-01

    An optical pulse stretcher and a mathematical algorithm for the detailed calculation of its design and performance is disclosed. The optical pulse stretcher has a plurality of optical cavities, having multiple optical reflectors such that an optical path length in each of the optical cavities is different. The optical pulse stretcher also has a plurality of beam splitters, each of which intercepts a portion of an input optical beam and diverts the portion into one of the plurality of optical cavities. The input optical beam is stretched and a power of an output beam is reduced after passing through the optical pulse stretcher and the placement of the plurality of optical cavities and beam splitters is optimized through a model that takes into account optical beam divergence and alignment in the pluralities of the optical cavities. The optical pulse stretcher system can also function as a high-repetition-rate (MHz) laser pulse generator, making it suitable for use as a stroboscopic light source for high speed ballistic projectile imaging studies, or it can be used for high speed flow diagnostics using a laser light sheet with digital particle imaging velocimetry. The optical pulse stretcher system can also be implemented using fiber optic components to realize a rugged and compact optical system that is alignment free and easy to use.

  17. A theoretical performance study of an external cavity fiber Fabry-Perot interferometer for displacement measurement

    Science.gov (United States)

    Arumugam, Kumar

    The objective of this research is to explore a mathematical model developed by Wilkinson and Pratt for the external cavity fiber-based Fabry-Perot interferometer (EFPI) and to create a Michelson interferometer setup to validate a frequency modulation component of this model. A laser diode with nominal wavelength 635 nm is modulated by oscillating the diode current of maximum amplitude 22.62 mA to create correspondingly varying wavelength. Experiments are included to evaluate a rotating vector representation of the modulation harmonics in the signal received at the photodetector as of a cube corner translated by a piezo-electric actuator is displaced. Wavelength modulation as a function of diode current, the coherence length of the laser, and characteristics of the modulation harmonics are evaluated. A real time DAQ system and two lock-in amplifiers are utilized for detecting three side-band harmonics of the signal. For short range displacements this interferometer setup is monitored using a capacitance displacement sensor. The capacitance displacement measurement differed from the Michelson interferometer by 160 nm. The piezoelectric stage actuated with a 15 V Ramp signal produced 2.54 mum displacement of the cube corner. The setup is tested with Ramp signals of 75 V to 1.5 V and with the Ramp periods of 1 to 20 seconds to find the resolution of the interferometer, modulation of the wavelength sensitivity and the coherence length of the laser as 10.53 nm, 1.786 nm·A-1 and >1 m respectively. The best quadrature signal achieved corresponded to modulating the laser at amplitude of 18.86 mA at 1 kHz frequency with a path length difference of 6.35 mm. The amplitude comparison of side-band harmonics with Bessel function curves is consistent with a modulation amplitude of 1.28 rad corresponding to amplitude ratios of 0.5 (second and first) , 0.15 (third and second) and 0.06 (third and first) in the first through third Bessel function values.

  18. Clinical observation of external dacryocystorhinostomy without packing anastomosis cavity

    Directory of Open Access Journals (Sweden)

    Li-Dan Liu

    2014-10-01

    Full Text Available AIM: To find an efficient and simple surgical procedure of the external dacryocystorhinostomy(EXT- DCRin the treatment of chronic dacryocystitis.METHODS: A total of 270 cases were performed in this retrospective study. A comparison of clinical effects and hemorrhage complications between the experimental group, in which 189 eyes of 167 patients that underwent traditional EXT-DCR without packing, and the control group, in which 121 eyes of 103 patients that underwent traditional EXT-DCR with Vaseline gauze were performed. The postoperative follow-up ranged from 6 to 36mo(the mean follow-up was 15±3.6mo.RESULTS: There were no significant differences in the curative rates between the two groups(97.9% vs 97.5%, P>0.05. But the incidence rate of moderate or severe postoperative nasal bleeding was lower in the experimental group(15.9%, 30 eyesthan the control group(31.4%, 38 eyesand PCONLUSION: The traditional EXT-DCR without packingis an effective procedure and is more effective in reducing moderate or severe postoperative bleeding when the intraoperative anastomose and the postoperative drainage are well done and the intraoperative bleeding is well controlled.

  19. Laser polishing for topography management of accelerator cavity surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Liang [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Klopf, J. Mike [College of William and Mary, Williamsburg, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Kelley, Michael J. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2015-07-20

    Improved energy efficiency and reduced cost are greatly desired for advanced particle accelerators. Progress toward both can be made by atomically-smoothing the interior surface of the niobium superconducting radiofrequency accelerator cavities at the machine's heart. Laser polishing offers a green alternative to the present aggressive chemical processes. We found parameters suitable for polishing niobium in all surface states expected for cavity production. As a result, careful measurement of the resulting surface chemistry revealed a modest thinning of the surface oxide layer, but no contamination.

  20. Selective oxidization cavity confinement for low threshold vertical cavity transistor laser

    Science.gov (United States)

    Wu, M. K.; Liu, M.; Tan, F.; Feng, M.; Holonyak, N.

    2013-07-01

    Data are presented for a low threshold n-p-n vertical cavity transistor laser (VCTL) with improved cavity confinement by trench opening and selective oxidation. The oxide-confined VCTL with a 6.5 × 7.5 μm2 oxide aperture demonstrates a threshold base current of 1.6 mA and an optical power of 150 μW at IB = 3 mA operating at -80 °C due to the mismatch between the quantum well emission peak and the resonant cavity optical mode. The VCTL operation switching from spontaneous to coherent stimulated emission is clearly observed in optical output power L-VCE characteristics. The collector output IC-VCE characteristics demonstrate the VCTL can lase in transistor's forward-active mode with a collector current gain β = 0.48.

  1. Dependence of mis-alignment sensitivity of ring laser gyro cavity on cavity parameters

    Energy Technology Data Exchange (ETDEWEB)

    Sun Feng; Zhang Xi; Zhang Hongbo; Yang Changcheng, E-mail: sunok1234@sohu.com [Huazhong Institute of Electro-Optics - Wuhan National Lab for Optoelectronics, Wuhan, Hubei (China)

    2011-02-01

    The ring laser gyroscope (RLG), as a rotation sensor, has been widely used for navigation and guidance on vehicles and missiles. The environment of strong random-vibration and large acceleration may deteriorate the performance of the RLG due to the vibration-induced tilting of the mirrors. In this paper the RLG performance is theoretically analyzed and the parameters such as the beam diameter at the aperture, cavity mirror alignment sensitivities and power loss due to the mirror tilting are calculated. It is concluded that by carefully choosing the parameters, the significant loss in laser power can be avoided.

  2. A Coupled Cavity Micro Fluidic Dye Ring Laser

    CERN Document Server

    Gersborg-Hansen, M; Mortensen, N A; Kristensen, A

    2004-01-01

    We present a laterally emitting, coupled cavity micro fluidic dye ring laser, suitable for integration into lab-on-a-chip micro systems. The micro-fluidic laser has been successfully designed, fabricated, characterized and modelled. The resonator is formed by a micro-fluidic channel bounded by two isosceles triangle mirrors. The micro-fluidic laser structure is defined using photo lithography in 10 microns thick SU-8 polymer on a glass substrate. The micro fluidic channel is sealed by a glass lid, using PMMA adhesive bonding. The laser is characterized using the laser dye Rhodamine 6G dissolved in ethanol or ethylene glycol as the active gain medium, which is pumped through the micro-fluidic channel and laser resonator. The dye laser is optically pumped normal to the chip plane at 532 nm by a pulsed, frequency doubled Nd:YAG laser and lasing is observed with a threshold pump pulse energy flux of around 55 micro-Joule/square-milimeter. The lasing is multi-mode, and the laser has switchable output coupling into...

  3. Improved Monoblock laser brightness using external reflector.

    Science.gov (United States)

    Hays, A D; Nettleton, John; Barr, Nick; Hough, Nathaniel; Goldberg, Lew

    2014-03-01

    The Monoblock laser has become the laser of choice in long-range, eye-safe laser range finders. It is eye-safe with emission at 1570 nm, high pulse energy, simple construction, and high efficiency when pumped by a laser-diode stack. Although the output beam divergence of a typical Monoblock with a 3  mm×3  mm cross section is relatively large (10-12 mrad), it can be reduced to 2.5× reduction from the unmodified laser. Performance using this technique with various feedback and etalon spacings is presented.

  4. Laser stabilization using saturated absorption in a cavity QED system

    CERN Document Server

    Tieri, D A; Christensen, Bjarke T R; Thomsen, J W; Holland, M J

    2015-01-01

    We consider the phase stability of a local oscillator (or laser) locked to a cavity QED system comprised of atoms with an ultra-narrow optical transition. The atoms are cooled to millikelvin temperatures and then released into the optical cavity. Although the atomic motion introduces Doppler broadening, the standing wave nature of the cavity causes saturated absorption features to appear, which are much narrower than the Doppler width. These features can be used to achieve an extremely high degree of phase stabilization, competitive with the current state-of-the-art. Furthermore, the inhomogeneity introduced by finite atomic velocities can cause optical bistability to disappear, resulting in no regions of dynamic instability and thus enabling a new regime accessible to experiments where optimum stabilization may be achieved.

  5. A laser feedback control design for passive ring laser gyros in a very high finesse cavity

    Science.gov (United States)

    Lorenz, M. A.

    1985-12-01

    The Frank J. Seiler Research Laboratory is currently developing a Passive Resonant Ring Laser Gyroscope (PRRLG) enclosing 58 sq m for proposed use in testing high precision rate sensors and for possibly validating the Theory of General Relativity. The sensitivities required for such experiments are in the 10 to the minus 7th power to 10 to the minus 10th power Earth Rate Unit (ERU) range. This high sensitivity necessitates the use of a large, high finesse cavity. In dealing with high finesse cavities new considerations arise. For example, the cavity linewidth is narrower than linewidths of commercially available stabilized He-Ne lasers. The stability of the laser then becomes the limiting factor in the performance of the PRRLG because of the increased signal-to-noise ratio that arises in this situation. In addition, high finesse cavities exhibit photon lifetimes on the order of 10 to the minus 3rd power to 10 to the minus 6th power seconds, which limits the bandwidth of practical controllers. In this research, a PRRLG was constructed in which a He-Ne laser was frequency locked to 25,000 finesse, 169 sq. cm. resonant cavity, as opposed to the more traditional technique of locking the resonant condition of the cavity to the laser frequency.

  6. Influence of Er:YAG laser ablation on cavity surface and cavity shape

    Science.gov (United States)

    Jelinkova, Helena; Dostalova, Tatjana; Krejsa, Otakar; Hamal, Karel; Kubelka, Jiri; Prochazka, Stanislav

    1996-04-01

    The cavity surface and shape after Er:YAG laser ablation at different energies, number of pulses and at a different repetition rate were observed. Longitudinal sections of extracted human incisors and transverse sections of ivory tusk were cut and polished to flat and glazed surfaces. The samples thickness was from 3 to 5 mm. The Er:YAG laser was operating in a free-running (long pulse) mode. The laser radiation was focused onto the tooth surface by CaF2 lens (f equals 55 mm). During the experiment, the teeth were steady and the radiation was delivered by a special mechanical arm fixed in a special holder; fine water mist was also used (water-mJ/min, a pressure of two atm, air-pressure three atm). The shapes of the prepared cavities were studied either by using a varying laser energies (from 70 mJ to 500 mJ) for a constant number of pulses, or a varying number of pulses (from one to thirty) for constant laser energy. The repetition rate was changed from 1 to 2 Hz. For evaluating the surfaces, shapes, and profiles, scanning electron microscopy and photographs from a light microscope were used. The results were analyzed both quantitatively and qualitatively. It is seen that there is no linear relation between the radiation pulse energy and the size of the prepared holes. With increasing the incident energy the cavity depth growth is limited. There exists some saturation not only in the enamel and dentin but especially in the homogeneous ivory.

  7. Integrated closed-loop cavity of a tunable laser

    Science.gov (United States)

    Ren, M.; Cai, H.; Gu, Y. D.; Chin, L. K.; Radhakrishnan, K.; Ser, W.; Sun, H. D.; Liang, Q. X.; Kwong, D.-L.; Liu, A. Q.

    2016-10-01

    In this paper, a closed-loop cavity of a tunable laser integrated onto a silicon chip is demonstrated. The closed-loop cavity consists of a semiconductor optical amplifier chip, two separated micro-ring resonators, and a U-shaped waveguide sub-loop, enabling dominating lasing in the counterclockwise direction. The lasing wavelength is tuned by varying the effective refractive index of the thermal ring-resonators. It has achieved wide tuning range (55.4 nm), high spectral purity (50-dB side mode suppression ratio), ˜1-mW output power, and 36-dB counter-propagation power suppression ratio. The integrated tunable laser has high potential in applications such as optical network, optical sensing, and integrated optoelectronic systems.

  8. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.

    2012-06-07

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  9. Development of superconducting acceleration cavity technology for free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Min; Lee, Byung Cheol; Kim, Sun Kook; Jeong, Young Uk; Cho, Sung Oh

    2000-10-01

    As a result of the cooperative research between the KAERI and Peking University, the key technologies of superconducting acceleration cavity and photoelectron gun have been developed for the application to high power free electron lasers. A 1.5-GHz, 1-cell superconducting RF cavity has been designed and fabricated by using pure Nb sheets. The unloaded Q values of the fabricated superconducting cavity has been measured to be 2x10{sup 9} at 2.5K, and 8x10{sup 9} at 1.8K. The maximum acceleration gradient achieved was 12 MeV/m at 2.5K, and 20MV/m at 1.8 K. A cryostat for the 1-cell superconducting cavity has been designed. As a source of electron beam, a DC photocathode electron gun has been designed and fabricated, which is composed of a photocathode evaporation chamber and a 100-keV acceleration chamber. The efficiency of the Cs2Te photocathode is 3% nominally at room temperature, 10% at 290 deg C. The superconducting photoelectron gun system developed has been estimated to be a good source of high-brightness electron beam for high-power free electron lasers.

  10. Analysis and Design of Vertical Cavity Surface Emitting Lasers

    Science.gov (United States)

    Yu, S. F.

    2003-08-01

    A practical, hands-on guidebook for the efficient modeling of VCSELs Vertical Cavity Surface Emitting Lasers (VCSELs) are a unique type of semiconductor laser whose optical output is vertically emitted from the surface as opposed to conventional edge-emitting semiconductor lasers. Complex in design and expensive to produce, VCSELs nevertheless represent an already widely used laser technology that promises to have even more significant applications in the future. Although the research has accelerated, there have been relatively few books written on this important topic. Analysis and Design of Vertical Cavity Surface Emitting Lasers seeks to encapsulate this growing body of knowledge into a single, comprehensive reference that will be of equal value for both professionals and academics in the field. The author, a recognized expert in the field of VCSELs, attempts to clarify often conflicting assumptions in order to help readers achieve the simplest and most efficient VCSEL models for any given problem. Highlights of the text include: * A clear and comprehensive theoretical treatment of VCSELs * Detailed derivations for understanding the operational principles of VCSELs * Mathematical models for the investigation of electrical, optical, and thermal properties of VCSELs * Case studies on the mathematical modeling of VCSELs and the implementation of simulation programs

  11. Integrated optoelectronic probe including a vertical cavity surface emitting laser for laser Doppler perfusion monitoring

    NARCIS (Netherlands)

    Serov, Alexander N.; Nieland, Janharm; Oosterbaan, Sjoerd; Mul, de Frits F.M.; Kranenburg, van Herma; Bekman, Herman H.P.Th.; Steenbergen, Wiendelt

    2006-01-01

    An integrated optoelectronic probe with small dimensions, for direct-contact laser Doppler blood flow monitoring has been realized. A vertical cavity surface emitting laser (VCSEL), and a chip with photodetectors and all necessary electronics are integrated in a miniature probe head connected to a l

  12. Integrated Optoelectronic Probe Including a Vertical Cavity Surface Emitting Laser for Laser Doppler Perfusion Monitoring

    NARCIS (Netherlands)

    Serov, A.N.; Nieland, J.; Oosterbaan, S.; Steenbergen, W.; Bekman, H.H.P.T.; Mul, F.F.M. de; Kranenburg, H. van

    2006-01-01

    An integrated optoelectronic probe with small dimensions, for direct-contact laser Doppler blood flow monitoring has been realized. A vertical cavity surface emitting laser (VCSEL), and a chip with photodetectors and all necessary electronics are integrated in a miniature probe head connected to a l

  13. Stable anticipation synchronization in mutually coupled vertical-cavity surface-emitting lasers system

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Two vertical-cavity surface-emitting lasers(VCSELs) are mutually coupled through a partially transparent mirror (PTM) placed in the pathway. The PTM plays the role of external mirror,which controls the feedback strength and coupling strength.We numerically simulate this system by establishing a visible SIMULINK model.The results demonstrate that the anticipation synchronization is achieved and it can tolerate some extent frequency detuning.Moreover,the system shows similar chaos-pass filtering effect on unidirectionally coupled system even both VCSELs are modulated.This system allows simultaneously bidirectional secure message transmission on public channels.

  14. Rate equations model and optical external efficiency of optically pumped electrically driven terahertz quantum cascade lasers

    Science.gov (United States)

    Hamadou, A.; Thobel, J.-L.; Lamari, S.

    2016-10-01

    A four level rate equations model for a terahertz optically pumped electrically driven quantum cascade laser is here introduced and used to model the system both analytically and numerically. In the steady state, both in the presence and absence of the terahertz optical field, we solve the resulting nonlinear system of equations and obtain closed form expressions for the levels occupation, population inversion as well as the mid-infrared pump threshold intensity in terms of the device parameters. We also derive, for the first time for this system, an analytical formula for the optical external efficiency and analyze the simultaneous effects of the cavity length and pump intensity on it. At moderate to high pump intensities, we find that the optical external efficiency scales roughly as the reciprocal of the cavity length.

  15. Role of externally induced coherent superposition in demonstrating quantum nonlocality in a correlated emission laser

    Energy Technology Data Exchange (ETDEWEB)

    Tesfa, Sintayehu [Physics Department, Addis Ababa University, PO Box 1176, Addis Ababa (Ethiopia); Physics Department, Dilla University, PO Box 419, Dilla (Ethiopia)], E-mail: sint_tesfa@yahoo.com

    2008-12-28

    Analysis of the effects of external pumping on the quantum features, including entanglement, quantum nonlocality and nonclassical photon number correlations, of the cavity radiation of a correlated emission laser is presented. It turns out that the contribution of externally induced coherent superposition in demonstrating quantum nonlocality is significant. Despite the available evidence that entangled states can exhibit nonlocality for certain values of the rate at which the atoms are injected into the cavity and amplitude of the driving radiation, a direct relation between the degree of entanglement and quantum nonlocality cannot be established. However, it seems likely to make a consistent connection between the Cauchy-Schwarz and Bell-Clauser-Horne-Shimony-Holt inequalities. It is evident that comparison among various nonclassical correlations enhances the understanding of the otherwise intricate quantum theoretical predictions.

  16. Symptomatic hemangioma of oral cavity treated with CO2 laser

    Science.gov (United States)

    Nicola, Ester M. D.; Coutinho, Adriana A.; Nicola, Jorge H.; Gusmao, Reinaldo J.

    1995-05-01

    The CO2 laser has been used by our group as a secure and efficient tool for the treatment of symptomatic oral cavity hemangiomas which can be responsible for disturbance for swallowing, phonation and in hygienic, besides discomfort and bleeding to patients. During the last four years, twelve patients with symptomatic oral cavity hemangioma were treated at the Laser Unit of our University. The treatment consisted in the application of CO2 laser at medium to low intensity according to characteristics and location of the lesions. For hemangiomas located at sites of easy surgical access such as anterior 1/3 of the tongue, lips, bucal vestibule we use 10 to 37 J/mm2 over the surface of the lesion. When the hemangioma was located at difficult surgical access sites, such as, tonsils, posterior 1/3 of tongue, or at pharyngeal wall we used 3.0 to 4.0 J/mm2 encircling the whole hemangioma. This causes reduction in the size of the lesion throughout sclerosis of nutrition vessels. After this initial procedure we applied 0.8 to 1.0 J/mm2 over the whole extent of the lesion. For both procedures we observed no significant bleeding or inflammatory reaction. The patients referred minimal post-operative discomfort with good cicatricial evolution. The evident reduction in the vascularization and size could be confirmed by photographic documentation. The good results described above, with disappearance of symptoms lead to the conclusion that CO2 laser is an efficient and secure method of treatment for symptomatic hemangioma of the oral cavity.

  17. Realization of 1.5 W 780 nm single-frequency laser by using cavity-enhanced frequency doubling of an EDFA boosted 1560 nm diode laser

    Science.gov (United States)

    Ge, Yulong; Guo, Shanlong; Han, Yashuai; Wang, Junmin

    2015-01-01

    We demonstrated a continuous-wave (CW) 780 nm laser with Watt-level output power by using external-cavity-enhanced frequency doubling of an Erbium-doped fiber amplifier (EDFA) boosted 1560 nm diode laser in a periodically-poled magnesium-oxide-doped lithium niobate (PPMgO:LN) bulk crystal. A 780 nm laser with maximum output power of 1.5 W is obtained at an incident 1560 nm laser of 2.05 W, corresponding to a doubling efficiency of 73%. The typical fluctuation of 780 nm laser's power is 1.2% (rms) in about 30 min. This 780 nm laser can be potentially applied to laser cooling and manipulation of rubidium atoms, generating 1560 nm squeezed vacuum field as well as 1560 nm continuous-variable entanglement based on optical parametric oscillator if additional locking and noise suppression is applied.

  18. 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.

  19. Novel laser machining of optical fibers for long cavities with low birefringence

    CERN Document Server

    Takahashi, Hiroki; Orucevic, Fedja; Noguchi, Atsushi; Kassa, Ezra; Keller, Matthias

    2015-01-01

    We present a novel method of machining optical fiber surfaces with a CO${}_2$ laser for use in Fiber-based Fabry-Perot Cavities (FFPCs). Previously FFPCs were prone to large birefringence and limited to relatively short cavity lengths ($\\le$ 200 $\\mu$m). These characteristics hinder their use in some applications such as cavity quantum electrodynamics with trapped ions. We optimized the laser machining process to produce large, uniform surface structures. This enables the cavities to achieve high finesse even for long cavity lengths. By rotating the fibers around their axis during the laser machining process the asymmetry resulting from the laser's transverse mode profile is eliminated. Consequently we are able to fabricate fiber mirrors with a high degree of rotational symmetry, leading to remarkably low birefringence. Through measurements of the cavity finesse over a range of cavity lengths and the polarization dependence of the cavity linewidth, we confirmed the quality of the produced fiber mirrors for us...

  20. High Q-factor micro-cavity laser: Fabrication and lasing emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Pham Van Hoi; Ha Xuan Vinh; Chu Thi Thu Ha; Tran Thi Cham [Institute of Materials Science, Vietname Academy of Science and Technology 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam); Bui Van Thien [Faculty of Natural Science, College of Medicine, Thai Nguyen (Viet Nam); Gruzintsev, A N [Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences (IPMT-RAS) (Russian Federation)], E-mail: hoipv@ims.vast.ac.vn

    2009-09-01

    In this article the fabrication method and lasing emission properties of High-Q micro-cavity lasers based on High-concentration Erbium-doped silica-alumina glasses are presented in detail. The configurations of micro-cavities were spherical and/or modified toroidal forms. The lasing threshold of micro-cavity laser pumped by laser diodes was of hundred micro-watts and Q-factor of cavity had been achieved up-to 10{sup 8} in experiment. The emission power of one whispering-gallery-mode (WGM) lasing from micro-cavity laser was of 0.05-0.5 mW that would be enough for applying in the quantum information and optical sensor techniques. The modified toroidal micro-cavity permits to decrease the polar-mode of WGMs, which help to obtain the single-mode emission from micro-cavity lasers.

  1. Ultralow Threshold Red Vertical-Cavity Surface-Emitting Lasers

    Institute of Scientific and Technical Information of China (English)

    程澎; 高俊华; 康学军; 林世鸣; 张光斌; 刘世安; 胡国新

    2000-01-01

    Visible Vertical-cavity Surface-emitting Lasers (VCSELs) have been designed and fabricated by using metalorganic vapor phase epitaxy. Using the 8λ optical cavities with 3 quan tum wells in A1GaInP/AlGaAs VCSEL's to reduce the drift leakage current and enhance the model gain, the device can operate continuous wave at wavelength of 670nm. For better performance, a misoriented (100) substrate (6~10° to (110)) has been used to reduce the ordering of AlGaInP. However, as the angle of misorientation increased, the symmetry of the structure became worse. This made it difficult to achieve little aperture device. By using 45° rotated selective oxidation method, a little aperture (1 × 1μm2) device with low threshold of 0.25mA can operate continuous wave at room temperature.

  2. 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.

  3. 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.

  4. Optimal design of radial Bragg cavities and lasers.

    Science.gov (United States)

    Ben-Bassat, Eyal; Scheuer, Jacob

    2015-07-01

    We present a new and optimal design approach for obtaining maximal confinement of the field in radial Bragg cavities and lasers for TM polarization. The presented approach outperforms substantially the previously employed periodic and semi-periodic design schemes of such lasers. We show that in order to obtain maximal confinement, it is essential to consider the complete reflection properties (amplitude and phase) of the propagating radial waves at the interfaces between Bragg layers. When these properties are taken into account, we find that it is necessary to introduce a wider ("half-wavelength") layer at a specific radius in the "quarter-wavelength" radial Bragg stack. It is shown that this radius corresponds to the cylindrical equivalent of Brewster's angle. The confinement and field profile are calculated numerically by means of transfer matrix method.

  5. Use of laser diodes in cavity ring-down spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zare, R.N.; Paldus, B.A.; Ma, Y.; Xie, J. [Stanford Univ., CA (United States)

    1997-12-31

    We have demonstrated that cavity ring-down spectroscopy (CRDS), a highly sensitive absorption technique, is versatile enough to serve as a complete diagnostic for materials process control. In particular, we have used CRDS in the ultraviolet to determine the concentration profile of methyl radicals in a hot-filament diamond reactor; we have applied CRDS in the mid-infrared to detect 50 ppb of methane in a N{sub 2} environment; and, we have extended CRDS so that we can use continuous-wave diode laser sources. Using a laser diode at 810 nm, we were able to achieve a sensitivity of 2 x 10{sup -8} cm{sup -1}. Thus, CRDS can be used not only as an in situ diagnostic for investigating the chemistry of diamond film deposition, but it can also be used as a gas purity diagnostic for any chemical vapor deposition system.

  6. Noise Effects in the Mode-Locked External Cavity Lasers

    Institute of Scientific and Technical Information of China (English)

    Nuran Dogru; M. Sadettin Ozyazici

    2003-01-01

    Effect of high level of spontaneous and carrier noise on mode-locked hybrid soliton pulse source and relative intensity noise is described. Transform limited pulses are not generated over a wide frequency range because of these noises.

  7. Evolution of the Novalux extended cavity surface-emitting semiconductor laser (NECSEL)

    Science.gov (United States)

    McInerney, John G.

    2016-03-01

    Novalux Inc was an enterprise founded by Aram Mooradian in 1998 to commercialise a novel electrically pumped vertical extended cavity semiconductor laser platform, initially aiming to produce pump lasers for optical fiber telecommunication networks. Following successful major investment in 2000, the company developed a range of single- and multi-mode 980 nm pump lasers emitting from 100-500 mW with excellent beam quality and efficiency. This rapid development required solution of several significant problems in chip and external cavity design, substrate and DBR mirror optimization, thermal engineering and mode selection. Output coupling to single mode fiber was exceptional. Following the collapse of the long haul telecom market in late 2001, a major reorientation of effort was undertaken, initially to develop compact 60-100 mW hybrid monolithically integrated pumplets for metro/local amplified networks, then to frequency-doubled blue light emitters for biotech, reprographics and general scientific applications. During 2001-3 I worked at Novalux on a career break from University College Cork, first as R&D Director managing a small group tasked with producing new capabilities and product options based on the NECSEL platform, including high power, pulsed and frequency doubled versions, then in 2002 as Director of New Product Realization managing the full engineering team, leading the transition to frequency doubled products.

  8. An inductively heated hot cavity catcher laser ion source

    CERN Document Server

    Reponen, M; Pohjalainen, I; Rothe, S; Savonen, M; Sonnenschein, V; Voss, A

    2015-01-01

    An inductively heated hot cavity catcher has been constructed for the production of low-energy ion beams of exotic, neutron-deficient Agisotopes. A proof-of-principle experiment has been realized by implanting primary 107Ag21+ ions from a heavy-ion cyclotron into a graphite catcher. A variable-thickness nickel foil was used to degrade the energy of the primary beam in order to mimic the implantation depth expected from the heavy-ion fusion-evaporation recoils of N = Z94Ag. Following implantation, the silver atoms diffused out of the graphite and effused into the catcher cavity and transfer tube, where they were resonantly laser ionized using a three-step excitation and ionization scheme. Following mass separation, the ions were identified by scanning the frequency of the first resonant excitation step while recording the ion count rate. Ion release time profiles were measured for different implantation depths and cavity temperatures with the mean delay time varying from 10 to 600 ms. In addition, the diffusio...

  9. Transoral laser resections of oral cavity and oropharyngeal tumors

    Directory of Open Access Journals (Sweden)

    M. V. Bolotin

    2016-01-01

    Full Text Available The incidence of squamous cell carcinoma of the head and neck remains high and ranks tenth in the structure of overall cancer morbidity. Surgical radicality has remained one of the major determinants of the long-term results of treatment so far. In the period December 2014 to January 2016, our clinic performed surgical interventions as transoral laser oral cavity and oropharyngeal resections using carbon dioxide (CO2 laser in 34 patients. Tumors are most commonly located in the area of the tongue root and oropharynx in 16 (47.1 % patients, tongue (its anterior two thirds in 14 (41.2 %, and mouth floor in 4 (11.7 %. The average length of hospital stay after transoral laser resections was 10.14 days. A nasogastric tube was postoperatively placed in 6 (17.6 % patients for 8 to 17 days. According to the results of planned histological examination, surgical interventions were microscopically radical in all cases. Transoral CO2 laser resections make possible to perform rather large radical surgical interventions with a satisfactory functional and cosmetic results, without deteriorating the long-term results of treatment. 

  10. An Efficient Photon Conversion Efficiency Ammonia Terahertz Cavity Laser

    Institute of Scientific and Technical Information of China (English)

    QI Chun-Chao; ZUO Du-Luo; Lu Yan-Zhao; TANG Jian; YANG Chen-Guang; KE Lin-Da; CHENG Zu-Hai

    2009-01-01

    An efficient ammonia terahertz(THz)cavity laser is reported experimentally.Unlike the past design schemes such as hole couplers and freestanding mesh couplers,in our systems the input and output couplers are fabricated by depositing nickel capacitive metallic meshes on ZnSe and high-resistivity silicon substrates.Thus the couplers not only can be constructed as an F-P oscillator but also can be used as sealed windows that are easier to perform the adjustment of alignment with.To enhance THz laser output energy and photon conversion efficiency,the dominant factors such as pump intensity and gas pressure are investigated experimentally.Finally,a 1.35 mJ terahertz radiation of ammonia laser with 90μm wavelength(3.33THz)operating at 1.09kPa pumped by a 402mJ TEA CO_2 laser with 9R(16)line is generated,and photon conversion efficiencies of 6.5% are achieved.

  11. Laser-assisted cavity preparation and adhesion to erbium-lased tooth structure: part 1. Laser-assisted cavity preparation.

    Science.gov (United States)

    De Moor, Roeland Jozef Gentil; Delmé, Katleen Ilse Maria

    2009-12-01

    The use of the ruby laser (693.4 nm) was first described in 1960, and it was applied for hard tissue ablation in 1964. Different wavelengths [Nd:YAG (1.065 microm), CO2 (9.6 microm), Ho:YAG (2.12 microm)] were consequently explored. Due to massive thermal side effects, these wavelengths caused increased temperature in dental pulp, as well as microcracks and carbonization. The use of this laser for dental hard tissue preparation was eventually abandoned. At the end of the 1980s, excimer lasers (ultraviolet) and the erbium laser (infrared) were developed, with the advantages of improved temperature control and smaller penetration depths. With the development of smaller devices and improved knowledge of how to limit damage to the surrounding tissues, new ablation techniques were established in the 1990s. There is still contradiction in the current literature, however, in that different wavelengths are advocated for hard tissue removal, and heterogeneity in laser parameters and power densities remain. In this review, the effects of the wavelengths presently used for cavity preparation are evaluated. We conclude that erbium lasers (Er:YAG and Er,Cr:YSGG) are most efficient and, with the right parameters, the thermal side effects are small. There is a substantial need for "gold standards", although this is difficult to establish in practice owing to different laser parameters (including pulse repetition rate, amount of cooling, energy delivered per pulse, and types of pulses) and target specificity (tissue interaction with sound or decayed enamel or dentin, and the extent of (de)mineralization) which influence tissue interaction.

  12. 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.

  13. Dual-cavity Nd:YAG laser with Laguerre-Gaussian (LG0n) mode output

    Science.gov (United States)

    Kim, D. J.; Kim, J. W.

    2017-01-01

    Direct excitation of an arbitrary Laguerre-Gaussian (LG0n) mode with helical wavefronts in a diode-end-pumped solid state laser employing a dual-cavity configuration is reported. Through simple adjustments of the intra-cavity apertures in the dual-cavity laser configuration, the spatial gain distribution and the cavity loss could be optimized for the targeted LG0 n mode. This approach has been applied to a diode-pumped Nd: YAG laser to achieve selective lasing of the LG01, LG02, and LG03 modes. Also, an optical vortex laser beam was produced directly from the laser resonator by determining the wavefront handedness of each LG mode output using an intra-cavity etalon. The prospects of further power scaling and laser performance improvements will be discussed.

  14. Laser of optical fiber composed by two coupled cavities: application as optical fiber sensor; Laser de fibra optica compuesto por dos cavidades acopladas: aplicacion como sensor de fibra optica

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez S, R.A.; Kuzin, E.A.; Ibarra E, B. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), A.P. 51 y 216, 72000 Puebla (Mexico); May A, M. [Universidad Autonoma del Carmen (UNACAR) Av. 56 No. 4 por Av. Concordia, Campeche (Mexico); Shlyagin, M.; Marquez B, I. [Centro de Investigacion Cientifica y de Ensenanza Superior de Ensenada (CICESE), 22860 Ensenada, Baja California (Mexico)]. e-mail: ravsa100@hotmail.com

    2004-07-01

    We show an optical fiber laser sensor which consist of two cavities coupled and three fiber Bragg gratings. We used one Bragg grating (called reference) and two Bragg gratings (called sensors), which have the lower reflection wavelength. The reference grating with the two sensors grating make two cavities: first one is the internal cavity which has 4230 m of length and the another one is the external cavity which has 4277 m of length. Measuring the laser beating frequency for a resonance cavity and moving the frequency peaks when the another cavity is put in resonance, we prove that the arrangement can be used as a two points sensor for determining the difference of temperature or stress between these two points. (Author)

  15. 100 GHz Externally Modulated Laser for Optical Interconnects Applications

    DEFF Research Database (Denmark)

    Ozolins, Oskars; Pang, Xiaodan; Iglesias Olmedo, Miguel

    2017-01-01

    We report on a 116 Gb/s on-off keying (OOK), four pulse amplitude modulation (PAM) and 105-Gb/s 8-PAM optical transmitter using an InP-based integrated and packaged externally modulated laser for high-speed optical interconnects with up to 30 dB static extinction ratio and over 100-GHz 3-d...

  16. Optical feedback characteristics in a dual-frequency laser during laser cavity tuning

    Institute of Scientific and Technical Information of China (English)

    Liu Gang; Zhang Shu-Lian; Li Yan; Zhu Jun

    2005-01-01

    The optical feedback characteristics in a Zeeman-birefringence dual-frequency laser are studied during the laser cavity tuning in three different kinds of optical feedback conditions: (i) only //-light is fed back; (ii) only (┴)-light is fed back; (iii) both lights are fed back. A compact displacement sensor is designed using the experimental result that there is a nearly 90 degrees phase delay between the two lights' cosine optical feedback signals when both lights are fed back into the laser cavity. The priority order that the two lights' intensity curves appear can be used for direction discrimination. The resolution of the displacement sensor is at least 79 nm, and the sensor can discriminate the target's moving direction easily.

  17. Effect of External Radiation Filed on the Properties of the Atoms and Cavity Field in the Tavis-Cummings Model

    Institute of Scientific and Technical Information of China (English)

    王忠纯

    2004-01-01

    @@ We study the properties of the atoms and cavity field in the Tavis-Cummings Model where the two atoms interact each other and also are driven by an external classical field.We consider the special case that the cavity is initially in a coherent state.After work out the atomic inversion, the average photons number and the Mandel parameter in the driven Tavis-Cummings Model, we do numerical analysis of them, and pay special attention to the dynamical behavior of the atoms and the cavity field modified by the external field.

  18. Widely tunable linear-cavity multiwavelength fiber laser with distributed Brillouin scattering

    Institute of Scientific and Technical Information of China (English)

    M. Ajiya; M. H. Al-Mansoori; M. A. Mahdi

    2011-01-01

    We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration. The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end. Due to the weak reflectivity provided by the virtual mirror, self-lasing cavity modes are completely suppressed from the laser cavity. At Brillouin pump and 1480-nm pump powers of 2 and 130 mW, respectively, 11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.%@@ We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration.The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end.Due to the weak reflectivity provided by the virtual mirror, self-lasing cavity modes are completely suppressed from the laser cavity.At Brillouin pump and 1480-nm pump powers of 2 and 130 mW, respectively, 11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.

  19. Digital control of laser modes with an intra-cavity spatial light modulator

    CSIR Research Space (South Africa)

    Ngcobo, S

    2014-02-01

    Full Text Available In this paper we outline a simple laser cavity which produces customised on-demand digitally controlled laser modes by replacing the end-mirror of the cavity with an electrically addressed reflective phase-only spatial light modulator as a digital...

  20. Compact intra-cavity frequency doubled line beam green laser by a laser diode array pumped

    Science.gov (United States)

    Yan, Boxia; Qi, Yan; Wang, Yanwei

    2016-10-01

    Compact, high power, and low-cost green laser light sources are needed in projection-related applications such as digital cinema, rear-projection television, simulators, and command and control stations. We report a LD array directly pumped intracavity SHG Nd:YVO4/PPMgLN laser without lens or waveguide in this letter. A compact 3.12 W green laser was demonstrated by intra-cavity frequency doubled using a PPMgLN bulk crystal by a 19-emitter LD array pumped(single bar), the conversion efficiency from input LD array was 9.2%. A line-beam output suitable for laser projectors was generated, which has the potential to be scalable to small volumes and low costs for laser projection displays.

  1. Single transverse mode selectively oxidized vertical cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    CHOQUETTE,KENT D.; GEIB,KENT M.; BRIGGS,RONALD D.; ALLERMAN,ANDREW A.; HINDI,JANA JO

    2000-04-26

    Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.

  2. Laser-induced autofluorescence of oral cavity hard tissues

    Science.gov (United States)

    Borisova, E. G.; Uzunov, Tz. T.; Avramov, L. A.

    2007-03-01

    In current study oral cavity hard tissues autofluorescence was investigated to obtain more complete picture of their optical properties. As an excitation source nitrogen laser with parameters - 337,1 nm, 14 μJ, 10 Hz (ILGI-503, Russia) was used. In vitro spectra from enamel, dentine, cartilage, spongiosa and cortical part of the periodontal bones were registered using a fiber-optic microspectrometer (PC2000, "Ocean Optics" Inc., USA). Gingival fluorescence was also obtained for comparison of its spectral properties with that of hard oral tissues. Samples are characterized with significant differences of fluorescence properties one to another. It is clearly observed signal from different collagen types and collagen-cross links with maxima at 385, 430 and 480-490 nm. In dentine are observed only two maxima at 440 and 480 nm, related also to collagen structures. In samples of gingival and spongiosa were observed traces of hemoglobin - by its re-absorption at 545 and 575 nm, which distort the fluorescence spectra detected from these anatomic sites. Results, obtained in this study are foreseen to be used for development of algorithms for diagnosis and differentiation of teeth lesions and other problems of oral cavity hard tissues as periodontitis and gingivitis.

  3. The use of nonlinear dynamics of erbium-doped fiber laser at pump modulation for intra-cavity sensing

    Science.gov (United States)

    Arellano-Sotelo, H.; Kir'yanov, A. V.; Barmenkov, Yu. O.; Aboites, V.

    2011-02-01

    We report the use of nonlinear dynamics of an erbium-doped fiber laser (EDFL) at pump modulation, namely the period-1 pulsed regime, for intra-cavity loss sensing and demonstrate noticeable sensitivity enhancement of an EDFL-based sensor, provided by this arrangement. Experimentally, we obtain a ten-fold increase of the sensor response, i.e. peak-to-peak pulse amplitude against loss variation, as compared with the standard sensing schemes using a low-power wide-spectrum light emitting diode (LED) or fiber laser without external modulation. This advantage originates from a strong dependence of pulse amplitude in the period-1 regime on intra-cavity loss variable that is, in turn, determined by the interrelation of relaxation frequency (an internal EDFL parameter) and frequency and depth of external (pump) modulation. A modeling of the EDFL-based sensor, presented for the case when the laser operates in the period-1 regime, allows an insight into the sensor operation details and opens the gate to its further optimization. The proposed sensing method seems to be a proper choice for the applications where an intra-cavity sensor's head has high internal loss (≥10 dB) while sensed loss is varied within a quite narrow range (a few dB).

  4. Microprocessor based interface unit for coupling a picosecond laser oscillator with external laser amplifiers

    Science.gov (United States)

    Navathe, C. P.; Ansari, M. S.; Upadhyaya, J.; Sreedhar, N.; Chandra, R.; Kumbhare, S. R.; Chakera, J. A.; Gupta, P. D.

    1996-07-01

    A microprocessor based interface unit for coupling a commercial picosecond Nd:YLF laser oscillator amplifier to external high power Nd:phosphate glass laser amplifier stages is described. The system generates charging and firing signals required for the picosecond oscillator, and also carries out the charging and firing sequence of external amplifiers for a single shot or a repetitive mode of operation. The electronics developed is simple and modular, with sufficient scope for expansion of the system, and resistant to electromagnetic interference.

  5. Microleakage of composite resin restoration in cavities prepared by Er,Cr:YSGG laser irradiation and etched bur cavities in primary teeth.

    Science.gov (United States)

    Hossain, Mozammal; Nakamura, Yukio; Yamada, Yoshishige; Murakami, Yoshiko; Matsumoto, Koukichi

    2002-01-01

    In this in vitro study, the surface alterations of enamel and dentin in cavities prepared by Er,Cr:YSGG laser irradiation was investigated by scanning electron microscopy and compared to the microleakage degree after composite resin restoration with etched bur cavities in human primary teeth. The results confirmed that laser cavity surface facilitated a good adhesion with the restorative materials; the acid etch step can be easily avoided with the laser treatment.

  6. Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gargas, D.J.; Toimil-Molares, M.E.; Yang, P.

    2008-11-17

    We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal microscopy. In addition, three-dimensional (3D) mapping of the photoluminescence emission performed in both planar and vertical dimensions demonstrates height-selective imaging useful for vertical nanowires and heteronanostructures emerging in the field of optoelectronics and nanophotonics.

  7. Noise-cancelled, cavity-enhanced saturation laser spectroscopy for laser frequency stabilisation

    Energy Technology Data Exchange (ETDEWEB)

    Vine, Glenn de; McClelland, David E; Gray, Malcolm B [Centre for Gravitational Physics, Faculty of Science, Australian National University, Canberra, ACT 0200 (Australia)

    2006-03-02

    We employ a relatively simple experimental technique enabling mechanical-noise free, cavityenhanced spectroscopic measurements of an atomic transition and its hyperfine structure. We demonstrate this technique with the 532 nm frequency doubled output from a Nd:YAG laser and an iodine vapour cell. The resulting cavity-enhanced, noise-cancelled, iodine hyperfine error signal is used as a frequency reference with which we stabilise the frequency of the 1064nm Nd:YAG laser. Preliminary frequency stabilisation results are then presented.

  8. Vertical-Cavity Surface-Emitting Lasers: Advanced Modulation Formats and Coherent Detection

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto

    transmission link with real-time demodulation. Furthermore, advanced modulation formats are considered in this thesis to expand the state-of-the-art in high-speed short-range data transmission system based on VCSELs. First, directly modulation of a VCSEL with a 4-level pulse amplitude modulation (PAM-4) signal......This thesis expands the state-of-the-art in coherent detection for optical fiber access networks employing vertical-cavity surface-emitting lasers (VCSELs) as light sources. Bit rates up to 10 Gb/s over 25 km single-mode fibre (SMF) transmission distance have been achieved supporting a passive...... generation optical fiber access networks regarding long reach, high splitting ratio, no optical amplification, no external modulation, and use of a single fiber for upstream and downstream transmission. An important contribution of this thesis is the novel concept of chirpassisted coherent detection...

  9. High-resolution birefringence cartography of a vertical cavity semiconductor laser

    CERN Document Server

    Wang, T

    2015-01-01

    We report on spatially resolved birefringence measurements in a multimode vertical-cavity surface-emitting laser (VCSEL) by using the emission wavelength distribution mapping. The point-by-point, polarization-resolved spectral information lends itself to the identification of anisotropies in the material and enables the estimate of refractive index differences and gradients in the two orthogonal polarization components with high spatial resolution. Compared with classical optical microscopy techniques, we can easily recognize the position of the emission wavelength split (which carefully points to the position of defects) with a much better spectral sensitivity (potentially as low as 3 GHz). The presented method is general and can be used with any bulk, light-emitting source (even passive, if external illumination is added) and may prove very useful for device fabrication, quality checks and process improvements.

  10. Bistable Output from a Coupled-Resonator Vertical-Cavity Laser Diode

    Energy Technology Data Exchange (ETDEWEB)

    FISCHER,ARTHUR J.; CHOQUETTE,KENT D.; CHOW,WENG W.; ALLERMAN,ANDREW A.; GEIB,KENT M.

    2000-07-20

    The authors report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits bistable behavior in the light output versus injection current. Large bistability regions over current ranges as wide as 18 mA have been observed with on/off contrast ratios of greater than 20 dB. The position and width of the bistability region can be varied by changing the bias to the top cavity. Switching between on and off states can be accomplished with changes as small as 250 {micro}W to the electrical power applied to the top cavity. Theoretical analysis suggests that the bistable behavior is the response of the nonlinear susceptibility in the top cavity to the changes in the bottom intracavity laser intensity as the bottom cavity reaches the thermal rollover point.

  11. III-V/SOI vertical cavity laser structure for 120 Gbit/s speed

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Mørk, Jesper;

    2015-01-01

    Ultrashort-cavity structure for III-V/SOI vertical cavity laser with light output into a Si waveguide is proposed, enabling 17 fJ/bit efficiency or 120 Gbit/s speed. Experimentally, 27-GHz bandwidth is demonstrated at 3.5 times of threshold. © 2015 OSA.......Ultrashort-cavity structure for III-V/SOI vertical cavity laser with light output into a Si waveguide is proposed, enabling 17 fJ/bit efficiency or 120 Gbit/s speed. Experimentally, 27-GHz bandwidth is demonstrated at 3.5 times of threshold. © 2015 OSA....

  12. Laser ablation of titanium in liquid in external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Serkov, A.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); The Federal State Educational Institution of Higher Professional Education, “Moscow Institute of Physics and Technology (State University)”, 9 Institutskiy per., 141700, Dolgoprudny, Moscow Region (Russian Federation); Barmina, E.V., E-mail: barminaev@gmail.com [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31, Kashirskoye Highway, 115409 Moscow (Russian Federation); Voronov, V.V. [A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation)

    2015-09-01

    Highlights: • Ablation of a bulk Ti target by 10 ps laser pulses in liquid is experimentally studied in external DC electric field. • Applied cathodic bias leads to increase in average size of self-organized nanostructures formed upon ablation of titanium target. • Laser ablation of Ti target in external electric field results in generation of elongated titanium oxide nanoparticles. - Abstract: Ablation of a bulk Ti target by 10 ps laser pulses in water is experimentally studied in external DC electric field. It is demonstrated that both lateral size of nanostructures (NS) on Ti surface and their density depend on the electric field applied to the target. Scanning Electron Microscopy of NS reveals the shift of their size distribution function toward larger sizes with applied field (cathodic bias, 25 V DC). Density of mushroom-like NS with applied electric field amounts to 10{sup 10} cm{sup −2}. X-ray diffraction of generated nanoparticles (NPs) shows difference in the crystallographic structure of NPs of non-stoichiometric Ti oxides generated with and without electric field. This conclusion is corroborated with the optical absorption spectroscopy of obtained colloids. Transmission Electron Microscopy of NPs also shows difference in morphology of particles produced with and without cathodic bias. The results are interpreted on the basis of instability of the melt on Ti surface in the electric field.

  13. A method for cleaning optical precision surface of laser gyro cavity

    Science.gov (United States)

    Cui, Ying; Jiao, Ling Yan; Lin, Na Na; Zhang, Dong

    2016-10-01

    Laser gyro is the only one non-electromechanical high-precision inertial sensitive instruments in aircraft inertial guidance systems. Ultra high vacuum acquisition is a key segment during the manufacturing process of laser gyro. The surface cleanliness and integrity have decisive influence on the sealing performance of ultra-high vacuum. A cleaning technology for the optical surface of laser gyro cavity was found by experiment. Meanwhile, the analysis of the adsorption mechanism of contaminant on the laser gyro cavity surface and overview of common optical element cleaning technology were given. The result showed that the new cleaning technology improved the cleanliness of the cavity optical surface without any damage and provided a reliable solution for chronic leak of high precision laser gyro cavity.

  14. Design and Fabrication of Externally heated Copper Bromide Laser

    Directory of Open Access Journals (Sweden)

    J.P. Dudeja

    1993-04-01

    Full Text Available An externally-heated, longitudinally-discharged, low-repetition-rate copper bromide laser, was designed and fabricated. The green-coloured wavelength at 5106 A from this laser can be used for underwater ranging and detection of submerged objects. Several new changes in the design of discharge tube, heating technique, buffer-gas-flow sub-system and electrical circuit have been conceived and incorporated advantageously in our system. Various parameters, for example, the type of buffer gas and its flow rate, mixture of gases, temperature of the discharge tube, delay between dissociation and excitation pulses, dissociation and excitation energies, and various resonator configurations are being optimised to get the maximum output power/energy from the laser system.

  15. Laser heating of a cavity versus a plane surface for metal targets utilizing photothermal deflection measurements

    Science.gov (United States)

    Jeong, S. H.; Greif, R.; Russo, R. E.

    1996-08-01

    The effects of a cylindrical cavity in a metal surface on the energy coupling of a laser beam with the solid were investigated by using a photothermal deflection technique. The photothermal deflection of a probe beam over the cavity was measured while the bottom of the cavity was heated with a Nd-YAG laser with a wavelength of 1064 nm. Cavities in three different materials and with two different aspect ratios were used for the experiment. Temperature distributions in the solid and the surrounding air were computed numerically and used to calculate photothermal deflections for cavity heating and for plane surface heating. Reflection of the heating laser beam inside the cavity increased the photothermal deflection amplitude significantly with larger increases for materials with larger thermal diffusivity. The computed photothermal deflections agreed more closely with the experimental results when reflection of the heating laser beam inside the cavity was included in the numerical model. The overall energy coupling between a heating laser and a solid is enhanced by a cavity.

  16. Study of evaluation methods for in-vessel corium retention through external vessel cooling and safety of reactor cavity

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Hoon; Chang, Soon Heung; Kim, Soo Hyung; Kim, Kee Poong; Lee, Hyoung Wook; Jang, Kwang Keol; Jeong, Yong Hoon; Kim, Sang Jin; Lee, Seong Jin [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of); Park, Jae Hong [Korea Institute of Nuclear Safety, Taejon (Korea, Republic of)

    2001-03-15

    In this work, assessment system for methodology for reactor pressure vessel integrity is developed. Assessment system is make up of severe accident assessment code which can calculate the conditions of plant and structural analysis code which can assess the integrity of reactor vessel using given plant conditions. An assessment of cavity flooding using containment spray system has been done. As a result, by the containment spray, cavity can be flooded successfully and CCI can be reduced. The technical backgrounds for external vessel cooling and corium cooling on the cavity are summarized and provided in this report.

  17. Effectiveness of Er:YAG laser in cavity preparation for retrograde filling--in vitro study.

    Science.gov (United States)

    Karlović, Zoran; Grgurević, Lovro; Verzak, Zeljko; Modrić, Vesna-Erika; Sorić, Pjetra; Grgurević, Josko

    2014-06-01

    The purpose of this study was to determine the sealing quality of Super EBA cement in laser prepared root-end cavities in comparison with root-end cavities classically prepared with steel burrs. Two groups of three millimeter root sections were prepared. The first group was prepared with the Er:YAG laser and the second group with a steel burr mounted on a surgical handpiece. The sections were filled with Super EBA cement and tested for leakage with fluid transport techniques. The sealing quality of Super EBA cement in the classically prepared root-end cavities was better, but there was no statistically significant difference between the two preparation techniques. The possible reason for greater leakage in the laser prepared root-end cavities was probably the irregular shape of the root-end cavity.

  18. A simple model for cavity-enhanced laser-driven ion acceleration from thin foil targets

    CERN Document Server

    Rączka, Piotr

    2012-01-01

    A scenario for the laser-driven ion acceleration off a solid target is considered, where the reflected laser pulse is redirected towards the target by reflection at the inner cavity wall, thus recycling to some extent the incident laser energy. This scenario is discussed in the context of sub-wavelength foil acceleration in the radiation pressure regime, when plasma dynamics is known to be reasonably well described by the laser-sail model. A semi-analytic extension of the 1D laser-sail model is constructed, which takes into account the effect of reflections at the inner cavity wall. The effect of cavity reflections on sub-wavelength foil acceleration is then illustrated with two concrete examples of intense laser pulses of picosecond and femtosecond duration.

  19. Relaxation oscillations, stability, and cavity feedback in a superradiant Raman laser

    CERN Document Server

    Bohnet, Justin G; Weiner, Joshua M; Cox, Kevin C; Thompson, James K

    2012-01-01

    We experimentally study the relaxation oscillations and amplitude stability properties of an optical laser operating deep into the bad-cavity regime using a laser-cooled $^{87}$Rb Raman laser. By combining measurements of the laser light field with non-demolition measurements of the atomic populations, we infer the response of the the gain medium represented by a collective atomic Bloch vector. The results are qualitatively explained with a simple model. Measurements and theory are extended to include the effect of intermediate repumping states on the closed-loop stability of the oscillator and the role of cavity-feedback on stabilizing or enhancing relaxation oscillations. This experimental study of the stability of an optical laser operating deep into the bad-cavity regime will guide future development of superradiant lasers with ultranarrow linewidths.

  20. Relaxation oscillations, stability, and cavity feedback in a superradiant Raman laser.

    Science.gov (United States)

    Bohnet, Justin G; Chen, Zilong; Weiner, Joshua M; Cox, Kevin C; Thompson, James K

    2012-12-21

    We experimentally study the relaxation oscillations and amplitude stability properties of an optical laser operating deep into the bad-cavity regime using a laser-cooled ^{87}Rb Raman laser. By combining measurements of the laser light field with nondemolition measurements of the atomic populations, we infer the response of the gain medium represented by a collective atomic Bloch vector. The results are qualitatively explained with a simple model. Measurements and theory are extended to include the effect of intermediate repumping states on the closed-loop stability of the oscillator and the role of cavity feedback on stabilizing or enhancing relaxation oscillations. This experimental study of the stability of an optical laser operating deep into the bad-cavity regime will guide future development of superradiant lasers with ultranarrow linewidths.

  1. Study of low work function materials for hot cavity resonance ionization laser ion sources

    CERN Document Server

    Schwellnus, F; Crepieux, B; Fedosseev, V N; Marsh, B A; Mattolat, Ch; Menna, M; Österdahl, F K; Raeder, S; Stora, T; Wendta, K

    2009-01-01

    The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization of the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high temperature, low work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE/CERN, Geneva and RISIKO/University of Mainz.

  2. Study of Low Work Function Materials for Hot Cavity Resonance Ionization Laser Ion Sources

    CERN Document Server

    Catherall, R; Fedosseev, V; Marsh, B; Mattolat, C; Menna, Mariano; Österdahl, F; Raeder, S; Schwellnus, F; Stora, T; Wendt, K; CERN. Geneva. AB Department

    2008-01-01

    The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization on the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high-temperature, low-work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE / CERN, Geneva and RISIKO / University of Mainz.

  3. Vertical-cavity laser with a novel grating mirror

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol

    ) mirror formed in the Si layer of a Si-on-insulator (SOI) wafer. The hybrid VCLs have a promising potential for very high-speed operation and low energy consumption, which is ideal for optical interconnects as well as large data center applications. For the experimental demonstration of hybrid VCLs, CMOS...... VCLs have been fabricated. The first version of hybrid VCL is designed for demonstrating in-plane emission into a Si waveguide. The in-plane emission is enabled by the bottom HCG abutting the Si waveguide, which not only functions as a highly reflective mirror but also routes the light from......-HCG with a very short evanescent tail. This reduces the photon lifetime of the laser cavity significantly without reducing the mirror reflectivity, leading to a very high intrinsic speed. A 3 dB frequency of 27.2 GHz was measured at a pumping power corresponding to a current injection of 0.7 mA. Since the pumping...

  4. Novel laser machining of optical fibers for long cavities with low birefringence.

    Science.gov (United States)

    Takahashi, Hiroki; Morphew, Jack; Oručević, Fedja; Noguchi, Atsushi; Kassa, Ezra; Keller, Matthias

    2014-12-15

    We present a novel method of machining optical fiber surfaces with a CO₂ laser for use in Fiber-based Fabry-Perot Cavities (FFPCs). Previously FFPCs were prone to large birefringence and limited to relatively short cavity lengths (≤ 200 μm). These characteristics hinder their use in some applications such as cavity quantum electrodynamics with trapped ions. We optimized the laser machining process to produce large, uniform surface structures. This enables the cavities to achieve high finesse even for long cavity lengths. By rotating the fibers around their axis during the laser machining process the asymmetry resulting from the laser's transverse mode profile is eliminated. Consequently we are able to fabricate fiber mirrors with a high degree of rotational symmetry, leading to remarkably low birefringence. Through measurements of the cavity finesse over a range of cavity lengths and the polarization dependence of the cavity linewidth, we confirmed the quality of the produced fiber mirrors for use in low-birefringence FFPCs.

  5. Influence of low-intensity laser radiation upon the microflora of carious cavities and root canal

    Science.gov (United States)

    Shumilovitch, Bogdan R.; Nekrylov, Valery; Mazo, Leonid

    1995-04-01

    Laser stomatology- a relatively young branch of stomatology -has been developing actively lately. Bactericidal action of laser radiation enables to use it widely for processing carious cavities and root canals in the treatment of caries and its complications. 113 patients were studied by us. The 40 patients had antiseptic procedure of the caries cavity and then the procedure of laser therapy, so micro-organisms were found out in 26% cases. The 63 patients had antiseptic procedure only, so micro-organisms were found out in 70% cases. Control group were consisted of patients, where laser therapy was carried out without antiseptic remedies.

  6. Use of proper cavity loss for a stable single-longitudinal-mode erbium fiber laser

    Science.gov (United States)

    Yeh, Chien-Hung; Zhuang, Yuan-Hong; Tsai, Ning; Chow, Chi-Wai; Chen, Jing-Heng

    2017-06-01

    A stable and selectable erbium-doped fiber (EDF) ring laser configuration with single-longitudinal-mode (SLM) output is proposed and demonstrated in this paper. In the proposed laser scheme, a proper cavity loss is utilized for significant suppression of the side mode. In the experiment, the different coupling ratios required to produce various cavity losses in the proposed fiber laser are analyzed. Here, to reach the wavelength selection, several fiber Bragg gratings (FBGs) and an optical tunable bandpass filter (OTBF) in the C-band range are employed for demonstration. In addition, the output performance with respect to stability and SLM in the proposed EDF ring laser are also investigated simultaneously.

  7. External laser locking using a pressure-tunable microbubble resonator

    CERN Document Server

    Madugani, Ramgopal; Le, Vu H; Ward, Jonathan M; Chormaic, Síle Nic

    2015-01-01

    The tunability of an optical cavity is an essential requirement for many areas of research especially for the rapidly progressing field of photonics. In particular, low-cost laser tuning methods and miniaturization of the optical components are desirable. By applying aerostatic pressure to the interior surface of a microbubble resonator, optical mode shift rates of around $58$ GHz/MPa are achieved. The micobubble can measure pressure with a limit of detection of $2\\times 10^{-4}$ MPa. Here we use the Pound-Drever-Hall technique, whereby a laser is locked to a whispering gallery mode (WGM) of the microbubble resonator, to show that linear tuning of the WGM and the corresponding locked laser display almost zero hysteresis. The long-term frequency stability of this tuning method for different input pressures is measured. The frequency noise of the WGM, measured over 10 minutes, with a maximum input pressure of 0.5 MPa has a standard deviation of 36 MHz.

  8. A Q-switched, mode-locked fiber laser employing subharmonic cavity modulation.

    Science.gov (United States)

    Chang, You Min; Lee, Junsu; Lee, Ju Han

    2011-12-19

    We present a new and simple approach for the generation of Q-switched, mode-locked pulses from a laser cavity. The approach is based on cavity loss modulation that employs a subharmonic frequency of the fundamental intermode frequency spacing. A range of experiments have been carried out using an erbium-doped fiber-based ring cavity laser in order to verify that this simple approach can readily produce high quality Q-switched, mode-locked pulses. An active tuning of the Q-switched envelope repetition rate is also shown to be easily achievable by adjusting the order of the applied subharmonic frequency.

  9. Influence of external cooling on the femtosecond laser ablation of dentin.

    Science.gov (United States)

    Le, Q T; Vilar, R; Bertrand, C

    2017-07-11

    In the present work, the influence of external cooling on the temperature rise in the tooth pulpal chamber during femtosecond laser ablation was investigated. The influence of the cooling method on the morphology and constitution of the laser-treated surfaces was studied as well. The ablation experiments were performed on dentin specimens using an Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs, 1030 nm). Cavities were created by scanning the specimens at a velocity of 5 mm/s while pulsing the stationary laser beam at 1 kHz and with fluences in the range of 2-14 J/cm(2). The experiments were performed in air and with surface cooling by a lateral air jet and by a combination of an air jet and water irrigation. The temperature in the pulpal chamber of the tooth was measured during the laser experiments. The ablation surfaces were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The temperature rise reached 17.5 °C for the treatments performed with 14 J/cm(2) and without cooling, which was reduced to 10.8 ± 1.0 and 6.6 ± 2.3 °C with forced air cooling and water cooling, respectively, without significant reduction of the ablation rate. The ablation surfaces were covered by ablation debris and resolidified droplets containing mainly amorphous calcium phosphate, but the amount of redeposited debris was much lower for the water-cooled specimens. The redeposited debris could be removed by ultrasonication, revealing that the structure and constitution of the tissue remained essentially unaltered. The present results show that water cooling is mandatory for the femtosecond laser treatment of dentin, in particular, when high fluences and high pulse repetition rates are used to achieve high material removal rates.

  10. STUDY OF THE PROPAGATION OF SHORT PULSE LASER WITH CAVITY USING NUMERICAL SIMULATION SOFTWARE

    Directory of Open Access Journals (Sweden)

    S. Terniche

    2015-07-01

    Full Text Available The purpose of this representation is to show the potentialities (Computational Time, access to the dynamic and feasibility of systematic studies of the numerical study of the nonlinear dynamics in laser cavity, assisted by software. We will give as an example, one type of cavity completely fibered composed of several elements and then studying the physical parameters of a pulse propagating into this cavity, determining its characteristics at the output. The results are interesting but we also projects to verify them experimentally by making assemblies similar to this type of cavities.

  11. Optimization of cavity size for spatial confined laser-induced breakdown spectroscopy.

    Science.gov (United States)

    Su, Xuejiao; Zhou, Weidong; Qian, Huiguo

    2014-11-17

    Spatial confinement with a small cavity is known to enhance the signal intensity of laser-induced breakdown spectroscopy. In this study, the optical emission intensity and signal stability in terms of the relative standard deviation of laser-induced plasmas generated from brass samples with and without the presence of small cylindrical cavities were carefully investigated. The cylindrical cavities were prefabricated by drilling on a set of aluminum plates with variable diameters and heights, which were then placed near the sample surface. Both plasma emission intensity and stability were influenced by cavity diameter and height. With increased cavity diameter from 1.5 mm to 6 mm, the emission intensity of the confined plasma initially increased and then decreased. Furthermore, if a suitable cavity size was selected, both line intensity and stability of the confined plasma emission improved. Based on these observed signal characters with varying cavities, the optimized cavity size for the best signal quality of the laser-induced plasma emission on brass sample was obtained.

  12. A cavity-stabilized laser with acceleration sensitivity below $10^{-12}$/g

    CERN Document Server

    Leibrandt, David R; Rosenband, Till

    2013-01-01

    We characterize the frequency-sensitivity of a cavity-stabilized laser to inertial forces and temperature fluctuations, and perform real-time feed-forward to correct for these sources of noise. We measure the sensitivity of the cavity to linear accelerations, rotational accelerations, and rotational velocities by rotating it about three axes with accelerometers and gyroscopes positioned around the cavity. The worst-direction linear acceleration sensitivity of the cavity is $2(1) \\times 10^{-11}$/g measured over 0-50 Hz, which is reduced by a factor of 50 to below $10^{-12}$/g for low-frequency accelerations by real-time feed-forward corrections of all of the aforementioned inertial forces. A similar idea is demonstrated in which laser frequency drift due to temperature fluctuations is reduced by a factor of 70 via real-time feed-forward from a temperature sensor located on the outer wall of the cavity vacuum chamber.

  13. Effect of cylindrical cavity height on laser-induced breakdown spectroscopy with spatial confinement

    Science.gov (United States)

    Junfeng, Shao; Tingfeng, Wang; Jin, Guo; Anmin, Chen; Mingxing, Jin

    2017-02-01

    In this paper, we present a study on the spatial confinement effect of laser-induced plasma with a cylindrical cavity in laser-induced breakdown spectroscopy (LIBS). The emission intensity with the spatial confinement is dependent on the height of the confinement cavity. It is found that, by selecting the appropriate height of cylindrical cavity, the signal enhancement can be significantly increased. At the cylindrical cavity (diameter = 2 mm) with a height of 6 mm, the enhancement ratio has the maximum value (approximately 8.3), and the value of the relative standard deviation (RSD) (7.6%) is at a minimum, the repeatability of LIBS signal is best. The results indicate that the height of confinement cavity is very important for LIBS technique to reduce the limit of detection and improve the precision.

  14. Highly efficient accelerator of dense matter using laser-induced cavity pressure acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Badziak, J.; Jablonski, S.; Pisarczyk, T.; Raczka, P.; Chodukowski, T.; Kalinowska, Z.; Parys, P.; Rosinski, M.; Borodziuk, S. [Institute of Plasma Physics and Laser Microfusion, 01-497 Warsaw (Poland); Krousky, E. [Institute of Physics, AS CR, 182 21 Prague 8 (Czech Republic); Liska, R.; Kucharik, M. [Czech Technical University, FNSPE, 160 41 Prague 6 (Czech Republic); Ullschmied, J. [Institute of Plasma Physics, AS CR, 182 20 Prague 8 (Czech Republic)

    2012-05-15

    Acceleration of dense matter to high velocities is of high importance for high energy density physics, inertial confinement fusion, or space research. The acceleration schemes employed so far are capable of accelerating dense microprojectiles to velocities approaching 1000 km/s; however, the energetic efficiency of acceleration is low. Here, we propose and demonstrate a highly efficient scheme of acceleration of dense matter in which a projectile placed in a cavity is irradiated by a laser beam introduced into the cavity through a hole and then accelerated in a guiding channel by the pressure of a hot plasma produced in the cavity by the laser beam or by the photon pressure of the ultra-intense laser radiation trapped in the cavity. We show that the acceleration efficiency in this scheme can be much higher than that achieved so far and that sub-relativisitic projectile velocities are feasible in the radiation pressure regime.

  15. Ultra low-energy switch based on a cavity soliton laser with pump modulation

    Science.gov (United States)

    Eslami, M.; Gandomani, S. Z.; Prati, F.; Tajalli, H.; Kheradmand, R.

    2017-01-01

    We study the effects of pump modulation in a cavity soliton laser consisting of a vertical cavity surface emitting laser with an intra-cavity saturable absorber. We show that a drifting soliton experiences enhanced mobility features by modulating the pump at the resonance frequency, and the effects are even larger below resonance. In particular, pump modulation reduces the rest time of the soliton in the initial stage of the motion and it increases its drift velocity in this regime. Moreover, pump modulation allows a decrease in the switching energy of the soliton to an amount equal to 36 photons. These results indicate that pump modulation is a promising way for the use of a cavity soliton laser as a fast optical buffer and an ultra low-energy optical switch.

  16. Threshold for strong thermal dephasing in periodically poled KTP in external cavity frequency doubling

    DEFF Research Database (Denmark)

    Lundeman, Jesper Holm; Jensen, Ole Bjarlin; Andersen, Peter E.;

    2009-01-01

    We present a measurement series of the efficiency of periodically poled KTP used for second-harmonic generation in an external phase-locked cavity. Due to the high absorption (0.01 cm^−1) in the PPKTP crystal at the pump wavelength a strong thermal dephasing of the periodically poled grating...... is observed for high pump powers. For four different resonator setups, it was experimentally found that a threshold parameter could be defined as the ratio between the focal intensity in the crystal and the single-pass conversion efficiency. The value of this threshold for the onset of strong thermal...... dephasing was found to be 1.41×10^10 W^2 m^-2 in our 30-mm long PPKTP sample. This threshold parameter marks the onset of thermally induced instability that leads to a degradation of the SHG conversion efficiency. Above the threshold the shape of the resonance peaks of the resonator changed from symmetrical...

  17. Transverse-mode-selectable microlens vertical-cavity surface-emitting laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Debernardi, Pierluigi; Lee, Yong Tak

    2010-01-01

    A new vertical-cavity surface-emitting laser structure employing a thin microlens is suggested and numerically investigated. The laser can be made to emit in either a high-power Gaussian-shaped single-fundamental mode or a high-power doughnut-shaped higher-order mode. The physical origin of the m...

  18. Selection of a LGp0-shaped fundamental mode in a laser cavity: Phase versus amplitude masks

    CSIR Research Space (South Africa)

    Hasnaoui, A

    2012-01-01

    Full Text Available Laser beams of a single high-order transverse mode have been of interest to the laser community for several years now. In order to achieve such a mode as the fundamental mode of the cavity, mode selecting elements in the form of a phase or amplitude...

  19. Transverse Mode Structure and Pattern Formation in Oxide Confined Vertical Cavity Semiconductor Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Geib, K.M.; Hegarty, S.P.; Hou, H.Q.; Huyet, G.; McInerney, J.G.; Porta, P.

    1999-07-06

    We analyze the transverse profiles of oxide-confined vertical cavity laser diodes as a function of aperture size. For small apertures we demonstrate that thermal lensing can be the dominant effect in determining the transverse resonator properties. We also analyze pattern formation in lasers with large apertures where we observe the appearance of tilted waves.

  20. Stability of a laser cavity with non-parabolic phase transformation elements

    CSIR Research Space (South Africa)

    Litvin, IA

    2013-05-01

    Full Text Available In this paper we present a general approach to determine the stability of a laser cavity which can include non-conventional phase transformation elements. We consider two pertinent examples of the detailed investigation of the stability of a laser...

  1. Cavities

    Science.gov (United States)

    ... may pass these bacteria to a child through kissing, sampling the child's food, or sharing eating utensils. ... pass decay-causing bacteria to their children through kissing or sharing eating utensils. Symptoms of Cavities Whether ...

  2. A study on surface roughness and microleakage test in cavities prepared by Er:YAG laser irradiation and etched bur cavities.

    Science.gov (United States)

    Hossain, M; Yamada, Y; Nakamura, Y; Murakami, Y; Tamaki, Y; Matsumoto, K

    2003-01-01

    The purposes of this study were to investigate the surface morphology, suface roughness of cavities prepared by Er:YAG laser irradiation, and compared the microleakage degree after composite resin restoration with etched bur cavities, in vitro. In each of the 30 human extracted teeth, two shallow cavities were prepared; one prepared with the Er:YAG laser system on the buccal surface, and one produced on the lingual (palatal) surface with a high-speed turbine. Five cavities from each group were investigated by scanning electron microscopy (SEM), and five were subjected to surface roughness analysis by a colour laser three-dimensional (3D) microscope. The remaining cavities were filled with a composite resin and subjected to a microleakage test under thermocycling. Only bur cavities were acid-etched before filling. Statistical analysis was performed using the Mann-Whitney U test; a value of p roughness was significantly increased with the laser system. Microleakage test revealed no significant differences between the laser and bur cavities. Crosscut sections of the cavities with no microleakage showed no gap at the interface. Laser cavity may facilitate good adaptation of composite resin with enamel and dentine, because an increase of surface roughness and the openings of dentinal tubules may facilitate the formation of a hybrid zone, since a primer and an adhesive can penetrate the surface better when the smear layer is removed. It can be concluded that shallow cavity prepared by Er:YAG laser is capable of decreasing microleakage of composite resin restorations, and its efficiency is similar to etched bur cavities.

  3. Pulse shaping in mode-locked fiber lasers by in-cavity spectral filter.

    Science.gov (United States)

    Boscolo, Sonia; Finot, Christophe; Karakuzu, Huseyin; Petropoulos, Periklis

    2014-02-01

    We numerically show the possibility of pulse shaping in a passively mode-locked fiber laser by inclusion of a spectral filter into the laser cavity. Depending on the amplitude transfer function of the filter, we are able to achieve various regimes of advanced temporal waveform generation, including ones featuring bright and dark parabolic-, flat-top-, triangular- and saw-tooth-profiled pulses. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for controlling the dynamics of mode-locked fiber lasers.

  4. Adaptable beam profiles from a dual-cavity Nd:YAG laser.

    Science.gov (United States)

    Kim, D J; Mackenzie, J I; Kim, J W

    2016-04-15

    We report a technique to tailor a laser beam profile from a donut to quasi-top-hat intensity distribution, directly from the laser, simply achieved by simultaneous excitation and control of the relative contributions of the fundamental (TEM00) and first-order Laguerre-Gaussian (LG01) transverse modes. Exploiting a dual-cavity configuration with a single Nd:YAG gain element, adaptable continuous-wave laser beam profiles from the primary cavity could be obtained by varying the diffraction loss of an acousto-optic modulator in the secondary cavity. We investigate the resultant beam profiles as a function of pump power and the AOM diffraction loss, and discuss the prospects for tunable laser beams profiles.

  5. Generation of Low Jitter Laser Diode Pulse With External Pulse Injection

    Institute of Scientific and Technical Information of China (English)

    Wang Yuncai; Olaf Reimann; Dieter Huhse; Dieter Bimberg

    2003-01-01

    One gain-switched laser diode(LD) was used as external injection seeding source, to reduce the timing jitter of another gain-switched LD, This technique can generate low jitter, frequency-free and wavelength tunable laser pulse.

  6. Investigation of Synthetic Jets Efficiency to Control Cavity Flotation with Subsonic External Flow by High-Resolution RANS / ILES Method

    Directory of Open Access Journals (Sweden)

    D. A. Lyubimov

    2015-01-01

    Full Text Available Cavities often found in airplanes: a niche for the landing gear, various weapons, etc. Reducing fluctuations of pressure and temperature in the cavity is a relevant practical problem. The article presents simulation results of external subsonic flow around the cavity (M = 0.85, T = 300K. . Calculations were performed using the high-resolution RANS/ILES (Reynolds Averaged Navier-Stokes - RANS, Implicit Large Eddy Simulation - ILES method. To control flow the authors propose to use synthetic jets. Synthetic jets are produced by periodic ejection and suction of fluid from a slot induced by the movement of a diaphragm (generator of synthetic jets inside a cavity. They are compact and efficient and do not require a special working body and the ways for its supply. Instead of calculating the flow in the synthetic jet generator was used the modified boundary condition on the wall where the output slots was positioned. Under consideration there were two variants of slots for synthetic jets output: in front of the cavity and inside the cavity on the front wall. The frequency and amplitude values of the synthetic jet specified a mode of each jet. For a jet inside the cavity two modes have been reviewed, namely: 100 Hz and 50m/s, 200Hz and 50m/s. For jet in front of the cavity three modes have been reviewed, specifically: 20Hz and 20m/s, 100Hz and 50m/s, 200Hz and 50m/s. Analysis of calculation results showed that for all modes under examination, the synthetic jets reduced fluctuation of static pressure and temperature on the bottom and back walls of the cavity. The mode with parameters 200Hz, 50 m/s and synthetic jet located in front of the cavity was the most efficient. Furthermore, we compared the results of calculations for two-and three-dimensional cavities, which have the same length and depth. Research has shown that the simplified quasi-two-dimensional calculations cannot be used to evaluate the pressure and temperature fluctuations. This is due to

  7. Photonic crystal fibre Brillouin laser based on Bragg grating Fabry-Perot cavity

    Institute of Scientific and Technical Information of China (English)

    Geng Dan; Yang Dong-Xiao; Shen Guo-Feng; Zhang Xian-Min

    2008-01-01

    A photonic crystal fibre Brillouin laser based on fibre Bragg grating Fabry-Perot cavity is presented. A highly nonlinear photonic crystal fibre 25 m in length is used as Brillouin gain medium and fibre Bragg grating Fabry-Perot cavity is chosen in order to enhance the laser conversion efficiency and suppress the higher-order Stokes waves. The laser reaches the threshold at input power of 35 mW, and the experimental laser conversion efficiency achieves 18% of the input power of 140 mW and does not show higher-order Stokes waves. A photonic crystal fibre BriUouin laser withshorter fibre length and lower threshold is experimentally realized.

  8. Electro-optical cavity-dumped Ce:Nd:YAG laser for aesthetic medicine

    Science.gov (United States)

    Lv, Yuandong; Liu, Jiaqi; Hao, Lijun

    2012-11-01

    An electro-optical cavity-dumped 20 Hz Ce:Nd:YAG laser with an optimized thermal-insensitive concavo-convex cavity for aesthetic medicine was demonstrated. The pulse width remained constant at 6.0 ns. The maximum output energy and peak power were 120 mJ and 20 MW, respectively. The average output energy was very stable. The fluctuations of average output energy within 6 cycles and 10 min were 0.89% and 7.9%, respectively.

  9. Polarization-selectable cavity locking method for generation of laser Compton scattered γ-rays.

    Science.gov (United States)

    Kosuge, Atsushi; Mori, Michiaki; Okada, Hajime; Hajima, Ryoichi; Nagashima, Keisuke

    2014-03-24

    Nowadays, generation of energy-tunable, monochromatic γ-rays is needed to establish a nondestructive assay method of nuclear fuel materials. The γ-rays are generated by collision of laser photons stored in a cavity and relativistic electrons. We propose a configuration of an enhancement cavity capable of performing polarization control fabricated by a combination of a four-mirror ring cavity with a small spot inside a cavity and a three-mirror of reflective optics as an image inverter for polarization-selectable γ-rays. The image inverter introduces a phase shift of specific polarization which can be used to generate an error signal to lock an optical cavity at a resonance condition.

  10. Evaluation of ultrasonic and ErCr:YSGG laser retrograde cavity preparation.

    Science.gov (United States)

    Batista de Faria-Junior, Norberto; Tanomaru-Filho, Mário; Guerreiro-Tanomaru, Juliane Maria; de Toledo Leonardo, Renato; Camargo Villela Berbert, Fábio Luiz

    2009-05-01

    Root end cavity preparation techniques aim to create a clean and properly shaped cavity in a short time. Although the use of ultrasonics has been widely recommended, a laser can also be used. This study evaluated the time required and quality of retrograde cavity preparations using ultrasonics or ErCr:YSGG laser. Thirty single-rooted teeth were instrumented, root filled, submitted to apicectomies, and grouped. Root end cavities were prepared by using the following: group 1 (G1): CVD (6.1107-6) ultrasonic retrotips (CVD-Vale, São José dos Campos, Brazil); group 2 (G2): EMS (DT-060/Berutti) ultrasonic retrotips (EMS, LeSentier, Switzerland); and group 3 (G3): ErCr:YSGG (G6/Waterlase; Biolase Technology, San Clemente, CA) laser tips. The time taken to complete the preparation was recorded. Epoxy resin replicas of the root apices were examined under a scanning electron microscope. The parameters for evaluation were the presence of fractures, and the quality of the preparations. The Waterlase showed the highest mean time for preparation of the root end cavities (p 0.05). Fractures in the cavosurface angle occurred only in G2. G1 and G2 showed better scores for quality of preparation than G3 (p < 0.05). These results suggest that root end cavities should be prepared by ultrasonic tips.

  11. High power dual-wavelength tunable fiber laser in linear and ring cavity configurations

    Institute of Scientific and Technical Information of China (English)

    H. Ahmad; A. A. Latif; M. Z. Zulkifli; N. A. Awang; S. W. Harun

    2012-01-01

    We describe and compare the performances of two crucial configurations for a tunable dual-wavelength fiber laser,namely,the linear and ring configurations.The performances of these two cavities and the tunability in the dual-wavelength output varied from 0.8 to 11.9 nm are characterized.The ring cavity provides a better performance,achieving an average output power of 0.5 dBm,with a power fluctuation of only 1.1 dB and a signal-to-noise ratio (SNR) of 66 dB.Moreover,the ring cavity has minimal or no background amplified spontaneous emission (ASE).

  12. Free-Electron Laser as a Driver for a Resonant Cavity at 35 GHz

    Science.gov (United States)

    Lefevre, T.; Gardelle, J.; Rullier, J. L.; Vermare, C.; Donohue, J. T.; Meurdesoif, Y.; Lidia, S. M.

    2000-02-01

    An intense beam of relativistic electrons (800 A, 6.7 MeV) has been bunched at 35 GHz by a free-electron laser, in which output power levels exceeding 100 MW were obtained. The beam was then extracted and transported through a resonant cavity, which was excited by its passage. Microwave power levels of 10 MW were extracted from the cavity, in reasonable agreement with the simple formula which relates power to known properties of both the beam and the cavity.

  13. Fabrication of three-dimensional plasmonic cavity by femtosecond laser-induced forward transfer.

    Science.gov (United States)

    Chen, Wei Ting; Tseng, Ming Lun; Liao, Chun Yen; Wu, Pin Chieh; Sun, Shulin; Huang, Yao-Wei; Chang, Chia Min; Lu, Chung Hao; Zhou, Lei; Huang, Ding-Wei; Liu, Ai Qun; Tsai, Din Ping

    2013-01-14

    We fabricated a three-dimensional five-layered plasmonic resonant cavity by low-cost, efficient and high-throughput femtosecond laser-induced forward transfer (fs-LIFT) technique. The fabricated cavity was characterized by optical measurements, showing two different cavity modes within the measured wavelength region which is in good agreement with numerical simulations. The mode volume corresponding to each resonance is found to be squeezed over 10(4) smaller than the cube of incident wavelength. This property may facilitate many applications in integrated optics, optical nonlinearities, and luminescence enhancement, etc.

  14. Investigation on the effect of EDFA location in ring cavity Brillouin-Erbium fiber laser.

    Science.gov (United States)

    Hambali, Nor Azura Malini A; Mahdi, Mohd Adzir; Al-Mansoori, Mohammed Hayder; Abas, Ahmad Fauzi; Saripan, M Iqbal

    2009-07-06

    We have investigated the characteristics of Brillouin-Erbium fiber laser (BEFL) with variation of Erbium-doped fiber amplifier (EDFA) locations in a ring cavity configuration. Three possible locations of the EDFA in the laser cavity have been studied. The experimental results show that the location of EDFA plays vital role in determining the output power and the tuning range. Besides the Erbium gain, Brillouin gain also contributes to the performance of the BEFL. By placing the EDFA next to the Brillouin gain medium (dispersion compensating fiber), the Brillouin pump signal is amplified thereby generating higher intensities of Brillouin Stokes line. This efficient process suppresses the free running self-lasing cavity modes from oscillating in cavity as a result of higher Stokes laser power and thus provide a wider tuning range. At the injected Brillouin pump power of 1.6 mW and the maximum 1480 nm pump power of 135 mW, the maximum Stokes laser power of 25.1 mW was measured and a tuning range of 50 nm without any self-lasing cavity modes was obtained.

  15. Waves and rays in plano-concave laser cavities: I. Geometric modes in the paraxial approximation

    Science.gov (United States)

    Barré, N.; Romanelli, M.; Lebental, M.; Brunel, M.

    2017-05-01

    Eigenmodes of laser cavities are studied theoretically and experimentally in two companion papers, with the aim of making connections between undulatory and geometric properties of light. In this first paper, we focus on macroscopic open-cavity lasers with localized gain. The model is based on the wave equation in the paraxial approximation; experiments are conducted with a simple diode-pumped Nd:YAG laser with a variable cavity length. After recalling fundamentals of laser beam optics, we consider plano-concave cavities with on-axis or off-axis pumping, with emphasis put on degenerate cavity lengths, where modes of different order resonate at the same frequency, and combine to form surprising transverse beam profiles. Degeneracy leads to the oscillation of so-called geometric modes whose properties can be understood, to a certain extent, also within a ray optics picture. We first provide a heuristic description of these modes, based on geometric reasoning, and then show more rigorously how to derive them analytically by building wave superpositions, within the framework of paraxial wave optics. The numerical methods, based on the Fox-Li approach, are described in detail. The experimental setup, including the imaging system, is also detailed and relatively simple to reproduce. The aim is to facilitate implementation of both the numerics and of the experiments, and to show that one can have access not only to the common higher-order modes but also to more exotic patterns.

  16. Assessing the Performance of the Laser Fluorescence Technique in Detecting Proximal Caries Cavities

    Directory of Open Access Journals (Sweden)

    Majid Akbari

    Full Text Available Introduction: Diagnosing the necessity of cavity preparation and restoration in demineralized proximal areas is always considered as a challenge in restorative treatment planning. The purpose of this study was to assess the performance of the laser fluorescence (LF technique in detection of proximal cavities.Materials & Methods: In this clinical trial, 44 proximal surfaces in 38 dental students were evaluated. The selected patients had radiolucent proximal lesions restricted to inner half of enamel or outer third of dentine in bitewing radiographs (BW. DIAGNOdent pen (LF pen device was used to determine the presence or absence of caries cavities in suspected proximal surfaces. Orthodontic elastic separators were then placed in the contact areas to provide enough space for direct visual and tactile examination. The sensitivity, specificity and accuracy of the laser fluorescence technique were calculated versus the reference standard. The ROC curve was drawn and the best cut-off to determine the presence or absence of proximal cavities was determined.Results: Using DIAGNOdent pen, the optimal cut-off for detecting proximal cavities was 18. The sensitivity, specificity and accuracy of DIAGNOdent pen for diagnosing proximal caries cavities were 100 per cent, 97.3 per cent and 97.7 per cent, respectively. Conclusion: Due to the high diagnostic accuracy of DIAGNOdent pen in detecting proximal caries cavities, it can be used as a valuable supplement in restorative treatment planning.

  17. 589-nm yellow laser generation by intra-cavity sum-frequency mixing in a T-shaped Nd:YAG laser cavity

    Institute of Scientific and Technical Information of China (English)

    Xiuyan Chen; Xiu Li; Haolei Zhang; Haowei Chen; Jintao Bai; Zhaoyu Ren

    2009-01-01

    To obtain high power 589-nm yellow laser,a T-shaped thermal-insensitive cavity is designed.The optimal power ratio of 1064- and 1319-nm beams is considered and the fundamental spot size distribution from the output mirror to the two laser rods are calculated and simulated,respectively.As a result,a 589-nm yellow laser with the average output power of 5.7 W is obtained in the experiment when the total pumping power is 695 W.The optical-to-optical conversion efficiency from the fundamental waves to the sum frequency generation is about 15.2% and the pulse width is 150 ns at the repetition rate of 18 kHz.The instability of the yellow laser is also measured,which is less than 2% within 3 h.The beam quality factors are M2x =4.96 and M2y= 5.08.

  18. Tunable mode-locked laser with micro-air gap cavity

    Science.gov (United States)

    Ahmad, H.; Aidit, S. N.; Hassan, N. A.; Ooi, S. I.; Tiu, Z. C.

    2017-02-01

    A tunable mode-locked laser with a micro-air gap cavity acting as a high resolution tuning is proposed and demonstrated. The laser utilizes the nonlinear polarization technique in the cavity to obtain a reliable and stable mode locking over the whole tuning range at a resolution of 1 nm. The micro-air gap is constructed by aligning two fiber facets coaxially, and the variation of micro-air gap introduces a tuning mechanism where it changes the gain saturation compensation in the gain medium and thus induces wavelength shifting on the generated solitons.

  19. Photonic crystal vertical-cavity surface-emitting laser based on GaAs material

    Institute of Scientific and Technical Information of China (English)

    XU XingSheng; WANG ChunXia; SONG Qian; DU Wei; HU HaiYang; ZHAO ZhiMin; LU Lin; KAN Qiang; CHEN HongDa

    2007-01-01

    A photonic crystal vertical-cavity-surface-emitting laser (PC-VCSEL) with a wavelength of about 850 nm was realized. The direct-current electrically-driven PC-VCSELs with a minimum threshold current of 2 mA and a maximum threshold current of 13.5 mA were obtained. We fabricated a series of PC-VCSEL chips whose lattice constants are in the range from 0.5 to 3 ?m with different filling factors, and found that the laser characterization depends on the lattice constant, the filling factor, the size of cavity, etc.

  20. Nd:YAG laser in endodontics: filling-material edge bordering on a root channel laser cavity

    Science.gov (United States)

    Belikov, Andrei V.; Sinelnik, Yuri A.; Moroz, Boris T.; Pavlovskaya, Irina V.

    1997-12-01

    For the very first time it is represented a study of filling material edge bordering upon root channel cavity modified with a laser. As a filling material it is used a glass ionomer cement. It is demonstrated that Nd:YAG laser radiation effects on increase of grade of edge bordering on the average of 20 - 30% at temperature rise of no more than 2 - 3 degrees in periodontium area in a period of operation.

  1. Assessing microleakage of composite restorations in class V cavities prepared by Er:YAG laser irradiation or diamond bur

    Directory of Open Access Journals (Sweden)

    Sakineh Arami

    2014-01-01

    Full Text Available Introduction: The aim of this study was to make a comparison between microleakage of conventionally restored class V cavities using bur and acid etchant and, the ones prepared and conditioned by Er:YAG laser. Materials and Methods: 30 recently extracted intact caries and filling free human permanent molars were used for this study. Then, Cold cure acrylic resin was used to seal the apices. The samples were randomly assigned to 5 groups of six each. Class V cavities were prepared one on buccal and one on lingual surface of each sample. Group 1: cavity preparation by diamond bur and turbine + acid etch, Group 2: cavity preparation by Er:YAG laser + acid etch, Group 3: cavity preparation by Er:YAG laser + Laser etching, Group 4: cavity preparation by diamond bur and turbine + laser etching, Group 5: cavity preparation by Er:YAG laser with no conditioning procedure. The cavities restored with restorative composite resin. Samples were then immersed in 2% methylene blue solution for 24 hours. The data were then analyzed using Wilcoxon signed ranks test and Kruskal-Wallis statistical tests. Results: The Kruskal Wallis test showed a significant difference (P < 0.05 between enamel and cementum margin microleakage, while the higher microleakage was related to the cementum margin of restorations. Conclusion: There was no significant difference in evaluating microleakeage degree of cavities prepared by Er:YAG laser and diamond bur.

  2. The influence of an external cavity on the emission spectrum of a mercury germicidal lamp

    Science.gov (United States)

    Solomonov, V. I.; Surkov, Yu. S.; Gorbunkov, V. I.

    2016-09-01

    The spectrum of emission from the cylindrical duralumin cavity of a TUV 8wG8 T5 UV industrial germicidal mercury lamp is studied. It is shown that, due to reflection from the inner surface of the cavity and reabsorption in the gas discharge, the resonance line of a mercury atom is significantly weakened. The dependence of the resonance line intensity on the discharge current has a maximum, and the discharge current corresponding to the intensity maximum depends on the reflection coefficient of the inner surface of the cavity.

  3. Dual-wavelength distributed Bragg reflector semiconductor laser based on a composite resonant cavity

    Science.gov (United States)

    Chen, Cheng; Zhao, Ling-Juan; Qiu, Ji-Fang; Liu, Yang; Wang, Wei; Lou, Cai-Yun

    2012-09-01

    We report a monolithic integrated dual-wavelength laser diode based on a distributed Bragg reflector (DBR) composite resonant cavity. The device consists of three sections, a DBR grating section, a passive phase section, and an active gain section. The gain section facet is cleaved to work as a laser cavity mirror. The other laser mirror is the DBR grating, which also functions as a wavelength filter and can control the number of wavelengths involved in the laser action. The reflection bandwidth of the DBR grating is fabricated to have an appropriate value to make the device work at the dual-wavelength lasing state. We adopt the quantum well intermixing (QWI) technique to provide low-absorption loss grating and passive phase section in the fabrication process. By tuning the injection currents on the DBR and the gain sections, the device can generate 0.596 nm-spaced dual-wavelength lasing at room temperature.

  4. Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement

    Science.gov (United States)

    Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Hrabina, Jan; Lazar, Josef; Číp, Ondřej

    2016-01-01

    The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm tuning range has been suppressed with an unbalanced heterodyne fiber interferometer. The frequency noise of laser has been suppressed by 40 dB across the Fourier frequency range 30–300 Hz and by 20 dB up to 4 kHz and the linewidth of the laser below 300 kHz. The relative resolution of the measurement was 10−9 that corresponds to 0.3 nm (sub-nm) for 0.178 m long cavity with ability of displacement measurement of 0.5 mm. PMID:27608024

  5. Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement

    Directory of Open Access Journals (Sweden)

    Radek Šmíd

    2016-09-01

    Full Text Available The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm tuning range has been suppressed with an unbalanced heterodyne fiber interferometer. The frequency noise of laser has been suppressed by 40 dB across the Fourier frequency range 30–300 Hz and by 20 dB up to 4 kHz and the linewidth of the laser below 300 kHz. The relative resolution of the measurement was 10 − 9 that corresponds to 0.3 nm (sub-nm for 0.178 m long cavity with ability of displacement measurement of 0.5 mm.

  6. Dynamic properties of a pulse-pumped fiber laser with a short, high-gain cavity

    Science.gov (United States)

    Yang, Chaolin; Guo, Junhong; Wei, Pu; Wan, Hongdan; Xu, Ji; Wang, Jin

    2016-09-01

    We demonstrate a pulsed high-gain all-fiber laser without intracavity modulators, where a short and heavily Erbium-doped fiber is used as the gain medium in a ring cavity. By pulsed-pumping this short high gain cavity and tuning an intracavity variable optical coupler, the laser generates optical pulses with a pulse-width of μs at a repetition rate in the order of kHz down to one-shot operation. Furthermore, dynamic properties of this laser are investigated theoretically based on a traveling-wave-model, in which an adaptive-discrete-grid-finite-difference-method is applied. The simulation results validate the experimental results. The demonstrated pulsed laser is compact, flexible and cost-effective, which will have great potential for applications in all-optical sensing and communication systems.

  7. Reduce of the Linewidth of a Diode Laser by Locking to a High-Finesse Fabry-Perot Cavity

    Institute of Scientific and Technical Information of China (English)

    HUANG Kai-Kai; ZHANG Jian-Wei; CHEN Jing-Biao; YANG Dong-Hai

    2006-01-01

    @@ We report frequency locking of a commercial 657nm diode laser to a high finesse Fabry-Perot cavity by the Pound-Drever-Hall method. The laser linewidth relative to the cavity is estimated to be about 6 kHz.

  8. Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors

    Science.gov (United States)

    Chen, H.; Li, H.; Sun, Yc.; Wang, Y.; Lü, Pj.

    2016-02-01

    To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application.

  9. Spatial distribution of the intensity noise of a vertical-cavity surface-emitting semiconductor laser.

    Science.gov (United States)

    Bramati, A; Hermier, J P; Khoury, A Z; Giacobino, E; Schnitzer, P; Michalzik, R; Ebeling, K J; Poizat, J P; Grangier, P

    1999-07-01

    We studied anticorrelated quantum fluctuations between the TEM(00) and the TEM(01) transverse modes of a vertical-cavity surface-emitting semiconductor laser by measuring the transverse spatial distribution of the laser beam intensity noise. Our experimental results are found to be in good agreement with the predictions of a phenomenological model that accounts for quantum correlations between transverse modes in a light beam.

  10. Electrically tunable terahertz quantum cascade lasers based on a two-sections interdigitated distributed feedback cavity

    Energy Technology Data Exchange (ETDEWEB)

    Turčinková, Dana; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme [ETH Zurich, Institute for Quantum Electronics, Auguste-Piccard-Hof 1, 8093 Zurich (Switzerland); Amanti, Maria Ines [ETH Zurich, Institute for Quantum Electronics, Auguste-Piccard-Hof 1, 8093 Zurich (Switzerland); Univ. Paris Diderot, Lab. Matererk iaux et Phenomenes Quantiques, F-75205 Paris (France)

    2015-03-30

    The continuous electrical tuning of a single-mode terahertz quantum cascade laser operating at a frequency of 3 THz is demonstrated. The devices are based on a two-section interdigitated third-order distributed feedback cavity. The lasers can be tuned of about 4 GHz at a constant optical output power of 0.7 mW with a good far-field pattern.

  11. Dual-Cylinder Laser Reference Cavities for LISA Project

    Data.gov (United States)

    National Aeronautics and Space Administration — "Summary: The Laser Interferometer Space Antenna (LISA) mission is under consideration by NASA and ESA as a joint mission to study gravitational wave signals from a...

  12. Cavity formation and surface modeling of laser milling process under a thin-flowing water layer

    Science.gov (United States)

    Tangwarodomnukun, Viboon

    2016-11-01

    Laser milling process normally involves a number of laser scans over a workpiece to selectively remove the material and then to form cavities with shape and dimensions required. However, this process adversely causes a heat accumulation in work material, which can in turn damage the laser-milled area and vicinity in terms of recast deposition and change of material properties. Laser milling process performing in a thin-flowing water layer is a promising method that can overcome such damage. With the use of this technique, water can flush away the cut debris and at the same time cool the workpiece during the ablation. To understand the potential of this technique for milling application, the effects of process parameters on cavity dimensions and surface roughness were experimentally examined in this study. Titanium sheet was used as a workpiece to be milled by a nanosecond pulse laser under different water flow velocities. A smooth and uniform cut feature can be obtained when the metal was ablated under the high laser pulse frequency and high water flow velocity. Furthermore, a surface model based on the energy balance was developed in this study to predict the cavity profile and surface roughness. By comparing to the experiments, the predicted profiles had a good agreement with the measured ones.

  13. Stainless steel surface wettability control via laser ablation in external electric field

    Science.gov (United States)

    Serkov, A. A.; Shafeev, G. A.; Barmina, E. V.; Loufardaki, A.; Stratakis, E.

    2016-12-01

    Laser ablation of stainless steel in external electric field (up to 10 kV/cm) is experimentally studied. The dependencies of both morphology and chemical properties of surface structures on laser parameters and electric field strength are investigated. Surface wettability properties of the laser-treated samples are considered by means of contact angle measurement. It is shown that under certain conditions laser irradiation in external electric field can render the surface superhydrophobic. Influence of electric field on the laser surface treatment is discussed on basis of its impact on melt solidification and oxidation processes.

  14. Plasmonic emission and plasma lattice structures induced by pulsed laser in Purcell cavity on silicon

    Institute of Scientific and Technical Information of China (English)

    黄伟其; 黄忠梅; 苗信建; 刘世荣; 秦朝建

    2015-01-01

    The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma lattice structures induced by the nanosecond pulsed laser in the cavity may be similar to the Wigner crystal structure. It is interesting that the beautiful diffraction pattern could be observed in the plasma lattice structure. The radiation lifetime could be shortened to the nanosecond range throughout the entire spectral range and the relaxation time could be lengthened for higher emission efficiency in the Purcell cavity, which results in the fact that the plasmonic emission is stronger and its threshold is lower.

  15. Buried heterostructure vertical-cavity surface-emitting laser with semiconductor mirrors

    CERN Document Server

    Zhao, G; Deppe, D G; Konthasinghe, K; Muller, A

    2012-01-01

    We report a buried heterostructure vertical-cavity surface-emitting laser fabricated by epitaxial regrowth over an InGaAs quantum well gain medium. The regrowth technique enables microscale lateral confinement that preserves a high cavity quality factor (loaded $Q\\approx$ 4000) and eliminates parasitic charging effects found in existing approaches. Under optimal spectral overlap between gain medium and cavity mode (achieved here at $T$ = 40 K) lasing was obtained with an incident optical power as low as $P_{\\rm th}$ = 10 mW ($\\lambda_{\\rm p}$ = 808 nm). The laser linewidth was found to be $\\approx$3 GHz at $P_{\\rm p}\\approx$ 5 $P_{\\rm th}$.

  16. Acetone vapor sensing using a vertical cavity surface emitting laser diode coated with polystyrene

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2009-01-01

    We report theoretical and experimental on a new vapor sensor, using a single-mode vertical-cavity surface-emitting laser (VCSEL) coated with a polymer sensor coating, which can detect acetone vapor at a volume fraction of 2.5%. The sensor provides the advantage of standard packaging, small form-f...

  17. Vertical-cavity surface-emitting laser vapor sensor using swelling polymer reflection modulation

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgård; Dohn, Søren

    2012-01-01

    Vapor detection using a low-refractive index polymer for reflection modulation of the top mirror in a vertical-cavity surface-emitting laser (VCSEL) is demonstrated. The VCSEL sensor concept presents a simple method to detect the response of a sensor polymer in the presence of volatile organic...

  18. Single mode cavities for parametric oscillatory instability suppression in laser gravitational wave detectors

    Science.gov (United States)

    Poplavskiy, Mikhail V.

    Parametric oscillatory instability will be a serious problem restricting the power circulating in laser gravitation wave detectors (aLIGO). For parametric oscillatory instability suppression we suggest to use practically "single mode" Fabry-Perot (FP) cavity with little changed mirror's specular surface.

  19. Self-mixing interferometry in vertical-cavity surface-emitting lasers for nanomechanical cantilever sensing

    DEFF Research Database (Denmark)

    Larsson, David; Greve, Anders; Hvam, Jørn Märcher;

    2009-01-01

    We have experimentally investigated self-mixing interference produced by the feedback of light from a polymer micrometer-sized cantilever into a vertical-cavity surface-emitting laser for sensing applications. In particular we have investigated how the visibility of the optical output power and t...

  20. Polarization switching in vertical-cavity surface emitting lasers observed at constant active region temperature

    Science.gov (United States)

    Martín-Regalado, J.; Chilla, J. L. A.; Rocca, J. J.; Brusenbach, P.

    1997-06-01

    Polarization switching in gain-guided, vertical-cavity, surface-emitting lasers was studied as a function of the active region temperature. We show that polarization switching occurs even when the active region temperature is kept constant during fast pulse low duty cycle operation. This temperature independent polarization switching phenomenon is explained in terms of a recently developed model.

  1. [Cavity preparation using an Er:YAG laser in the adult dentition].

    Science.gov (United States)

    Delmé, K; Meire, M; De Bruyne, M; Nammour, S; De Moor, R

    2009-01-01

    Many lasers (i.e., different wavelengths) are available today for clinical applications. Not all lasers are to be used for cavity preparation and removal of carious tissues. Erbiumlasers (Er:YAG and Er,Cr:YSGG) are suitable for these purposes (the wavelengths coincide with the highest absorption peaks of water and hydroxyapatite). The advantages during cavity preparation and caries removal are smear layer free cavity walls, selective and localised removal of tooth substance, a restricted need or the absence of anaesthesia, and cavity walls with a higher acid resistance resulting in a better protection against secondary decay. Possible side effects of erbium lasers with water cooling and used with respect for correct power setting are minimal and can be compared with those of rotary instruments. Erbium laser tooth preparation is now one of the options in the minimal invasive approach. The needs for acid etching has been debated for long. At present it has become clear that acid etching is mandatory to obtain a good adhesion and retention with resin composites.

  2. Mirror reflectivity and doping considerations for high performance oxide-confined vertical cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    Geib, K.M.; Choquette, K.D.; Chui, H.C.; Hou, H.Q.; Hammons, B.E.

    1996-01-01

    We report the effects of mirror doping and reflectivity in 850 and 780 nm oxide-confined vertical cavity surface emitting lasers. Decreased doping throughout the n-type mirror produces significantly higher quantum efficiency, while the optimum reflectivity is dependent upon the gain material.

  3. Acetone vapor sensing using a vertical cavity surface emitting laser diode coated with polystyrene

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2009-01-01

    We report theoretical and experimental on a new vapor sensor, using a single-mode vertical-cavity surface-emitting laser (VCSEL) coated with a polymer sensor coating, which can detect acetone vapor at a volume fraction of 2.5%. The sensor provides the advantage of standard packaging, small form...

  4. Ultrafast nanomechanics in vertical cavity surface-emitting lasers (Conference Presentation)

    Science.gov (United States)

    Akimov, Andrey V.; Czerniuk, Thomas; Yakovlev, Dmitri R.; Bayer, Manfred

    2017-02-01

    The existence of both optical and sub-THz nanomechanical resonances in the same laser microcavity results in strong photon-phonon interaction, and may be explored for the ultrafast control of vertical lasers. In the talk the experiments involving the injection of picosecond strain pulses into optically and electrically pumped vertical lasers, and monitoring of the modulated output laser intensity will be discussed. The results of three recent experiments will be presented: • In the experiments with an optically pumped quantum dot laser, an increase of the lasing output induced by strain pulses by two orders of magnitude has been observed on a picosecond time scale. Such strong and ultrafast increase is due to the inhomogeneous quantum dot ensemble with a spectral broadening much larger than the optical cavity mode width. Thus, the optical resonance required for lasing is achieved for a tiny dot fraction only while non-resonant dots store optical excitation for long time. The strain pulse brings "non-resonant" quantum dots into the resonance with the cavity mode and the stored energy releases almost simultaneously in a form of the intense laser pulses. • Experiments with electrically pumped micropillar lasers show the modulation of the emission wavelength on the frequencies equal to the resonant GHz nanomechanical modes of the micropillar. • Experiments with a quantum well vertical laser showed intensity modulation with the mechanical resonance frequencies (20-40 GHz) of the optomechanical nanoresonator. Prospective application for nanophotonics are discussed.

  5. Waveguide and articulated arm for Er:YAG laser system: shape and depth of laser cavity in hard dental tissues

    Science.gov (United States)

    Jelinkova, Helena; Dostalova, Tatjana; Miyagi, Mitsunobu; Wang, You; Shi, Yi-Wei; Dolezalova, Libuse; Hamal, Karel; Krejsa, Otakar; Kubelka, Jiri; Prochazka, Stanislav

    1998-04-01

    The aim of our study was to verify the efficiency of delivery systems for Er:YAG laser radiation which could be used in dentistry. The influence of increasing energy and number of pulses on a profile and depth of drilled holes was investigated. Er:YAG laser was operating in a free-running mode, generating a length of pulses 200 microsecond with a maximum energy of 500 mJ. The delivery systems investigated were an articulated arm and a fluorocarbon polymer-coated silver hollow glass waveguide. The prepared hard tissues were a sliced part of enamel, dentine and ivory. The laser radiation was directed on them by focusing optics (CaF2 lens) together with the cooling water to ensure that the tissues will not be burned. For the evaluation of shapes, depth and profiles of the prepared cavities the metallographic microscope, x-ray microtomograph and scanning electron microscope were used. From the results it was observed that the profile and depth of the cavities prepared by the laser radiation delivered by the various systems (waveguide or articulated arm) are not the same. The laser radiation delivered by waveguide produces a larger diameter cavity with a lower depth. The holes are smoother and without side effects.

  6. Non-linear Spectroscopy of Sr Atoms in an Optical Cavity for Laser Stabilization

    CERN Document Server

    Christensen, Bjarke T R; Schäffer, Stefan A; Westergaard, Philip G; Ye, Jun; Holland, Murray; Thomsen, Jan W

    2015-01-01

    We study the non-linear interaction of a cold sample of strontium-88 atoms coupled to a single mode of a low finesse optical cavity in the so-called bad cavity limit and investigate the implications for applications to laser stabilization. The atoms are probed on the weak inter-combination line $\\lvert 5s^{2} \\, ^1 \\textrm{S}_0 \\rangle \\,-\\, \\lvert 5s5p \\, ^3 \\textrm{P}_1 \\rangle$ at 689 nm in a strongly saturated regime. Our measured observables include the atomic induced phase shift and absorption of the light field transmitted through the cavity represented by the complex cavity transmission coefficient. We demonstrate high signal-to-noise-ratio measurements of both quadratures - the cavity transmitted phase and absorption - by employing FM spectroscopy (NICE-OHMS). We also show that when FM spectroscopy is employed in connection with a cavity locked to the probe light, observables are substantially modified compared to the free space situation where no cavity is present. Furthermore, the non-linear dynami...

  7. VUV free electron laser with a distributed feedback cavity

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J.; Fujita, M.; Asakawa, M. [Osaka Univ. (Japan)] [and others

    1995-12-31

    Development of FEL to the VUV/x-ray regime is looked as one of the possible directions to its success. For eliminating the need for optical cavities, difficult to be built at that regime, we propose a VUV (50nm) SASE FEL. According to Pellegrini`s scaling law, for a 290MeV/200A e-beam passing through a 10.8m long and 2cm period wiggler, a high peak power 85.5MW and a high average brightness 2.44 X 10{sup +21} (photons/[mm{sup 2}.mrad{sup 2}.bw]) can be obtained. However, it requires {epsilon} n=2.3mm.mrad and {Delta}{gamma}/{gamma} = 0.15% about one order above the practical parameters we can realize. For enhancing the efficiency and decreasing the requirements on the e-beam quality and the wiggler length, we put forward a concept of VUV FEL with a distributed feedback cavity. In x-ray region, the natural periodicity of crystals provides strong Bragg coupling and it has been demonstrated as the parametric radiation. In vuv region, current intense research on superlattice can provide a periodical structure with a short period in 250 {Angstrom} order. High-performance vuv multilayer coatings on the inner-wall of the waveguide are used to guide the spontaneous emission and decrease the x-ray ohmic losses on the roundtrip passes. By this DFB cavity structure, it is expected to realize the lasing in a smaller size. Other practical methods such as the optical klystron for shortening the wiggler length and the tapper wiggler for enhancing the saturation power are also considered. The analytical considerations are based on the 1-D FEL equations and 1-D perturbation theory of dielectric waveguide.

  8. VUV free electron laser with a distributed feedback cavity

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J.; Fujita, M.; Asakawa, M. [Osaka Univ. (Japan)] [and others

    1995-12-31

    Development of FEL to the VUV/x-ray regime is looked as one of the possible directions to its success. For eliminating the need for optical cavities, difficult to be built at that regime, we propose a VUV (50nm) SASE FEL. According to Pellegrini`s scaling law, for a 290MeV/200A e-beam passing through a 10.8m long and 2cm period wiggler, a high peak power 85.5MW and a high average brightness 2.44 X 10{sup +21} (photons/[mm{sup 2}.mrad{sup 2}.bw]) can be obtained. However, it requires {epsilon} n=2.3mm.mrad and {Delta}{gamma}/{gamma} = 0.15% about one order above the practical parameters we can realize. For enhancing the efficiency and decreasing the requirements on the e-beam quality and the wiggler length, we put forward a concept of VUV FEL with a distributed feedback cavity. In x-ray region, the natural periodicity of crystals provides strong Bragg coupling and it has been demonstrated as the parametric radiation. In vuv region, current intense research on superlattice can provide a periodical structure with a short period in 250 {Angstrom} order. High-performance vuv multilayer coatings on the inner-wall of the waveguide are used to guide the spontaneous emission and decrease the x-ray ohmic losses on the roundtrip passes. By this DFB cavity structure, it is expected to realize the lasing in a smaller size. Other practical methods such as the optical klystron for shortening the wiggler length and the tapper wiggler for enhancing the saturation power are also considered. The analytical considerations are based on the 1-D FEL equations and 1-D perturbation theory of dielectric waveguide.

  9. The Effects of Laser Energy Deposition on Supersonic Cavity Flow

    Science.gov (United States)

    2009-01-01

    to be 1.246. K is taken as 0.55 for this cavity configuration (Hankey and Shang, 1979). For the computations, one of the Beowulf computer clusters of...zone are 95 X 54 X 35. and 177 X 62 X 70 in the outside zone, in the x, y. z directions, respectively. Grid clustering was employed at several places in...Rutgers University (mphase) was used. The core of the mphase cluster consists of 60 dual and single processor Linux machines. A total of 32 processors

  10. Comparison of Dentin Permeability After Tooth Cavity Preparation with Diamond Bur and Er:YAG Laser

    OpenAIRE

    Masoumeh Hasani Tabatabaei; Sara Shirmohammadi; Esmaeil Yasini; Mansoureh Mirzaei; Sakineh Arami; Hamid Kermanshah; Ladan Ranjbar Omrani; Azar Alimi; Nasim Chiniforush; Afrooz Nakhostin; Mahdi Abbasi

    2015-01-01

    Objectives: The aim of this study was to compare the permeability of dentin after using diamond bur and Er:YAG laser.Materials and Methods: Seventy-two recently extracted, intact, and restoration-free human permanent molars were used in this study. The samples were randomly divided into three groups of 24 each and class I cavities were prepared as follows. Group 1: High speed diamond bur with air and water spray. Group 2: Er:YAG laser. Group 3: Er:YAG laser followed by additional sub-ablative...

  11. Compact, robust, and spectrally pure diode-laser system with filter cavity

    CERN Document Server

    Kirilov, Emil; Segl, Maximilian; Nägerl, Hanns-Christoph

    2014-01-01

    We report on a design of a compact laser system composed of an extended cavity diode laser with high passive stability and a pre-filter Fabri-Perot cavity. The laser is frequency stabilized relative to the cavity using a serrodyne technique with a correction bandwidth of $\\geq 6$ MHz and a dynamic range of $\\geq 700$ MHz. The free running laser system has a power spectral density (PSD) $\\leq 100$ Hz$^{2}$/Hz centered mainly in the acoustic frequency range. A highly tunable $0.5-1.3$ GHz copy of the spectrally pure output beam is provided, which can be used for further stabilization of the laser system to an ultra-stable reference. We demonstrate a simple one-channel lock to such a reference that brings down the PSD to the sub-Hz level. The system is easy to operate, scalable, and highly applicable to atomic/molecular experiments demanding high spectral purity, long-term stability, and robustness.

  12. Compact resonantly intra-cavity pumped tunable Ho:Sc2SiO5 laser

    Science.gov (United States)

    Yang, Xiao-tao; Song, En-zhe; Xie, Wen-qiang

    2017-09-01

    A compact intra-cavity pumped low threshold continuous-wave Ho:Sc2SiO5 laser is reported. The characteristics of output wavelength tuning are investigated by use a intra-cavity briefringent (BF) filter. A wavelength tunable range of 140 nm from 2020 to 2160 nm is achieved. For the free-running mode, the laser slope efficiency is 24.8%, when the output central wavelength is 2110 nm. The laser threshold is about 820 mW of incident pump power. With the BF filter, a maximum output power of 870 mW is obtained at the incident pump power of 5 W, corresponding to a slope efficiency of 20.3%. The characteristics of output wavelength verse the crystal temperature are also investigated.

  13. Microleakage of composite resin restoration in cavities prepared by Er:YAG laser irradiation in primary teeth.

    Science.gov (United States)

    Yamada, Y; Hossain, M; Nakamura, Y; Murakami, Y; Matsumoto, K

    2002-03-01

    AIM: The purposes of this study were to investigate the surface morphology of cavities prepared by Er:YAG laser irradiation and to compare the microleakage degree after composite resin restoration with etched bur cavities in primary teeth, in vitro. MATERIALS AND METHODS: On the buccal (facial) and lingual (palatal) surfaces of 25 primary teeth, a round cavity was prepared with the Er:YAG laser system and with a high-speed diamond bur, respectively. Five cavities from each group were investigated by scanning electron microscopy (SEM). The remaining cavities were filled with a composite resin and subjected to a microleakage test (0.6% rodamine B solution) under thermocycling. Only bur cavities were acid-etched before filling. Statistical analysis was performed using the Mann-Whitney's U test; a value of p adhesion between the restorative material and dental hard tissues; there was also no gap at the interface. DISCUSSION: The highly irregular surface or the removal of the debris-like smear layer after laser irradiation may facilitate good adhesion of composite resin with enamel or dentine, and these surfaces might play a major role in decreasing microleakage of laser cavities. CONCLUSION: It can be concluded that cavities prepared by Er:YAG laser are capable of decreasing microleakage of composite resin restorations in primary teeth, and the efficiency is similar to etched bur cavities.

  14. Effect of an external radiation field on the properties of the atoms and cavity field in the two-atom Tavis-Cummings model

    Institute of Scientific and Technical Information of China (English)

    王忠纯; 王琪; 张永生; 郭光灿

    2005-01-01

    We study the properties of atoms and cavity field in the two-atom Tavis-Cummings model where the two atoms interact with each other and are also driven by an external classical field. We consider the special case that the cavity is initially in a coherent state. The atomic inversion, the average photons number and the Mandel parameter in the driven Tavis-Cummings model are given and analysed numerically. We pay special attention to the dynamical behaviour of the atoms and the cavity field modified by the external field.

  15. Precise force measurement method by a Y-shaped cavity dual-frequency laser

    Institute of Scientific and Technical Information of China (English)

    Guangzong Xiao; Xingwu Long; Bin Zhang; Geng Li

    2011-01-01

    A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed. The principle of force measurement with this method is analyzed, and the analytic relation expression between the input force and the change in the output beat frequency is derived. Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed; they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range. The maximum scale factor is observed as 5.02×109 Hz/N, with beat frequency instability equivalent resolution of 10-5 N. By optimizing the optical and geometrical parameters of the laser sensor, a force measurement resolution of 10-6i N could be expected.%A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed.The principle of force measurement with this method is analyzed,and the analytic relation expression between the input force and the change in the output beat frequency is derived.Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed;they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range.The maximum scale factor is observed as 5.02× 109 Hz/N,with beat frequency instability equivalent resolution of 10-5 N.By optimizing the optical and geometrical parameters of the laser sensor,a force measurement resolution of 10 -6 N could be expected.Precise measurement of force and force-related nagnitudes,such as acceleration,pressure,and mass,is an often demanded task in modern engineering and science[1-3].In recent decades,some research efforts have been intensified to utilize optical measnrement procedures for obtaining precise force measurement.

  16. Flow and heat transfer in gas turbine disk cavities subject to nonuniform external pressure field

    Energy Technology Data Exchange (ETDEWEB)

    Roy, R.P.; Kim, Y.W.; Tong, T.W. [Arizona State Univ., Tempe, AZ (United States)

    1995-10-01

    Injestion of hot gas from the main-stream gas path into turbine disk cavities, particularly the first-stage disk cavity, has become a serious concern for the next-generation industrial gas turbines featuring high rotor inlet temperature. Fluid temperature in the cavities increases further due to windage generated by fluid drag at the rotating and stationary surfaces. The resulting problem of rotor disk heat-up is exacerbated by the high disk rim temperature due to adverse (relatively flat) temperature profile of the mainstream gas in the annular flow passage of the turbine. A designer is concerned about the level of stresses in the turbine rotor disk and its durability, both of which are affected significantly by the disk temperature distribution. This distribution also plays a major role in the radial position of the blade tip and thus, in establishing the clearance between the tip and the shroud. To counteract mainstream gas ingestion as well as to cool the rotor and the stator disks, it is necessary to inject cooling air (bled from the compressor discharge) into the wheel space. Since this bleeding of compressor air imposes a penalty on the engine cycle performance, the designers of disk cavity cooling and sealing systems need to accomplish these tasks with the minimum possible amount of bleed air without risking disk failure. This requires detailed knowledge of the flow characteristics and convective heat transfer in the cavity. The flow in the wheel space between the rotor and stator disks is quite complex. It is usually turbulent and contains recirculation regions. Instabilities such as vortices oscillating in space have been observed in the flow. It becomes necessary to obtain both a qualitative understanding of the general pattern of the fluid motion as well as a quantitative map of the velocity and pressure fields.

  17. Extraction of enhanced, ultrashort laser pulses from a passive 10-MHz stack-and-dump cavity

    Science.gov (United States)

    Breitkopf, Sven; Wunderlich, Stefano; Eidam, Tino; Shestaev, Evgeny; Holzberger, Simon; Gottschall, Thomas; Carstens, Henning; Tünnermann, Andreas; Pupeza, Ioachim; Limpert, Jens

    2016-12-01

    Periodic dumping of ultrashort laser pulses from a passive multi-MHz repetition-rate enhancement cavity is a promising route towards multi-kHz repetition-rate pulses with Joule-level energies at an unparalleled average power. Here, we demonstrate this so-called stack-and-dump scheme with a 30-m-long cavity. Using an acousto-optic modulator, we extract pulses of 0.16 mJ at 30-kHz repetition rate, corresponding to 65 stacked input pulses, representing an improvement in three orders of magnitude over previously extracted pulse energies. The ten times longer cavity affords three essential benefits over former approaches. First, the time between subsequent pulses is increased to 100 ns, relaxing the requirements on the switch. Second, it allows for the stacking of strongly stretched pulses (here from 800 fs to 1.5 ns), thus mitigating nonlinear effects in the cavity optics. Third, the choice of a long cavity offers increased design flexibility with regard to thermal robustness, which will be crucial for future power scaling. The herein presented results constitute a necessary step towards stack-and-dump systems providing access to unprecedented laser parameter regimes.

  18. Study of evaluation methods for in-vessel corium retention through external vessel cooling and safety of reactor cavity

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Hoon; Chang, Soon Heung; Choi, Tae Hoon; Kim, Hyun Sop; Yang, Soo Hyung; Kim, Soo Hyung; Kim, Seung Hop; An Hyung Taek; Jeong, Yong Hoon; Huh, Gyun Young [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1998-03-15

    Cooling methodologies for the molten corium resulted from the severe accident of the nuclear power plant is suggested as one of most important items for the safety of the NPP. In this regard, considerable experimental and analytical works have been devoted. In the 1st phase of this project, present status related to the external reactor vessel cooling for the retention of the corium in the reactor vessel and corium at the reactor cavity have been investigated and preliminary studies have been accomplished for the detail evaluation of the each cooling methodology. The preliminary studies include the analysis and detail investigation of the possible phenomena, investigation of the heat transfer correlations and preliminary evaluation of the external reactor vessel cooling using the developed computer code.

  19. Evaluation of depth and profile cavity after laser ablation with different energy of Er:YAG laser radiation

    Science.gov (United States)

    Dostalova, Tatjana; Jelinkova, Helena; Hamal, Karel; Krejsa, Otakar; Kubelka, Jiri; Prochazka, Stanislav

    1996-01-01

    Depth and profile cavity were studied after laser ablation with different energy of Er:YAG laser beam. Longitudinal sections of extracted human teeth were cut and polished to the flat surfaces. The thickness of layer of prepared teeth was from 3 to 5 mm. The check group contained glazed samples of ivory with the similar thickness. The Er:YAG laser drilling machine was operating in a free-running mode. For the preparation we used the energy up to 500 mJ. The repetition rate was 1 or 2 Hz. The laser radiation was focused on the tooth surface using CaF2 lens (f equals 55 mm). During the experiment, teeth were steady and the radiation was delivered by the mechanical arm which was fixed in a special holder. The fine water mist (water - 50 ml/min with the pressure to atm, air-pressure three atm) was used. Samples with the flat surfaces from the enamel, dentin and ivory were irradiated with five different energies from 100 to 500 mJ. Quantities of one, five, ten, twenty and thirty pulses were used. The depth of cavity and its profile were observed and measured. It was found that depth of cavity depends on the value of energy, type of hard dental tissue and number of pulses. With increasing energy or number of pulses the saturation effect in depth of holes in dentine or enamel were proved.

  20. Accuracy of navigated control concepts using an Er: Yag-laser for cavity preparation.

    Science.gov (United States)

    Wolff, Regine; Weitz, Jochen; Poitzsch, Luise; Hohlweg-Majert, Bettina; Deppe, Herbert; Lueth, Tim C

    2011-01-01

    This paper describes a method for measuring the shape accuracy of a cylindrical hole which is created by means of an automatically power-controlled laser system using navigated control. In dental surgery, drills or mills are used for bone treatment. For most patients the use of these instruments is very inconvenient. Furthermore, the bone treatment with rotating instruments can lead to thermal necrosis. Using a laser system could be a good alternative for the patient. The utilization of a laser system could also facilitate bone treatment without any severe thermal damage. An optical navigation system can be used for a safer handling of a laser system. The position and the orientation of the laser handpiece relative to the patient can be calculated. Thereby, the laser can be automatically switched off, if the end of the laser beam does not hit the preoperative planned area. In order to measure the accuracy of such a laser system, we created several cavities in a phantom with a manually guided, automatically power-controlled laser. Afterwards, the deviation between the planned shape and the shape created by manually guided automatically power-controlled laser treatment has been measured. The application of this system showed, that the required accuracy of <1 mm for dental implantology applications, could not be reached.

  1. Nanotube-mode-locked linear-cavity fiber laser delivering switchable ultrafast solitons

    Science.gov (United States)

    Han, X. X.

    2015-02-01

    We propose a linear-cavity switchable fiber laser based on a single-wall carbon nanotube mode-locker for the first time to the best of our knowledge. Two chirped fiber Bragg gratings (CFBGs) in series and an optical circulator are employed as end mirrors of the linear cavity. The linear-cavity fiber laser is simple and cost-efficient. By adjusting the polarization controllers, a switchable mode-locking operation is obtained at 1551.3 and 1557.9 nm respectively, corresponding to the central wavelengths of two series-wound CFBGs. The pulse duration and spectral bandwidth of ultrafast solitons are ~4.4 ps and ~0.65 nm for the short wavelength operation at 1551.3 nm and ~3.9 ps and ~0.71 nm for the long wavelength operation at 1557.9 nm, respectively. Our experimental observations are well confirmed by the numerical results. The linear-cavity all-fiber laser reduces the cost and is very attractive for ultrafast optics.

  2. Optical feedback characteristics in a helium neon laser with a birefringent internal cavity

    Institute of Scientific and Technical Information of China (English)

    Mao Wei; Zhang Shu-Lian; Xu Ting; Wan Xin-Jun; Liu Gang

    2007-01-01

    The output characteristics of optical feedback in a helium-neon laser with a birefringent internal cavity are studied systematically in five different regions of the gain curve for the two orthogonally polarized modes. When the laser operates in the two end regions of the laser gain curve, one of the two orthogonally polarized modes will be a leading one in optical feedback. Strong mode competition can be observed. However, when the laser operates in the middle region of the laser gain curve, the two modes can oscillate equally with optical feedback. Besides the intensity of the two polarized lights, the total light intensity is also studied at the same time. M-shaped optical feedback curves are found. Particularly, when the average intensities of the two lights are comparable, the intensity modulation curve of the total light is doubled, which can be used to improve the resolution of an optical feedback system.

  3. Optically controllable dual-mode switching in single-mode Fabry-Pérot laser diode subject to one side-mode feedback and external single mode injection

    Science.gov (United States)

    Wu, Jian-Wei; Won, Yong Hyub

    2017-06-01

    In this paper, broadly tunable dual-mode lasing system is presented and demonstrated based on single-mode Fabry-Pérot laser diode subject to the feedback of one side mode amplified by an erbium-doped fiber amplifier in the external feedback cavity. The spacing between two resonance modes in output lasing spectrum is broadly tuned by introducing differently amplified side mode into the single-mode laser via the external cavity consisted of amplifier, filter, and polarization controller so that two difference frequencies of 1 THz and 0.6 THz are given to display the tunable behavior of dual-mode emission in this work. Therefore, under an external injection mode into the laser condition, the power dependent injection locking and optical bistability of generated dual-mode emission are discussed in detail. At different wavelength detunings, the emitted two resonance modes including the dominant and feedback modes are switched to on- or off-state by selecting proper high-low power level of the external injection mode. As a consequence, the maximum value of achieved dual-mode on-off ratio is as high as up to 45 dB.

  4. High efficiency cholesteric liquid crystal lasers with an external stable resonator.

    Science.gov (United States)

    Shirvani-Mahdavi, Hamidreza; Fardad, Shima; Mohajerani, Ezeddin; Wu, Shin-Tson

    2010-06-21

    An amplified cholesteric liquid crystal (CLC) laser performance is demonstrated by utilizing a binary-dye mixture (with 62 wt% DCM and 38 wt% PM597) as the active medium and an external stable resonator. The measured results show that the laser efficiency is enhanced as compared to the highest efficiency of each individual dye. Furthermore, using such an active CLC in an external stable resonator leads to a approximately 92X improved efficiency over the single CLC laser. In this instance, the binary-dye doped CLC simultaneously functions as laser oscillator and amplifier.

  5. Research of seal materials adhesion to walls of cavity in enamel and dentin formation by Er laser radiation

    Science.gov (United States)

    Altshuler, Gregory B.; Belikov, Andrei V.; Vlasova, Svetlana N.; Erofeev, Andrew V.

    1994-12-01

    The present work represents the results of research of mechanical strength formed by submillisecond pulses of Er-laser at the border of enamel-seal and dentine-seal in a cavity. Comparative research of an adhesion of three of the most widespread types of modern seal materials (cement, amalgam, polymer) to walls of the laser cavity are conducted. The comparison of `laser adhesion' with adhesion of these materials to the walls of the cavity has been made by the usual mechanical tools. The dependence of free adhesion energy from the geometry of the cavity and energy density of laser radiation is considered. This work informs the reader about the results of research removal efficiency of some modern seal materials. The influence of water-spray on the efficiency of seal materials laser treatment process is considered.

  6. Methods for determining optical power, for power-normalizing laser measurements, and for stabilizing power of lasers via compliance voltage sensing

    Energy Technology Data Exchange (ETDEWEB)

    Taubman, Matthew S; Phillips, Mark C

    2015-04-07

    A method is disclosed for power normalization of spectroscopic signatures obtained from laser based chemical sensors that employs the compliance voltage across a quantum cascade laser device within an external cavity laser. The method obviates the need for a dedicated optical detector used specifically for power normalization purposes. A method is also disclosed that employs the compliance voltage developed across the laser device within an external cavity semiconductor laser to power-stabilize the laser mode of the semiconductor laser by adjusting drive current to the laser such that the output optical power from the external cavity semiconductor laser remains constant.

  7. Enhanced efficiency of plasma acceleration in the laser-induced cavity pressure acceleration scheme

    Science.gov (United States)

    Badziak, J.; Rosiński, M.; Jabłoński, S.; Pisarczyk, T.; Chodukowski, T.; Parys, P.; Rączka, P.; Krousky, E.; Ullschmied, J.; Liska, R.; Kucharik, M.

    2015-01-01

    Among various methods for the acceleration of dense plasmas the mechanism called laser-induced cavity pressure acceleration (LICPA) is capable of achieving the highest energetic efficiency. In the LICPA scheme, a projectile placed in a cavity is accelerated along a guiding channel by the laser-induced thermal plasma pressure or by the radiation pressure of an intense laser radiation trapped in the cavity. This arrangement leads to a significant enhancement of the hydrodynamic or electromagnetic forces driving the projectile, relative to standard laser acceleration schemes. The aim of this paper is to review recent experimental and numerical works on LICPA with the emphasis on the acceleration of heavy plasma macroparticles and dense ion beams. The main experimental part concerns the research carried out at the kilojoule sub-nanosecond PALS laser facility in Prague. Our measurements performed at this facility, supported by advanced two-dimensional hydrodynamic simulations, have demonstrated that the LICPA accelerator working in the long-pulse hydrodynamic regime can be a highly efficient tool for the acceleration of heavy plasma macroparticles to hyper-velocities and the generation of ultra-high-pressure (>100 Mbar) shocks through the collision of the macroparticle with a solid target. The energetic efficiency of the macroparticle acceleration and the shock generation has been found to be significantly higher than that for other laser-based methods used so far. Using particle-in-cell simulations it is shown that the LICPA scheme is highly efficient also in the short-pulse high-intensity regime and, in particular, may be used for production of intense ion beams of multi-MeV to GeV ion energies with the energetic efficiency of tens of per cent, much higher than for conventional laser acceleration schemes.

  8. Split-disk micro-lasers: Tunable whispering gallery mode cavities

    Directory of Open Access Journals (Sweden)

    T. Siegle

    2017-09-01

    Full Text Available Optical micro-cavities of various types have emerged as promising photonic structures, for both the investigation of fundamental science in cavity quantum electrodynamics and simultaneously for various applications, e.g., lasers, filters, or modulators. In either branch a demand for adjustable and tunable photonic devices becomes apparent, which has been mainly based on the modification of the refractive index of the micro-resonators so far. In this paper, we report on a novel type of whispering gallery mode resonator where resonance tuning is achieved by modification of the configuration. This is realized by polymeric split-disks consisting of opposing half-disks with an intermediate air gap. Functionality of the split-disk concept and its figures of merit like low-threshold lasing are demonstrated for laser dye-doped split-disks fabricated by electron beam lithography on Si substrates. Reversible resonance tuning is achieved for split-disks structured onto elastomeric substrates by direct laser writing. The gap width and hence the resonance wavelength can be well-controlled by mechanically stretching the elastomer and exploiting the lateral shrinkage of the substrate. We demonstrate a broad spectral tunability of laser modes by more than three times the free spectral range. These cavities have the potential to form a key element of flexible and tunable photonic circuits based on polymers.

  9. Split-disk micro-lasers: Tunable whispering gallery mode cavities

    Science.gov (United States)

    Siegle, T.; Remmel, M.; Krämmer, S.; Kalt, H.

    2017-09-01

    Optical micro-cavities of various types have emerged as promising photonic structures, for both the investigation of fundamental science in cavity quantum electrodynamics and simultaneously for various applications, e.g., lasers, filters, or modulators. In either branch a demand for adjustable and tunable photonic devices becomes apparent, which has been mainly based on the modification of the refractive index of the micro-resonators so far. In this paper, we report on a novel type of whispering gallery mode resonator where resonance tuning is achieved by modification of the configuration. This is realized by polymeric split-disks consisting of opposing half-disks with an intermediate air gap. Functionality of the split-disk concept and its figures of merit like low-threshold lasing are demonstrated for laser dye-doped split-disks fabricated by electron beam lithography on Si substrates. Reversible resonance tuning is achieved for split-disks structured onto elastomeric substrates by direct laser writing. The gap width and hence the resonance wavelength can be well-controlled by mechanically stretching the elastomer and exploiting the lateral shrinkage of the substrate. We demonstrate a broad spectral tunability of laser modes by more than three times the free spectral range. These cavities have the potential to form a key element of flexible and tunable photonic circuits based on polymers.

  10. Faraday laser using 1.2 km fiber as an extended cavity

    Science.gov (United States)

    Tao, Zhiming; Zhang, Xiaogang; Pan, Duo; Chen, Mo; Zhu, Chuanwen; Chen, Jingbiao

    2016-07-01

    We demonstrate a Faraday laser using a 1.2 km fiber as an extended cavity, which provides optical feedback and obtains small free spectrum range (FSR) of 83 kHz, and have succeeded in limiting the laser frequency to a crossover transition {5}2{S}1/2,F=2\\to {5}2{P}3/2,F\\prime =1,3 of the natural 87Rb at 780 nm. The Faraday laser is based on a Faraday anomalous dispersion optical filter (FADOF) with an ultra-narrow bandwidth and the long fiber extended cavity of 1.2 km. The peak transmission assigned to the crossover transition F=2\\to F\\prime =1,3 in the FADOF is 20.5% with an ultra-narrow bandwidth of 29.1 MHz. The Allan deviation of the Faraday laser is around 6.0× {10}-11 in 0.06 to 1 s sampling time. Laser frequency is always kept in the center of the transmitted peak assigned to F=2\\to F\\prime =1,3. The Faraday laser realized here can provide light exactly resonant with an atomic transition used for atom-photon interaction experiments and is insensitive to diode temperature and injection current fluctuations.

  11. Evaluation of micromorphological changes in tooth enamel after mechanical and ultrafast laser preparation of surface cavities.

    Science.gov (United States)

    Luengo, Ma Cruz Lorenzo; Portillo, M; Sánchez, J M; Peix, M; Moreno, P; García, A; Montero, J; Albaladejo, A

    2013-01-01

    The aim of this in vitro study was to evaluate the morphological changes that occur in tooth enamel after mechanical instrumentation and after femtosecond laser irradiation with different parameters via light and scanning electron microscopy (SEM). Twelve totally impacted third molars were collected and sectioned to provide several cut surfaces. These surfaces were exposed to infrared (λ = 795 nm, 120 fs, 1-kHz repetition rate, maximum mean power 1 W) laser pulses and machined by means of a conventional mechanical technique. Two very different geometrical patterns were performed with femtosecond laser pulses: shallow rectangular cavities and deep cylindrical ones. The results of both machining procedures were examined using light and scanning electron microscopy. The SEM images show the femtosecond laser ability to produce high-precision cavities in tooth enamel. No signs of collateral damage, burning, melting, or cracks were observed despite the far different laser pulse energies used (ranging from 7 to 400 μJ), unlike what is seen with conventional mechanical techniques. The femtosecond laser has the potential to become an optimal tool for the treatment of dental decay and as an alternative to the conventional drill to reduce mechanical damage during removal of the hard dental tissue.

  12. Self-consistent Maxwell-Bloch model of quantum-dot photonic-crystal-cavity lasers

    Science.gov (United States)

    Cartar, William; Mørk, Jesper; Hughes, Stephen

    2017-08-01

    We present a powerful computational approach to simulate the threshold behavior of photonic-crystal quantum-dot (QD) lasers. Using a finite-difference time-domain (FDTD) technique, Maxwell-Bloch equations representing a system of thousands of statistically independent and randomly positioned two-level emitters are solved numerically. Phenomenological pure dephasing and incoherent pumping is added to the optical Bloch equations to allow for a dynamical lasing regime, but the cavity-mediated radiative dynamics and gain coupling of each QD dipole (artificial atom) is contained self-consistently within the model. These Maxwell-Bloch equations are implemented by using Lumerical's flexible material plug-in tool, which allows a user to define additional equations of motion for the nonlinear polarization. We implement the gain ensemble within triangular-lattice photonic-crystal cavities of various length N (where N refers to the number of missing holes), and investigate the cavity mode characteristics and the threshold regime as a function of cavity length. We develop effective two-dimensional model simulations which are derived after studying the full three-dimensional passive material structures by matching the cavity quality factors and resonance properties. We also demonstrate how to obtain the correct point-dipole radiative decay rate from Fermi's golden rule, which is captured naturally by the FDTD method. Our numerical simulations predict that the pump threshold plateaus around cavity lengths greater than N =9 , which we identify as a consequence of the complex spatial dynamics and gain coupling from the inhomogeneous QD ensemble. This behavior is not expected from simple rate-equation analysis commonly adopted in the literature, but is in qualitative agreement with recent experiments. Single-mode to multimode lasing is also observed, depending on the spectral peak frequency of the QD ensemble. Using a statistical modal analysis of the average decay rates, we also

  13. Using active resonator impedance matching for shot-noise limited, cavity enhanced amplitude modulated laser absorption spectroscopy.

    Science.gov (United States)

    Chow, Jong H; Littler, Ian C M; Rabeling, David S; McClelland, David E; Gray, Malcolm B

    2008-05-26

    We introduce a closed-loop feedback technique to actively control the coupling condition of an optical cavity, by employing amplitude modulation of the interrogating laser. We show that active impedance matching of the cavity facilitates optimal shot-noise sensing performance in a cavity enhanced system, while its control error signal can be used for intra-cavity absorption or loss signal extraction. We present the first demonstration of this technique with a fiber ring cavity, and achieved shot-noise limited loss sensitivity. We also briefly discuss further use of impedance matching control as a tool for other applications.

  14. Evolution of Gaussian beams and pulsed laser action in laser with unstable resonant cavities

    Energy Technology Data Exchange (ETDEWEB)

    Isaev, A.A.; Kazarian, M.A.; Petrash, G.G.; Rautian, S.G.; Shalagin, A.M.

    1975-06-01

    A recurrent formula is derived which describes the passage of a Gaussian beam through an unstable resonant cavity and through a periodic optical system. The changes in the position and in the beam neck at the mirror within an arbitrary unstable cavity are analyzed as a function of the beam's initial parameters and the number of passages in the cavity. The evolution of nonaxial Gaussian beams is studied, and a generalization of the Lagrange-Helmholtz theorem is proposed.

  15. Flip-chip bonding of vertical-cavity surface-emitting lasers using laser-induced forward transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, K. S., E-mail: Kaur.Kamalpreet@elis.ugent.be; Missinne, J.; Van Steenberge, G. [Centre for Microsystems Technology, imec/Ghent University, Technologiepark 914A, B-9052 Gent (Belgium)

    2014-02-10

    This letter reports the use of the Laser-Induced Forward Transfer (LIFT) technique for the fabrication of indium micro-bumps for the flip-chip (FC) bonding of single vertical-cavity surface-emitting laser chips. The FC bonded chips were electrically and optically characterized, and the successful functioning of the devices post-bonding is demonstrated. The die shear and life-time tests carried out on the bonded chips confirmed the mechanical reliability of the LIFT-assisted FC bonded assemblies.

  16. Numerical Investigation of Vertical Cavity Lasers With High-Contrast Gratings Using the Fourier Modal Method

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2016-01-01

    , the scattering losses of several HCG-based vertical cavities with inplane heterostructures which have promising prospects for fundamental physics studies and on-chip laser applications, are investigated. This type of parametric study of 3D structures would be numerically very demanding using spatial......We explore the use of a modal expansion technique, Fourier modal method (FMM), for investigating the optical properties of vertical cavities employing high-contrast gratings (HCGs). Three techniques for determining the resonance frequency and quality factor (Q-factor) of a cavity mode are compared......, and the computational uncertainties in the resonance frequency and Qfactor calculations are analyzed. Moreover, a method for reducing a three-dimensional (3D) simulation to lower-dimensional simulations is suggested, which allows for very fast and approximate analysis of a 3D structure. By using the implemented FMM...

  17. Displacement- and laser-noise-free gravitational-wave detection with two Fabry-Perot cavities

    CERN Document Server

    Rakhubovsky, Andrey A

    2008-01-01

    We propose two Fabry-Perot cavities, each pumped through both the mirrors, positioned in line as a toy model of the gravitational-wave (GW) detector free from displacement noise of the test masses. It is demonstrated that the displacement noise of cavity mirrors as well as laser noise can be completely excluded in a proper linear combination of the cavities output signals. We show that in low-frequency approximation (gravitational wave length $\\lambda-\\text{gw}$ is much greater than distance $L$ between mirrors $\\lambda_\\text{gw}\\gg L$) the decrease of response signal is about $(L/\\lambda_\\text{gw})^2$, i.e. signal is stronger than the one of the interferometer recently proposed by S. Kawamura and Y. Chen.

  18. Preparatory procedure and equipment for the European x-ray free electron laser cavity implementation

    Energy Technology Data Exchange (ETDEWEB)

    Reschke, D.; Bandelmann, R.; Buettner, T.; Escherich, K.; Goessel, A.; v.d.Horst, B.; Iversen, J.; Klinke, D.; Kreps, G.; Krupka, N.; Lilje, L.; /DESY /Fermilab

    2010-07-01

    The European x-ray free electron laser is under construction at Deutsches Elektronen-Synchrotron (DESY). The electron beam energy of up to 17.5 GeV will be achieved by using superconducting accelerator technology. Final prototyping, industrialization, and new infrastructure are the actual challenges with respect to the accelerating cavities. This paper describes the preparation strategy optimized for the cavity preparation procedure in industry. For the industrial fabrication and preparation, several new hardware components have been already developed at DESY. The design and construction of a semiautomated rf-measurement machine for dumbbells and end groups are described. In a collaboration among FNAL, KEK, and DESY, an automatic cavity tuning machine has been designed and four machines are under construction. The functionality of these machines with special attention to safety aspects is described in this paper. A new high pressure rinsing system has been developed and is operational.

  19. Optimization of the multiwavelength erbium-doped fiber laser in a unidirectional cavity without isolator

    Science.gov (United States)

    Sun, Guoyong; Chung, Youngjoo; Luo, Zhengqian; Cai, Zhiping; Ye, Chenchun

    2007-07-01

    Highly uniform multiwavelength erbium-doped fiber ring laser with an intra-cavity sine phase modulator is demonstrated. The flat output spectrum is achieved by optimizing the cavity structure, modulation amplitude and frequency of the sine phase modulator. 15 lasing lines with wavelength spacing of 0.9 nm appear simultaneously and stably in power differences less than 2 dB and the side mode suppression ratio higher than 32 dB. In addition, the proposed cavity can support unidirectional operation without optical isolators. The output power difference of about 20 dB is realized between counterclockwise and clockwise direction, which is almost independent of the pump power and lasing wavelengths.

  20. Simple vibration insensitive cavity for laser stabilization at the 10^{-16} level

    CERN Document Server

    Keller, Jonas; Webster, Stephen A; Mehlstäubler, Tanja E

    2013-01-01

    We present the design and realization of two reference cavities for ultra-stable lasers addressing narrow transitions in mixed-species (In+ / Yb+) Coulomb crystals. With a simple setup, we achieve a fractional frequency instability close to the thermal noise limit of a 12 cm long cavity, reaching 4.7*10^{-16} at 10 s with a linear drift of 53 mHz/s. We discuss the individual instability contributions and show that in a setup with a lower thermal noise floor and vibration sensitivity, an instability of 1*10^{-16} can be reached. To achieve this, we implement a vibration insensitive design for a 30 cm long cavity mounted horizontally and conduct first tests that show a sensitivity of 1.8*10^{-11} / ms^{-2} to vertical accelerations. Mechanical tolerances and ways to further reduce the sensitivity are discussed.

  1. External and Internal Reconnection in Two Filament-Carrying Magnetic Cavity Solar Eruptions

    Science.gov (United States)

    Sterling, Alphonse C.; Moore, Ronald L.

    2004-01-01

    We observe two near-limb solar filament eruptions. one of 2000 February 26 and the other of 2002 January 4. For both we use 195 A Fe XII images from the Extreme-Ultraviolet Imaging Telescope (EIT) and magnetograms from the Michelson Doppler Imager (MDI). both of which are on the Solar and Heliospheric Observatory. (SOHO). For the earlier event we also use soft X-ray telescope (SXT). hard X-ray telescope (HXT). and Bragg Crystal Spectrometer (BCS) data from the Yohkoh satellite. and hard X-ray data from the BATSE experiment on the Compton Gamma Ray Observatory. (CGRO). Both events occur in quadrupolar magnetic regions. and both have coronal features that we infer belong to the same magnetic cavity structures as the filaments. In both cases. the cavity and filament first rise slowly at approx. 10 km/s prior to eruption and then accelerate to approx. 100 km/s during the eruption. although the slow-rise movement for the higher altitude cavity elements is clearer in the later event. We estimate that both filaments and both cavities contain masses of approx. 10(exp14) - 1 0(exp 15) and approx. l0(exp 15) - l0(exp 16) g. respectively. We consider whether two specific magnetic reconnection-based models for eruption onset. the "tether cutting" and the "breakout" models. are consistent with our observations. In the earlier event, soft X-rays from SXT show an intensity increase during the 12 minute interval over which fast eruption begins. which is consistent with tether- cutting-model predictions. Substantial hard X-ray. however. do not occur until after fast eruption is underway. and so this is a constraint the tether-cutting model must satisfy. During the same 12 minute interval over which fast eruption begins, there are brightenings and topological changes in the corona indicative of high-altitude reconnection early in the eruption. and this is consistent with breakout predictions. In both eruptions. the state of the overlying loops at the time of onset of the fast

  2. External and Internal Reconnection in Two Filament-Carrying Magnetic-Cavity Solar Eruptions

    Science.gov (United States)

    Sterling, Alphonse C.; Moore, Ronald L.

    2004-01-01

    We observe two near-limb solar filament eruptions, one of 2000 February 26 and the other of 2002 January 4. For both we use 195 A Fe XII images from the Extreme-Ultraviolet Imaging Telescope (EIT) and magnetograms from the Michelson Doppler Imager (MDI), both of which are on the Solar and Heliospheric Observatory (SOHO). For the earlier event we also use soft X-ray telescope (SXT), hard X-ray telescope (HXT), and Bragg Crystal Spectrometer (BCS) data from the Yohkoh satellite, and hard X-ray data from the BATSE experiment on the Compton Gamma Ra.v Observatory (CGRO). Both events occur in quadrupolar magnetic regions, and both have coronal features that we infer belong to the same magnetic cavity structures as the filaments. In both cases, the cavity and filament first rise slowly at approx.10 km/s prior to eruption and then accelerate to approx.100 km/s during the eruption, although the slow-rise movement for the higher altitude cavity elements is clearer in the later event. We estimate that both filaments and both cavities contain masses of approx.10(exp 14)-10(exp 15) and approx.10(exp 15)-10(exp 16) g, respectively. We consider whether two specific magnetic reconnection-based models for eruption onset, the "tether cutting" and the "breakout" models, are consistent with our observations. In the earlier event, soft X-rays from SXT show an intensity increase during the 12 minute interval over which fast eruption begins, which is consistent with tether- cutting-model predictions. Substantial hard X-rays, however, do not occur until after fast eruption is underway, and so this is a constraint the tether-cutting model must satisfy. During the same 12 minute interval over which fast eruption begins, there are brightenings and topological changes in the corona indicative of high-altitude reconnection early in the eruption, and this is consistent with breakout predictions. In both eruptions, the state of the overlying loops at the time of onset of the fast-rise phase of

  3. Intra-cavity frequency-doubled mode-locked semiconductor disk laser at 325 nm.

    Science.gov (United States)

    Bek, Roman; Baumgärtner, Stefan; Sauter, Fabian; Kahle, Hermann; Schwarzbäck, Thomas; Jetter, Michael; Michler, Peter

    2015-07-27

    We present a passively mode-locked semiconductor disk laser (SDL) emitting at 650nm with intra-cavity second harmonic generation to the ultraviolet (UV) spectral range. Both the gain and the absorber structure contain InP quantum dots (QDs) as active material. In a v-shaped cavity using the semiconductor samples as end mirrors, a beta barium borate (BBO) crystal is placed in front of the semiconductor saturable absorber mirror (SESAM) for pulsed UV laser emission in one of the two outcoupled beams. Autocorrelation (AC) measurements at the fundamental wavelength reveal a FWHM pulse duration of 1.22ps. With a repetition frequency of 836MHz, the average output power is 10mW per beam for the red emission and 0.5mW at 325nm.

  4. Diffraction coupled phase-locked arrays of quantum cascade lasers with monolithically integrated Talbot cavities

    CERN Document Server

    Wang, Lei; Jia, Zhi-Wei; Zhao, Yue; Liu, Chuan-Wei; Liu, Ying-Hui; Zhai, Shen-Qiang; Zhuo, Ning; Liu, Feng-Qi; Xu, Xian-Gang

    2016-01-01

    Diffraction coupled arrays of quantum cascade laser are presented. The phase-locked behavior is achieved through monolithic integration of a Talbot cavity at one side of the laser array. The principle is based on fractional Talbot effect. By controlling length of Talbot cavity to be a quarter of Talbot distance (Zt/4), in-phase mode operation is selected. Measured far-field radiation patterns reflect stable in-phase mode operation under different injection currents, from threshold current to full power current. Diffraction-limited performance is shown from the lateral far-field, where three peaks can be obtained and main peak and side peak interval is 10.5{\\deg}. The phase-locked arrays with in-phase mode operation may be a feasible solution to get higher output power and maintain well beam quality meanwhile.

  5. Polymer-coated vertical-cavity surface-emitting laser diode vapor sensor

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2010-01-01

    We report a new method for monitoring vapor concentration of volatile organic compounds using a vertical-cavity surface-emitting laser (VCSEL). The VCSEL is coated with a polymer thin film on the top distributed Bragg reflector (DBR). The analyte absorption is transduced to the electrical domain ...... through modulation of the VCSEL output power as the polymer swell. We have investigated the responsivity of this technique experimentally using a plasma polymerized polystyrene coating and explain the results theoretically as a reflectance modulation of the top DBR.......We report a new method for monitoring vapor concentration of volatile organic compounds using a vertical-cavity surface-emitting laser (VCSEL). The VCSEL is coated with a polymer thin film on the top distributed Bragg reflector (DBR). The analyte absorption is transduced to the electrical domain...

  6. Dynamic Range of Vertical Cavity Surface Emitting Lasers in Multimode Links

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.L.T.; Dalal, R.V.; Ram, R.J.; Choquette, K.D.

    1999-07-07

    The authors report spurious free dynamic range measurements of 850nm vertical cavity surface emitting lasers in short multimode links for radio frequency communication. For a 27m fiber link, the dynamic range at optimal bias was greater than 95dB-Hz{sup 2/3} for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free space link, they have measured the highest dynamic range in an 850nm vertical cavity surface emitting laser of 113dB-Hz{sup 2/3} at 900MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.

  7. Effective index model predicts modal frequencies of vertical-cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    SERKLAND,DARWIN K.; HADLEY,G. RONALD; CHOQUETTE,KENT D.; GEIB,KENT M.; ALLERMAN,ANDREW A.

    2000-04-18

    Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

  8. 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.

  9. Theoretical investigation of external injection schemes for laser wakefield acceleration

    NARCIS (Netherlands)

    Luttikhof, Mark Jan Hendrik

    2010-01-01

    This thesis reports on laser wakefield acceleration, a radically new approach for particle acceleration that builds on the huge electric fields that a plasma wave can provide. In this approach, an ultra-short laser pulse of high intensity is sent through a plasma. At sufficient intensity, the radiat

  10. Tunable Vertical-Cavity Surface-Emitting Lasers Integrated with Two Wafers

    Institute of Scientific and Technical Information of China (English)

    REN Xiu-Juan; GUAN Bao-Lu; GUO Shuai; LI Shuo; LI Chuan-Chuan; HAO Cong-Xia; ZHOU Hong-Yi; GUO Xiao

    2011-01-01

    A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs)is presented. The VCSEL is composed by two wafers: one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a "half-VCSEL" wafer consisting of a fixed bottom mirror and an amplifying active region. The measurement results of the electricity pumped tunable VCSEL with more than 9mW output power at room temperature over the tuning range prove the feasibility of the proposition.%@@ A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs) is presented.The VCSEL is composed by two wafers: one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a "half-VCSEL" wafer consisting of a fixed bottom mirror and an amplifying active region.The measurement results of the electricity pumped tunable VCSEL with more than 9mW output power at room temperature over the tuning range prove the feasibility of the proposition.

  11. Reflective SOA fiber cavity adaptive laser source for measuring dynamic strains

    Science.gov (United States)

    Wei, Heming; Tao, Chuanyi; Krishnaswamy, Sridhar

    2016-04-01

    Smart sensors based on Optical fiber Bragg gratings (FBGs) are suitable for structural health monitoring of dynamic strains in civil, aerospace, and mechanical structures. In these structures, dynamic strains with high frequencies reveal acoustic emissions cracking or impact loading. It is necessary to find a practical tool for monitoring such structural damages. In this work, we explore an intelligent system based on a reflective semiconductor optical amplifier (RSOA)- FBG composed as a fiber cavity for measuring dynamic strain in intelligent structures. The ASE light emitted from a RSOA laser and reflected by a FBG is amplified in the fiber cavity and coupled out by a 90:10 coupler, which is demodulated by a low frequency compensated Michelson interferometer using a proportional-integral-derivative (PID) controller and is monitored via a photodetector. As the wavelength of the FBG shifts due to dynamic strain, the wavelength of the optical output from the laser cavity shifts accordingly, which is demodulated by the Michelson Interferometer. Because the RSOA has a quick transition time, the RSOA- FBG fiber cavity shows an ability of high frequency response to the FBG reflective spectrum shift, with frequency response extending to megahertz.

  12. Cavity ringdown laser absorption spectroscopy detection of formyl (HCO) radical in a low pressure flame

    Science.gov (United States)

    Scherer, J. J.; Rakestraw, D. J.

    1997-01-01

    The formyl radical has been detected via the ÖX˜ system in a low pressure CH 4/N 2/O 2 flame using cavity ringdown laser absorption spectroscopy. The direct absorption data obtained in these initial studies allows determination of the absolute HCO concentration in the flame of ca. 2.1(±0.9) × 10 13 mol cm -3, which is in excellent agreement with flame chemistry simulations. The extrapolated detection limit at 300 K of ≈ 1.4(±0.6) × 10 11 mol cm -3 is comparable to that of other methods, including intracavity laser absorption spectroscopy.

  13. Operational characteristics of dual gain single cavity Nd:YVO4 laser

    Indian Academy of Sciences (India)

    Pranab K Mukhopadhyay; Jogy George; S K Sharma; P K Gupta; T P S Nathan

    2002-01-01

    Operational characteristics of a dual gain single cavity Nd:YVO4 laser have been investigated. With semiconductor diode laser pump power of 2 W, 800 mW output was obtained with a slope efficiency of 49%. Further, by changing the relative orientation of the two crystals the polarization characteristics of the output could be varied. In particular by keeping the two Nd:YVO4 crystals with their -axes orthogonal to each other and adjusting the gain of the crystals so that both operate at approximately the same power level, completely unpolarized beams could be obtained.

  14. Modulation of a CO/sub 2/ laser by plasma injection into the cavity

    Energy Technology Data Exchange (ETDEWEB)

    John, P.K. (Western Ontario, University, London, Canada); Box, S.J.C.

    1980-05-01

    Observations of simultaneous Q-switching and mode-locking have been made in a TEA CO/sub 2/ laser when a low density underdense plasma was injected into the cavity. The plasma which was produced in an electromagnetic shock tube had a density of 10 to the 17th per cu cm. A likely mechanism for mode-locking is the time dependent plasma refractive index leading to phase perturbation.

  15. Digital wavelength switching by thermal and carrier injection effects in V-coupled cavity semiconductor laser

    Institute of Scientific and Technical Information of China (English)

    Jialiang Jin; Lei Wang; Jianjun He

    2012-01-01

    Consecutive wavelength switching characteristics of a simple,compact,and digitally wavelength-switchable laser based on V-coupled cavities are reported.Wavelength switching through thermal and carrier injection effects is examined.Without using band gap engineering for the tuning section,26- and 9-channel wavelength switching schemes are achieved via thermal and carrier injection effects,respectively.The performances of these two tuning schemes are then compared.

  16. Conditioning effects of cavities prepared with an Er,Cr:YSGG laser and an air-turbine.

    Science.gov (United States)

    Kato, Chikage; Taira, Yoshihisa; Suzuki, Masaya; Shinkai, Koichi; Katoh, Yoshiroh

    2012-07-01

    The purpose of this study was to examine, morphologically and histochemically, five types of conditioning effects on cavities prepared with an Er,Cr:YSGG laser and an air-turbine. Cavities were prepared using a Waterlase(®) MD turbo handpiece (W) and an air-turbine (AT) on human extracted molars. The cavity conditionings used were non-conditioned (G1), K-etchant Gel (G2), K-etchant Gel + AD Gel (G3), Clearfil SE Bond primer (G4) and Clearfil S(3) Bond (G5). On naked eye observations, enamel of G1, G2 and G3 in the W cavities and etched enamel of G2 and G3 in the AT cavities were observed as rough and dull in appearance. G4 and G5 in W and AT cavities were observed as shiny surfaces. On SEM observations, no smeared layer was observed in W cavities, while a smeared layer and bur-scratches were observed in AT cavities. In W cavities, rough surfaces were observed on enamel. That is, cracks and minute rough surfaces were observed. In contrast, equally etched scale-shaped enamel rods were observed in AT cavities. Widely opened dentinal tubules and protruding peritubular matrices of dentin were observed in W cavities. A few remaining smeared plugs could be observed at the AT cavities. On LM observations, 13-16 μm layers of the dentin in G1, G2, G4 and G5 of W cavities were stained red in color by the Azan staining method, while redness was not observed in G3. No groups were stained red in AT cavities. It was considered that layers stained red in color were thermal degeneration layers of dentin induced by W. Namely 30 s etching of 40% phosphoric acid gel followed by 90 s treatment of 10% NaClO gel should be recommended for use when combined with an Er,Cr:YSGG laser for cavity preparation.

  17. Effects of output coupler reflectivity on the performance of a linear cavity Brillouin/erbium fiber laser

    Indian Academy of Sciences (India)

    X S Cheng; S W Harun; H Ahmad

    2007-03-01

    The effect of output coupler reflectivity (or output coupling ratio) on the performance of a linear cavity Brillouin/erbium fiber laser (BEFL) is demonstrated. The operating wavelength, output laser power and number of channels vary with changes in the coupling ratio in the linear cavity system. The optimum BEFL operation is obtained with an output coupling of 40%, i.e., 60% of the laser power is allowed to oscillate in the cavity. A stable laser comb consisting of up to 40 channels with line spacings of approximately 0.09 nm are obtained at the Brillouin pump and 980 nm pump with powers of 2.5 mW and 100 mW, respectively. The linear cavity BEFL has the potential to be used in inexpensive wavelength division multiplexing system.

  18. Wavelength tunable CW red laser generated based on an intracavity-SFG composite cavity

    Science.gov (United States)

    Zhang, Z. N.; Bai, Y.; Lei, G. Z.; Bai, B.; Sun, Y. X.; Hu, M. X.; Wang, C.; Bai, J. T.

    2016-12-01

    We report a wavelength-tunable watt-level continuous wave (CW) red laser that uses a composite cavity based on an intracavity sum-frequency generation (SFG). The composite cavity is composed of a LD side-pumped Nd: GdVO4 p-polarized 1062.9 nm resonant cavity and a resonant optical parametric oscillator (SRO) of s-polarized signal light using a periodically poled crystal MgO: PPLN. Based on the temperature tuning from 30 °C to 200 °C, the CW red laser beams are obtained in a tunable waveband from 634.4 nm to 649.1 nm, corresponding to a tunable output waveband from 3278.0 nm to 2940.2 nm of the mid-infrared idler lights. The maximum CW output power of the red laser at 634.4 nm and the idler light at 3278.0 nm reach 3.03 W and 4.13 W under 30 °C, respectively.

  19. Investigations of repetition rate stability of a mode-locked quantum dot semiconductor laser in an auxiliary optical fiber cavity

    DEFF Research Database (Denmark)

    Breuer, Stefan; Elsässer, Wolfgang; McInerney, J.G.

    2010-01-01

    We have investigated experimentally the pulse train (mode beating) stability of a monolithic mode-locked multi-section quantum-dot laser with an added passive auxiliary optical fiber cavity. Addition of the weakly coupled (¿ -24dB) cavity reduces the current-induced shift d¿/dI of the principal...

  20. Effect of cavity length on low-energy single longitudinal mode pre-lase Q-switched laser

    Science.gov (United States)

    Qing-Song, Li; Yuan, Dong; Yu, Liu; Xi-He, Zhang; Yong-Ji, Yu; Guang-Yong, Jin

    2017-09-01

    In this paper, the effect of cavity length on a low-energy single longitudinal mode (SLM) pre-lase Q-switched laser is analyzed and demonstrated. Taking a Pr:YLF laser as an example, the basic output characteristics under pre-lase technology are shown. The SLM is degraded when the cavity length is as large as 25 mm. Further, for cavity lengths of 15 or 20 mm, SLM is achieved with different output characteristics. Compared with a long cavity (20 mm), the short-cavity case (15 mm) is indeed helpful for obtaining an SLM laser; however, the single-pulse energy, pulse width, and energy extraction efficiency are decreased by 4.7, 48, and 6.7%, respectively. The results of this analysis show that the cavity length influences the output characteristics and determines the realization of SLM in a pre-lase Q-switched laser. This is because the short cavity induces a relatively strong gain identification for the seed signal. Then, the time cost of the mode competition decreases and SLM can be achieved easily. However, a long cavity is conducive to mode competition, which generates superior output characteristics.

  1. Reliability of high power laser diodes with external optical feedback

    Science.gov (United States)

    Bonsendorf, Dennis; Schneider, Stephan; Meinschien, Jens; Tomm, Jens W.

    2016-03-01

    Direct diode laser systems gain importance in the fields of material processing and solid-state laser pumping. With increased output power, also the influence of strong optical feedback has to be considered. Uncontrolled optical feedback is known for its spectral and power fluctuation effects, as well as potential emitter damage. We found that even intended feedback by use of volume Bragg gratings (VBG) for spectral stabilization may result in emitter lifetime reduction. To provide stable and reliable laser systems design, guidelines and maximum feedback ratings have to be found. We present a model to estimate the optical feedback power coupled back into the laser diode waveguide. It includes several origins of optical feedback and wide range of optical elements. The failure thresholds of InGaAs and AlGaAs bars have been determined not only at standard operation mode but at various working points. The influence of several feedback levels to laser diode lifetime is investigated up to 4000h. The analysis of the semiconductor itself leads to a better understanding of the degradation process by defect spread. Facet microscopy, LBIC- and electroluminescence measurements deliver detailed information about semiconductor defects before and after aging tests. Laser diode protection systems can monitor optical feedback. With this improved understanding, the emergency shutdown threshold can be set low enough to ensure laser diode reliability but also high enough to provide better machine usability avoiding false alarms.

  2. SEM evaluation of the hybrid layer after cavity preparation with Er:YAG laser.

    Science.gov (United States)

    de Barceleiro, Marcos Oliveira; Dias, Kátia Regina Hostílio Cervantes; Sales, Helena Xavier; Silva, Bárbara Carvalho; Barceleiro, Cristiane Gomes

    2008-01-01

    This study compared the thickness of the hybrid layer formed using Scotchbond Multi-Purpose Plus, Single Bond 2, Prime & Bond 2.1 and Xeno III on a dentin surface prepared with a diamond bur in a high speed handpiece or prepared with an Er:YAG laser used with two parameters of pulse energy (200 and 400 mJ) and two parameters of frequency (4 and 6 Hz). Flat dentin surfaces obtained from 20 human third molars were treated with the two methods and were then prepared with the dentin adhesive systems according to the manufacturers' instructions. After a layer of composite was applied, the specimens were sectioned, flattened, polished and prepared for Scanning Electronic Microscopy observation. Five different measurements of the hybrid layer thickness were obtained along the bonded surface in each specimen. The results were statistically analyzed using Analysis of Variance and Student-Newman-Keuls tests (p cavity preparation method, four groups were formed: Group I (diamond bur) > Group II (Laser 200 mJ/4 Hz) = Group III (Laser 200 mJ/6 Hz) > Group IV (Laser 400 mJ/4 Hz) > Group V (Laser 400 mJ/6 Hz). When comparing the dentin adhesive systems, there were no statistically significant differences. These results showed that the four tested dentin adhesive systems produced a 2.90 +/- 1.71 microm hybrid layer in dentin prepared with a diamond bur. This hybrid layer was regular and routinely found. In the laser groups, the dentin adhesive systems produced hybrid layers ranging from 0.41 +/- 1.00 microm to 2.06 +/- 2.49 microm, which were very irregular and not routinely found. It was also concluded that the Er:YAG laser, with the parameters used in this experiment, has a negative influence on the formation of a hybrid layer and cavity preparation methods influence formation of the hybrid layer.

  3. Minimal invasive method to treat hemangiomas of the oral cavity with a CO2 laser

    Science.gov (United States)

    Nicola, Ester M. D.; Nicola, Jorge H.; Gusmao, Reinaldo J.; Coutinho, Adriana A.; Cassitas, Nilceu P.

    1997-05-01

    During the last six years we have developed a new CO2 laser technique for the treatment of symptomatic oral cavity hemangioma. Our new technique, named 'laser encircling technique', has especially succeeded during hemangioma buccal maxillary surgeries. The treatment consisted in the application of a line of points of CO2 laser circling the lesion. Depending on the position and size of the lesion, we used from 0.4 to 4.0 Joules/mm2 laser energy density per pulse, causing reduction in the size of the lesion throughout the sclerosis of nutritional vessels which led to reduction in size, volume and color of the hemangiomas with no significant bleeding or inflammatory reaction. In this work forty male and female patients, twelve to fifty years old, presenting medium to small size hemangiomas situated in different sites of the oral cavity such as the tongue, mouth vestibule, pharynx, tonsil area and lips were treated by the procedure described above. The number of laser applications was defined by the peculiarities of each case, varying form 3 to 6 sessions at 4 week intervals, always under local or topic anesthesia. The patients complained about minimal posit operative discomfort and had good cicatrix evolution. The good results achieved by this technique lead to the conclusion that CO2 laser for these types of hemangioma is an efficient and very secure method of treatment. An important aspect of our technique is the fact that using relatively low laser power we do not perform real surgery but a less aggressive alternative of treatment.

  4. 1.34μm Nd:YVO4 high efficiency laser end-pumped by diode-laser of flat-concave cavity type

    Institute of Scientific and Technical Information of China (English)

    Shang Lian-Ju; Ning Ji-Ping

    2005-01-01

    The parameters of 1.34μm Nd:YVO4 laser end-pumped with flat-concave cavity are theoretically analysed. The analysis in this paper may be helpful to the designing of kindred lasers. The operation of 1.34μm Nd:YVO4 laser end-pumped by a diode-laser with flat-concave cavity is achieved. The output power of 3.51W at 1.34μm and optical to optical conversion efficiency of 39.0% are obtained at the pump power of 9.0W.

  5. Electrically Pumped Vertical-Cavity Amplifiers

    DEFF Research Database (Denmark)

    Greibe, Tine

    2007-01-01

    In this work, the design of electrically pumped vertical cavity semiconductor optical amplifiers (eVCAs) for use in a mode-locked external-cavity laser has been developed, investigated and analysed. Four different eVCAs, one top-emitting and three bottom emitting structures, have been designed...... and discussed. The thesis concludes with recommendations for further work towards the realisation of compact electrically pumped mode-locked vertical externalcavity surface emitting lasers....

  6. Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Axel

    2008-07-21

    In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10{sup -4} in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)

  7. VCSELs Fundamentals, Technology and Applications of Vertical-Cavity Surface-Emitting Lasers

    CERN Document Server

    2013-01-01

    The huge progress which has been achieved in the field is covered here, in the first comprehensive monograph on vertical-cavity surface-emitting lasers (VCSELs) since eight years. Apart from chapters reviewing the research field and the laser fundamentals, there are comprehensive updates on red and blue emitting VCSELs, telecommunication VCSELs, optical transceivers, and parallel-optical links for computer interconnects. Entirely new contributions are made to the fields of vectorial three-dimensional optical modeling, single-mode VCSELs, polarization control, polarization dynamics, very-high-speed design, high-power emission, use of high-contrast gratings, GaInNAsSb long-wavelength VCSELs, optical video links, VCSELs for optical mice and sensing, as well as VCSEL-based laser printing. The book appeals to researchers, optical engineers and graduate students.

  8. Recent Advances and Applications of External Cavity-QCLs towards Hyperspectral Imaging for Standoff Detection and Real-Time Spectroscopic Sensing of Chemicals

    Directory of Open Access Journals (Sweden)

    Ralf Ostendorf

    2016-05-01

    Full Text Available External-cavity quantum cascade lasers (EC-QCL are now established as versatile wavelength-tunable light sources for analytical spectroscopy in the mid-infrared (MIR spectral range. We report on the realization of rapid broadband spectral tuning with kHz scan rates by combining a QCL chip with a broad gain spectrum and a resonantly driven micro-opto-electro-mechanical (MOEMS scanner with an integrated diffraction grating in Littrow configuration. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets, as well as on hazardous substances, such as explosives. Furthermore, different applications for the EC-QCL technology in spectroscopic sensing are presented. These include the fields of process analysis with on- or even inline capability and imaging backscattering spectroscopy for contactless identification of solid and liquid contaminations on surfaces. Recent progress in trace detection of explosives and related precursors in relevant environments as well as advances in food quality monitoring by discriminating fresh and mold contaminated peanuts based on their MIR backscattering spectrum is shown.

  9. Simultaneous frequency stabilization and high-power dense wavelength division multiplexing (HP-DWDM) using an external cavity based on volume Bragg gratings (VBGs)

    Science.gov (United States)

    Hengesbach, Stefan; Klein, Sarah; Holly, Carlo; Witte, Ulrich; Traub, Martin; Hoffmann, Dieter

    2016-03-01

    Multiplexing technologies enable the development of high-brightness diode lasers for direct industrial applications. We present a High-Power Dense Wavelength Division Multiplexer (HP-DWDM) with an average channel spacing of 1.7 (1.5) nm and a subsequent external cavity mirror to provide feedback for frequency stabilization and multiplexing in one step. The "self-optimizing" multiplexing unit consists of four reflective Volume Bragg Gratings (VBGs) with 99% diffraction efficiency and seven dielectric mirrors to overlay the radiation of five input channels with an adjustable channel spacing of 1-2 nm. In detail, we focus on the analysis of the overall optical efficiency, the change of the beam parameter product and the spectral width. The performance is demonstrated using five 90 μm multimode 9xx single emitters with M2angular intensity distribution changes strongly and the beam parameter product decreases by a factor of 1.2 to 1.9. Thereby the angular intensity distribution is more affected than the width of the beam waist. The spectral width per emitter decreases to 3-200 pm (FWHM) depending on the injection current and the reflectance of the feedback mirror (0.75%, 1.5%, 4%, 6% or 8%). The overall optical multiplexing efficiency ranges between 77% and 86%. With some modifications (e.g. enhanced AR-coatings) we expect 90-95%.

  10. Impurity-free quantum well intermixing for large optical cavity high-power laser diode structures

    Science.gov (United States)

    Kahraman, Abdullah; Gür, Emre; Aydınlı, Atilla

    2016-08-01

    We report on the correlation of atomic concentration profiles of diffusing species with the blueshift of the quantum well luminescence from both as-grown and impurity free quantum wells intermixed on actual large optical cavity high power laser diode structures. Because it is critical to suppress catastrophic optical mirror damage, sputtered SiO2 and thermally evaporated SrF2 were used both to enhance and suppress quantum well intermixing, respectively, in these (Al)GaAs large optical cavity structures. A luminescence blueshift of 55 nm (130 meV) was obtained for samples with 400 nm thick sputtered SiO2. These layers were used to generate point defects by annealing the samples at 950 °C for 3 min. The ensuing Ga diffusion observed as a shifting front towards the surface at the interface of the GaAs cap and AlGaAs cladding, as well as Al diffusion into the GaAs cap layer, correlates well with the observed luminescence blue shift, as determined by x-ray photoelectron spectroscopy. Although this technique is well-known, the correlation between the photoluminescence peak blue shift and diffusion of Ga and Al during impurity free quantum well intermixing on actual large optical cavity laser diode structures was demonstrated with both x ray photoelectron and photoluminescence spectroscopy, for the first time.

  11. Hidden photon measurements using the long-baseline cavity of laser interferometric gravitational-wave detector

    CERN Document Server

    Inoue, Yuki

    2015-01-01

    We suggest a new application for the long-baseline and high powered cavities in a laser-interferometric gravitational-wave~(GW) detector to search for WISPs (weakly interacting sub-eV particles), such as a hidden U(1) gauge boson, called the hidden-sector photon. It is based on the principle of a light shining through the wall experiment, adapted to the laser with a wavelength of 1064 or 532 nm. The transition edge sensor (TES) bolometer is assumed as a detector, which the dark rate and efficiency are assumed as $0.000001~\\mathrm{s^{-1}}$ and 0.75, respectively. The TES bolometer is sufficiently sensitive to search for the low-mass hidden-sector photons. We assume that the reconversion cavity is mounted on the reconversion region of hidden-sector photons, which number of reflection and length are assumed as 1000 and 10, 100, and 1000m. We found that the second-point-five and the second generation GW experiments, such as KAGRA and Advanced LIGO with a regeneration cavity and TES bolometers. The expected lower ...

  12. THz cavities and injectors for compact electron acceleration using laser-driven THz sources

    Directory of Open Access Journals (Sweden)

    Moein Fakhari

    2017-04-01

    Full Text Available We present a design methodology for developing ultrasmall electron injectors and accelerators based on cascaded cavities excited by short multicycle THz pulses obtained from laser-driven THz generation schemes. Based on the developed concept for optimal coupling of the THz pulse, a THz electron injector and two accelerating stages are designed. The designed electron gun consists of a four cell cavity operating at 300 GHz and a door-knob waveguide to coaxial coupler. Moreover, special designs are proposed to mitigate the problem of thermal heat flow and induced mechanical stress to achieve a stable device. We demonstrated a gun based on cascaded cavities that is powered by only 1.1 mJ of THz energy in 300 cycles to accelerate electron bunches up to 250 keV. An additional two linac sections can be added with five and four cell cavities both operating at 300 GHz boosting the bunch energy up to 1.2 MeV using a 4-mJ THz pulse.

  13. Laser and cavity cooling of a mechanical resonator with a nitrogen-vacancy center in diamond

    Science.gov (United States)

    Giannelli, Luigi; Betzholz, Ralf; Kreiner, Laura; Bienert, Marc; Morigi, Giovanna

    2016-11-01

    We theoretically analyze the cooling dynamics of a high-Q mode of a mechanical resonator, when the structure is also an optical cavity and is coupled with a nitrogen-vacancy (NV) center. The NV center is driven by a laser and interacts with the cavity photon field and with the strain field of the mechanical oscillator, while radiation pressure couples the mechanical resonator and cavity field. Starting from the full master equation we derive the rate equation for the mechanical resonator's motion, whose coefficients depend on the system parameters and on the noise sources. We then determine the cooling regime, the cooling rate, the asymptotic temperatures, and the spectrum of resonance fluorescence for experimentally relevant parameter regimes. For these parameters, we consider an electronic transition, whose linewidth allows one to perform sideband cooling, and show that the addition of an optical cavity in general does not improve the cooling efficiency. We further show that pure dephasing of the NV center's electronic transitions can lead to an improvement of the cooling efficiency.

  14. A pulsated weak-resonant-cavity laser diode with transient wavelength scanning and tracking for injection-locked RZ transmission.

    Science.gov (United States)

    Lin, Gong-Ru; Chi, Yu-Chieh; Liao, Yu-Sheng; Kuo, Hao-Chung; Liao, Zhi-Wang; Wang, Hai-Lin; Lin, Gong-Cheng

    2012-06-18

    By spectrally slicing a single longitudinal-mode from a master weak-resonant-cavity Fabry-Perot laser diode with transient wavelength scanning and tracking functions, the broadened self-injection-locking of a slave weak-resonant-cavity Fabry-Perot laser diode is demonstrated to achieve bi-directional transmission in a 200-GHz array-waveguide-grating channelized dense-wavelength-division-multiplexing passive optical network system. Both the down- and up-stream slave weak-resonant-cavity Fabry-Perot laser diodes are non-return-to-zero modulated below threshold and coherently injection-locked to deliver the pulsed carrier for 25-km bi-directional 2.5 Gbits/s return-to-zero transmission. The master weak-resonant-cavity Fabry-Perot laser diode is gain-switched at near threshold condition and delivers an optical coherent pulse-train with its mode linewidth broadened from 0.2 to 0.8 nm by transient wavelength scanning, which facilitates the broadband injection-locking of the slave weak-resonant-cavity Fabry-Perot laser diodes with a threshold current reducing by 10 mA. Such a transient wavelength scanning induced spectral broadening greatly releases the limitation on wavelength injection-locking range required for the slave weak-resonant-cavity Fabry-Perot laser diode. The theoretical modeling and numerical simulation on the wavelength scanning and tracking effects of the master and slave weak-resonant-cavity Fabry-Perot laser diodes are performed. The receiving power sensitivity for back-to-back transmission at bit-error-rate transmission is less than 2 dB for all 16 channels.

  15. Application of FPGA technology for control of superconducting TESLA cavities in free electron laser

    Science.gov (United States)

    Pozniak, Krzysztof T.

    2006-10-01

    Contemporary fundamental research in physics, biology, chemistry, pharmacology, material technology and other uses frequently methods basing on collision of high energy particles or penetration of matter with ultra-short electromagnetic waves. Kinetic energy of involved particles, considerably greater than GeV, is generated in accelerators of unique construction. The paper presents a digest of working principles of accelerators. There are characterized research methods which use accelerators. A method to stabilize the accelerating EM field in superconducting (SC) resonant cavity was presented. An example was given of usage of TESLA cavities in linear accelerator propelling the FLASH free electron laser (FEL) in DESY, Hamburg. Electronic and photonic control system was debated. The system bases on advanced FPGA circuits and cooperating fast DSP microprocessor chips. Examples of practical solutions were described. Test results of the debated systems in the real-time conditions were given.

  16. Sensitive and rapid laser diagnostic for shock tube kinetics studies using cavity-enhanced absorption spectroscopy.

    Science.gov (United States)

    Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

    2014-04-21

    We report the first application of cavity-enhanced absorption spectroscopy (CEAS) using a coherent light source for sensitive and rapid gaseous species time-history measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 83 with a measurement time resolution of 20 µs was demonstrated for C2H2 detection using a near-infrared transition near 1537 nm, corresponding to a noise-equivalent detection limit of 20 ppm at 296 K and 76 ppm at 906 K at 50 kHz. This substantial gain in signal, relative to conventional single-pass absorption, will enable ultra-sensitive species detection in shock tube kinetics studies, particularly useful for measurements of minor species and for studies of dilute reactive systems.

  17. Surface-Plasmon-Polariton Laser based on an Open-Cavity Fabry-Perot Resonator

    CERN Document Server

    Zhu, Wenqi; Agrawal, Amit; Lezec, Henri J

    2016-01-01

    Recent years have witnessed growing interest in the development of small-footprint lasers for potential applications in small-volume sensing and on-chip optical communications. Surface-plasmons, electromagnetic modes evanescently confined to metal-dielectric interfaces, offer an effective route to achieving lasing at nanometer-scale dimensions when resonantly amplified in contact with a gain-medium. Here, we achieve visible frequency ultra-narrow linewidth lasing at room-temperature by leveraging surface plasmons propagating in an open Fabry-Perot cavity formed by a flat metal surface coated with a subwavelength-thick layer of optically-pumped gain medium and orthogonally bound by a pair of flat metal sidewalls. Low perturbation transmission-configuration sampling of the lasing plasmon mode is achieved via an evanescently coupled recessed nanoslit, opening the way to high-figure-of-merit refractive-index sensing of analytes interacting with the open cavity.

  18. Optimization of the multiwavelength erbium-doped fiber laser in a unidirectional cavity without an isolator

    Science.gov (United States)

    Sun, Guo-Yong; Qu, Ronghui; Yang, Jingxin; Wang, Xiangzhao

    2005-09-01

    A highly uniform multiwavelength erbium-doped fiber ring laser with an intracavity sine phase modulator is demonstrated. The flat output spectrum is achieved by optimizing the cavity structure, modulation amplitude, and frequency of the sine phase modulator. Fifteen lasing lines with wavelength spacing of 0.9 nm appear simultaneously and stably with power differences less than 2 dB and side-mode suppression ratio higher than 32 dB. In addition, the proposed cavity can support unidirectional operation without optical isolators. An output power difference of about 20 dB is realized between the counterclockwise and clockwise directions, which is almost independent of the pump power and lasing wavelengths.

  19. Performance of the x-ray free-electron laser oscillator with crystal cavity

    Directory of Open Access Journals (Sweden)

    R. R. Lindberg

    2011-01-01

    Full Text Available Simulations of the x-ray free-electron laser (FEL oscillator are presented that include the frequency-dependent Bragg crystal reflectivity and the transverse diffraction and focusing using the two-dimensional FEL code GINGER. A review of the physics of Bragg crystal reflectors and the x-ray FEL oscillator is made, followed by a discussion of its numerical implementation in GINGER. The simulation results for a two-crystal cavity and realistic FEL parameters indicate ∼10^{9} photons in a nearly Fourier-limited, ps pulse. Compressing the electron beam to 100 A and 100 fs results in comparable x-ray characteristics for relaxed beam emittance, energy spread, and/or undulator parameters, albeit in a larger radiation bandwidth. Finally, preliminary simulation results indicate that the four-crystal FEL cavity can be tuned in energy over a range of a few percent.

  20. Modeling and optimization of single-mode vertical cavity surface emitting lasers

    Science.gov (United States)

    Dahiya, Sandeep; Kumar, Suresh; Kaushik, Brajesh Kumar

    2016-10-01

    Vertical cavity surface emitting laser (VCSEL) plays a vital role in optical network. The present investigation reports the performance comparison of the modeling of single-mode VCSELs at room temperature for continuous wave operation. VCSEL for the study consists of InGaAsP-based cavity or active region sandwiched between GaAs/AlGaAs top mirror and GaAs/AlAs bottom mirrors with the aim of increasing the power conversion efficiency (PCE), lasing power, and decreasing the threshold current. It is observed that VCSELs with lower diameter are most suitable to achieve energy-efficient operation. The PCE obtained is ˜50% for the proposed single-mode VCSELs. The proposed VCSELs are suitable for short-reach optical interconnects such as chip-to-chip and board-to-board communication in high-performance computers.

  1. SUBJOULE DIODE-PUMPED YTTERBIUM-ERBIUM GLASS LASER WITH CAVITY DUMPING FOR CATARACT EXTRACTION

    Directory of Open Access Journals (Sweden)

    A. V. Belikov

    2015-11-01

    Full Text Available Subject of Study. The paper discusses the breadboarding results of compact diode pumped laser. The laser is based on Yb,Er:glass slab active element and frustrated total internal reflection (FTIR shutter and features of the impact of generated pulses at the water-containing media. The transmitter working in cavity dumping mode provides generation of single microsecond pulses or regular trains of these pulses with peak power up to 100 kW and average output power up to 8 W. The laser allows varying output parameters of radiation in wide range and is designed for the usage in technology and biomedical applications. The possibilities of the laser radiation parameters adapting for application in a compact laser cataract extraction complex are examined. Method. The energy efficient for three level active medium method of lasing pulses repetition rate increasing was investigated, which comprises the generation of pulse trains by several FTIR shutter switching on one pump pulse. We carried out analysis of application possibility for microsecond laser pulses with peak power of tens of kilowatts at wavelength of 1,54 μm in the processing of water-containing tissues. The acoustic response on the interaction of radiation with a model environment was studied. Main Results. In the modulation mode of useful (active losses lasing pulses have been obtained with microsecond duration and energy more than 100 mJ and trains of pulses with total energy of 0,5 J at the effective pulse repetition rate of more than 50 Hz. The minimal permissible period of laser pulses in train (300 μs has been established experimentally on the basis of optoacoustic studies. It meets the criteria of operation noninvasiveness consisting in prevention of the risk of posterior lens capsule damage with laser radiation. Practical Relevance. The results obtained with the layout of diode pumped Yb,Er:glass laser with cavity dumping and slab active element are presently record for diode

  2. The impact of external optical feedback on the degradation behavior of high-power diode lasers

    DEFF Research Database (Denmark)

    Hempel, Martin; Chi, Mingjun; Petersen, Paul Michael;

    2013-01-01

    The impact of external feedback on high-power diode laser degradation is studied. For this purpose early stages of gradual degradation are prepared by accelerated aging of 808-nm-emitting AlGaAs-based devices. While the quantum well that actually experiences the highest total optical load remains...... unaffected, severe impact is observed to the cladding layers and the waveguide. Consequently hardening of diode lasers for operation under external optical feedback must necessarily involve claddings and waveguide, into which the quantum well is embedded.......The impact of external feedback on high-power diode laser degradation is studied. For this purpose early stages of gradual degradation are prepared by accelerated aging of 808-nm-emitting AlGaAs-based devices. While the quantum well that actually experiences the highest total optical load remains...

  3. Q-switched mode-locking of an erbium-doped fiber laser using cavity modulation frequency detuning.

    Science.gov (United States)

    Chang, You Min; Lee, Junsu; Jhon, Young Min; Lee, Ju Han

    2012-07-20

    We present the results of an investigation regarding a Q-switched mode-locked fiber laser scheme based on a cavity modulation frequency detuning technique. The approach is based on undamped laser relaxation oscillations occurring due to frequency detuning in the fundamental cavity resonance frequency. Through a range of experiments with an erbium-doped, fiber-based, ring-cavity laser, this approach has been shown to be capable of generating high-quality Q-switched mode-locked pulses from an optical fiber-based laser. The maximum frequency detuning range for a stable Q-switched mode-locking operation has been observed to vary depending on the pump power used. We found that the highest pulse peak power was obtained at the frequency detuning threshold at which the operation changed from the mode-locking to the Q-switched mode-locking regime.

  4. 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.

  5. Design and Analysis of Enhanced Modulation Response in Integrated Coupled Cavities DBR Lasers Using Photon-Photon Resonance

    OpenAIRE

    Paolo Bardella; Chow, Weng W.; Ivo Montrosset

    2016-01-01

    In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of two distributed Bragg reflector (DBR) lasers allowing one to extend the modulation bandwidth. Such an extension is obtained introducing in the dynamic response a photon-photon resonance (PPR) at a ...

  6. Electron Raman scattering in a double quantum well tuned by an external nonresonant intense laser field

    Science.gov (United States)

    Tiutiunnyk, A.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. M.; Restrepo, R. L.; Ungan, F.; Martínez-Orozco, J. C.; Kasapoglu, E.; Duque, C. A.

    2017-02-01

    In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,Al)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm-1. The system proposed here is an alternative choice for the development of AlxGa1-xAs semiconductor laser diodes that can be tuned via an external nonresonant intense laser field.

  7. Odontoblast response to cavity preparation with Er:YAG laser in rat molars: an immunohistochemical study.

    Science.gov (United States)

    Shigetani, Yoshimi; Suzuki, Hironobu; Ohshima, Hayato; Yoshiba, Kunihiko; Yoshiba, Nagako; Okiji, Takashi

    2013-07-01

    This study aimed to examine the dynamics of odontoblast-lineage cells following cavity preparation with erbium:yttrium-aluminum-garnet (Er:YAG) laser in rat molars. Cavity preparation was made with Er:YAG laser in the mesial surface of the maxillary left first molar of 8-week-old Wistar rats. Contralateral first molar served as unirradiated control. Immediately, 6 and 12 h and 1, 2, 3, 5 and 7 days after the lasing (n = 5, each), specimens were collected and processed for immunohistochemistry for heat-shock protein (HSP)-25 and nestin as markers for odontoblast-lineage cells. Cell proliferation assay using bromodeoxyuridine (BrdU) labeling was also performed. Unirradiated teeth showed HSP-25- and nestin-immunoreactivity in odontoblasts. At 6-12 h after irradiation, the odontoblastic layer was disorganized and some of odontoblasts lost the immunoreactivity to HSP-25 and nestin. At 1-2 days, however, HSP-25- and nestin-immunoreactivities in the odontoblast layer showed a noticeable recovery, resulting in the rearrangement of odontoblast-like cells intensely immunoreactive to HSP-25 and nestin at 3-7 days. BrdU-positive cells showed a significant increase at 2 days (P cavity preparation with Er:YAG laser induced mild and reversible damage to odontoblasts. The reparative process was characterized by the rearrangement of HSP-25- and nestin-immunoreactive odontoblast-like cells, which took place subsequent to the odontoblastic layer disorganization with partial loss of these immunoreactivities.

  8. Towards monolithic integration of mode-locked vertical cavity surface emitting laser

    Science.gov (United States)

    Aldaz, Rafael I.

    2007-12-01

    The speed and performance of today's high end computing and communications systems have placed difficult but still feasible demands on off-chip electrical interconnects. However, future interconnect systems may need aggregate bandwidths well into the terahertz range thereby making electrical bandwidth, density, and power targets impossible to meet. Optical interconnects, and specifically compact semiconductor mode-locked lasers, could alleviate this problem by providing short pulses in time at 10s of GHz repetition rates for Optical Time Division Multiplexing (OTDM) and clock distribution applications. Furthermore, the characteristic spectral comb of frequencies of these lasers could also serve as a multi-wavelength source for Wavelength Division Multiplexing (WDM) applications. A fully integrated mode-locked Vertical Cavity Surface Emitting Laser (VCSEL) is proposed as a low-cost high-speed source for these applications. The fundamental laser platform for such a device has been developed and a continuous-wave version of these lasers has been fabricated and demonstrated excellent results. Output powers close to 60mW have been obtained with very high beam quality factor of M2 unassisted ultrafast QD saturable absorbers, without the need to incorporate high concentrations of non radiative recombination centers by either ion-implantation or low temperature growth.

  9. Femtosecond filament initiated, microwave heated cavity-free nitrogen laser in air

    Science.gov (United States)

    Kartashov, Daniil; Shneider, Mikhail N.

    2017-03-01

    We present the results of numerical modeling of the igniter-heater concept for initiation of standoff, cavity free lasing action in the atmosphere when a femtosecond laser filament is used for plasma generation (igniter) and a microwave heater provides electron-collision pumping of electronic states in molecular nitrogen. By solving numerically the kinetic equation for the energy distribution function of electrons, generated in a femtosecond laser filament and heated by a microwave beam, we identify the conditions enabling single-pass, standoff UV-laser from molecular nitrogen in the atmosphere. The plasma density, the minimum amplitude of the microwave field, and the small-signal gain, necessary to achieve the lasing, are determined. We demonstrate that lasing build up time can be minimized and efficiency improved by using elliptically polarized laser pulses for filamentation. It is shown that realization of the filament-igniter, microwave-heater concept of the sky laser at low altitudes would require a microwave source of hundreds of kilowatt-megawatt power. The required microwave power can be reduced by several orders of magnitude when the igniter-heater scheme is used at the 10-30 km range of altitudes.

  10. [The treatment of otosclerosis using laser assisted stapedotomy with mini incision in external auditory meatus].

    Science.gov (United States)

    Hao, Xinping; Chen, Shubin; Yu, Zilong; Liang, Fenghe; Li, Yongxin

    2016-03-01

    To investigate the feasibility of the treatment of otosclerosis using laser stapedotomy with mini incision in the external auditory meatus. Thirteen patients(15 ears) with otosclerosis evidence on clinic history. They were all operated using the laser assisted stapedotomy by mini incision in external auditory meatus because of the wide straight canal. Laser resection the tendo musculistapedius and anterior and postrior arch, breaking the articulatioincudostapedia, removing the stapes superstructure, making a hole of 6mm diameter in the rear of stapes footplate by laser drilling, implanting the corresponding length Piston artificial ossicle. All the surgeries were successful and the operation time was about one hour. There was only one patient manifested vertigo and nausea after the operation. But the symptoms improved three days later after the expectant treatment. All the incisions were healed in the externals. There was significant difference between the preoperative and postoperative PTA. The air conduct improved in every frequent and the bone conduct improved in 1 kHz, 2 kHz and 4 kHz. Laser assisted stapedotomy by mini incision in the external auditory meatus in patients having wide straight canal with otosclerosis can shorten the operation time, minimize the tissue damage, fasten the healing of the incision and reduce the complications postoperatively. In addition, the mini incision is beauty and easy to nurse.

  11. Scanning electron microscopy study of cavity preparation in deciduous teeth using the Er:YAG laser with different powers.

    Science.gov (United States)

    Zhang, Sun; Chen, Tao; Ge, Li-hong

    2012-01-01

    Using scanning electron microscopy (SEM) we evaluated the morphology of cavity surfaces in deciduous teeth prepared in vitro with the Er:YAG laser with different power parameters. Eight extracted cavity-free deciduous teeth with an intact crown were prepared using a traditional handpiece or an Er:YAG laser with different parameters (10 Hz/200 mJ, 10 Hz/300 mJ and 10 Hz/400 mJ). Samples were then processed and cavity surface morphology was evaluated by SEM to detect open dentinal tubules, or melting or cracking of the dentin. SEM showed that laser cavity preparation in deciduous teeth using different parameters left no smear layer and the dentinal tubules were clear. Dentin melting was not seen after cavity preparation at 200 mJ or 300 mJ, while visible dentin melting and cracks were detected at 400 mJ. The use of the laser at 10 Hz/200 mJ and 10 Hz/300 mJ for cavity preparation in deciduous teeth is safe and effective, but higher powers may damage the dentin.

  12. Parity-Time Symmetry in Coherently Coupled Vertical Cavity Laser Arrays

    CERN Document Server

    Gao, Zihe; Thompson, Bradley J; Carney, P Scott; Choquette, Kent D

    2016-01-01

    Parity-time (PT) symmetry in optics has been demonstrated in a variety of passive or optically pumped platforms. Here we discuss the notion of PT symmetry in the context of electrically pumped coherently coupled vertical cavity surface emitting laser arrays. Effects of both asymmetric gain distribution and local frequency detuning are considered using temporal coupled mode theory. It is shown theoretically that beam steering, mode evolution and mode hopping are all related to PT symmetry. Experimentally we observed the predicted mode evolution, mode hopping and PT symmetry breaking with quantitative agreement with the theory.

  13. Pump-probe differencing technique for cavity-enhanced, noise-canceling saturation laser spectroscopy

    CERN Document Server

    De Vine, G; Close, J D; Gray, M B; Vine, Glenn de; Clelland, David E. Mc; Close, John D.; Gray, Malcolm B.

    2004-01-01

    We present an experimental technique enabling mechanical-noise free, cavity-enhanced frequency measurements of an atomic transition and its hyperfine structure. We employ the 532nm frequency doubled output from a Nd:YAG laser and an iodine vapour cell. The cell is placed in a traveling-wave Fabry-Perot interferometer (FPI) with counter-propagating pump and probe beams. The FPI is locked using the Pound-Drever-Hall (PDH) technique. Mechanical noise is rejected by differencing pump and probe signals. In addition, this differenced error signal gives a sensitive measure of differential non-linearity within the FPI.

  14. Graphene mode-locked multipass-cavity femtosecond Cr4+: forsterite laser

    OpenAIRE

    Baylam, Işınsu; Çizmeciyan, Melisa Natali; Sennaroğlu, Alphan; Ozharar, Sarper; Balcı, Osman; Pince, Ercag; Kocabaş, Coşkun

    2013-01-01

    We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr4+: forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short resonator was reduced to 4.51 MHz, which resulted in the generation of 100 fs, nearly transform-limited pulses at 1252 nm with a peak power of 53 kW. To the best of our knowledge, this is the highest peak power obtained from a room-temperature, femtosecond Cr4+: forster...

  15. Controllable spiking patterns in long-wavelength vertical cavity surface emitting lasers for neuromorphic photonics systems

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, Antonio, E-mail: antonio.hurtado@strath.ac.uk [Institute of Photonics, SUPA Department of Physics, University of Strathclyde, TIC Centre, 99 George Street, Glasgow G1 1RD (United Kingdom); Javaloyes, Julien [Departament de Fisica, Universitat de les Illes Balears, c/Valldemossa km 7.5, 07122 Mallorca (Spain)

    2015-12-14

    Multiple controllable spiking patterns are achieved in a 1310 nm Vertical-Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely, parallel and orthogonal. Furthermore, reproducible spiking responses are demonstrated experimentally at sub-nanosecond speed resolution and with a controlled number of spikes fired. This work opens therefore exciting research avenues for the use of VCSELs in ultrafast neuromorphic photonic systems for non-traditional computing applications, such as all-optical binary-to-spiking format conversion and spiking information encoding.

  16. Temperature characteristics of InGaAs/GaAs vertical cavity surface emitting laser

    Institute of Scientific and Technical Information of China (English)

    QU Hong-wei; GUO Xia; DONG Li-min; WANG Hong-hang; DENG Jun; LIAN Peng; ZHOU De-shu; SHEN Guang-di

    2005-01-01

    The temperature characteristics for the different lasing modes at 300 K of intracavity contacted InGaAs/GaAs Vertical Cavity Surface Emitting Lasers(VCSELs) have been investigated experimentally by using the SV-32 cryostat and LD2002C5 test system.In combination with the simulation results of the reflective spectrum and the gain peak at different temperatures,the measurement results have been analyzed.In addition,the dependence of device size on temperature characteristics is discussed.The experimental data can be used to optimally design of VCSEL at high or cryogenic temperature.

  17. Design and modeling of a transistor vertical-cavity surface-emitting laser

    CERN Document Server

    Shi, Wei; Greenberg, Mark; Berggren, Jesper; Xiang, Yu; Hammar, Mattias; Lestrade, Michel; Li, Zhi-Qiang; Li, Z M Simon; Chrostowski, Lukas

    2011-01-01

    A multiple quantum well (MQW) transistor vertical-cavity surface-emitting laser (T-VCSEL) is designed and numerically modeled. The important physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a significant effect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the analytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps.

  18. Stabilization of class-B broad-area lasers emission by external optical injection

    CERN Document Server

    Pakhomov, A V

    2016-01-01

    We theoretically examine the effect of external optical injection on the spatio-temporal dynamics of class-B broad-area lasers. We demonstrate that optical injection can efficiently stabilize the intrinsic transverse instabilities in such lasers associated with both the boundaries of the pumping area and with the bulk nonlinearities of the active medium. Stabilizing action of optical injection is shown to be closely related to the suppression of inherent relaxation oscillations behavior.

  19. Ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting laser devices

    Science.gov (United States)

    Gerhardt, N. C.; Li, M.; Jaehme, H.; Soldat, H.; Hofmann, M. R.; Ackemann, T.

    2010-02-01

    Spin-polarized lasers offer new encouraging possibilities for future devices. We investigate the polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional spin injection at room temperature. We find that the circular polarization degree exhibits faster dynamics than the emitted light. Moreover the experimental results demonstrate a strongly damped ultrafast circular polarization oscillation due to spin injection with an oscillation frequency of approximately 11GHz depending on the birefringence in the VCSEL device. We compare our experimental results with theoretical calculations based on rate-equations. This allows us to predict undamped long persisting ultrafast polarization oscillations, which reveal the potential of spin-VCSELs for ultrafast modulation applications.

  20. Selective oxidation of buried AlGaAs for fabrication of vertical-cavity lasers

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Geib, K.M.; Chui, H.C.; Hou, H.Q. [Sandia National Labs., Albuquerque, NM (United States). Photonics Research Dept.; Hull, R. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science

    1996-06-01

    The authors discuss the selective conversion of buried layers of AlGaAs to a stable oxide and the implementation of this oxide into high performance vertical-cavity surface emitting lasers (VCSELs). The rate of lateral oxidation is shown to be linear with an Arrhenius temperature dependence. The measured activation energies vary with Al composition, providing a high degree of oxidation selectivity between AlGaAs alloys. Thus buried oxide layers can be selectively fabricated within the VCSEL through small compositional variations in the AlGaAs layers. The oxidation of AlGaAs alloys, as opposed to AlAs, is found to provide robust processing of reliable lasers. The insulating and low refractive index oxide provides enhanced electrical and optical confinement for ultralow threshold currents in oxide-apertured VCSELs.

  1. Theoretical study on phase conjugation in weakly injected vertical-cavity surface-emitting lasers

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Li; Pan Wei; Luo Bin; Li Xiao-Feng; Zou Xi-Hua; Wang Meng-Yao

    2008-01-01

    This paper gives a detailed theoretical investigation on phase conjugation induced by nearly degenerate fourwave mixing in single mode vertical-cavity surface-emitting lasers (VCSELs) with~weak optical injection.Considering VCSELs that can work in linearly polarized or elliptically polarized states,it derives the theoretical expression of the conjugated field by small signal analysis based on the vectoral rate equations--the spin-flip model.For linearly polarized state,VCSELs show similar conjugate spectra to edge-emitting semiconductor lasers.For the eUiptically polarized state,dichroism and birefringence parameters as well as the spin-flip rate can change the conjugate spectra.Especially,when frequency detuning of the probe and pump waves is between the positive and negative relaxation oscillation frequency,changes are evident.For specific values of parameters,conjugate efficiency between 20 dB to 40 dB are obtained.

  2. Low temperature laser scanning microscopy of a superconducting radio-frequency cavity.

    Science.gov (United States)

    Ciovati, G; Anlage, Steven M; Baldwin, C; Cheng, G; Flood, R; Jordan, K; Kneisel, P; Morrone, M; Nemes, G; Turlington, L; Wang, H; Wilson, K; Zhang, S

    2012-03-01

    An apparatus was developed to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about 2.4 mm and surface resistance resolution of ~1 μΩ at 3.3 GHz. A signal-to-noise ratio of about 10 dB was obtained with 240 mW laser power and 1 Hz modulation frequency. The various components of the apparatus, the experimental procedure and results are discussed in detail in this contribution.

  3. UV laser with an acousto-optic intra-cavity control for GaN-sapphire cut

    Science.gov (United States)

    Gradoboev, Yury G.; Kazaryan, Mishik A.; Mokrushin, Yury M.; Shakin, Oleg V.

    2012-09-01

    A copper vapor laser is proposed as the basic component of the installation for processing of sapphire substrates with a GaN-coating. Laser radiation is transformed to UV range by optical frequency doubling. Powerful UV lasers are prospective tools for crystal cutting, photolithography and recording of the fiber Bragg gratings. The proposed approach is more promising in comparison with the use of excimer radiation because of instabilities of excimer laser generation and low coherence of its radiation, which makes difficult precise focusing and using interference pattern of UV radiation for exposing materials. UV laser based on second harmonic radiation of copper vapors laser has been designed. The UV laser system of high operation stability has been developed with output power 1 W at wavelengths 255.5 nm, 271.1 nm, 289.1 nm and coherence length radiation about 4 cm. The original intra-cavity acousto-optic control of output radiation is developed. It is allows adjusting frequency and on-off time ratio of output laser pulses with high accuracy. The stable heat regime was achieved for an active element of copper vapor laser̤ The laser system allows to select an optimum mode of ultra-violet radiation exposition for production of different optical elements. Intra-cavity acousto-optic cell was used for controlling of single pulse amplitude and number of pulses without any power supply tuning providing the stable operation of the laser system.

  4. Effects of an external magnetic field in pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, T. [Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, C.P. 09790, Mexico DF (Mexico)], E-mail: tupacgarcia@yahoo.com; Posada, E. de [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico); Villagran, M. [CCADET, Universidad Nacional Autonoma de Mexico (UNAM), A.P. 70-186, C.P. 04510, Mexico DF (Mexico); Ll, J.L. Sanchez [Laboratorio de Magnetismo, Facultad de Fisica-IMRE, Universidad de La Habana, La Habana 10400 (Cuba); Bartolo-Perez, P.; Pena, J.L. [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico)

    2008-12-30

    Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe{sub 12}O{sub 19} target with and without the presence of a nonhomogeneous magnetic field of {mu}{sub 0}H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.

  5. Dynamics of the cavity radiation of a correlated emission laser initially seeded with a thermal light

    Energy Technology Data Exchange (ETDEWEB)

    Tesfa, Sintayehu, E-mail: sint_tesfa@yahoo.com [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Street 38, 01187 Dresden (Germany); Physics Department, Dilla University, PO Box 419, Dilla (Ethiopia)

    2011-10-15

    A detailed analysis of the time evolution of the two-mode squeezing, entanglement and intensity of the cavity radiation of a two-photon correlated emission laser initially seeded with a thermal light is presented. The dependences of the degree of two-mode squeezing and entanglement on the intensity of the thermal light and time are found to have a more or less similar nature, although the actual values differ, especially in the early stages of the process and when the atoms are initially prepared with nearly 50:50 probability to be in the upper and lower energy levels. Seeding the cavity degrades the nonclassical features significantly, particularly in the vicinity of t=0. It is also shown that the mean photon number in a wider time span has a dip when mode b is seeded but a peak when mode a is seeded. Moreover, it turns out that the effect of the seed light on the nonclassical features and intensity of the cavity radiation decreases significantly with time, an outcome essentially attributed to the pertinent emission-absorption mechanism. This can be taken as an encouraging aspect in the practical utilization of this model as a source of a bright entangled light.

  6. The pressure and temperature dependence of vertical cavity surface emitting semiconductor lasers

    CERN Document Server

    Knowles, G

    2002-01-01

    The factors affecting the performance of GalnP/AIGalnP vertical-cavity surface-emitting lasers (VCSELs) emitting at an attenuation minimum of PMMA plastic optical fibres (650nm) have been investigated. Using wide temperature-range and high pressure measurement techniques on equivalent (i.e the same active region) edge emitting lasers (EELs), emitting at 672nm, the temperature sensitive leakage current into the indirect X-minima is shown to be approx 20% of the total threshold current at room temperature. This is then estimated to rise to approx 70% for 655nm emission, but may be reduced to approx 50% by using a graded-index separate confinement heterostructure (GRINSCH). By making the same measurements on the full VCSEL structures and using a combination of thermal and gain spectrum models the performance modifying effect of the Bragg stacks have then been evaluated. It is found that temperature dependent tuning/detuning of the gain-peak and the cavity mode is significant at low temperature due to the relativ...

  7. Comparative analysis of energy-efficient long wavebands vertical cavity surface emitting lasers

    Science.gov (United States)

    Dahiya, Sandeep; Mishra, Hemant Kumar; Kumar, Suresh; Kaushik, Brajesh Kumar

    2016-10-01

    Vertical cavity surface emitting laser (VCSEL) is an important laser source for their evident plentiful applications in optical communication. The present investigation reports a comparison of the modeling and optimization of long wavelengths 1310 nm and 1550 nm high speed short cavity VCSEL for continuous wave operation at various temperature (283-3230K) for various diameters. The continuous wave lasing is demonstrated for the device diameter from 2 to 5 μm with threshold current of 1.07-1.33 mA with threshold power consumption of 1.86-2.57 mW for 1310 nm and threshold current of 0.94-1.24 mA and threshold power consumption 1.67-2.1 mW for 1550 nm VCSEL. The results demonstrate that the threshold current, peak emitted power and power consumption increases with the increase in device diameter. The results confirm that VCSELs with 2 μm diameter is most suitable to achieve energy-efficient operation. Although rollover current increases with the diameter, but, due to the advantage of lower threshold current and power consumption, VCSEL having smaller diameter is best suited. The power conversion efficiency for proposed long wavelength VCSELs is approximately 50% which is extremely useful for low power applications. The proposed VCSELs are suitable for very short reach (communication in high performance computers.

  8. Degradation Processes in High-Power Diode Lasers under External Optical Feedback

    DEFF Research Database (Denmark)

    Tomm, Jens. W.; Hempel, Martin; Petersen, Paul Michael;

    2013-01-01

    The effect of moderate external feedback on the gradual degradation of 808 nm emitting AlGaAs-based high-power broad-area diode lasers is analyzed. Eventually the quantum well that actually experiences the highest total optical load remains unaffected by the aging, while severe impact...

  9. The use of Erbium: Yttrium-aluminum-garnet laser in cavity preparation and surface treatment: 3-year follow-up.

    Science.gov (United States)

    Buyukhatipoglu, Isil; Secilmis, Asli

    2015-01-01

    From the currently available choices, esthetic restorative materials for posterior teeth are limited to composite and ceramic restoration. Ceramic inlays/onlays are reliable solutions for both of these treatments. For successful treatment planning, usable ceramic and adhesive systems should be chosen by the dentist. Since the Federal Drug Administration approval of the erbium: Yttrium-aluminum-garnet (Er:YAG) laser-for caries removal, cavity preparation and the conditioning of tooth substance-in 1997, there have been many reports on the use of this technique in combination with composite resins. In addition, cavity pretreatment with the Er:YAG laser (laser etching) has been proposed as an alternative to acid etching of enamel and dentin. This case report presents the use of the Er:YAG in cavity preparation for composite resin restoration and surface treatment for ceramic onlay restoration of adjacent permanent molars.

  10. The use of Erbium: Yttrium-aluminum-garnet laser in cavity preparation and surface treatment: 3-year follow-up

    Science.gov (United States)

    Buyukhatipoglu, Isil; Secilmis, Asli

    2015-01-01

    From the currently available choices, esthetic restorative materials for posterior teeth are limited to composite and ceramic restoration. Ceramic inlays/onlays are reliable solutions for both of these treatments. For successful treatment planning, usable ceramic and adhesive systems should be chosen by the dentist. Since the Federal Drug Administration approval of the erbium: Yttrium-aluminum-garnet (Er:YAG) laser-for caries removal, cavity preparation and the conditioning of tooth substance-in 1997, there have been many reports on the use of this technique in combination with composite resins. In addition, cavity pretreatment with the Er:YAG laser (laser etching) has been proposed as an alternative to acid etching of enamel and dentin. This case report presents the use of the Er:YAG in cavity preparation for composite resin restoration and surface treatment for ceramic onlay restoration of adjacent permanent molars. PMID:26038665

  11. Mode-locking optimization with a real-time feedback system in a Nd:yttrium lithium fluoride laser cavity

    Science.gov (United States)

    Marengoni, C.; Canova, F.; Batani, D.; Benocci, R.; Librizzi, M.; Narayanan, V.; Gomareschi, M.; Lucchini, G.; Kilpio, A.; Shashkov, E.; Stuchebrukhov, I.; Vovchenko, V.; Chernomyrdin, V.; Krasuyk, I.; Hall, T.; Bittanti, S.

    2007-01-01

    We present a control system, which allows an automatic optimization of the pulse train stability in a mode-locked laser cavity. In order to obtain real-time corrections, we chose a closed loop approach. The control variable is the cavity length, mechanically adjusted by gear system acting on the rear cavity mirror, and the controlled variable is the envelope modulation of the mode-locked pulse train. Such automatic control system maintains the amplitude of the mode-locking pulse train stable within a few percent rms during the working time of the laser. Full implementation of the system on an Nd:yttrium lithium fluoride actively mode-locked laser is presented.

  12. Effects of mode degeneracy in the LIGO Livingston Observatory recycling cavity

    CERN Document Server

    Gretarsson, Andri M; Frolov, Valery; O'Reilly, Brian; Fritschel, Peter K

    2007-01-01

    We analyze the electromagnetic fields in a Pound-Drever-Hall locked, marginally unstable, Fabry-Perot cavity as a function of small changes in the cavity length during resonance. More specifically, we compare the results of a detailed numerical model with the behavior of the recycling cavity of the Laser Interferometer Gravitational-wave Observatory (LIGO) detector that is located in Livingston, Louisiana. In the interferometer's normal mode of operation, the recycling cavity is stabilized by inducing a thermal lens in the cavity mirrors with an external CO2 laser. During the study described here, this thermal compensation system was not operating, causing the cavity to be marginally optically unstable and cavity modes to become degenerate. In contrast to stable optical cavities, the modal content of the resonating beam in the uncompensated recycling cavity is significantly altered by very small cavity length changes. This modifies the error signals used to control the cavity length in such a way that the zer...

  13. Power generation in a resonant cavity using a beam bunched at 35 GHz by a free electron laser

    Science.gov (United States)

    Donohue, J. T.; Gardelle, J.; Lefevre, T.; Rullier, J. L.; Vermare, C.; Lidia, S. M.; Meurdesoif, Y.

    2000-05-01

    An intense beam of relativistic electrons (800 A, 6.7 MeV) has been bunched at 35 GHz by a free-electron laser, in which output power levels exceeding 100 MW were obtained. The beam was then extracted and transported through a resonant cavity, that was excited by its passage. Microwave power levels of 10 MW were extracted from the cavity, in reasonable agreement with a simple formula which relates power output to known properties of the both beam and cavity.

  14. On-chip interference of single photons from an embedded quantum dot and an external laser

    Energy Technology Data Exchange (ETDEWEB)

    Prtljaga, N., E-mail: n.prtljaga@sheffield.ac.uk; Bentham, C.; O' Hara, J.; Royall, B.; Wilson, L. R.; Skolnick, M. S.; Fox, A. M. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Clarke, E. [Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2016-06-20

    In this work, we demonstrate the on-chip two-photon interference between single photons emitted by a single self-assembled InGaAs quantum dot and an external laser. The quantum dot is embedded within one arm of an air-clad directional coupler which acts as a beam-splitter for incoming light. Photons originating from an attenuated external laser are coupled to the second arm of the beam-splitter and then combined with the quantum dot photons, giving rise to two-photon quantum interference between dissimilar sources. We verify the occurrence of on-chip Hong-Ou-Mandel interference by cross-correlating the optical signal from the separate output ports of the directional coupler. This experimental approach allows us to use a classical light source (laser) to assess in a single step the overall device performance in the quantum regime and probe quantum dot photon indistinguishability on application realistic time scales.

  15. Microstructure fabrication with a CO2 laser system: characterization and fabrication of cavities produced by raster scanning of the laser beam.

    Science.gov (United States)

    Jensen, Martin F; Noerholm, Mikkel; Christensen, Leif Højslet; Geschke, Oliver

    2003-11-01

    In this paper we describe the use of a CO(2) laser for production of cavities and microstructures in poly(methyl methacrylate) (PMMA) by moving the laser beam over the PMMA surface in a raster pattern. The topography of the cavities thus produced is studied using stylus and optical profilometry and scanning electron microscopy (SEM). The microstructures display artifacts from the laser ablation process and we describe how the laser ablation parameters can be optimized in order to minimize these artifacts. Using this technique it is possible to generate structures with a depth from 50 microm and a minimum width of approximately 200 microm up to depth and widths of several mm, governed by the beam size and the laser settings.

  16. Vertical cavity surface emitting lasers emitting near 1.5 {mu}m with Sb-based reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Blum, O.; Klem, J.F.; Vawter, G.A. [and others

    1998-04-01

    We describe use of AlAsSb/AlGaAsSb lattice matched to InP for distributed Bragg reflectors. These structures are integral to several surface normal devices, in particular vertical cavity surface emitting lasers. The high refractive index ratio of these materials allows formation of a highly reflective mirror with relatively few mirror pairs. As a result, we have been able to show for the first time the 77K CW operation of an optically pumped, monolithic, all-epitaxial vertical cavity laser, emitting at 1.56 {mu}m.

  17. Single mode operation and extended scanning of anti-reflection coated visible laser diodes in a Littrow cavity

    Science.gov (United States)

    Lonsdale, D. J.; Andrews, D. A.; King, T. A.

    2004-05-01

    A method to increase the mode-hop-free tuning range is presented that is suitable for application with visible and short wavelength laser diodes, and relaxes the requirement on high tolerance mechanical components. Depending on the diode and cavity, the theory predicts an improvement of up to eight times the FSR of the extended cavity. In our system, an anti-reflection coated AlGaInP laser diode showed a mode-hop-free scan of 8 GHz, which is characteristic for the wavelength used in the device. Greater scanning ranges are predicted for shorter wavelength sources.

  18. Diode-pumped low noise CW 355-nm intra-cavity tripled laser up to 20 mW

    Science.gov (United States)

    Aubert, Nicolas; Georges, Thierry; Chauzat, Corinne; Le Bras, Raymond; Féron, Patrice

    2006-04-01

    Low noise lasers in the UV spectrum (355 nm) are important for many applications like spectroscopy, confocal microscopy, flow cytometry, cell sorting, CD mastering, semiconductor inspection and reprographics. The UV CW laser sources currently commercially available, are restricted to excimers lasers, gas ions lasers which suffer from low power efficiency (0.01% or less), high electrical consumption and bulky dimensions. These products, which are expensive, are still waiting for practical replacements. To our best knowledge, we report in this paper the first efficient low noise diode-pumped neodymium doped solid-state laser operating at 355 nm by intra-cavity third harmonic generation (THG). The fundamental infrared laser light is generated by a diode-pumped Nd:YVO 4 crystal optically contacted with others components of the laser cavity. Intra-cavity SHG and THG are achieved with a KTP and LBO respectively. Several configurations have led to low noise 355 nm single-frequency operation at a power exceeding 10 mW. We believe that this power can still be improved.

  19. Design and Applications of In-Cavity Pulse Shaping by Spectral Sculpturing in Mode-Locked Fibre Lasers

    Directory of Open Access Journals (Sweden)

    Sonia Boscolo

    2015-11-01

    Full Text Available We review our recent progress on the realisation of pulse shaping in passively-mode-locked fibre lasers by inclusion of an amplitude and/or phase spectral filter into the laser cavity. We numerically show that depending on the amplitude transfer function of the in-cavity filter, various regimes of advanced waveform generation can be achieved, including ones featuring parabolic-, flat-top- and triangular-profiled pulses. An application of this approach using a flat-top spectral filter is shown to achieve the direct generation of high-quality sinc-shaped optical Nyquist pulses with a widely tunable bandwidth from the laser oscillator. We also present the operation of an ultrafast fibre laser in which conventional soliton, dispersion-managed soliton (stretched-pulse and dissipative soliton mode-locking regimes can be selectively and reliably targeted by adaptively changing the dispersion profile and bandwidth programmed on an in-cavity programmable filter. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for achieving a high degree of control over the dynamics and output of mode-locked fibre lasers.

  20. Evaluation of Er:YAG laser radiation cavity preparation under transmitted and polarized light and by electron microanalyser

    Science.gov (United States)

    Dostalova, Tatjana; Krejsa, Otakar; Rokytova, Kveta; Jelinkova, Helena; Hamal, Karel

    1993-12-01

    The results of evaluation of Er:YAG radiation cavity preparation under transmitted and polarized light and by the electron microanalyzer are presented. We examined the longitudinal sections of intact teeth, teeth with early dental caries, teeth with laser preparation in enamel and teeth with Er:YAG laser preparation in enamel and dentine class I and V. We examined intact teeth and laser prepared teeth for the variation of mineralization. Phosphorus and calcium were regularly distributed. The margins of cavities had no necrosis zones. The defects of mineralization in caries depend on demineralization of hard tissues. In the structures was irregular loss of calcium and phosphorus. Thus, Er:YAG laser irradiation with water cooling has been found to be a non-invasive preparation technique.

  1. Generation of radially and azimuthally polarized beams in Yb:YAG laser with intra-cavity lens and birefringent crystal.

    Science.gov (United States)

    Thirugnanasambandam, Manasadevi P; Senatsky, Yuri; Ueda, Ken-ichi

    2011-01-31

    We demonstrated the operation of cw diode-pumped Yb:YAG laser in radial or azimuthal polarized (RP or AP) beams using a combination of birefringent uniaxial crystal (c-cut YVO4 or α-BBO) and lens as intra-cavity elements. RP and AP doughnut modes (M2 = 2-2.5, polarization extinction ratio 50-100:1) with output power up to 60 mW were generated. Apart from doughnut modes, RP or AP ring-like off-axis oscillations and multi-ring beams with mixed RP and AP were also observed at the output of this laser scheme. Using intra-cavity short focus lenses with spherical aberrations AP or RP modes of higher orders was obtained. Mechanism of mode selection in the laser is discussed. The large variety of beams with axially symmetric polarizations from the output of the proposed laser scheme may find applications in different fields.

  2. 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.

  3. Selection of Optical Cavity Surface Coatings for 1micron Laser Based Missions

    Science.gov (United States)

    Hedgeland, Randy J.; Straka, Sharon; Matsumura, Mark; Hammerbacher, Joseph

    2004-01-01

    The particulate surface cleanliness level on several coatings for aluminum and beryllium substrates were examined for use in the optical cavities of high pulse energy Nd:YAG Q-switched, diode-pumped lasers for space flight applications. Because of the high intensity of the lasers, any contaminants in the laser beam path could damage optical coatings and limit the instrument mission objectives at the operating wavelength of 1 micron (micrometer). Our goal was to achieve an EST-STD-CC1246D Level 100 particulate distribution or better to ensure particulate redistribution during launch would not adversely affect the performance objectives. Tapelifts were performed to quantify the amount of particles using in-house developed procedures. The primary candidate coatings included chromate conversion coating aluminum (Al), uncoated Al electroless Nickel (Ni) on Al, Ni-gold (Au) on Al, anodized Al, and gold (Au)/Ni on Beryllium (Be). The results indicate that there were advantages in Ni and Au coating applications for the two major substrates, Al and Be, when considering applications that need to meet launch environments.

  4. Laser Optomechanics

    CERN Document Server

    Yang, Weijian; Ng, Kar Wei; Rao, Yi; Chase, Christopher; Chang-Hasnain, Connie J

    2015-01-01

    Cavity optomechanics explores the coupling between the optical field and the mechanical oscillation to induce cooling and regenerative oscillation in a mechanical oscillator. So far, optomechanics relies on the detuning between the cavity and an external pump laser, where the laser acts only as a power supply. Here, we report a new scheme with mutual coupling between a mechanical oscillator that supports a mirror of a vertical-cavity surface-emitting laser (VCSEL) and the optical field, greatly enhancing the light-matter energy transfer. In this work, we used an ultra-light-weight (130 pg) high-contrast-grating (HCG) mirror in a VCSEL, whose reflectivity spectrum is designed to facilitate strong optomechanical coupling, to demonstrate optomechanically-induced regenerative oscillation of the laser optomechanical cavity with > 550 nm self-oscillation amplitude of the micro-mechanical oscillator, two to three orders of magnitude larger than typical. This new scheme not only offers an efficient approach for high-...

  5. In vivo comparison of cavity disinfection efficacy with APF gel, Propolis, Diode Laser, and 2% chlorhexidine in primary teeth

    Directory of Open Access Journals (Sweden)

    P.V.M. Uday Mohan

    2016-01-01

    Full Text Available Background: The survival of atraumatic restorative treatment (ART restorations would be enhanced if near total elimination of cariogenic microorganisms could be done in the process of cavity cleaning before placing a restoration. Thus, use of disinfecting agents for achieving this goal could herald a new beginning in the field of contemporary dentistry. Aim: To assess and compare the cavity disinfection efficacy of APF gel, Brazilian Propolis, Diode Laser, and 2% chlorhexidine (CHX. Materials and Methods: The study was a randomized, single blinded, parallel grouped, active controlled trial. Eighty primary molars in 68 children with cavitated dentinal occlusal caries were randomly assigned into four groups (20 teeth each Group I: APF gel; Group II: Propolis; Group III: Diode Laser, and Group IV: 2% CHX (control. After cavity preparation using ART procedure, dentinal samples collected before and after disinfection with respective agent of the group. These samples were subjected to microbiological evaluation, for total viable count (TVC on blood agar, Streptococcus mutans on mutans-sanguis (MS agar, and Lactobacilli (LB on Rogosa agar. Results: Intragroup comparison (Wilcoxon signed rank test showed significant reductions in TVC, MS, and LB counts in all the groups. Pairwise Mann–Whitney test showed APF gel had least bacterial reductions among the agents tested. Conclusion: This study illustrated the need for cavity disinfection. Diode Laser and Brazilian Propolis are equally effective as 2% CHX in cavity disinfection.

  6. In vivo comparison of cavity disinfection efficacy with APF gel, Propolis, Diode Laser, and 2% chlorhexidine in primary teeth

    Science.gov (United States)

    Mohan, P. V. M. Uday; Uloopi, K. S.; Vinay, C.; Rao, R. Chandrasekhar

    2016-01-01

    Background: The survival of atraumatic restorative treatment (ART) restorations would be enhanced if near total elimination of cariogenic microorganisms could be done in the process of cavity cleaning before placing a restoration. Thus, use of disinfecting agents for achieving this goal could herald a new beginning in the field of contemporary dentistry. Aim: To assess and compare the cavity disinfection efficacy of APF gel, Brazilian Propolis, Diode Laser, and 2% chlorhexidine (CHX). Materials and Methods: The study was a randomized, single blinded, parallel grouped, active controlled trial. Eighty primary molars in 68 children with cavitated dentinal occlusal caries were randomly assigned into four groups (20 teeth each) Group I: APF gel; Group II: Propolis; Group III: Diode Laser, and Group IV: 2% CHX (control). After cavity preparation using ART procedure, dentinal samples collected before and after disinfection with respective agent of the group. These samples were subjected to microbiological evaluation, for total viable count (TVC) on blood agar, Streptococcus mutans on mutans-sanguis (MS) agar, and Lactobacilli (LB) on Rogosa agar. Results: Intragroup comparison (Wilcoxon signed rank test) showed significant reductions in TVC, MS, and LB counts in all the groups. Pairwise Mann–Whitney test showed APF gel had least bacterial reductions among the agents tested. Conclusion: This study illustrated the need for cavity disinfection. Diode Laser and Brazilian Propolis are equally effective as 2% CHX in cavity disinfection. PMID:27041900

  7. On the use of a chirped Bragg grating as a cavity mirror of a picosecond Nd : YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Zubko, A E; Shashkov, E V; Smirnov, A V; Vorob' ev, N S [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Smirnov, V I [OptiGrate Corp., 562 South Econ Circle, Oviedo, Florida 32765-4311 (United States)

    2016-02-28

    The first experimental evidence is presented that the use of a chirped volume Bragg grating (CVBG) as a cavity mirror of a Q-switched picosecond Nd : YAG laser with self-mode-locking leads to significant changes in the temporal parameters of the laser output. Measurements have been performed at two positions of the CVBG: with the grating placed so that shorter wavelengths reflected from its front part lead longer wavelengths or with the grating rotated through 180°, so that longer wavelengths are reflected first. In the former case, the duration of individual pulses in a train increased from ∼35 to ∼300 ps, whereas the pulse train shape and duration remained the same as in the case of a conventional laser with a mirror cavity. In the latter case, the full width at half maximum of pulse trains increased from ∼70 ns (Nd : YAG laser with a mirror cavity) to ∼1 ms, and the duration of individual pulses increased from 35 ps to ∼1.2 ns, respectively, which is more typical of free-running laser operation. (laser crystals and braggg ratings)

  8. Influence of external magnetic and laser radiation fields on Feshbach resonances in collision of atoms

    CERN Document Server

    Gazazyan, E A; Chaltykyan, V O

    2012-01-01

    We study collision of two atoms with formation of Feshbach resonance at combined interaction with the external magnetic field and laser radiation. In cases of one- and two-photon resonances of laser radiation with two discrete vibrational molecular levels, we show that Feshbach resonances appear at interaction of external magnetic field with dressed states formed via Autler-Townes effect. In addition, in case of one-photon resonance the lower vibrational molecular state is coupled by laser radiation with the continuum of the elastic channel and forms laser-induced Feshbach resonance via both Autler-Townes effect and LICS mechanism. We study the combined process of formation of Feshbach resonances; this enables the control of Feshbach resonance by varying the magnetic field and intensity and frequency of laser radiation. We obtain the cross-sections of elastic and inelastic scattering and show that quenching of resonance occurs at the energy equal to that of the systems ground state. Dependence of the cross-se...

  9. Working characteristics of external distributed feedback polymer lasers with varying waveguiding structures

    Science.gov (United States)

    Huang, Wenbin; Shen, Su; Pu, Donglin; Wei, Guojun; Ye, Yan; Peng, Changsi; Chen, Linsen

    2015-12-01

    We report the fabrication and characterization of second-order external distributed feedback (DFB) lasers based on blue-emitting polymer poly (9, 9-dioctyl-fluorene) (PFO). The relief grating prepared in the photo-resist layer on top of the gain medium was directly employed as the resonator. The effect of various structural parameters including the thickness of the active film, the thickness of the residue layer, and the depth of the relief grating on performance of these polymer lasers was investigated. An analytical approach based on the slab waveguiding theory and the Bragg condition was developed to accurately determine the lasing wavelength. We found that laser threshold increases monotonously as the thickness of the residue layer increases. The presence of the residue layer between the relief grating and the organic semiconductor layer weakens the strength of light coupling between the two layers, leading to a decreased gain for the specific lasing mode. The lowest laser threshold level of 80 μJ cm-2 was obtained when the thickness of the gain medium was around 250 nm, indicating an optimum balance between light feedback provided by the grating and optical amplification in the organic semiconductor. Our results not only provide insights into working mechanisms of external DFB polymer lasers, but also design rules for fabricating them.

  10. Two-dimensional radial laser scanning for circular marker detection and external mobile robot tracking.

    Science.gov (United States)

    Teixidó, Mercè; Pallejà, Tomàs; Font, Davinia; Tresanchez, Marcel; Moreno, Javier; Palacín, Jordi

    2012-11-28

    This paper presents the use of an external fixed two-dimensional laser scanner to detect cylindrical targets attached to moving devices, such as a mobile robot. This proposal is based on the detection of circular markers in the raw data provided by the laser scanner by applying an algorithm for outlier avoidance and a least-squares circular fitting. Some experiments have been developed to empirically validate the proposal with different cylindrical targets in order to estimate the location and tracking errors achieved, which are generally less than 20 mm in the area covered by the laser sensor. As a result of the validation experiments, several error maps have been obtained in order to give an estimate of the uncertainty of any location computed. This proposal has been validated with a medium-sized mobile robot with an attached cylindrical target (diameter 200 mm). The trajectory of the mobile robot was estimated with an average location error of less than 15 mm, and the real location error in each individual circular fitting was similar to the error estimated with the obtained error maps. The radial area covered in this validation experiment was up to 10 m, a value that depends on the radius of the cylindrical target and the radial density of the distance range points provided by the laser scanner but this area can be increased by combining the information of additional external laser scanners.

  11. Two-Dimensional Radial Laser Scanning for Circular Marker Detection and External Mobile Robot Tracking

    Directory of Open Access Journals (Sweden)

    Jordi Palacín

    2012-11-01

    Full Text Available This paper presents the use of an external fixed two-dimensional laser scanner to detect cylindrical targets attached to moving devices, such as a mobile robot. This proposal is based on the detection of circular markers in the raw data provided by the laser scanner by applying an algorithm for outlier avoidance and a least-squares circular fitting. Some experiments have been developed to empirically validate the proposal with different cylindrical targets in order to estimate the location and tracking errors achieved, which are generally less than 20 mm in the area covered by the laser sensor. As a result of the validation experiments, several error maps have been obtained in order to give an estimate of the uncertainty of any location computed. This proposal has been validated with a medium-sized mobile robot with an attached cylindrical target (diameter 200 mm. The trajectory of the mobile robot was estimated with an average location error of less than 15 mm, and the real location error in each individual circular fitting was similar to the error estimated with the obtained error maps. The radial area covered in this validation experiment was up to 10 m, a value that depends on the radius of the cylindrical target and the radial density of the distance range points provided by the laser scanner but this area can be increased by combining the information of additional external laser scanners.

  12. Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices

    Science.gov (United States)

    Li, M. Y.; Jaehme, H.; Soldat, H.; Gerhardt, N. C.; Hofmann, M. R.; Ackemann, T.

    2011-03-01

    Spin-controlled vertical-cavity surface-emitting lasers (VCSELs) have been intensively studied in recent years because of the low threshold feasibility and the nonlinearity above threshold, which make spin-VCSELs very promising for spintronic devices. Here we investigate the circular polarization dynamics of VCSELs on a picosecond time scale after pulsed optical spin injection at room temperature. A hybrid excitation technique combining continuous-wave (cw) unpolarized electrical excitation slightly above threshold and pulsed polarized optical excitation is applied. The experimental results demonstrate ultrafast circular polarization oscillations with a frequency of about 11 GHz. The oscillations last inside the first undulation of the intensity relaxation oscillations. Via theoretical calculations based on a rate equation model we analyze these oscillations as well as the underlying physical mechanisms.

  13. Phase-locked arrays of vertical-cavity surface-emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Warren, M.E.; Lear, K.L.; Gourley, P.L.; Hadley, G.R.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Lott, J.A. [Air Force Institute of Technology, Wright Patterson Air Force Base, OH (United States); Chalmers, S.A. [Optical Solutions, Albany, CA (United States)

    1994-04-01

    Vertical-Cavity Surface-Emitting Lasers (VCSELS) are of increasing interest to the photonics community because of their surface-emitting structure, simple fabrication and packaging, wafer-level testability, and potential for low cost manufacture. Scaling VCSELs to higher power outputs requires increasing the device area, which leads to transverse mode control difficulties if devices become larger than about 5 microns. One approach to increasing the device size while maintaining a well controlled transverse mode profile is formation of coupled or phase-locked two-dimensional arrays of VCSELs that are individually single-transverse mode. Such arrays have unique optical properties, not all of which are desirable. This paper covers some of the basic principles of these devices and reviews recent work on device designs, fabrication and operation. A technique for improving the far-field properties of the arrays is demonstrated and performance limitations are discussed.

  14. Green monolithic II-VI vertical-cavity surface-emitting laser operating at room temperature

    Science.gov (United States)

    Kruse, C.; Ulrich, S. M.; Alexe, G.; Roventa, E.; Kröger, R.; Brendemühl, B.; Michler, P.; Gutowski, J.; Hommel, D.

    2004-02-01

    The realization of a monolithic all II-VI-based vertical cavity surface emitting laser (VCSEL) for the green spectral region is reported. Optically pumped lasing operation was achieved up to room temperature using a planar VCSEL structure. Taking advantage of distributed Bragg-reflectors based on MgS/Zn(Cd)Se superlattices as the low-refractive index material and ZnS0.06Se0.94 layers as the high-index material with a refractive index contrast of n = 0.6, a quality factor exceeding Q = 2000 is reached by using only 18 Bragg periods for the bottom DBR and 15 Bragg periods for the top DBR. The threshold power density is 0.32 MW/cm2 at a temperature of 10 K (emission wavelength 498.5 nm) and 1.9 MW/cm2 at room temperature (emission wavelength 502.3 nm).

  15. Enhanced x-rays from resonant betatron oscillations in laser wakefield with external wigglers

    Science.gov (United States)

    Zhang, Z. M.; Zhang, B.; Hong, W.; Yu, M. Y.; Deng, Z. G.; Teng, J.; He, S. K.; Gu, Y. Q.

    2016-11-01

    Generation of ultra-short betatron x-rays by laser-accelerated electron beams is of great research interest as it has many applications. In this paper, we propose a scheme for obtaining bright betatron x-rays by applying external wiggler magnetic field in the laser wakefield to resonantly drive the betatron oscillations of the accelerated electrons therein. This results in a significant enhancement of the betatron oscillation amplitude and generation of bright x-rays with high photon energy. The scheme is demonstrated using two-dimensional particle-in-cell simulation and discussed using a simple analytical model.

  16. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    KAUST Repository

    Leonard, J. T.

    2015-07-06

    © 2015 AIP Publishing LLC. We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3nm quantum well width, 1nm barriers, a 5nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406nm nonpolar VCSEL with a low threshold current density (∼16kA/cm2), a peak output power of ∼12μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  17. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    Science.gov (United States)

    Leonard, J. T.; Cohen, D. A.; Yonkee, B. P.; Farrell, R. M.; Margalith, T.; Lee, S.; DenBaars, S. P.; Speck, J. S.; Nakamura, S.

    2015-07-01

    We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3 nm quantum well width, 1 nm barriers, a 5 nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406 nm nonpolar VCSEL with a low threshold current density (˜16 kA/cm2), a peak output power of ˜12 μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  18. Single-mode low threshold current multi-hole vertical-cavity surface-emitting lasers

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhen-Bo; Xu Chen; Xie Yi-Yang; Zhou Kang; Liu Fa; Shen Guang-Di

    2012-01-01

    A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-reflector of an oxidationconfined 850 nm VCSEL.The single-mode output power of 2.6 mW,threshold current of 0.6 mA,full width of half maximum lasing spectrum of less than 0.1 nm,side mode suppression ratio of 28.4 dB,and far-field divergence angle of about 10° are obtained.The effects of different hole depths on the optical characteristics are simulated and analysed,including far-field divergence,spectrum and lateral cavity mode.The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter-hole spacing and the scattering loss at the bottom of the holes,particularly for higher order modes.

  19. Switchable different operation states in an erbium-doped fiber laser cavity with normal dispersion

    Science.gov (United States)

    Gao, Weiqing; Liao, Meisong; Kawashima, Hiroyasu; Suzuki, Takenobu; Ohishi, Yasutake

    2012-08-01

    We demonstrate different operation states which can be switched by the polarization control in an erbium-doped fiber laser cavity with normal dispersion, including passive single-pulse and multiple-pulse mode-locking, coherent pulse pattern, and passive Q-switching. The mode-locked single pulse has a smooth and broad rectangular-shaped spectrum. With increasing pump power, multiple pulses appear and finally six pulses are observed, where the pulses have no interaction with each other. Keeping the pump power at 407 mW and adjusting the polarization state, we observe the coherent pulse pattern with the pulse numbers from 2 to 5. It is the first time five coherent pulses in the 1.55 μm normal dispersion cavity have been observed, to our knowledge. The mode-locked spectra are highly modulated and the largest pulse separation of 31.9 ps is observed for the two-pulse case. When the pump power exceeds 180 mW, the mode-locked operation can be switched to the passively Q-switched operation by controlling the polarization state. The repetition rate and pulse width can be changed by pump power variation, and the spectrum is tunable in the range of 8.45 nm.

  20. Dynamic analysis of V-folded cavity for TEM00 operation of end-pumped solid-state laser

    Institute of Scientific and Technical Information of China (English)

    Cunfa Li; Xiangchun Shi

    2005-01-01

    Based on graphic analysis design method of optical resonator, a simple design expression of V-folded cavity of end-pumped solid-state lasers with TEMoo operation is described, which satisfies two criterias of the resonator design. We give numerical simulation of spot size as a function of thermal focal length using this design approach whose advantages axe validated experimentally.

  1. Oscillations in a Forward-Facing Cavity Measured Using Laser-Differential Interferometry in a Hypersonic Quiet Tunnel

    Science.gov (United States)

    2007-12-11

    Feedback Stabilization System . . . . . . . . . . . . . . . . . . . . . . 48 4 Results...a) induced vibration profile, b) induced vibration power spectrum . . . . 49 3.21 Schematic of feedback -stabilized LDI...Boeing/AFOSR Mach-6 Quiet Tunnel BFL Back Focal Length xvi CCA Constant Current Anemometer EFL Effective Focal Length FFC Forward Facing Cavity LDI Laser

  2. The effect of low level laser therapy on pain during dental tooth-cavity preparation in children.

    Science.gov (United States)

    Tanboga, I; Eren, F; Altinok, B; Peker, S; Ertugral, F

    2011-04-01

    To evaluate the effect of low level laser therapy on pain during cavity preparation with laser in paediatric dental patients. The study was carried out on 10 children aged 6 to 9 years old for a total of 20 primary molar teeth. For laser preparation an Er: YAG laser was used. Half of the preparations were treated by low level laser therapy (LLLT) before laser preparation and the remaining half without LLLT (non-LLLT) before laser preparation. All cavities were prepared by ER:YAG laser, restored with light-cured composite resin following the application of acid etching and bonding agent. Children were instructed to rate their pain on the visual analogue scale (VAS) from 0 to 5 points. Statistical analyses were performed using Mann Whitney U test. VAS Median (min-max) scores were 1(0-2) for LLLT and 3(1-4) for the non-LLT treated children. Between LLLT and non- LLLT groups results were statistically significant (ppain in paediatric dental patients.

  3. High Mach-number collisionless shock driven by a laser with an external magnetic field

    Directory of Open Access Journals (Sweden)

    Morita T.

    2013-11-01

    Full Text Available Collisionless shocks are produced in counter-streaming plasmas with an external magnetic field. The shocks are generated due to an electrostatic field generated in counter-streaming laser-irradiated plasmas, as reported previously in a series of experiments without an external magnetic field [T. Morita et al., Phys. Plasmas, 17, 122702 (2010, Kuramitsu et al., Phys. Rev. Lett., 106, 175002 (2011] via laser-irradiation of a double-CH-foil target. A magnetic field is applied to the region between two foils by putting an electro-magnet (∼10 T perpendicular to the direction of plasma expansion. The generated shocks show different characteristics later in time (t > 20ns.

  4. 2D substrate imaging of a tapered laser cavity based on InGaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Pagano, R; O' Callaghan, J; Mukherjee, J; Mclnerney, J G; Corbett, B [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland); Reithmaier, J P [Technische Physik Institute of Nanostructure Technologies and Analytics (INA) University of Kassel (Germany); Deubert, S; Forchel, A, E-mail: roberto.pagano@tyndall.i [Technische Physik, University of Wuerzburg, 97074 Wuerzburg (Germany)

    2009-11-15

    Tapered cavities are an excellent solution to obtaining high brightness semiconductor laser sources for use in applications from frequency doubling to material processing. The high power density levels reached in such lasers can lead to nonlinear mechanisms related to the refractive index variations that de-stabilise the optical field distribution inside the laser cavity. These mechanisms are detrimental to the beam quality of the laser limiting its focussing ability. In this work we map the spatial distribution and evolution of the carrier density in tapered lasers as a function of injection current. A device with a taper length of 2.75 mm, taper angle of 6{sup 0} and ridge length of 1.25 mm is used to demonstrate the principle. The active region consists of three layers of InGaAs quantum dots emitting around 950 nm. A window for imaging the spontaneous emission profile through the transparent GaAs substrate was formed by patterning the n-contact metal layer. The imaging was performed in the continuous wave regime to include the thermal-induced refractive index perturbation. The results show a non-uniform carrier and thermal distribution inside the cavity even at low current levels.

  5. Dynamic model and stability analysis of a laser using a nonlinear Fabry-Perot etalon as a cavity mirror

    Energy Technology Data Exchange (ETDEWEB)

    Li, S.; Pons, R. (Autonoma de Barcelona (Spain). Dept. of Fisica); Zhang, Y. (Chongqing Inst. of Posts and Telecommunications, Sichuan (China). Telecommunications Engineering Dept.)

    1994-08-01

    In this paper, the authors study a laser using a nonlinear Fabry-Perot etalon as a cavity mirror. First, using the semiclassical laser theory and the differential equation for the lossy nonlinear Fabry-Perot etalon, they develop dynamic equations describing this system for single-mode operation. In this model, the frequency-pulling effect, a finite response time of the nonlinear medium, and a finite-cavity round-trip time of the Fabry-Perot etalon are included. Second, based on this model, they analyze the stability of this laser and give some numerical results. The results show that (1) this system can exist in the stable state and in the unstable state; (2) there are not only saddle-node bifurcations but also Hopf bifurcations; (3) the detuning parameter will effect the characteristics of the bistability and the number and distribution of Hopf bifurcation points.

  6. Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

    Science.gov (United States)

    Teng, J.; Gu, Y. Q.; Zhu, B.; Hong, W.; Zhao, Z. Q.; Zhou, W. M.; Cao, L. F.

    2013-11-01

    This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

  7. High reflectivity III-nitride UV-C distributed Bragg reflectors for vertical cavity emitting lasers

    Science.gov (United States)

    Franke, A.; Hoffmann, M. P.; Kirste, R.; Bobea, M.; Tweedie, J.; Kaess, F.; Gerhold, M.; Collazo, R.; Sitar, Z.

    2016-10-01

    UV-C distributed Bragg reflectors (DBRs) for vertical cavity surface emitting laser applications and polariton lasers are presented. The structural integrity of up to 25 layer pairs of AlN/Al0.65Ga0.35N DBRs is maintained by balancing the tensile and compressive strain present between the single layers of the multilayer stack grown on top of an Al0.85Ga0.35N template. By comparing the structural and optical properties for DBRs grown on low dislocation density AlN and AlGaN templates, the criteria for plastic relaxation by cracking thick nitride Bragg reflectors are deduced. The critical thickness is found to be limited mainly by the accumulated strain energy during the DBR growth and is only negligibly affected by the dislocations. A reflectance of 97.7% at 273 nm is demonstrated. The demonstrated optical quality and an ability to tune the resonance wavelength of our resonators and microcavity structures open new opportunities for UV-C vertical emitters.

  8. Effect of external and internal magnetic fields on the bias stability in a Zeeman laser gyroscope

    Energy Technology Data Exchange (ETDEWEB)

    Kolbas, Yu Yu; Saveliev, I I; Khokhlov, N I [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation)

    2015-06-30

    With the specific features of electronic systems of a Zeeman laser gyroscope taken into account, the basic physical mechanisms of the magnetic field effect on the bias stability and the factors giving rise to the internal magnetic fields are revealed. The hardware-based methods of reducing the effect of external and internal magnetic fields are considered, as well as the algorithmic methods for increasing the stability of the bias magnetic component by taking into account its reproducible temperature and time dependences. Typical experimental temperature and time dependences of the magnetic component of the Zeeman laser gyro bias are presented, and by their example the efficiency of the proposed methods for reducing the effect of magnetic fields is shown. (laser gyroscopes)

  9. Semiconductor Laser with a Self-Pumped Phase Conjugate External Cavity

    Science.gov (United States)

    1992-10-01

    person or corporation; or as conveying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related...relationship is Aw = - = acoswr-- ar2rs + sin wT\\ A1 -- 2r2r3 osr + r 212 where x= Dr, , (3.25) r2 I’d Sacoswr - ar 2 r 3 - sinwr (3.26) \\1-2r 2 r 3 costo

  10. Femtosecond Laser Fabrication of Cavity Microball Lens (CMBL) inside a PMMA Substrate for Super-Wide Angle Imaging.

    Science.gov (United States)

    Zheng, Chong; Hu, Anming; Kihm, Kenneth D; Ma, Qian; Li, Ruozhou; Chen, Tao; Duley, W W

    2015-07-01

    Since microlenses have to date been fabricated primarily by surface manufacturing, they are highly susceptible to surface damage, and their microscale size makes it cumbersome to handle. Thus, cavity lenses are preferred, as they alleviate these difficulties associated with the surface-manufactured microlenses. Here, it is shown that a high repetition femtosecond laser can effectively fabricate cavity microball lenses (CMBLs) inside a polymethyl methacrylate slice. Optimal CMBL fabrication conditions are determined by examining the pertinent parameters, including the laser processing time, the average irradiation power, and the pulse repetition rates. In addition, a heat diffusion modeling is developed to better understand the formation of the spherical cavity and the slightly compressed affected zone surrounding the cavity. A micro-telescope consisting of a microscope objective and a CMBL demonstrates a super-wide field-of-view imaging capability. Finally, detailed optical characterizations of CMBLs are elaborated to account for the refractive index variations of the affected zone. The results presented in the current study demonstrate that a femtosecond laser-fabricated CMBL can be used for robust and super-wide viewing micro imaging applications.

  11. Investigation on characteristics of self-organization in Mach-Zehnder erbium-doped fiber laser cavity

    Institute of Scientific and Technical Information of China (English)

    Fengnian Liu; Bo Liu; Bangcai Huang; Guiyun Kai; Shuzhong Yuan; Xiaoyi Dong

    2008-01-01

    The characteristics of coherent coupling in Mach-Zehnder erbium-doped fiber laser cavity are experimentally studied.By virtue of a seemly controlling of length difference between two interferometric arms,the obtained comb-like spectrum of interferometer resonator with a period of 0.06 nm commendably agrees with the theory of self-organization coherence The coherent output exits from the output mirror of a fiber Bragg grating with 4.5% reflectivity.A high coherent combining efficiency of 94% is obtained.Investigation on characteristics of the leak power opens out self-organization mechanism in Mach-Zehnder composite cavity.

  12. Laser Plasmas : Density oscillations in laser produced plasma decelerated by external magnetic field

    Indian Academy of Sciences (India)

    V N Rai; M Shukla; H C Pant

    2000-11-01

    This paper presents the dynamics as well as the stability of laser produced plasma expanding across the magnetic field. Observation of some high frequency fluctuations superimposed on ion saturation current along with structuring in the pin hole images of x-ray emitting plasma plume indicate the presence of instability in the plasma. Two type of slope in the variation of x-ray emission with laser intensity in the absence and presence of magnetic field shows appearance of different threshold intensity of laser corresponding to each magnetic field at which this instability or density fluctuation sets on. This instability has been identified as a large Larmor radius instability instead of classical Rayleigh-Taylor (R-T) instability.

  13. Analysis of frequency noise properties of 729nm extended cavity diode laser with unbalanced Mach-Zehnder interferometer

    Science.gov (United States)

    Pham, Tuan M.; Čížek, Martin; Hucl, Václav; Lazar, Josef; Hrabina, Jan; Řeřucha, Šimon; Lešundák, Adam; Obšil, Petr; Filip, Radim; Slodička, Lukáš; Číp, Ondřej

    2016-12-01

    We report on the frequency noise investigation of a linewidth-suppressed Extended Cavity Diode Laser (ECDL), working at 729 nm. Since the ECDL is intended as an excitation laser for the forbidden transition in a trapped and laser cooled 40Ca+ ion, an Hz-level linewidth is required. We present the experimental design that comprises a two-stage linewidth narrowing and a facility for frequency and noise analysis. The linewidth is first narrowed with a phase lock loop of the ECDL onto a selected component of an optical frequency comb where the frequency noise was suppressed with a fast electronic servo-loop controller that drives the laser injection current with a high bandwidth. The second stage comprises locking the laser onto a selected mode of a high-finesse passive optical cavity. The frequency analysis used an unbalanced Mach-Zehnder interferometer with a fiber spool inserted in the reference arm in order to give a general insight into the signal properties by mixing two separated beams, one of them delayed by the spool, and processing it with a spectral analyzer. Such a frequency noise analysis reveals what are the most significant noises contributions to the laser linewidth, which is a crucial information in field of ion trapping and cooling. The presented experimental results show the effect of the linewidth narrowing with the first stage, where the linewidth of ECDL was narrowed down to a kHz level.

  14. V-shaped resonators for addition of broad-area laser diode arrays

    Science.gov (United States)

    Liu, Bo; Liu, Yun; Braiman, Yehuda Y.

    2012-12-25

    A system and method for addition of broad-area semiconductor laser diode arrays are described. The system can include an array of laser diodes, a V-shaped external cavity, and grating systems to provide feedback for phase-locking of the laser diode array. A V-shaped mirror used to couple the laser diode emissions along two optical paths can be a V-shaped prism mirror, a V-shaped stepped mirror or include multiple V-shaped micro-mirrors. The V-shaped external cavity can be a ring cavity. The system can include an external injection laser to further improve coherence and phase-locking.

  15. Electron energy boosting in laser-wake-field acceleration with external magnetic field B˜1 T and laser prepulses

    Science.gov (United States)

    Hosokai, Tomonao; Zhidkov, Alexei; Yamazaki, Atsushi; Mizuta, Yoshio; Uesaka, Mitsuru; Kodama, Ryosuke

    2010-03-01

    Hundred-mega-electron-volt electron beams with quasi-monoenergetic distribution, and a transverse geometrical emittance as small as ˜0.02 π mm mrad are generated by low power (7 TW, 45 fs) laser pulses tightly focused in helium gas jets in an external static magnetic field, B˜1 T. Generation of monoenergetic beams strongly correlates with appearance of a straight, at least 2 mm length plasma channel in a short time before the main laser pulse and with the energy of copropagating picosecond pedestal pulses (PPP). For a moderate energy PPP, the multiple or staged electron self-injection in the channel gives several narrow peaks in the electron energy distribution.

  16. Cavity enhanced absorption spectroscopy for N2O detection at 2.86μm using a continuous tunable color center laser

    Institute of Scientific and Technical Information of China (English)

    Shaocheng Li(李少成); Qingxu Yu(于清旭); Maarten van Herpen; Sacco te Lintel Hekkert; Frans J. M. Harren

    2003-01-01

    The cavity enhanced absorption technique is applied to N2O detection around 2.86 μm using a continuouswave color center laser. A high-finesse triangular ring cavity is used in this technology. Transmission through the cavity is obtained by jittering the cavity-length with a piezo on one of the cavity mirrors.A minimum detectable absorption coefficient of 2 × 10-6 cm-1 is achieved with a mirror reflectivity of 99.24%, corresponding to a N2O detection limit of 600 parts per billion.

  17. Experimental validation of a radio frequency photogun as external electron injector for a laser wakefield accelerator

    Science.gov (United States)

    Stragier, X. F. D.; Luiten, O. J.; van der Geer, S. B.; van der Wiel, M. J.; Brussaard, G. J. H.

    2011-07-01

    A purpose-built RF-photogun as external electron injector for a laser wakefield accelerator has been thoroughly tested. Different properties of the RF-photogun have been measured such as energy, energy spread and transverse emittance. The focus of this study is the investigation of the smallest possible focus spot and focus stability at the entrance of the plasma channel. For an electron bunch with 10 pC charge and 3.7 MeV kinetic energy, the energy spread was 0.5% with a shot-to-shot stability of 0.05%. After focusing the bunch by a pulsed solenoid lens at 140 mm from the middle of the lens, the focal spot was 40 μm with a shot-to-shot stability of 5 μm. Higher charge leads to higher energy spread and to a larger spot size, due to space charge effects. All properties were found to be close to design values. Given the limited energy of 3.7 MeV, the properties are sufficient for this gun to serve as injector for one particular version of laser wakefield acceleration, i.e., injection ahead of the laser pulse. These measured electron bunch properties were then used as input parameters for simulations of electron bunch injection in a laser wakefield accelerator. The arrival time jitter was deduced from measurements of the energy fluctuation, in combination with earlier measurements using THz coherent transition radiation, and is around 150 fs in the present setup. The bunch length in the focus, simulated using particle tracking, depends on the accelerated charge and goes from 100 fs at 0.1 pC to 1 ps at 50 pC. When simulating the injection of the 3.7 MeV electron bunch of 10 pC in front of a 25 TW laser pulse with a waist of 30 μm in a plasma with a density of 0.7 × 1024 m-3, the maximum accelerated charge was found to be 1.2 pC with a kinetic energy of ˜900 MeV and an energy spread of ˜5%. The experiments combined with the simulations show the feasibility of external injection and give a prediction of the output parameters that can be expected from a laser

  18. Quantum limit of the laser linewidth in chaotic cavities and statistics of residues of scattering matrix poles

    CERN Document Server

    Schomerus, H; Patra, M; Beenakker, C W J

    1999-01-01

    The quantum-limited linewidth of a laser cavity is enhanced above the Schawlow-Townes value by the Petermann factor K, due to the non-orthogonality of the cavity modes. We derive the relation between the Petermann factor and the residues of poles of the scattering matrix and investigate the statistical properties of the Petermann factor for cavities in which the radiation is scattered chaotically. For a single scattering channel we determine the complete probability distribution of K and find that the average Petermann factor $$ depends non-analytically on the area of the opening, and greatly exceeds the most probable value. For an arbitrary number N of scattering channels we calculate $$ as a function of the decay rate $\\Gamma$ of the lasing mode. We find for $N\\gg 1$ that for typical values of $\\Gamma$ the average Petermann factor $\\propto \\sqrt{N}\\gg 1$ is parametrically larger than unity.

  19. Laser-field-induced magnon amplification in a magnetic semiconductor quantum well under an external magnetic field

    Institute of Scientific and Technical Information of China (English)

    Peng Feng

    2003-01-01

    The laser-field induced magnon amplification in a magnetic semiconductor quantum well under an external magnetic field was discussed, it is shown that when the laser frequency is near to the electron cyclotron frequency, no matter how weaker the laser field is, the magnon amplification always occurs. In case of fixed laser frequency, the optical absorption of magnons obeys the definite selection rule to the laser field strength. The rate of change of magnon occupation is calculated, and the amplification condition is given.

  20. Atomic clocks based on extened-cavity diode laser in multimode operation

    Science.gov (United States)

    Yim, Sin; Cho, D.

    2011-05-01

    We demonstrated the possibilities to develope an atomic clock based on coherent population trapping (CPT) without using a local oscillator and a modulator. Instead of using a modulator, we use two modes from a single extended-cavity diode laser in multimode operation. Two different types of feedback system are applied to stabilize a difference frequency between the two modes and eliminate the need for an extra frequency modulation. In the first type, we employ an electronic feedback using dispersion of the CPT resonance as an error signal. The two modes are phase locked with reference to a dispersion signal from a CPT resonance of 85Rb at 3.036 GHz ground hyperfine splitting. We use D1 transition at 794.8 nm with lin ⊥lin polarizations to obtain large-contrast CPT signal. Allan deviation of the beat frequency between the two modes is 1 ×10-10 at 200-s integration time. In the second type, we employ optoelectronic feedback to construct an opto-electronic oscillator (OEO). In an OEO, the beating signal between two modes is recovered by a fast photodiode, and its output is amplified and fed back to the laser diode by using a direct modulation of an injection current. When the OEO loop is closed, oscillation frequency depends on variations of the loop length. In order to stabilize an OEO loop length and thereby its oscillation frequency, CPT cell is inserted to play a role of microwave band pass filter. Allan deviation of the CPT-stabilized OEO is 2 ×10-10 at 100-s integration time.