WorldWideScience

Sample records for external cavity length

  1. 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.

  2. 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.

  3. 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.

  4. 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...

  5. Cavity length below chute aerators

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    It is proved that air entrainment is one of the efficient measures dealing with cavi-tation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. One of the most important factors concerns the cavity length below the aerator,which has outstanding effects on air entrainment against cavitation damage. It is crucial to determine reasonable emergence angle for the calculation of the cavity length. In the present paper the overall effects of structural and hydraulic parameters on the emergence angle of the flow from the aerator were analyzed. Four improved expressions of the emer-gence angle with weight coefficient were investigated through experimental data of 68 points observed from 12 aerators of 6 hydropower projects,of both model and prototype,on the basis of error theory. A method to calculate the cavity length be-low aerators was suggested,which considers overall effects of the above men-tioned parameters. Comparison between the method in this paper and the other five methods of calculating the cavity length showed that the present method is much more reliable than the existing methods while the mean error of the method is less than others.

  6. Cavity length below chute aerators

    Institute of Scientific and Technical Information of China (English)

    WU JianHua; RUAN ShiPing

    2008-01-01

    It is proved that air entrainment is one of the efficient measures dealing with cavitation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. One of the most important factors concerns the cavity length below the aerator, which has outstanding effects on air entrainment against cavitation damage. It is crucial to determine reasonable emergence angle for the calculation of the cavity length. In the present paper the overall effects of structural and hydraulic parameters on the emergence angle of the flow from the aerator were analyzed. Four improved expressions of the emergence angle with weight coefficient were investigated through experimental data of 68 points observed from 12 aerators of 6 hydropower projects, of both model and prototype, on the basis of error theory. A method to calculate the cavity length below aerators was suggested, which considers overall effects of the above mentioned parameters. Comparison between the method in this paper and the other five methods of calculating the cavity length showed that the present method is much more reliable than the existing methods while the mean error of the method is less than others.

  7. Dither Cavity Length Controller with Iodine Locking

    Directory of Open Access Journals (Sweden)

    Lawson Marty

    2016-01-01

    Full Text Available A cavity length controller for a seeded Q-switched frequency doubled Nd:YAG laser is constructed. The cavity length controller uses a piezo-mirror dither voltage to find the optimum length for the seeded cavity. The piezo-mirror dither also dithers the optical frequency of the output pulse. [1]. This dither in optical frequency is then used to lock to an Iodine absorption line.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  11. 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.

  12. 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.

  13. 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%.

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. 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%.

  19. Effective optical path length for tandem diffuse cubic cavities as gas absorption cell

    Science.gov (United States)

    Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.

    2014-12-01

    Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.

  20. 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.

  1. Length measurement in absolute scale via low-dispersion optical cavity

    Science.gov (United States)

    Pravdova, Lenka; Lesundak, Adam; Smid, Radek; Hrabina, Jan; Rerucha, Simon; Cip, Ondrej

    2016-12-01

    We report on the length measuring instrument with the absolute scale that was based on the combination of an optical frequency comb and a passive optical cavity. The time spacing of short femtosecond pulses, generated by the optical frequency comb, is optically phase locked onto the cavity free spectral range with a derivative spectroscopy technique so that the value of the repetition frequency of the femtosecond laser is tied to and determines the measured displacement. The instantaneous value of the femtosecond pulse train frequency is counted by a frequency counter. This counted value corresponds to the length given by the spacing between the two mirrors of the passive cavity. The phase lock between the femtosecond pulsed beam and the passive cavity is possible due to the low-dispersion of the cavity mirrors, where the silver coating on the mirrors was used to provide the low dispersion for the broadband radiation of the comb. Every reflection on the output mirror feeds a portion of the beam back to the cavity so that the output beam is a result of multiple interfering components. The parameters of the output beam are given not only by the parameters of the mirrors but mainly by the absolute distance between the mirror surfaces. Thus, one cavity mirror can be considered as the reference starting point of the distance to be measured and the other mirror is the measuring probe surveying the unknown distance. The measuring mirror of the experimental setup of the low-dispersion cavity is mounted on a piezoelectric actuator which provides small changes in the cavity length we used to test the length measurement method. For the verification of the measurement accuracy a reference incremental interferometer was integrated into our system so that the displacement of the piezoelectric actuator could be obtained with both measuring methods simultaneously.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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...

  7. 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 ...

  8. 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.

  9. 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.

  10. Relationship between the length of the uterine cavity and clinical pregnancy rates after in vitro fertilization or intracytoplasmic sperm injection.

    Science.gov (United States)

    Chun, Sang Sik; Chung, Min Ji; Chong, Gun Oh; Park, Kee Sang; Lee, Taek Hoo

    2010-02-01

    In this prospective clinical study involving 354 IVF-intracytoplasmic sperm injection cycles, we determined the influence of the length of the uterine cavity on clinical pregnancy rates. Our data showed that clinical pregnancy and implantation rates are associated positively with an increased length of the uterine cavity.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    Energy Technology Data Exchange (ETDEWEB)

    P. Oshkai; M. Geveci; D. Rockwell; M. Pollack

    2002-12-12

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of,these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  20. Study Pulse Parameters versus Cavity Length for Both Dispersion Regimes in FM Mode Locked

    Directory of Open Access Journals (Sweden)

    Bushra Razooky Mhdi

    2015-03-01

    Full Text Available To demonstrate the effect of changing cavity length for  FM mode locked on pulse parameters and make comparison for both dispersion regime , a plot for each pulse parameter as Lr function are presented for normal and anomalous dispersion regimes. The analysis is based on the theoretical study and the results of numerical simulation using MATLAB. The effect of both normal and anomalous dispersion regimes on output pulses is investigate Fiber length effects on pulse parameters are investigated by driving the modulator into different values. A numerical solution for model equations using fourth-fifth order, Runge-Kutta method is performed through MATLAB 7.0 program. Fiber length effect on pulse parameters is investigated by driving the modulator into different values of lengths. Result shows that, the output pulse width from the FM mode locked equals to τ= 501ns anomalous regime and τ=518ns in normal regime.

  1. Temporal characterization of FEL micropulses as function of cavity length detuning using frequency-resolved optical gating

    Energy Technology Data Exchange (ETDEWEB)

    Richman, B.A. [Stanford Univ., CA (United States); DeLong, K.W.; Trebino, R. [Sandia National Lab., Livermore, CA (United States)

    1995-12-31

    Results of frequency resolved optical gating (FROG) measurements on the Stanford mid-IR FEL system show the effect of FEL cavity length detuning on the micropulse temporal structure. The FROG technique enables the acquisition of complete and uniquely invertible amplitude and phase temporal dependence of optical pulses. Unambiguous phase and amplitude profiles are recovered from the data. The optical pulses are nearly transform limited, and the pulse length increases with cavity length detuning.

  2. Optical vernier technique for in-situ measurement of the length of long Fabry-Perot cavities

    CERN Document Server

    Rakhmanov, M; Yamamoto, H

    1999-01-01

    We propose a method for in-situ measurement of the length of kilometer size Fabry-Perot cavities in laser gravitational wave detectors. The method is based on the vernier, which occurs naturally when the laser incident on the cavity has a sideband. By changing the length of the cavity over several wavelengths we obtain a set of carrier resonances alternating with sideband resonances. From the measurement of the separation between the carrier and a sideband resonance we determine the length of the cavity. We apply the technique to the measurement of the length of a Fabry-Perot cavity in the Caltech 40m Interferometer and discuss the accuracy of the technique.

  3. 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

  4. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    Energy Technology Data Exchange (ETDEWEB)

    P Oshkai; M Geveci; D Rockwell; M Pollack

    2004-05-24

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe, which give rise to flow tones, are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  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. 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.

  7. 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.

  8. 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.

  9. 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).

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. LIGHT SOURCE: RF deflecting cavity for bunch length measurement in Tsinghua Thomson scattering X-ray source

    Science.gov (United States)

    Shi, Jia-Ru; Chen, Huai-Bi; Tang, Chuan-Xiang; Huang, Wen-Hui; Du, Ying-Chao; Zheng, Shu-Xin; Ren, Li

    2009-06-01

    An RF deflecting cavity used for bunch length measurement has been designed and fabricated at Tsinghua University for the Thomson Scattering X-Ray Source. The cavity is a 2856 MHz, π-mode, 3-cell standing-wave cavity, to diagnose the 3.5 MeV beam produced by photocathode electron gun. With a larger power source, the same cavity will again be used to measure the accelerated beam with energy of 50 MeV before colliding with the laser pulse. The RF design using MAFIA for both the cavity shape and the power coupler is reviewed, followed by presenting the fabrication procedure and bench measurement results of two cavities.

  18. 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.

  19. On the length of an external branch in the Beta-coalescent

    CERN Document Server

    Dhersin, Jean-Stephane; Siri-Jegousse, Arno; Yuan, Linglong

    2012-01-01

    In this paper, we consider Beta$(2-{\\alpha},{\\alpha})$ (with $1<{\\alpha}<2$) and related ${\\Lambda}$-coalescents. If $T^{(n)}$ denotes the length of an external branch of the $n$-coalescent, we prove the convergence of $n^{{\\alpha}-1}T^{(n)}$ when $n$ tends to $ \\infty $, and give the limit. To this aim, we give asymptotics for the number $\\sigma^{(n)}$ of collisions which occur in the $n$-coalescent until the end of the chosen external branch, and for the block counting process associated with the $n$-coalescent.

  20. 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).

  1. 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....

  2. 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.)

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. 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.

  17. 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...

  18. 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.

  19. 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.

  20. 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 ...

  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. 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.

  3. Multiple-bunch-length operating mode design for a storage ring using hybrid low alpha and harmonic cavity method

    Science.gov (United States)

    Gao, Weiwei; Wang, Lin; Li, Heting

    2017-03-01

    In this paper we design a simultaneous three bunch length operating mode at the HLS-II (Hefei Light Source II) storage ring by installing two harmonic cavities and minimizing the momentum compaction factor. The short bunches (2.6 mm) presented in this work will meet the requirement of coherent millimeter-wave and sub-THz radiation experiments, while the long bunches (20 mm) will efficiently increase the total beam current. Therefore, this multiple-bunch-length operating mode allows present synchrotron users and coherent millimeter-wave users (or sub THz users) to carry out their experiments simultaneously. Since the relatively low energy characteristic of HLS-II we achieve the multiple-bunch-length operating mode without multicell superconducting RF cavities, which is technically feasible.

  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. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Importance of length and external diameter in left ventricular geometry. Normal values from the HUNT Study

    Science.gov (United States)

    Støylen, Asbjørn; Mølmen, Harald E; Dalen, Håvard

    2016-01-01

    Background We aimed to study left ventricular (LV) geometry assessed by length (LVWL), external diameter (LVEDD) and relative wall thickness (RWT) in relation to age, body size and gender in healthy individuals. Methods 1266 individuals underwent echocardiography in the Nord-Trøndelag Health Study (HUNT3), Norway. Septum thickness (IVS), posterior wall thickness (LVPWd) and end-diastolic internal diameter (LVIDD) were measured in M-mode, and LVEDD was calculated as the sum. Myocardial wall lengths were measured in a straight line from apex to the mitral ring in apical views at end diastole and averaged to LVWL. RWT ([IVSd+LVPWd]/LVIDD) and the ratio between length and diameter (L/D) were calculated. Results Normal age-related and gender-related values are provided. Conventional measures conform to previous studies. All measures correlated with body surface area (BSA) (r 0.29–0.60), and BSA indexed values were higher in women. Wall thickness (WT) and LVEDD, but not LVIDD, were higher with higher age. LVWL and L/D were lower with increasing age, but L/D was independent of BSA and similar in women and men (1.41 vs 1.40). RWT correlated with BSA and age (r 0.17 and 0.34). Conclusions LV WT increases and LVWL decreases with higher age. Excluding length in LV mass calculations increasingly overestimates mass with ageing. L/D is a BSA independent measure of LV age-related geometry and may be useful as a body size independent measure in LV hypertrophy. RWT depends on body size and age, and a single cut-off value is not warranted. PMID:27752332

  11. 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).

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Dynamics of Bright/Dark Solitons in Bose-Einstein Condensates with Time-Dependent Scattering Length and External Potential

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ai-Xia; XUE Ju-Kui

    2008-01-01

    We present an analytical study on the dynamics of bright and dark solitons in Bose-Einstein condensates with time-varying atomic scattering length in a time-varying external parabolic potential.A set of exact soliton solutions of the one-dimensional Gross-Pitaevskii equation are obtained,including fundamental bright solitons,higher-order bright solitons,and dark solitons.The results show that the soliton's parameters(amplitude,width,and period)can be changed in a controllable manner by changing the scattering length and external potential.This may be helpful to design experiments.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Appropriate timing of uterine cavity length measurement positively affects assisted reproduction cycle outcome.

    Science.gov (United States)

    Madani, Tahereh; Ashrafi, Mahnaz; Abadi, Akram Bahman; Kiani, Kiandokht

    2009-11-01

    An appropriate and easy embryo transfer has a direct impact on pregnancy rates. Proper evaluation of the uterocervical axis and uterine depth are necessary for suitable embryo transfer. The aim of this study was to assess the appropriate time for cervical axis evaluation and uterine measurement. A total of 124 patients undergoing IVF treatment were included in the study. They were divided equally into two groups. In group I (62 women), uterine cavity depth was measured and the uterocervical axis was determined on day 2 or 3 of the menstrual cycle, and in group II (62 women) at the time of oocyte retrieval. There was a statistically significant difference in clinical pregnancy rates between the two groups (P = 0.006). Thirty-four women became pregnant in group I (64.2%) versus 19 women in group II (35.8%). In conclusion, uterine cavity measurement is necessary for suitable embryo transfer. It seems that the time of measurement significantly affects clinical pregnancy rate in IVF cycles. The best time for uterine measurement is on day 2 or 3 of menstruation.

  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. Incontinence after primary repair of obstetric anal sphincter tears is related to relative length of reconstructed external sphincter

    DEFF Research Database (Denmark)

    Norderval, S; Røssaak, K.; Markskog, A;

    2012-01-01

    To determine if anatomic primary repair with end-to-end reconstruction of the external anal sphincter (EAS) in its full length combined with separate repair of coexisting internal anal sphincter (IAS) tear, when present, results in less incontinence and better anal sphincter integrity compared wi...

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. Length sensing and control of a Michelson interferometer with Power Recycling and Twin Signal Recycling cavities

    CERN Document Server

    Gräf, Christian; Vahlbruch, Henning; Danzmann, Karsten; Schnabel, Roman

    2012-01-01

    The techniques of power recycling and signal recycling have proven as key concepts to increase the sensitivity of large-scale gravitational wave detectors by independent resonant enhancement of light power and signal sidebands within the interferometer. Developing the latter concept further, twin signal recycling was proposed as an alternative to conventional detuned signal recycling. Twin signal recycling features the narrow-band sensitivity gain of conventional detuned signal recycling but furthermore facilitates the injection of squeezed states of light, increases the detector sensitivity over a wide frequency band and requires a less complex detection scheme for optimal signal readout. These benefits come at the expense of an additional recycling mirror, thus increasing the number of degrees of freedom in the interferometer which need to be controlled. In this article we describe the development of a length sensing and control scheme and its successful application to a tabletop-scale power recycled Michel...

  3. Length sensing and control of a Michelson interferometer with power recycling and twin signal recycling cavities.

    Science.gov (United States)

    Gräf, Christian; Thüring, André; Vahlbruch, Henning; Danzmann, Karsten; Schnabel, Roman

    2013-03-11

    The techniques of power recycling and signal recycling have proven as key concepts to increase the sensitivity of large-scale gravitational wave detectors by independent resonant enhancement of light power and signal sidebands within the interferometer. Developing the latter concept further, twin signal recycling was proposed as an alternative to conventional detuned signal recycling. Twin signal recycling features the narrow-band sensitivity gain of conventional detuned signal recycling but furthermore facilitates the injection of squeezed states of light, increases the detector sensitivity over a wide frequency band and requires a less complex detection scheme for optimal signal readout. These benefits come at the expense of an additional recycling mirror, thus increasing the number of degrees of freedom in the interferometer which need to be controlled.In this article we describe the development of a length sensing and control scheme and its successful application to a tabletop-scale power recycled Michelson interferometer with twin signal recycling. We were able to lock the interferometer in all relevant longitudinal degrees of freedom and thus laid the foundation for further investigations of this interferometer configuration to evaluate its viability for the application in gravitational wave detectors.

  4. The Study on the Variation of the Cavity Length's Influence on the Output Pulse Train of the Actively Mode-Locked Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    LUO Hong-e; TIAN Xiao-jian; GAO Bo

    2005-01-01

    The influence of actively mode-locked Erbium-Doped Fiber Laser(EDFL) cavity length variation on the noises of an optical pulse train is investigated, in theory and in MATLAB simulation. Using a simple model, the noise characteristics of the output pulse train are studied. The results show that the noises of the output pulse train increase with the increasing of the variation of the cavity length. The theory analysis and the simulation results agree well. This result is very significant for us to improve the reliability and the stability of the actively mode-locked fiber laser.

  5. 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...

  6. 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.

  7. 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.

  8. 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...

  9. Influence of fibre length, dissolution and biopersistence on the production of mesothelioma in the rat peritoneal cavity.

    Science.gov (United States)

    Miller, B G; Searl, A; Davis, J M; Donaldson, K; Cullen, R T; Bolton, R E; Buchanan, D; Soutar, C A

    1999-04-01

    A range of respirable man-made mineral fibres were tested for evidence of carcinogenicity by injection into the peritoneal cavity of male SPF Wistar rats; and differences in carcinogenicity were related to the dimensions and biopersistence of the injected fibres. The fibres tested included an amosite asbestos, a silicon carbide whisker, a special purpose glass microfibre, and a range of other man-made vitreous fibres (MMVFs) and refractory ceramic fibres (RCFs) from the TIMA fibre repository. The injected dose of each was designed as the estimated mass required to contain 10(9) fibres > 5 microns in length, as determined by optical microscopy. The numbers of long fibres (> 15 microns) contained in these doses ranged across fibres from 0.1 x 10(9) to 0.8 x 10(9) fibres; the number of long fibres thinner than 0.95 micron ranged from 0.015 x 10(9) to 0.4 x 10(9). The treatment groups contained between 18 and 24 animals. Animals were killed when they showed signs of debilitation. At autopsy, the diagnosis of mesothelioma was usually obvious macroscopically. Otherwise, histological examination of peritoneal organs was used to search for early tumour development. Judged by median survival time, four of the fibre types, in the doses administered, presented higher mesothelioma activity than amosite asbestos. The other fibres tested were less carcinogenic than the amosite. Only a ceramic material derived by extreme heating to simulate the effect of furnace or oven conditions, produced no mesotheliomas. Attempts were made, using regression models, to relate these differences to fibre dimensions and to measures of durability from separate experiments. The results pointed principally to a link with the injected numbers of fibres > 20 microns in length and with biopersistence in the rat lung of fibres longer than 5 microns. Improved quantification of the relative importance of fibre dimensions and biopersistence indices requires experimentation with a range of doses.

  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. 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.

  12. 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.

  13. 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.

  14. Numerical Study on the Flow Length in an Injection Molding Process with an External Air-Heating Step

    Directory of Open Access Journals (Sweden)

    Thanh Trung Do

    2017-04-01

    Full Text Available In this study, an external gas-assisted mold temperature control combined with water cooling was applied to achieve rapid mold-surface temperature control for observing the melt flow length in the thin-wall injection molding process. Variable part-thickness values of 0.2 mm, 0.4 mm, and 0.6 mm were used. Through a simulation and experiment, the injection molding process was achieved by using ABS and stamp insert temperatures ranging from 30 to 150 °C. In the simulation, when the stamp temperature was raised from 90 to 150 °C with part thickness of 0.2 mm, 0.4 mm, and 0.6 mm, the melt flow length increased by approximately 25.0%, 19.6%, and 12.8%, respectively. When the stamp temperature was higher than the glass-transition temperature of ABS, the improvement in the melt flow length was clearer, especially in the thinner part. In the experiment, the positive effect of stamp temperature was demonstrated; however, the improvement in the melt flow length was slightly different compared with the simulation owing to the heat transfer between the hot stamp and the environment.

  15. Telomere Length in Aged Mayak PA Nuclear Workers Chronically Exposed to Internal Alpha and External Gamma Radiation.

    Science.gov (United States)

    Scherthan, Harry; Sotnik, Natalia; Peper, Michel; Schrock, Gerrit; Azizova, Tamara; Abend, Michael

    2016-06-01

    Telomeres consist of GC-rich DNA repeats and the "shelterin" protein complex that together protect chromosome ends from fusion and degradation. Telomeres shorten with age due to incomplete end replication and upon exposure to environmental and intrinsic stressors. Exposure to ionizing radiation is known to modulate telomere length. However, the response of telomere length in humans chronically exposed to radiation is poorly understood. Here, we studied relative telomere length (RTL) by IQ-FISH to leukocyte nuclei in a group of 100 workers from the plutonium production facility at the Mayak Production Association (PA) who were chronically exposed to alpha-emitting ((239)Pu) radiation and/or gamma (photon) radiation, and 51 local residents serving as controls, with a similar mean age of about 80 years. We applied generalized linear statistical models adjusted for age at biosampling and the second exposure type on a linear scale and observed an age-dependent telomere length reduction. In those individuals with the lowest exposure, a significant reduction of about 20% RTL was observed, both for external gamma radiation (≤1 Gy) and internal alpha radiation (≤0.05-0.1 Gy to the red bone marrow). In highly exposed individuals (>0.1 Gy alpha, 1-1.5 Gy gamma), the RTL was similar to control. Stratification by gender revealed a significant (∼30%) telomere reduction in low-dose-exposed males, which was absent in females. While the gender differences in RTL may reflect different working conditions, lifestyle and/or telomere biology, absence of a dose response in the highly exposed individuals may reflect selection against cells with short telomeres or induction of telomere-protective effects. Our observations suggest that chronic systemic exposure to radiation leads to variable dose-dependent effects on telomere length.

  16. 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-...

  17. Effect of variation of length-to-depth ratio and Mach number on the performance of a typical double cavity scramjet combustor

    Science.gov (United States)

    Mahto, Navin Kumar; Choubey, Gautam; Suneetha, Lakka; Pandey, K. M.

    2016-11-01

    The two equation standard k-ɛ turbulence model and the two-dimensional compressible Reynolds-Averaged Navier-Stokes (RANS) equations have been used to computationally simulate the double cavity scramjet combustor. Here all the simulations are performed by using ANSYS 14-FLUENT code. At the same time, the validation of the present numerical simulation for double cavity has been performed by comparing its result with the available experimental data which is in accordance with the literature. The results are in good agreement with the schlieren image and the pressure distribution curve obtained experimentally. However, the pressure distribution curve obtained numerically is under-predicted in 5 locations by numerical calculation. Further, investigations on the variations of the effects of the length-to-depth ratio of cavity and Mach number on the combustion characteristics has been carried out. The present results show that there is an optimal length-to-depth ratio for the cavity for which the performance of combustor significantly improves and also efficient combustion takes place within the combustor region. Also, the shifting of the location of incident oblique shock took place in the downstream of the H2 inlet when the Mach number value increases. But after achieving a critical Mach number range of 2-2.5, the further increase in Mach number results in lower combustion efficiency which may deteriorate the performance of combustor.

  18. 58W LD side-pump Nd:YAG picosecond laser system at 1KHz with double length of regenerative cavity

    Science.gov (United States)

    Long, Ming Liang; Li, G.; Chen, Meng

    2016-11-01

    An average power of 58 W, pulse width of 40 ps at 1 KHz repetition rate of Nd:YAG picosecond laser is reported. It used an etalon to directly get pulse width of 135 ps from Nd:YVO4 mode locked laser in 1064 nm, which repetition rate was 88 MHz. When the seed pulses were injected into the double length of regenerative LD side-pump Nd:YAG cavity at 1 KHz repetition rate, the single pulse energy was amplified to 3 mJ, the pulse width was compressed to 99 ps, beam quality of M^2 factor was 1.3. The single pulse energy was amplified up to 58 mJ, the pulse width was self compressed to 40 ps, beam quality of M^2 factor was approximately 3.5 after single passing three stages of double high gain LD side-pump Nd:YAG module. Beam pointing was about 40 urad. The stability for pulse to pulse RMS was less than 3%. A thin-film polarizer and a quarter-wave plate was inserted into the regenerative amplification cavity to let pulses double travel the same geometric path basis on pulse polarization. Serrated aperture were used in the amplification. That's beneficial to decrease the nonlinear effect for the high power in the crystal. High gain LD side-pump Nd:YAG module could lead the pulse energy amplify more and self compress the pulse width. Double length of regenerative cavity was used to enhance the optical cavity length, it greatly decreased the laser's volume and improved stability of picosecond laser. It's a nice way for high power picosecond laser and the laser system would be more simple and smaller.

  19. 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

  20. Dielectric relaxation studies in 5CB nematic liquid crystal at 9 GHz under the influence of external magnetic field using microwave cavity spectrometer

    Indian Academy of Sciences (India)

    Manoj Johri; Abhay Saxena; S Johri; S Saxena; D P Singh

    2011-04-01

    Resonance width, shift in resonance frequency, relaxation time and activation energy of 5CB nematic liquid crystal are measured using microwave cavity technique under the influence of an external magnetic field at 9 GHz and at different temperatures. The dielectric response in liquid crystal at different temperatures and the effects of applied magnetic field on transition temperatures are studied in the present work. The technique needs a small quantity (< 0.001 cm3) of the sample and provides fruitful information about the macroscopic structure of the liquid crystal.

  1. 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.

  2. 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。

  3. 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

  4. 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.

  5. External loops at the ferredoxin-NADP(+) reductase protein-partner binding cavity contribute to substrates allocation.

    Science.gov (United States)

    Sánchez-Azqueta, Ana; Martínez-Júlvez, Marta; Hervás, Manuel; Navarro, José A; Medina, Milagros

    2014-02-01

    Ferredoxin-NADP(+) reductase (FNR) is the structural prototype of a family of FAD-containing reductases that catalyze electron transfer between low potential proteins and NAD(P)(+)/H, and that display a two-domain arrangement with an open cavity at their interface. The inner part of this cavity accommodates the reacting atoms during catalysis. Loops at its edge are highly conserved among plastidic FNRs, suggesting that they might contribute to both flavin stabilization and competent disposition of substrates. Here we pay attention to two of these loops in Anabaena FNR. The first is a sheet-loop-sheet motif, loop102-114, that allocates the FAD adenosine. It was thought to determine the extended FAD conformation, and, indirectly, to modulate isoalloxazine electronic properties, partners binding, catalytic efficiency and even coenzyme specificity. The second, loop261-269, contains key residues for the allocation of partners and coenzyme, including two glutamates, Glu267 and Glu268, proposed as candidates to facilitate the key displacement of the C-terminal tyrosine (Tyr303) from its stacking against the isoalloxazine ring during the catalytic cycle. Our data indicate that the main function of loop102-114 is to provide the inter-domain cavity with flexibility to accommodate protein partners and to guide the coenzyme to the catalytic site, while the extended conformation of FAD must be induced by other protein determinants. Glu267 and Glu268 appear to assist the conformational changes that occur in the loop261-269 during productive coenzyme binding, but their contribution to Tyr303 displacement is minor than expected. Additionally, loop261-269 appears a determinant to ensure reversibility in photosynthetic FNRs. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. 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。

  7. 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.

  8. 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.

  9. 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.

  10. Minimizing gain transient dynamics by optimizing the erbium concentration and cavity length of a gain clamped EDFA.

    Science.gov (United States)

    Chan, P; Tsang, H

    2005-09-19

    Erbium doped fiber amplifier (EDFA) gain transient dynamics are studied in the context of their application in optically reconfigurable networks. We address the question of how to design the EDFA in order to minimize the gain transients present in the output signals of the EDFA when the system is optically reconfigured such that the total average input power levels and wavelengths are changed. Both experimental measurements and theoretical simulations show that the amplitude transients depend on the length of the erbium doped fiber (EDF) and the erbium concentration. We show how it may be possible to reduce the gain transients by appropriate design of the EDFA.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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%.

  2. 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.

  3. 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.

  4. 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....

  5. External Cavity Coherent Transmitter Modules

    Science.gov (United States)

    1990-11-01

    6-15) PSK Homodyne 282 kHz FP + FDG 40 (+) (25-37) to 565 kHz FP + BDd 40 (+) (15-25) *preferred structure (+) -Minimum Practical Design ** - Figure... polarization occurs, which contains combination frequencies wi± n(wO - wi), where n=1,2,3,... The different polarizations at these beat frequencies...reflectivity, we ignore tlie polarization of lasing field. 182 ttowever, the reflectivity depends strongly on the polarization of the field. I, 1:as beer

  6. 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.

  7. 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.

  8. Control of the Cavity Length Consistency of Miniaturization Optical Fiber F-P Sensor%微型化光纤法布里-珀罗传感器腔长一致性的控制研究

    Institute of Scientific and Technical Information of China (English)

    童杏林; 文昌山; 朱小龙; 王夏; 纪涛; 冷卓燕

    2012-01-01

    A kind of optical fiber F-P sensor was studied for the control of the cavity length consistency. The cavity length was controlled by three-dimension frames. On the basis of the F-P cavity principle, the F-P cavity was under real-time detection by spectrum analyzer and then was adjusted. The F-P cavity was composed of hollow glass tube and optical fiber with the method of thermal fusion. The key parts of the processed F-P cavity were examined using optical microscope, and the fusion points were examined on their robustness. The results show that the F-P cavity length is better controlled and the consistency is good. The fusion areas are little out of shape and it has few influences on the F-P cavity's performance.%研究了光纤法布里-珀罗腔传感器的腔长一致性的控制技术,通过三维调整架组成微调装置来控制全光纤法布里-珀罗腔的腔长;结合法布里-珀罗腔的工作原理,利用光谱分析仪实时检测加工过程中法布里-珀罗腔的腔长并用装置予以修正;以热熔接的方法将毛细玻璃管与光纤加工成法布里-珀罗腔;利用超景深光学显微系统检查加工的法布里-珀罗腔的关键部位的结构,并对熔接点的牢固性进行了检测.实验结果和数据分析显示:法布里-珀罗腔的腔长得到了较好的控制及一致性,熔接部位的变形和对法布里-珀罗腔的性能的影响也很小.该工艺可用于制备全光纤法布里-珀罗腔传感器.

  9. 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.

  10. Influence of cavity loss on an extrinsic Fabry-Perot cavity intensity-based pressure sensor.

    Science.gov (United States)

    Lű, Tao

    2015-09-01

    We present an extrinsic Fabry-Perot cavity intensity-based pressure sensor that mainly comprises a single-mode fiber end and an elastic monocrystalline silicon layer bonded to a silicon diaphragm. We investigated the influence of cavity loss on the performance indexes (PIS) of the intensity-based extrinsic Fabry-Perot cavity optical fiber pressure sensor. A buffer unit made of three incompressible oil cavities attenuated outside pressure and transformed pressure information into cavity length microchange information. Experimental results indicated that, under center quadrature-points within the linear regions of adjacent fringes, for an applied 40 kPa external pressure, cavity length was modulated by pressures of 69.9 kPa-109.9 kPa, 150.1 kPa-190 kPa, 220.1 kPa-259.9 kPa, and 279.9 kPa-319.9 kPa, output intensity ranges increased as 1 μW, 1.02 μW, 1.03 μW, and 1.05 μW, sensitivity increased as 0.01909 μW/kPa, 0.01986 μW/kPa, 0.02127 μW/kPa, and 0.02387 μW/kPa, but linearity degraded, as indicated by the standard deviation of linear fits of 0.02607, 0.02664, 0.02935, and 0.04879 due to cavity loss. Furthermore, the pressure ranges within the same quarter period decreased as 40 kPa, 37.45 kPa, 32.4 kPa, and 30.15 kPa. Consequently, the same lengths of linear regions within adjacent fringes of an approximately sinusoidal curve corresponded to different measurement ranges, linearities, and sensitivities. Initial cavity length must be chosen to optimize both signal strength and the PIS studied here in manufacturing this type sensor.

  11. 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.

  12. Supersonic flows over cavities

    Institute of Scientific and Technical Information of China (English)

    Tianwen FANG; Meng DING; Jin ZHOU

    2008-01-01

    The characteristics of supersonic cold flows over cavities were investigated experimentally and numer-ically, and the effects of cavities of different sizes on super-sonic flow field were analyzed. The results indicate that the ratio of length to depth L/D within the range of 5-9 has little relevance to integral structures of cavity flow. The bevel angle of the rear wall does not alter the overall structure of the cavity flow within the range of 30°-60°, but it can exert obvious effect on the evolvement of shear layer and vortexes in cavities.

  13. Thermal modeling of a pressurized air cavity receiver for solar dish Stirling system

    Science.gov (United States)

    Zou, Chongzhe; Zhang, Yanping; Falcoz, Quentin; Neveu, Pierre; Li, Jianlan; Zhang, Cheng

    2017-06-01

    A solar cavity receiver model for the dish collector system is designed in response to growing demand of renewable energy. In the present research field, no investigations into the geometric parameters of a cavity receiver have been performed. The cylindrical receiver in this study is composed of an enclosed bottom at the back, an aperture at the front, a helical pipe inside the cavity and an insulation layer on the external surface of the cavity. The influence of several critical receiver parameters on the thermal efficiency is analyzed in this paper: cavity inner diameter and cavity length. The thermal model in this paper is solved considering the cavity dimensions as variables. Implementing the model into EES, each parameter influence is separately investigated, and a preliminary optimization method is proposed.

  14. 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

  15. SPS RF cavity

    CERN Multimedia

    1974-01-01

    The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. A power of up to 790 kW can be supplied to each giving a total accelerating voltage of about 8 MV. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities.

  16. High Finesse Fiber Fabry-Perot Cavities: Stabilization and Mode Matching Analysis

    CERN Document Server

    Gallego, Jose; Alavi, Seyed Khalil; Alt, Wolfgang; Martinez-Dorantes, Miguel; Meschede, Dieter; Ratschbacher, Lothar

    2015-01-01

    Fiber Fabry-Perot cavities, formed by micro-machined mirrors on the end-facets of optical fibers, are used in an increasing number of technical and scientific applications, where they typically require precise stabilization of their optical resonances. Here, we study two different approaches to construct fiber Fabry-Perot resonators and stabilize their length for experiments in cavity quantum electrodynamics with neutral atoms. A piezo-mechanically actuated cavity with feedback based on the Pound-Drever-Hall locking technique is compared to a novel rigid cavity design that makes use of the high passive stability of a monolithic cavity spacer and employs thermal self-locking and external temperature tuning. Furthermore, we present a general analysis of the mode matching problem in fiber Fabry-Perot cavities, which explains the asymmetry in their reflective line shapes and has important implications for the optimal alignment of the fiber resonators. Finally, we discuss the issue of fiber-generated background ph...

  17. 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.

  18. SPS RF Accelerating Cavity

    CERN Multimedia

    1979-01-01

    This picture shows one of the 2 new cavities installed in 1978-1979. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also increased: to the first 2 MW plant a second 2 MW plant was added and by end 1979 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412016X, 7412017X, 7411048X

  19. SPS RF Cavity

    CERN Multimedia

    1975-01-01

    The picture shows one of the two initially installed cavities. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also gradually increased: by end 1980 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412017X, 7411048X, 7505074.

  20. 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.

  1. Dental cavities

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/001055.htm Dental cavities To use the sharing features on this page, please enable JavaScript. Dental cavities are holes (or structural damage) in the ...

  2. Power coupler for the ILC crab cavity

    Energy Technology Data Exchange (ETDEWEB)

    Burt, G.; Dexter, A.; Jenkins, R.; /Lancaster U.; Beard, C.; Goudket, P.; McIntosh, P.A.; /Daresbury; Bellantoni, Leo; /Fermilab

    2007-06-01

    The ILC crab cavity will require the design of an appropriate power coupler. The beam-loading in dipole mode cavities is considerably more variable than accelerating cavities, hence simulations have been performed to establish the required external Q. Simulations of a suitable coupler were then performed and were verified using a normal conducting prototype with variable coupler tips.

  3. Time-delay signatures in multi-transverse mode VCSELs subject to double-cavity polarization-rotated optical feedback

    Science.gov (United States)

    Lin, Hong; Khurram, Aliza; Hong, Yanhua

    2016-10-01

    Time delay (TD) signatures are studied experimentally in orthogonal polarizations and in individual transverse modes respectively in a VCSEL operating with three transverse modes. Different types of concealment of the TD signatures are observed when the polarization of feedback is rotated through large angles. Effects of feedback strength and external cavity length on the TD signatures are investigated. Weak feedback leads to better concealment of the TD signatures in the dominant polarization. When the round-trip time difference between the two external cavities is close to a half of the relaxation oscillation period, the TD signatures are minimized.

  4. 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)

  5. Comparison Analysis of MR Images Before and After External Beam Radiotherapy in Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Eun Hye; Baek, Chung Seok; Lee, Sung Yong; Byun, Young Sik [Dept. of Radiation Oncology, Cheil General Hospital, Seoul (Korea, Republic of)

    2011-03-15

    To analyze availability of MR images before and after external beam radiotherapy in brachytherapy, we will acquire MR images before and after external beam radiotherapy and compare the change of direction of uterine cavity and analyze the accuracy of applicator insertion. From January 2009 to December 2010, we compared MR images before and after external beam radiotherapy for uterine cervical cancer only with radical purpose treatment. MR images which was acquired after external beam radiotherapy has done with inserted status of CT/MR applicator. As a consequence, the tumor was markedly reduced after external beam radiotherapy. The change of anteflexion of uterus turned into retroflexion of the uterine cavity was 17.1%. The case of wrong insertion of tandem include direction or length was 14.3%. According to MR images taken after external beam radiotherapy, we recognized not only reduced the tumor volume but the marked change of exact direction or length of the uterine cavity. So the confirmation of accurate insertion based on MR images before brachytherapy could be very helpful for optimal brachytherapy treatment planning with reduced applicator insertion errors.

  6. JLEIC SRF cavity RF Design

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shaoheng [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Guo, Jiquan [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Wang, Haipeng [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Rimmer, Robert A. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-05-01

    The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchro-tron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback sys-tem will be necessary.

  7. accelerating cavity

    CERN Multimedia

    On the inside of the cavity there is a layer of niobium. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment.

  8. 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

  9. radiofrequency cavity

    CERN Multimedia

    1988-01-01

    The pulse of a particle accelerator. 128 of these radio frequency cavities were positioned around CERN's 27-kilometre LEP ring to accelerate electrons and positrons. The acceleration was produced by microwave electric oscillations at 352 MHz. The electrons and positrons were grouped into bunches, like beads on a string, and the copper sphere at the top stored the microwave energy between the passage of individual bunches. This made for valuable energy savings as it reduced the heat generated in the cavity.

  10. Nanofriction in Cavity Quantum Electrodynamics.

    Science.gov (United States)

    Fogarty, T; Cormick, C; Landa, H; Stojanović, Vladimir M; Demler, E; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

  11. SPS RF System an Accelerating Cavity

    CERN Multimedia

    CERN PhotoLab

    1975-01-01

    The picture shows one of the two initially installed cavities. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also gradually increased: by end 1980 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412017X, 7411048X.

  12. 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.

  13. Observations on oesophageal length.

    Science.gov (United States)

    Kalloor, G J; Deshpande, A H; Collis, J L

    1976-01-01

    The subject of oesophageal length is discussed. The great variations in the length of the oesophagus in individual patients is noted, and the practical use of its recognition in oesophageal surgery is stressed. An apprasial of the various methods available for this measurement is made; this includes the use of external chest measurement, endoscopic measurement, and the measurement of the level of the electrical mucosal potential change. Correlative studies of these various methods are made, and these show a very high degree of significance. These studies involved simultaneous measurement of external and internal oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal reflux symptoms, 42 patients with sliding type hiatal hernia, and 17 patients with a peptic stricture in association with hiatal hernia. The method of measuring oesophageal length by the use of the external chest measurement, that is, the distance between the lower incisor teeth and the xiphisternum, measured with the neck fully extended and the patient lying supine, is described in detail, its practical application in oesophageal surgery is illustrated, and its validity tested by internal measurements. The findings of this study demonstrate that the external chest measurement provides a mean of assessing the true static length of the oesophagus, corrected for the size of the individual. Images PMID:941114

  14. 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.

  15. 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。

  16. Finemet cavity impedance studies

    CERN Document Server

    Persichelli, S; Migliorati, M; Salvant, B

    2013-01-01

    The aim of the study is to evaluate the impedance of the Finemet kicker cavity to be installed in the PS straight section 02 during LS1, under realistic assumptions of bunch length. Time domain simulations with CST Particle Studio have been performed in order to get the impedance of the cavity and make a comparison with the longitudinal impedance measured for a single cell prototype. The study has been performed on simplified 3D geometries imported from a mechanical CATIA drawing, assuming that the simplications have small impact on the nal results. Simulations confirmed that the longitudinal impedance observed with measurements can be excited by bunches circulating in the PS. In the six-cells Finemet cavity, PS bunches circulating in the center can excite a longitudinal impedance, the real part of which has a maximum of 2 kOhm at 4 MHz. This mode does not seem to have any transverse component. All the eigenmodes of the cavity are strongly damped by the Finemet rings: we predict to have no issues regarding tr...

  17. Filling a Conical Cavity

    Science.gov (United States)

    Nye, Kyle; Eslam-Panah, Azar

    2016-11-01

    Root canal treatment involves the removal of infected tissue inside the tooth's canal system and filling the space with a dense sealing agent to prevent further infection. A good root canal treatment happens when the canals are filled homogeneously and tightly down to the root apex. Such a tooth is able to provide valuable service for an entire lifetime. However, there are some examples of poorly performed root canals where the anterior and posterior routes are not filled completely. Small packets of air can be trapped in narrow access cavities when restoring with resin composites. Such teeth can cause trouble even after many years and lead the conditions like acute bone infection or abscesses. In this study, the filling of dead-end conical cavities with various liquids is reported. The first case studies included conical cavity models with different angles and lengths to visualize the filling process. In this investigation, the rate and completeness at which a variety of liquids fill the cavity were observed to find ideal conditions for the process. Then, a 3D printed model of the scaled representation of a molar with prepared post spaces was used to simulate the root canal treatment. The results of this study can be used to gain a better understanding of the restoration for endodontically treated teeth.

  18. Cavity quantum electrodynamics: coherence in context.

    Science.gov (United States)

    Mabuchi, H; Doherty, A C

    2002-11-15

    Modern cavity quantum electrodynamics (cavity QED) illuminates the most fundamental aspects of coherence and decoherence in quantum mechanics. Experiments on atoms in cavities can be described by elementary models but reveal intriguing subtleties of the interplay of coherent dynamics with external couplings. Recent activity in this area has pioneered powerful new approaches to the study of quantum coherence and has fueled the growth of quantum information science. In years to come, the purview of cavity QED will continue to grow as researchers build on a rich infrastructure to attack some of the most pressing open questions in micro- and mesoscopic physics.

  19. Novel Geometries for the LHC Crab Cavity

    Energy Technology Data Exchange (ETDEWEB)

    B. Hall, G. Burt, C. Lingwood, R. Rimmer, H. Wang

    2010-05-23

    The planned luminosity upgrade to LHC is likely to necessitate a large crossing angle and a local crab crossing scheme. For this scheme crab cavities align bunches prior to collision. The scheme requires at least four such cavities, a pair on each beam line either side of the interaction point (IP). Upstream cavities initiate rotation and downstream cavities cancel rotation. Cancellation is usually done at a location where the optics has re-aligned the bunch. The beam line separation near the IP necessitates a more compact design than is possible with elliptical cavities such as those used at KEK. The reduction in size must be achieved without an increase in the operational frequency to maintain compatibility with the long bunch length of the LHC. This paper proposes a suitable superconducting variant of a four rod coaxial deflecting cavity (to be phased as a crab cavity), and presents analytical models and simulations of suitable designs.

  20. Cavity magnomechanics

    Science.gov (United States)

    Zou, Chang-Ling; Zhang, Xufeng; Jiang, Liang; Tang, Hong

    2016-05-01

    Recently, cavity magnonics has attracted much attention for potential applications of coherent information transduction and hybrid quantum devices. The magnon is a collective spin wave excitation in ferromagnetic material. It is magnetically tunability, with long coherence time and non-reciprocical interaction with electro-magnetic fields. We report the coherent coupling between magnon, microwave photon and phonon. First, we demonstrate strong coupling and ultrastrong coupling between the magnon in YIG sphere and microwave photon in three-dimensional cavity. Then, based on the hybridized magnon-photon modes, we observe the triply resonant magnon-mcirowave photon-phonon coupling, where the ultrahigh-Q mechanical vibration of YIG sphere is dispersively coupled with the magnon via magnetostrictive interaction. We observe interesting phenomena, including electromagnetically induced transparency/absorption and parametric amplification. In particular, benefit from the large tunability of the magnon, we demonstrate a tunable microwave amplifier with gain as high as 30 dB. The single crystal YIG also has excellent optical properties, and thus provide a unique platform bridging MHz, GHz and THz information carriers. Finally, we present the latest progress towards coherent magnon to optical photon conversion.

  1. Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haipeng [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Cheng, Guangfeng [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Clemens, William [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Davis, G [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Macha, Kurt [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Overton, Roland [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Spell, D. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2015-09-01

    After the electromagnetic design and the mechanical design of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported.

  2. Novel Geometries for the LHC Crab Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Hall, B. [Lancaster Univ. (United Kingdom); Burt, G. [Lancaster Univ. (United Kingdom); Smith, J. D.A. [Lancaster Univ. (United Kingdom); Rimmer, R. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Wang, H. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Delayen, J. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Calaga, R. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2009-05-01

    In 2017 the LHC is envisioned to increase its luminosity via an upgrade. This upgrade is likely to require a large crossing angle hence a crab cavity is required to align the bunches prior to collision. There are two possible schemes for crab cavity implementation, global and local. In a global crab cavity the crab cavity is far from the IP and the bunch rotates back and forward as it traverses around the accelerator in a closed orbit. For this scheme a two-cell elliptical squashed cavity at 800 MHz is preferred. To avoid any potential beam instabilities all the parasitic modes of the cavities must be damped strongly, however crab cavities have lower order and same order modes in addition to the usual higher order modes and hence a novel damping scheme must be used to provide sufficient damping of these modes. In the local scheme two crab cavities are placed at each side of the IP two start and stop rotation of the bunches. This would require crab cavities much smaller transversely than in the global scheme but the frequency cannot be increased any higher due to the long bunch length of the LHC beam. This will require a novel compact crab cavity design. A superconducting version of a two rod coaxial deflecting cavity as a suitable design is proposed in this paper.

  3. Cavities/Tooth Decay

    Science.gov (United States)

    Cavities/tooth decay Overview By Mayo Clinic Staff Cavities are permanently damaged areas in the hard surface of your teeth ... into tiny openings or holes. Cavities, also called tooth decay or caries, are caused by a combination of ...

  4. 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...

  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. Ferrite-filled cavities for compact planar resonators

    Science.gov (United States)

    Keatley, P. S.; Durrant, C. J.; Berry, S. J.; Sirotkin, E.; Hibbins, A. P.; Hicken, R. J.

    2014-01-01

    Sub-wavelength metallic planar cavities, closed at one end, have been constructed by wrapping aluminium foil around teflon or ferrite slabs. Finite cavity width perturbs the fundamental cavity mode frequency of ferrite-filled cavities due to different permeability inside and outside of the cavity, in contrast to teflon-filled cavities, while the cavity length required to achieve a specific resonance frequency is significantly reduced for a ferrite-filled cavity. Ferrite-filled cavities may be excited by an in-plane alternating magnetic field and may be advantageous for high-frequency (HF) and ultra HF tagging and radio frequency identification of metallic objects within security, manufacturing, and shipping environments.

  7. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  8. The ESS elliptical cavity cryomodules

    Science.gov (United States)

    Darve, Christine; Bosland, Pierre; Devanz, Guillaume; Olivier, Gilles; Renard, Bertrand; Thermeau, Jean-Pierre

    2014-01-01

    The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today's leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. The superconducting section of the Linac accelerates the beam from 80 MeV to 2.0 GeV. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. These cryomodules contain four elliptical Niobium cavities operating at 2 K and at a frequency of 704.42 MHz. This paper introduces the thermo-mechanical design, the prototyping and the expected operation of the ESS elliptical cavity cryomodules. An Elliptical Cavity Cryomodule Technology Demonstrator (ECCTD) will be built and tested in order to validate the ESS series production.

  9. The ESS spoke cavity cryomodules

    Science.gov (United States)

    Bousson, Sebastien; Darve, Christine; Duthil, Patxi; Elias, Nuno; Molloy, Steve; Reynet, Denis; Thermeau, Jean-Pierre

    2014-01-01

    The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today's leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. This paper introduces the thermo-mechanical design and expected operation of the ESS spoke cavity cryomodules. These cryomodules contain two double spoke bulk Niobium cavities operating at 2 K and at a frequency of 352.21 MHz. The superconducting section of the Spoke Linac accelerates the beam from 90 MeV to 220 MeV. A Spoke Cavity Cryomodule Technology Demonstrator will be built and tested in order to validate the ESS series production.

  10. Spontaneous Photon Emission in Cavities

    Directory of Open Access Journals (Sweden)

    Alber G.

    2014-01-01

    Full Text Available We investigate spontaneous photon emission processes of two-level atoms in parabolic and ellipsoidal cavities thereby taking into account the full multimode scenario. In particular, we calculate the excitation probabilities of the atoms and the energy density of the resulting few-photon electromagnetic radiation field by using semiclassical methods for the description of the multimode scenario. Based on this approach photon path representations are developed for relevant transition probability amplitudes which are valid in the optical frequency regime where the dipole and the rotating-wave approximations apply. Comparisons with numerical results demonstrate the quality of these semiclassical results even in cases in which the wave length of a spontaneously emitted photon becomes comparable or even larger than characteristic length scales of the cavity. This is the dynamical regime in which diffraction effects become important so that geometric optical considerations are typically not applicable.

  11. Incompressible Laminar Flow Over a Three-Dimensional Rectangular Cavity

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper investigates unsteady incompressible flow over cavities,Previous research in in compressible cavity-flow has included flow inside and past a 2-dimensional cavity,and flow inside a 3-dimensional cavity,driven by a moving lid.The present research is focused on incompressible flow past a 3-dimensional open shallow cavity.This involves the complex interaction etween the external flow and the re-circulating flow within the cavity.In particular,computation was performed on a 3-dimensonal shallow rectangular cavity with a laminar boundary layer at the cavity and a Reynolds number of 5,000 and 10,000,respectively,A CFD approach,based on the unsteady Navier-Stokes equation for 3-dimensional incompressible flow,was used in the study.Typical results of the computation are presented.Theses results reveal the highly unsteady and complex vortical structures at high Reynolds numbers.

  12. Entanglement of fields in coupled cavities: Effects of pumping and fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Sivakumar, S., E-mail: siva@igcar.gov.i [Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

    2010-04-05

    A system of two coupled cavities is studied in the context of bipartite, continuous variable entanglement. One of the cavities is pumped by an external classical source that is coupled quadratically, to the cavity field. Dynamics of entanglement, quantified by covariance measure [V.V. Dodonov, et al., Phys. Lett. A 296 (2002) 73], in the presence of cavity-cavity coupling and external pumping is investigated. The importance of tailoring the coupling between the cavities is brought out by studying the effects of pump fluctuations on the entanglement.

  13. Crab Cavity Development

    CERN Document Server

    Calaga, R; Burt, G; Ratti, A

    2015-01-01

    The HL-LHC upgrade will use deflecting (or crab) cavities to compensate for geometric luminosity loss at low β* and non-zero crossing angle. A local scheme with crab cavity pairs across the IPs is used employing compact crab cavities at 400 MHz. Design of the cavities, the cryomodules and the RF system is well advanced. The LHC crab cavities will be validated initially with proton beam in the SPS.

  14. 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.

  15. 805 MHz and 201 MHz RF cavity development for MUCOOL

    Energy Technology Data Exchange (ETDEWEB)

    Li, Derun [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Corlett, J [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Ladran, A [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); MacGill, R [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Wallig, J [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Zisman, M [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Moretti, A [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Rowe, A [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Qian, Z B [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Wu, V [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Rimmer, R A [Jefferson Lab, Newport News, VA 23606 (United States); Norem, J [Argonne National Laboratory, Argonne, IL 60439 (United States); Summers, D [University of Mississippi at Oxford, MS 38677 (United States); Torun, Y [Illinois Institute of Technology, Chicago, IL 60616 (United States)

    2003-08-01

    A muon cooling channel calls for very high accelerating gradient RF structures to restore the energy lost by muons in the absorbers. The RF structures have to be operated in a strong magnetic field and thus the use of superconducting RF cavities is excluded. To achieve a high shunt impedance while maintaining a large enough aperture to accommodate a large transverse emittance muon beam, the cavity design adopted is a pillbox-like geometry with thin Be foils to terminate the electromagnetic field at the cavity iris. The possibility of using grids of thin-walled metallic tubes for the termination is also being explored. Many of the RF-related issues for muon cooling channels are being studied both theoretically and experimentally using an 805 MHz cavity that has a pillbox-like geometry with thin Be windows to terminate the cavity aperture. The design and performance of this cavity are reported here. High-power RF tests of the 805 MHz cavity are in progress at Lab G in Fermilab. The cavity has exceeded its design gradient of 30 MV m{sup -1}, reaching 34 MV m{sup -1} without external magnetic field. No surface damage was observed at this gradient. The cavity is currently under conditioning at Lab G with an external magnetic field of 2.5 T. We also present here a 201 MHz cavity design for muon cooling channels. The proposed cavity design is also suitable for use in a proof-of-principle muon ionization cooling experiment.

  16. Cavity method in the spherical Sherrington-Kirkpatrick model

    OpenAIRE

    Panchenko, Dmitry

    2006-01-01

    We develop a cavity method in the spherical Sherrington-Kirkpatrick model at high temperature and small external field. As one application we compute the limit of the covariance matrix for fluctuations of the overlap and magnetization.

  17. In vivo measurements of uterine cavities in 795 women of fertile age

    OpenAIRE

    Haspels, A A; Tadesse, E; Kurz, K.H.

    1984-01-01

    The uterine sound length, the functional length of the cervix including the zone of internal cervical os and the fundus transversal were determined in 795 fertile women in vivo using a measuring device, the Cavimeter. The functional cavity length was calculated by subtracting the functional length of the cervix from the uterine sound length. With growing parity, the uterine length and width increase, but with advance in age, the uterine cavity changes are not so distinct. The wide ranges foun...

  18. Geometric Model of a Coronal Cavity

    Science.gov (United States)

    Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.; hide

    2010-01-01

    We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities

  19. Geometric Model of a Coronal Cavity

    Science.gov (United States)

    Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.; Schmidt, D. J.; Sterling, A. C.; Tripathi, D. K.; Williams, D. R.; Zhang, M.

    2010-01-01

    We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities

  20. Hydrodynamic Drag on Streamlined Projectiles and Cavities

    KAUST Repository

    Jetly, Aditya

    2016-04-19

    The air cavity formation resulting from the water-entry of solid objects has been the subject of extensive research due to its application in various fields such as biology, marine vehicles, sports and oil and gas industries. Recently we demonstrated that at certain conditions following the closing of the air cavity formed by the initial impact of a superhydrophobic sphere on a free water surface a stable streamlined shape air cavity can remain attached to the sphere. The formation of superhydrophobic sphere and attached air cavity reaches a steady state during the free fall. In this thesis we further explore this novel phenomenon to quantify the drag on streamlined shape cavities. The drag on the sphere-cavity formation is then compared with the drag on solid projectile which were designed to have self-similar shape to that of the cavity. The solid projectiles of adjustable weight were produced using 3D printing technique. In a set of experiments on the free fall of projectile we determined the variation of projectiles drag coefficient as a function of the projectiles length to diameter ratio and the projectiles specific weight, covering a range of intermediate Reynolds number, Re ~ 104 – 105 which are characteristic for our streamlined cavity experiments. Parallel free fall experiment with sphere attached streamlined air cavity and projectile of the same shape and effective weight clearly demonstrated the drag reduction effect due to the stress-free boundary condition at cavity liquid interface. The streamlined cavity experiments can be used as the upper bound estimate of the drag reduction by air layers naturally sustained on superhydrophobic surfaces in contact with water. In the final part of the thesis we design an experiment to test the drag reduction capacity of robust superhydrophobic coatings deposited on the surface of various model vessels.

  1. A hemispherical, high-solid-angle optical micro-cavity for cavity-QED studies

    Science.gov (United States)

    Cui, Guoqiang; Hannigan, J. M.; Loeckenhoff, R.; Matinaga, F. M.; Raymer, M. G.; Bhongale, S.; Holland, M.; Mosor, S.; Chatterjee, S.; Gibbs, H. M.; Khitrova, G.

    2006-03-01

    We report a novel hemispherical micro-cavity that is comprised of a planar integrated semiconductor distributed Bragg reflector (DBR) mirror, and an external, concave micro-mirror having a radius of curvature 50 µm. The integrated DBR mirror containing quantum dots (QD), is designed to locate the QDs at an antinode of the field in order to maximize the interaction between the QD and cavity. The concave micro-mirror, with high-reflectivity over a large solid-angle, creates a diffraction-limited (sub-micron) mode-waist at the planar mirror, leading to a large coupling constant between the cavity mode and QD. The half-monolithic design gives more spatial and spectral tuning abilities, relatively to fully monolithic structures. This unique micro-cavity design will potentially enable us to both reach the cavity quantum electrodynamics (QED) strong coupling regime and realize the deterministic generation of single photons on demand.

  2. Parasitic Cavities Losses in SPEAR-2

    Energy Technology Data Exchange (ETDEWEB)

    Sands, Matt

    2016-12-19

    In PEP the large number of particles in a bunch, together with the small bunch length, may cause grievous energy loss from the beam to parasitic modes in the accelerating cavities. I have recently tried to estimate the parasitic cavity in PEP, based on a paper of Keil and I have obtained the result that the loss to parasitic modes will be about 10 MeV per particle per revolution for a bunch length of about 10 cm. In this note, I bring together some of the considerations that might bear on an experimental investigation of the loss using SPEAR-2.

  3. Dawn of Cavity Spintronics

    OpenAIRE

    Hu, Can-Ming

    2015-01-01

    Merging the progress of spintronics with the advancement in cavity quantum electrodynamics and cavity polaritons, a new field of Cavity Spintronics is forming, which connects some of the most exciting modern physics, such as quantum information and quantum optics, with one of the oldest science on the earth, the magnetism.

  4. 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.

  5. Beam cavity interaction

    CERN Document Server

    Gamp, A

    2011-01-01

    We begin by giving a description of the rf generator-cavity-beam coupled system in terms of basic quantities. Taking beam loading and cavity detuning into account, expressions for the cavity impedance as seen by the generator and as seen by the beam are derived. Subsequently methods of beam-loading compensation by cavity detuning, rf feedback, and feed-forward are described. Examples of digital rf phase and amplitude control for the special case of superconducting cavities are also given. Finally, a dedicated phase loop for damping synchrotron oscillations is discussed.

  6. RESONANT CAVITY EXCITATION SYSTEM

    Science.gov (United States)

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  7. 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.

  8. Cavity turnover and equilibrium cavity densities in a cottonwood bottomland

    Science.gov (United States)

    Sedgwick, James A.; Knopf, Fritz L.

    1992-01-01

    A fundamental factor regulating the numbers of secondary cavity nesting (SCN) birds is the number of extant cavities available for nesting. The number of available cavities may be thought of as being in an approximate equilibrium maintained by a very rough balance between recruitment and loss of cavities. Based on estimates of cavity recruitment and loss, we ascertained equilibrium cavity densities in a mature plains cottonwood (Populus sargentii) bottomland along the South Platte River in northeastern Colorado. Annual cavity recruitment, derived from density estimates of primary cavity nesting (PCN) birds and cavity excavation rates, was estimated to be 71-86 new cavities excavated/100 ha. Of 180 active cavities of 11 species of cavity-nesting birds found in 1985 and 1986, 83 were no longer usable by 1990, giving an average instantaneous rate of cavity loss of r = -0.230. From these values of cavity recruitment and cavity loss, equilibrium cavity density along the South Platte is 238-289 cavities/100 ha. This range of equilibrium cavity density is only slightly above the minimum of 205 cavities/100 ha required by SCN's and suggests that cavity availability may be limiting SCN densities along the South Platte River. We submit that snag management alone does not adequately address SCN habitat needs, and that cavity management, expressed in terms of cavity turnover and cavity densities, may be more useful.

  9. Development of rebunching cavities at IAP

    CERN Document Server

    Welsch, C P; Schempp, A

    2000-01-01

    A focus of work at IAP has been the development and optimization of spiral loaded cavities since the 1970s [A. Schempp et al, NIM 135, 409 (1976)]. These cavities feature a high efficiency, a compact design and a big variety of possible fields of application. They find use both as bunchers and post accelerators to vary the final energy of the beam. In comparison to other available designs, the advantage of these structures lies in their small size. Furthermore they can easily be tuned to the required resonance frequency by varying the length of the spiral. Due to the small size of the cavities the required budget can also be kept low. Here, two slightly different types of spiral loaded cavities, which were built for the REX-ISOLDE project at CERN and the intensity upgrade program at GSI are being discussed.

  10. 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.

  11. 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.

  12. 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...

  13. 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.

  14. Flux expulsion variation in SRF cavities

    CERN Document Server

    Posen, S; Romanenko, A; Melnychuk, O; Sergatskov, D A; Martinello, M; Checchin, M; Crawford, A C

    2015-01-01

    Treating a cavity with nitrogen doping significantly increases $Q_0$ at medium fields, reducing cryogenic costs for high duty factor linear accelerators such as LCLS II. N-doping also makes cavities more sensitive to increased residual resistance due to trapped magnetic flux, making it critical to either have extremely effective magnetic shielding, or to prevent flux from being trapped in the cavity during cooldown. In this paper, we report on results of a study of flux expulsion. We discuss possible ways in which flux can be pinned in the inner surface, outer surface, or bulk of a cavity, and we present experimental results studying these mechanisms. We show that grain structure appears to play a key role and that a cavity that expelled flux poorly changed to expelling flux well after a high temperature furnace treatment. We further show that after furnace treatment, this cavity exhibited a significant improvement in quality factor when cooled in an external magnetic field. We conclude with implications for ...

  15. CEBAF Upgrade Bunch Length Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mahmoud [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

  16. LEP copper accelerating cavities

    CERN Multimedia

    Laurent Guiraud

    1999-01-01

    These copper cavities were used to generate the radio frequency electric field that was used to accelerate electrons and positrons around the 27-km Large Electron-Positron (LEP) collider at CERN, which ran from 1989 to 2000. The copper cavities were gradually replaced from 1996 with new superconducting cavities allowing the collision energy to rise from 90 GeV to 200 GeV by mid-1999.

  17. Analysis of mechanical fabrication experience with CEBAF`s production SRF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Mammosser, J.; Kneisel, P.; Benesch, J.

    1993-06-01

    CEBAF has received a total of 360 five-cell niobium cavities, the largest group of industrially fabricated superconducting cavities so far. An extensive data base exists on the fabrication, surface treatment, assembly and cavity performance parameters. Analysis of the mechanical features of the cavities includes the following: the spread in fabrication tolerances of the cells derived from field profiles of the ``as fabricated`` cavities and the ``as fabricated`` external Q-values of the fundamental power coupler compared to dimensional deviations. A comparison is made of the pressure sensitivity of cavities made of materials from different manufacturers between 760 torr (4.2 K) and 23 torr (2 K).

  18. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  19. Avaliação quantitativa das dimensões óculo-palpebrais em portadores de cavidade anoftálmica em uso de prótese ocular externa Quantitative eyelid evaluation of anophthalmic cavity carriers with external ocular prosthesis

    Directory of Open Access Journals (Sweden)

    Rodrigo Ueno Takahagi

    2005-08-01

    alteration. The superior eyelid sulcus distance had shorter values with the prosthesis and higher values were seen analyzing the other parameters when the external prosthesis was in place. CONCLUSION: All patients had some abnormalities, which show us how difficult it is to provide a normal aspect for anophthalmic cavity carriers. The image processing allowed objective evaluations of the measures contributing to the follow-up of the patients.

  20. Assembling one of the RF cavities for the SPS

    CERN Multimedia

    1974-01-01

    The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. A power of up to 790 kW can be supplied to each giving a total accelerating voltage of about 8 MV. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities.

  1. Cavity Optomechnics with 150nm-thick GaAs Membrane

    DEFF Research Database (Denmark)

    Usami, K.; Melholt Nielsen, B.; Naesby, A.

    2010-01-01

    -coupled to a Fabry-P´erot cavity formed between the membrane and a mirror (Finesse: 24) inside a vacuum chamber (10 7Torr), is used to lock the cavity length at the cavity resonant slope and to induce mechanical oscillations by modulating the intensity from the offset level for ring down measurements. We observe...

  2. Cavity spin optodynamics

    CERN Document Server

    Brahms, N

    2010-01-01

    The dynamics of a large quantum spin coupled parametrically to an optical resonator is treated in analogy with the motion of a cantilever in cavity optomechanics. New spin optodynamic phenonmena are predicted, such as cavity-spin bistability, optodynamic spin-precession frequency shifts, coherent amplification and damping of spin, and the spin optodynamic squeezing of light.

  3. SPS accelerating cavity

    CERN Multimedia

    1980-01-01

    One of the SPS acceleration cavities (200 MHz, travelling wave structure). On the ceiling one sees the coaxial transmission line which feeds the power from the amplifier, located in a surface building above, to the upstream end of the cavity. See 7603195 for more details, 7411032 for the travelling wave structure, and also 8104138, 8302397.

  4. Superconducting cavities for LEP

    CERN Multimedia

    1983-01-01

    Above: a 350 MHz superconducting accelerating cavity in niobium of the type envisaged for accelerating electrons and positrons in later phases of LEP. Below: a small 1 GHz cavity used for investigating the surface problems of superconducting niobium. Albert Insomby stays on the right. See Annual Report 1983 p. 51.

  5. SPS accelerating cavity

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    One of the SPS accelerating cavities (200 MHz, travelling wave structure). The power that is fed into the upstream end of the cavity is extracted at the downstream end and sent into a dump load. See 7603195 for more details, 7411032 for the travelling wave structure, and also 8011289, 8302397.

  6. In vivo measurements of uterine cavities in 795 women of fertile age.

    Science.gov (United States)

    Kurz, K H; Tadesse, E; Haspels, A A

    1984-06-01

    The uterine sound length, the functional length of the cervix including the zone of internal cervical os and the fundus transversal were determined in 795 fertile women in vivo using a measuring device, the Cavimeter. The functional cavity length was calculated by subtracting the functional length of the cervix from the uterine sound length. With growing parity, the uterine length and width increase, but with advance in age, the uterine cavity changes are not so distinct. The wide ranges found by the investigation demonstrate the individuality of the uterine cavity and the desire to measure it prior to fitting an IUD. The use of adapted IUDs according to the size of the uterine cavity leads to a remarkable reduction of side effects, particularly expulsion, bleeding and cramps caused mainly by dimensional incompatibility. Therefore prefit uterine cavity measurement can lead to better efficacy of IUDs, increased rates of acceptance and higher continuation rates.

  7. External Otitis (Swimmer's Ear)

    Science.gov (United States)

    ... to Pneumococcal Vaccine Additional Content Medical News External Otitis (Swimmer's Ear) By Bradley W. Kesser, MD, Associate ... the Outer Ear Ear Blockages Ear Tumors External Otitis (Swimmer's Ear) Malignant External Otitis Perichondritis External otitis ...

  8. Leaky Modes of Dielectric Cavities

    CERN Document Server

    Mansuripur, Masud; Jakobsen, Per

    2016-01-01

    In the absence of external excitation, light trapped within a dielectric medium generally decays by leaking out (and also by getting absorbed within the medium). We analyze the leaky modes of a parallel-plate slab, a solid glass sphere, and a solid glass cylinder, by examining those solutions of Maxwell's equations (for dispersive as well as non-dispersive media) which admit of a complex-valued oscillation frequency. Under certain circumstances, these leaky modes constitute a complete set into which an arbitrary distribution of the electromagnetic field residing inside a dielectric body can be expanded. We provide completeness proofs, and also present results of numerical calculations that illustrate the relationship between the leaky modes and the resonances of dielectric cavities formed by a simple parallel-plate slab, a glass sphere, and a glass cylinder.

  9. 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.

  10. A hemispherical, high-solid-angle optical micro-cavity for cavity-QED studies

    OpenAIRE

    Cui, Guoqiang; Hannigan, J. M.; Loeckenhoff, R.; Matinaga, F. M.; Raymer, M. G.; Bhongale, S.; Holland, M.; Mosor, S.; Chatterjee, S.; Gibbs, H. M.; Khitrova, G.

    2006-01-01

    We report a novel hemispherical micro-cavity that is comprised of a planar integrated semiconductor distributed Bragg reflector (DBR) mirror, and an external, concave micro-mirror having a radius of curvature $50\\mathrm{\\mu m}$. The integrated DBR mirror containing quantum dots (QD), is designed to locate the QDs at an antinode of the field in order to maximize the interaction between the QD and the cavity. The concave micro-mirror, with high-reflectivity over a large solid-angle, creates a d...

  11. Cavity-enhanced spectroscopies

    CERN Document Server

    van Zee, Roger

    2003-01-01

    ""Cavity-Enhanced Spectroscopy"" discusses the use of optical resonators and lasers to make sensitive spectroscopic measurements. This volume is written by the researcchers who pioneered these methods. The book reviews both the theory and practice behind these spectroscopic tools and discusses the scientific discoveries uncovered by these techniques. It begins with a chapter on the use of optical resonators for frequency stabilization of lasers, which is followed by in-depth chapters discussing cavity ring-down spectroscopy, frequency-modulated, cavity-enhanced spectroscopy, intracavity spectr

  12. Tuned optical cavity magnetometer

    Science.gov (United States)

    Okandan, Murat; Schwindt, Peter

    2010-11-02

    An atomic magnetometer is disclosed which utilizes an optical cavity formed from a grating and a mirror, with a vapor cell containing an alkali metal vapor located inside the optical cavity. Lasers are used to magnetically polarize the alkali metal vapor and to probe the vapor and generate a diffracted laser beam which can be used to sense a magnetic field. Electrostatic actuators can be used in the magnetometer for positioning of the mirror, or for modulation thereof. Another optical cavity can also be formed from the mirror and a second grating for sensing, adjusting, or stabilizing the position of the mirror.

  13. Plasmonic coaxial waveguide-cavity devices.

    Science.gov (United States)

    Mahigir, Amirreza; Dastmalchi, Pouya; Shin, Wonseok; Fan, Shanhui; Veronis, Georgios

    2015-08-10

    We theoretically investigate three-dimensional plasmonic waveguide-cavity structures, built by side-coupling stub resonators that consist of plasmonic coaxial waveguides of finite length, to a plasmonic coaxial waveguide. The resonators are terminated either in a short or an open circuit. We show that the properties of these waveguide-cavity systems can be accurately described using a single-mode scattering matrix theory. We also show that, with proper choice of their design parameters, three-dimensional plasmonic coaxial waveguide-cavity devices and two-dimensional metal-dielectric-metal devices can have nearly identical transmission spectra. Thus, three-dimensional plasmonic coaxial waveguides offer a platform for practical implementation of two-dimensional metal-dielectric-metal device designs.

  14. Design of a folded, multi-pass Fabry–Perot cavity for displacement metrology

    NARCIS (Netherlands)

    Joo, K.M.; Ellis, J.D.; Spronck, J.W.; Munnig Schmidt, R.H.

    2009-01-01

    We present a folded, multi-pass cavity design for displacement measuring Fabry–Perot interferometry. The cavity length is designed to be one-quarter of the physical length needed for a typical Fabry–Perot interferometer by using a quarter-wave plate and a retroreflector. This enhances the displaceme

  15. Self-sustained oscillation for compressible cylindrical cavity flows

    Directory of Open Access Journals (Sweden)

    Kung-Ming CHUNG

    2017-08-01

    Full Text Available The presence of a cavity changes the mean and fluctuating pressure distributions. Similarities are observed between a cylindrical cavity and a rectangular cavity for a compressible flow. The type of cavity flow field depends on the diameter-to-depth ratio and the length-to-depth ratio. The feedback loop is responsible for the generation of discrete acoustic tones. In this study, the self-sustained oscillation for a compressible cylindrical cavity flow was investigated experimentally. For open-type cavities, the power spectra show that the strength of resonance depends on the diameter-to-depth ratio (4.43–43.0 and the incoming boundary layer thickness-to-depth ratio (0.72–7.0. The effective streamwise length is used as the characteristic length to estimate the Strouhal number. At higher modes, there is a large deviation from Rossiter’s formula for rectangular cavities. The gradient-based searching method was used to evaluate the values of the empirical parameters. Less phase lag and a lower convection velocity are observed.

  16. SPS accelerating cavity

    CERN Multimedia

    1976-01-01

    The SPS started up with 2 accelerating cavities (each consisting of 5 tank sections) in LSS3. They have a 200 MHz travelling wave structure (see 7411032 and 7802190) and 750 kW of power is fed to each of the cavities from a 1 MW tetrode power amplifier, located in a surface building above, via a coaxial transmission line. Clemens Zettler, builder of the SPS RF system, is standing at the side of one of the cavities. In 1978 and 1979 another 2 cavities were added and entered service in 1980. These were part of the intensity improvement programme and served well for the new role of the SPS as proton-antiproton collider. See also 7411032, 8011289, 8104138, 8302397.

  17. accelerating cavity from LEP

    CERN Multimedia

    This is an accelerating cavity from LEP, with a layer of niobium on the inside. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment. These challenging requirements pushed European industry to new achievements. 256 of these cavities are now used in LEP to double the energy of the particle beams.

  18. Dental Sealants Prevent Cavities

    Science.gov (United States)

    ... MMWR RSS VitalSigns RSS Error processing SSI file Dental Sealants Prevent Cavities Effective protection for children Language: ... more use of sealants and reimbursement of services. Dental care providers can Apply sealants to children at ...

  19. Indirect Coupling between Two Cavity Photon Systems via Ferromagnetic Resonance

    CERN Document Server

    Hyde, Paul; Harder, Michael; Match, Christophe; Hu, Can-Ming

    2016-01-01

    We experimentally realize indirect coupling between two cavity modes via strong coupling with the ferromagnetic resonance in Yttrium Iron Garnet (YIG). We find that some indirectly coupled modes of our system can have a higher microwave transmission than the individual uncoupled modes. Using a coupled harmonic oscillator model, the influence of the oscillation phase difference between the two cavity modes on the nature of the indirect coupling is revealed. These indirectly coupled microwave modes can be controlled using an external magnetic field or by tuning the cavity height. This work has potential for use in controllable optical devices and information processing technologies.

  20. Different optical properties in different periodic slot cavity geometrical morphologies

    Science.gov (United States)

    Zhou, Jing; Shen, Meng; Du, Lan; Deng, Caisong; Ni, Haibin; Wang, Ming

    2016-09-01

    In this paper, optical properties of two-dimensional periodic annular slot cavity arrays in hexagonal close-packing on a silica substrate are theoretically characterized by finite difference time domain (FDTD) simulation method. By simulating reflectance spectra, electric field distribution, and charge distribution, we confirm that multiple cylindrical surface plasmon resonances can be excited in annular inclined slot cavities by linearly polarized light, in which the four reflectance dips are attributed to Fabry-Perot cavity resonances in the coaxial cavity. A coaxial waveguide mode TE11 will exist in these annular cavities, and the wavelengths of these reflectance dips are effectively tailored by changing the geometrical pattern of slot cavity and the dielectric materials filled in the cavities. These resonant wavelengths are localized in annular cavities with large electric field enhancement and dissipate gradually due to metal loss. The formation of an absorption peak can be explained from the aspect of phase matching conditions. We observed that the proposed structure can be tuned over the broad spectral range of 600-4000 nm by changing the outer and inner radii of the annular gaps, gap surface topography. Meanwhile, different lengths of the cavity may cause the shift of resonance dips. Also, we study the field enhancement at different vertical locations of the slit. In addition, dielectric materials filling in the annular gaps will result in a shift of the resonance wavelengths, which make the annular cavities good candidates for refractive index sensors. The refractive index sensitivity of annular cavities can also be tuned by the geometry size and the media around the cavity. Annular cavities with novel applications can be implied as surface enhanced Raman spectra substrates, refractive index sensors, nano-lasers, and optical trappers. Project supported by the National Natural Science Foundation of China (Grant No. 61178044), the Natural Science Foundation

  1. 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....

  2. Single photon delayed feedback: a way to stabilize intrinsic quantum cavity electrodynamics.

    Science.gov (United States)

    Carmele, Alexander; Kabuss, Julia; Schulze, Franz; Reitzenstein, Stephan; Knorr, Andreas

    2013-01-01

    We propose a scheme to control cavity quantum electrodynamics in the single photon limit by delayed feedback. In our approach a single emitter-cavity system, operating in the weak coupling limit, can be driven into the strong coupling-type regime by an external mirror: The external loop produces Rabi oscillations directly connected to the electron-photon coupling strength. As an expansion of typical cavity quantum electrodynamics, we treat the quantum correlation of external and internal light modes dynamically and demonstrate a possible way to implement a fully quantum mechanical time-delayed feedback. Our theoretical approach proposes a way to experimentally feedback control quantum correlations in the single photon limit.

  3. Surface explosion cavities

    CERN Document Server

    Benusiglio, Adrien; Clanet, Christophe

    2012-01-01

    We present a fluid dynamics video on cavities created by explosions of firecrackers at the water free surface. We use three types of firecrackers containing 1, 1.3 and 5 g of flash powder. The firecrackers are held with their center at the surface of water in a cubic meter pool. The movies are recorded from the side with a high-speed video camera. Without confinement the explosion produces an hemispherical cavity. Right after the explosion this cavity grows isotropically, the bottom then stops while the sides continue to expand. In the next phase the bottom of the cavity accelerates backwards to the surface. During this phase the convergence of the flow creates a central jet that rises above the free surface. In the last part of the video the explosion is confined in a vertical open tube made of glass and of centimetric diameter. The explosion creates a cylindrical cavity that develops towards the free end of the tube. Depending on the charge, the cavity can either stop inside the tube or at its exit, but nev...

  4. The Superconducting TESLA Cavities

    CERN Document Server

    Aune, B.; Bloess, D.; Bonin, B.; Bosotti, A.; Champion, M.; Crawford, C.; Deppe, G.; Dwersteg, B.; Edwards, D.A.; Edwards, H.T.; Ferrario, M.; Fouaidy, M.; Gall, P-D.; Gamp, A.; Gössel, A.; Graber, J.; Hubert, D.; Hüning, M.; Juillard, M.; Junquera, T.; Kaiser, H.; Kreps, G.; Kuchnir, M.; Lange, R.; Leenen, M.; Liepe, M.; Lilje, L.; Matheisen, A.; Möller, W-D.; Mosnier, A.; Padamsee, H.; Pagani, C.; Pekeler, M.; Peters, H-B.; Peters, O.; Proch, D.; Rehlich, K.; Reschke, D.; Safa, H.; Schilcher, T.; Schmüser, P.; Sekutowicz, J.; Simrock, S.; Singer, W.; Tigner, M.; Trines, D.; Twarowski, K.; Weichert, G.; Weisend, J.; Wojtkiewicz, J.; Wolff, S.; Zapfe, K.

    2000-01-01

    The conceptional design of the proposed linear electron-positron colliderTESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with anaccelerating gradient of Eacc >= 25 MV/m at a quality factor Q0 > 5E+9. Thedesign goal for the cavities of the TESLA Test Facility (TTF) linac was set tothe more moderate value of Eacc >= 15 MV/m. In a first series of 27industrially produced TTF cavities the average gradient at Q0 = 5E+9 wasmeasured to be 20.1 +- 6.2 MV/m, excluding a few cavities suffering fromserious fabrication or material defects. In the second production of 24 TTFcavities additional quality control measures were introduced, in particular aneddy-current scan to eliminate niobium sheets with foreign material inclusionsand stringent prescriptions for carrying out the electron-beam welds. Theaverage gradient of these cavities at Q0 = 5E+9 amounts to 25.0 +- 3.2 MV/mwith the exception of one cavity suffering from a weld defect. Hence only amoderate improvement in production and preparation technique...

  5. In vivo measurements of uterine cavities in 795 women of fertile age

    NARCIS (Netherlands)

    Haspels, A.A.; Tadesse, E.; Kurz, K.H.

    1984-01-01

    The uterine sound length, the functional length of the cervix including the zone of internal cervical os and the fundus transversal were determined in 795 fertile women in vivo using a measuring device, the Cavimeter. The functional cavity length was calculated by subtracting the functional length o

  6. 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....

  7. Optimising Blackbody Cavity Shape for Spatially Uniform Integrated Emissivity

    Science.gov (United States)

    Saunders, P.

    2017-01-01

    The emissivity of a blackbody cavity, as seen by a radiation thermometer viewing the cavity, depends on both the field of view of the thermometer and the distribution of local effective emissivity values within the field of view. For cylindro-conical cavities, the local effective emissivity generally attains a maximum value at the apex of the cone and drops along the conical section. Thus, radiation thermometers with different fields of view see different blackbody emissivity values. This impacts, particularly, on the calibration of wide-angle low-temperature radiation thermometers and thermal imaging systems where each pixel responds to a different radiance. The spatial uniformity of the effective emissivity profile depends principally on the cone angle, with a weaker dependence on the length-to-diameter ratio of the cavity, the intrinsic emissivity of the cavity surfaces, and the temperature gradient along the cavity. In this paper, a nonlinear least-squares method is used to determine the optimal cone angle as a function of the cavity parameters. It is concluded that full cone angles close to 160° provide the flattest effective emissivity profile across the conical section of the cavity for typical cavity parameters. A method is also described for calculating the value of integrated emissivity, which includes the umbral and penumbral regions seen by an imaging radiation thermometer.

  8. RESEARCH ON THE FLOW PROPERTY IN THREE DIMENSIONAL CAVITY OF MICRO-CHANNEL

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The vortical property in a three dimensional cavity of micro-channel flow, which is very important, was investigated numerically. The results show that the rotation direction of vortex in the cavity depends on the dimension and shape of the cavity as well as the viscosity of the fluid. With the dimension and shape of the cavity fixed, there exists a critical inlet velocity. When the inlet velocity is less than the critical value, the rotation direction of vortex in the cavity will change. The critical velocity is directly proportional to the viscosity of the fluid, and inversely proportional to square of the thickness, length and depth of cavity. For the ratio of length and depth of cavity equals to one, there is a critical dimensionless parameter Re(cr), when R(e) is less than Re(cr), the rotation direction of vortex will change too. Re(cr) is equal to 11.8 approximately.

  9. Millimeter-long fiber Fabry-Perot cavities.

    Science.gov (United States)

    Ott, Konstantin; Garcia, Sebastien; Kohlhaas, Ralf; Schüppert, Klemens; Rosenbusch, Peter; Long, Romain; Reichel, Jakob

    2016-05-01

    We demonstrate fiber Fabry-Perot (FFP) cavities with concave mirrors that can be operated at cavity lengths as large as 1.5 mm without significant deterioration of the finesse. This is achieved by using a laser dot machining technique to shape spherical mirrors with ultralow roughness and employing single-mode fibers with large mode area for good mode matching to the cavity. Additionally, in contrast to previous FFPs, these cavities can be used over an octave-spanning frequency range with adequate coatings. We also show directly that shape deviations caused by the fiber's index profile lead to a finesse decrease as observed in earlier attempts to build long FFP cavities, and show a way to overcome this problem.

  10. Millimeter-long Fiber Fabry-Perot cavities

    CERN Document Server

    Ott, Konstantin; Kohlhaas, Ralf; Schüppert, Klemens; Rosenbusch, Peter; Long, Romain; Reichel, Jakob

    2016-01-01

    We demonstrate fiber Fabry-Perot (FFP) cavities with concave mirrors that can be operated at cavity lengths as large as 1.5mm without significant deterioration of the finesse. This is achieved by using a laser dot machining technique to shape spherical mirrors with ultralow roughness and employing single-mode fibers with large mode area for good mode matching to the cavity. Additionally, in contrast to previous FFPs, these cavities can be used over an octave-spanning frequency range with adequate coatings. We also show directly that shape deviations caused by the fiber's index profile lead to a finesse decrease as observed in earlier attempts to build long FFP cavities, and show a way to overcome this problem.

  11. Cavity preparation machine for the standardization of in vitro preparations

    Directory of Open Access Journals (Sweden)

    Carlos José Soares

    2008-09-01

    Full Text Available Several in vitro studies employ the confection of cavity preparations that are difficult to standardize by means of manual high speed handpieces. This study presents the development of a cavity preparation machine designed to standardize in vitro cavity preparations. A metal base of 25 mm x 25 mm x 4 mm (length x width x height was coupled to a small mobile table which was designed to be able to move by means of two precision micrometers (0.01-mm accuracy in the horizontal directions (right-left, and back-front. A high speed handpiece was coupled to a metallic connecting rod which had an accurate dial indicator enabling control of the vertical movement. The high speed handpiece is also able to move 180° around its longitudinal axis and 360° around its transversal axis. The suggested cavity preparation machine precisely helps in the standardization of cavity preparations for in vitro studies.

  12. Cavity preparation machine for the standardization of in vitro preparations.

    Science.gov (United States)

    Soares, Carlos José; Fonseca, Rodrigo Borges; Gomide, Henner Alberto; Correr-Sobrinho, Lourenço

    2008-01-01

    Several in vitro studies employ the confection of cavity preparations that are difficult to standardize by means of manual high speed handpieces. This study presents the development of a cavity preparation machine designed to standardize in vitro cavity preparations. A metal base of 25 mm x 25 mm x 4 mm (length x width x height) was coupled to a small mobile table which was designed to be able to move by means of two precision micrometers (0.01-mm accuracy) in the horizontal directions (right-left, and back-front). A high speed handpiece was coupled to a metallic connecting rod which had an accurate dial indicator enabling control of the vertical movement. The high speed handpiece is also able to move 180 degrees around its longitudinal axis and 360 degrees around its transversal axis. The suggested cavity preparation machine precisely helps in the standardization of cavity preparations for in vitro studies.

  13. Post-external dacryocystorhinostomy lagophthalmos.

    Science.gov (United States)

    Odat, Thabit A; Odat, Haitham A; Khraisat, Heba; Odat, Mohannad A; Alzoubi, Firas Q

    2015-06-01

    To describe lagophthalmos and eyelid closure abnormality after external dacryocystorhinostomy (DCR). A retrospective review of medical records and postoperative photographs of 79 patients who underwent external DCR for nasolacrimal duct obstruction and developed eyelid closure abnormality and lagophthalmos with or without exposure keratopathy was conducted. Collected data included age, sex, indication for surgery, laterality, length and type of incision, length of follow-up duration, presence of punctate epithelial keratopathy, and time for resolution of eyelid closure abnormalities. Twenty-seven patients with 28 external dacryocystorhinostomy had postoperative eyelid closure abnormalities. Male to female ratio was 1:6. The mean age was 40.1 years (range 9-80 years). All surgeries were performed through diagonal skin incision. Lagophthalmos involving the medial third of the palpebral fissure was noticed in 28.6 % of cases. All patients had hypometric blink mainly of the upper eyelid. One patient had punctate epithelial keratopathy. Resolution of lagophthalmos was noticed over a period of 1-5 weeks with an average of 3 weeks. None of the patients continued to have residual hypometric blink or punctate keratopathy at the last follow-up time. The mean follow-up period was 4.2 months (range 3-6 months). Eyelid closure abnormality and lagophthalmos after external DCR are underestimated problems. Spontaneous resolution is seen in all cases weeks to months after surgery.

  14. Femoral Reconstruction Using External Fixation

    Directory of Open Access Journals (Sweden)

    Yevgeniy Palatnik

    2011-01-01

    Full Text Available Background. The use of an external fixator for the purpose of distraction osteogenesis has been applied to a wide range of orthopedic problems caused by such diverse etiologies as congenital disease, metabolic conditions, infections, traumatic injuries, and congenital short stature. The purpose of this study was to analyze our experience of utilizing this method in patients undergoing a variety of orthopedic procedures of the femur. Methods. We retrospectively reviewed our experience of using external fixation for femoral reconstruction. Three subgroups were defined based on the primary reconstruction goal lengthening, deformity correction, and repair of nonunion/bone defect. Factors such as leg length discrepancy (LLD, limb alignment, and external fixation time and complications were evaluated for the entire group and the 3 subgroups. Results. There was substantial improvement in the overall LLD, femoral length discrepancy, and limb alignment as measured by mechanical axis deviation (MAD and lateral distal femoral angle (LDFA for the entire group as well as the subgroups. Conclusions. The Ilizarov external fixator allows for decreased surgical exposure and preservation of blood supply to bone, avoidance of bone grafting and internal fixation, and simultaneous lengthening and deformity correction, making it a very useful technique for femoral reconstruction.

  15. Pressurized rf cavities in ionizing beams

    Science.gov (United States)

    Freemire, B.; Tollestrup, A. V.; Yonehara, K.; Chung, M.; Torun, Y.; Johnson, R. P.; Flanagan, G.; Hanlet, P. M.; Collura, M. G.; Jana, M. R.; Leonova, M.; Moretti, A.; Schwarz, T.

    2016-06-01

    A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf) test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF6 and O2 were measured.

  16. Pressurized rf cavities in ionizing beams

    Directory of Open Access Journals (Sweden)

    B. Freemire

    2016-06-01

    Full Text Available A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF_{6} and O_{2} were measured.

  17. Estimation of genome length

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The genome length is a fundamental feature of a species. This note outlined the general concept and estimation method of the physical and genetic length. Some formulae for estimating the genetic length were derived in detail. As examples, the genome genetic length of Pinus pinaster Ait. and the genetic length of chromosome Ⅵ of Oryza sativa L. were estimated from partial linkage data.

  18. Heat loss investigation from spherical cavity receiver of solar concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Shewale, V. C. [Dept. of Mechanical Engineering, NDMVPS KBT College of Engineering, Nashik (India); Dongarwar, P. R. [Dept. of Mechanical Engineering, College of Military Engineering, Pune (India); Gawande, R. P. [Dept. of Mechanical Engineering, B.D.C.O.E. Wardha, Nagpur University, NagpurI (India)

    2016-11-15

    The heat losses are mainly affects on the performance of cavity receiver of solar concentrator. In this paper, the experimental and numerical study is carried out for different heat losses from spherical cavity receiver of 0.385 m cavity diameter and 0.154 m opening diameter. The total and convection losses are studied experimentally to no wind and wind conditions for the temperature range of 150 °C to 300 °C at 0°, 30°, 45°, 60° and 90° inclination angle of cavity receiver. The experimental set up mainly consists of copper tube material cavity receiver wrapped with nichrome heating coil to heat the cavity and insulated with glasswool insulation. The numerical analysis was carried out with Fluent Computational fluid dynamics (CFD) software, to study connective heat losses for no wind condition only. The numerical results are compared with experimental results and found good agreement with maximum deviation of 12 %. The effect of inclination angle of cavity receiver on total losses and convection losses shows that as the inclination angle increases from 0o to 90o, both losses decreased due to decreased in convective zone into the cavity receiver. The effect of operating temperature of cavity shows that as the temperature of cavity receiver increases, the total and convective losses goes on increasing. The effect of external wind at 2 m/s and 4 m/s in two directions (side-on wind and head-on wind) is also studied experimentally for total and convective heat losses. The result shows that the heat losses are higher for head-on wind condition compared to side-on wind and no wind condition at all inclination angle of cavity receiver. The present results are also compared to the convective losses obtained from the correlations of Stine and Mcdonald and M. Prakash. The convective loss from these correlations shows nearest prediction to both experimental and numerical results.

  19. Postischemic intestinal motility in rat is inversely correlated to length of ischemia. An in vivo animal model.

    Science.gov (United States)

    Udassin, R; Eimerl, D; Schiffman, J; Haskel, Y

    1995-05-01

    An inverse correlation between postischemic gastrointestinal motility and the length of intestinal ischemia was found in an animal model. Intestinal ischemia was caused without concurrent laparotomy and for a predetermined time period (ischemia time) by pulling on an external nylon thread that was threaded through a double-lumen catheter. This catheter was passed into the abdominal cavity to encircle the superior mesenteric artery. Gastrointestinal motility was determined by the introduction of a color-marked meal into the animal's stomach and the measurement of the proportionate length of the small bowel filled with it (transit index). This simple and reliable animal model can also be used for the evaluation of techniques and pharmacological manipulations aimed at modulation of the effects of intestinal ischemia on intestinal motility and its consequences.

  20. Effects of Cavity Configurations on Flameholding and Performances of Kerosene Fueled Scramjet Combustor

    Science.gov (United States)

    Shi, Deyong; Song, Wenyan; Wang, Yuhang; Wang, Yanhua

    2017-08-01

    In this work, the effects of cavity flameholder configurations on flameholding and performances of kerosene fueled scramjet combustor were studied experimentally and numerically. For experiments, a directly connected ground facility was used and clean high enthalpy air, with a total temperature of 800 K and a total pressure of 800 Kpa, was provided by an electricity resistance heater. To investigate the effects of cavity configurations on flameholding capacity and reacting-flow characteristics, three different flameholders, one single cavity flameholder and two tandem cavity flameholders, were used in experiments. For the two combustors with tandem cavity flameholders, the location and configurations of its up-stream cavity were same with the single cavity flameholder, and the length-to-depth ratios for down-stream cavities were 9 and 11 respectively. The experimental results showed that stabilize kerosene combustion were achieved for combustor with tandem cavity flameholders mounted, and none for that with single cavity flameholder. The none-reacting and reacting flows of combustor models with tandem cavity flameholders were compared and studied with numerical and experimental results. The results showed that higher combustion efficiencies and pressure recovery ratios were achieved for the combustor with down-stream cavity length-to-depth ratio of 9.

  1. Experimental investigation of cavity flows

    Energy Technology Data Exchange (ETDEWEB)

    Loeland, Tore

    1998-12-31

    This thesis uses LDV (Laser Doppler Velocimetry), PIV (Particle Image Velocimetry) and Laser Sheet flow Visualisation to study flow inside three different cavity configurations. For sloping cavities, the vortex structure inside the cavities is found to depend upon the flow direction past the cavity. The shape of the downstream corner is a key factor in destroying the boundary layer flow entering the cavity. The experimental results agree well with numerical simulations of the same geometrical configurations. The results of the investigations are used to find the influence of the cavity flow on the accuracy of the ultrasonic flowmeter. A method to compensate for the cavity velocities is suggested. It is found that the relative deviation caused by the cavity velocities depend linearly on the pipe flow. It appears that the flow inside the cavities should not be neglected as done in the draft for the ISO technical report on ultrasonic flowmeters. 58 refs., 147 figs., 2 tabs.

  2. Performance of a dual Fabry-Perot cavity refractometer.

    Science.gov (United States)

    Egan, Patrick F; Stone, Jack A; Hendricks, Jay H; Ricker, Jacob E; Scace, Gregory E; Strouse, Gregory F

    2015-09-01

    We have built and characterized a refractometer that utilizes two Fabry-Perot cavities formed on a dimensionally stable spacer. In the typical mode of operation, one cavity is held at vacuum, and the other cavity is filled with nitrogen gas. The differential change in length between the cavities is measured as the difference in frequency between two helium-neon lasers, one locked to the resonance of each cavity. This differential change in optical length is a measure of the gas refractivity. Using the known values for the molar refractivity and virial coefficients of nitrogen, and accounting for cavity length distortions, the device can be used as a high-resolution, multi-decade pressure sensor. We define a reference value for nitrogen refractivity as n-1=(26485.28±0.3)×10(-8) at p=100.0000  kPa, T=302.9190  K, and λ(vac)=632.9908  nm. We compare pressure determinations via the refractometer and the reference value to a mercury manometer.

  3. Immunopathological response in external dental resorption

    OpenAIRE

    Gabriela Wagner Ximenes; Alessandra Dutra da Silva; Paulo Oliva de Borba

    2015-01-01

    The study of root resorption and its immunopathogenesis is extremely important for preserving teeth within the oral cavity. Resorption may be infl ammatory or by substitution and it can be triggered by traumatism, induced movement of teeth, periapical disease, periodontal treatment and whitening of non-vital teeth. During odontogenesis, dentin is protected from the immune system and later this protection is provided externally by the cementum, cementoblasts and enamel and internally by the od...

  4. Triangular and honeycomb lattices of cold atoms in optical cavities

    Science.gov (United States)

    Safaei, Shabnam; Miniatura, Christian; Grémaud, Benoît.

    2015-10-01

    We consider a two-dimensional homogeneous ensemble of cold bosonic atoms loaded inside two optical cavities and pumped by a far-detuned external laser field. We examine the conditions for these atoms to self-organize into triangular and honeycomb lattices as a result of superradiance. By collectively scattering the pump photons, the atoms feed the initially empty cavity modes. As a result, the superposition of the pump and cavity fields creates a space-periodic light-shift external potential and atoms self-organize into the potential wells of this optical lattice. Depending on the phase of the cavity fields with respect to the pump laser, these minima can either form a triangular or a hexagonal lattice. By numerically solving the dynamical equations of the coupled atom-cavity system, we have shown that the two stable atomic structures at long times are the triangular lattice and the honeycomb lattice with equally populated sites. We have also studied how to drive atoms from one lattice structure to another by dynamically changing the phase of the cavity fields with respect to the pump laser.

  5. Paired modes of heterostructure cavities in photonic crystal waveguides with split band edges

    DEFF Research Database (Denmark)

    Mahmoodian, Sahand; Sukhorukov, Andrey A.; Ha, Sangwoo

    2010-01-01

    We investigate the modes of double heterostructure cavities where the underlying photonic crystal waveguide has been dispersion engineered to have two band-edges inside the Brillouin zone. By deriving and using a perturbative method, we show that these structures possess two modes. For unapodized...... cavities, the relative detuning of the two modes can be controlled by changing the cavity length, and for particular lengths, a resonant-like effect makes the modes degenerate. For apodized cavities no such resonances exist and the modes are always non-degenerate....

  6. Intra-cavity metamorphosis of a Gaussian beam to flat-top distribution

    CSIR Research Space (South Africa)

    Naidoo, Darryl

    2014-02-01

    Full Text Available We explore an intra-cavity beam shaping approach to generate a Gaussian distribution by the metamorphosis of a Gaussian beam into a flat-top distribution on opposing mirrors. The concept is tested external to the cavity through the use of two...

  7. Decreased vibrational susceptibility of Fabry-Perot cavities via designs of geometry and structural support

    Institute of Scientific and Technical Information of China (English)

    Yang Tao; Li Wen-Bo; Zang Er-Jun; Chen Li-Sheng

    2007-01-01

    Ultra-stable optical cavities are widely used for laser frequency stabilization. In these experiments the laser performance relies on the length stability of the Fabry-Perot cavities. Vibration-induced deformation is one of the dominant factors that affect the stability of ultra-stable optical cavities. We have quantitatively analysed the elastic deformation of Fabry-Perot cavities with various shapes and mounting configurations. Our numerical result facilitates a novel approach for the design of ultra-stable cavities that are insensitive to vibrational perturbations. This approach can be applied to many experiments such as laser frequency stabilization, high-precision laser spectroscopy, and optical frequency standards.

  8. Statistical electromagnetics: Complex cavities

    NARCIS (Netherlands)

    Naus, H.W.L.

    2008-01-01

    A selection of the literature on the statistical description of electromagnetic fields and complex cavities is concisely reviewed. Some essential concepts, for example, the application of the central limit theorem and the maximum entropy principle, are scrutinized. Implicit assumptions, biased choic

  9. LEP superconducting cavity

    CERN Multimedia

    1995-01-01

    Engineers work in a clean room on one of the superconducting cavities for the upgrade to the LEP accelerator, known as LEP-2. The use of superconductors allow higher electric fields to be produced so that higher beam energies can be reached.

  10. Melatonin and oral cavity.

    Science.gov (United States)

    Cengiz, Murat İnanç; Cengiz, Seda; Wang, Hom-Lay

    2012-01-01

    While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers.

  11. Melatonin and Oral Cavity

    Directory of Open Access Journals (Sweden)

    Murat İnanç Cengiz

    2012-01-01

    Full Text Available While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers.

  12. Niobium superconducting cavity

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    This 5-cell superconducting cavity, made from bulk-Nb, stems from the period of general studies, not all directed towards direct use at LEP. This one is dimensioned for 1.5 GHz, the frequency used at CEBAF and also studied at Saclay (LEP RF was 352.2 MHz). See also 7908227, 8007354, 8209255, 8210054, 8312339.

  13. 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...

  14. The External Degree.

    Science.gov (United States)

    Houle, Cyril O.

    This book examines the external degree in relation to the extremes of attitudes, myths, and data. Emphasis is placed on the emergence of the American external degree, foreign external-degree programs, the purpose of the external degree, the current scene, institutional issues, and problems of general policy. (MJM)

  15. LIGA-fabricated compact mm-wave linear accelerator cavities.

    Energy Technology Data Exchange (ETDEWEB)

    Song, J.J.; Bajikar, S.S.; DeCarlo, F.; Kang, Y.W.; Kustom, R.L.; Mancini, D.C.; Nassiri, A.; Lai, B.; Feinerman, A.D.; White, V.

    1998-03-23

    Millimeter-wave rf cavities for use in linear accelerators, free-electron lasers, and mm-wave undulatory are under development at Argonne National Laboratory. Typical cavity dimensions are in the 1000 mm range, and the overall length of the accelerator structure, which consists of 30-100 cavities, is about 50-100 mm. An accuracy of 0.2% in the cavity dimensions is necessary in order to achieve a high Q-factor of the cavity. To achieve this these structures are being fabricated using deep X-ray lithography, electroforming, and assembly (LIGA). The first prototype cavity structures are designed for 108 GHz and 2p/3-mode operation. Input and output couplers are integrated with the cavity structures. The cavities are fabricated on copper substrates by electroforming copper into 1-mm-thick PMMA resists patterned by deep x-ray lithography and polishing the copper down to the desired thickness. These are fabricated separately and subsequently assembled with precision spacing and alignment using microspheres, optical fibers, or microfabricated spacers/alignment pieces. Details of the fabrication process, alignment, and assembly work are presented in here.

  16. Experimental Investigation on the Pressure Characteristics of Cavity Closure Region

    Institute of Scientific and Technical Information of China (English)

    Yadong Wang; Xulong Yuan; Yuwen Zhang

    2012-01-01

    The most complicated component in cavitating flow and pressure distribution is the flow in the cavity closure line.The cavitating flow and pressure distribution provide critical aspects of flow field details in the region.The integral of pressure results of the hydrodynamic forces,indicate domination in the design of a supercavitating vehicle.An experiment was performed in a water tunnel to investigate the pressure characteristics of the cavity closure region.Ventilation methods were employed to generate artificial cavity,and the ventilation rate was adjusted accordingly to obtain the desired cavity length.An array of pressure transducers was laid down the cavity closure line to capture pressure distribution in this region.The experimental results show that there is a pressure peak in the cavity closure region,and the rise rate of pressure in space tends to be higher in the upwind side when the flow is non-axisymmetric.The transient pressure variations during the cavity formation procedure were also present.The method of measurement in this paper can be referenced by engineers.The result helps to study the flow pattern of cavity closure region,and it can also be used to analyze the formation of supercavitating vehicle hydrodynamics.

  17. Systematic measurement of maximum efficiencies and detuning lengths at the JAERI free-electron laser

    CERN Document Server

    Nishimori, N; Nagai, R; Minehara, E J

    2002-01-01

    We made a systematic measurement of efficiency detuning curves at several gain and loss parameters. The absolute detuning length (delta L) of an optical cavity was measured within an accuracy of 0.1 mu m around the maximum efficiency by a pulse-stacking method using an external laser. The FEL gain was controlled by the undulator gap instead of bunch charge, because we can change the gain rapidly while maintaining constant electron bunch conditions. For the high-gain and low-loss regions, the maximum efficiency is obtained at delta L=0 mu m and is larger than the value derived from the theoretical scaling law in the superradiant regime, while for the low-gain region the maximum efficiency is obtained for delta L shorter than 0 mu m and is similar to the scaling law.

  18. Three-Dimensional Morphology of a Coronal Prominence Cavity

    Science.gov (United States)

    Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.; Seaton, D. B.; Sterling, A. C.; Tripathi, D.; Williams, D. R.; Zhang, M.

    2010-01-01

    We present a three-dimensional density model of coronal prominence cavities, and a morphological fit that has been tightly constrained by a uniquely well-observed cavity. Observations were obtained as part of an International Heliophysical Year campaign by instruments from a variety of space- and ground-based observatories, spanning wavelengths from radio to soft-X-ray to integrated white light. From these data it is clear that the prominence cavity is the limb manifestation of a longitudinally-extended polar-crown filament channel, and that the cavity is a region of low density relative to the surrounding corona. As a first step towards quantifying density and temperature from campaign spectroscopic data, we establish the three-dimensional morphology of the cavity. This is critical for taking line-of-sight projection effects into account, since cavities are not localized in the plane of the sky and the corona is optically thin. We have augmented a global coronal streamer model to include a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. We have developed a semi-automated routine that fits ellipses to cross-sections of the cavity as it rotates past the solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI) observations from the two Solar Terrestrial Relations Observatory (STEREO) spacecraft. This defines the morphological parameters of our model, from which we reproduce forward-modeled cavity observables. We find that cavity morphology and orientation, in combination with the viewpoints of the observing spacecraft, explains the observed variation in cavity visibility for the east vs. west limbs

  19. Cavity-enhanced dual-comb spectroscopy

    CERN Document Server

    Bernhardt, Birgitta; Jacquet, Patrick; Jacquey, Marion; Kobayashi, Yohei; Udem, Thomas; Holzwarth, Ronald; Guelachvili, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2009-01-01

    The sensitivity of molecular fingerprinting is dramatically improved when placing the absorbing sample in a high-finesse optical cavity, thanks to the large increase of the effective path-length. As demonstrated recently, when the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace-gases may be identified within a few milliseconds. Analyzing efficiently the light transmitted through the cavity however still remains challenging. Here, a novel approach, cavity-enhanced frequency comb Fourier transform spectroscopy, fully overcomes this difficulty and measures ultrasensitive, broad-bandwidth, high-resolution spectra within a few tens of $\\mu$s. It could be implemented from the Terahertz to the ultraviolet regions without any need for detector arrays. We recorded, within 18 $\\mu$s, spectra of the 1.0 $\\mu$m overtone bands of ammonia spanning 20 nm with 4.5 GHz resolution and a noise-equivalent-absorption at one-second-averaging per ...

  20. Teleportation of Cavity Field States via Cavity QED

    CERN Document Server

    Guerra, E S

    2004-01-01

    In this article we discuss two schemes of teleportation of cavity field states. In the first scheme we consider cavities prepared in a coherent state and in the second scheme we consider cavities prepared in a superposition of zero and one Fock states.

  1. Magnetic field mapping for HIE-ISOLDE cavities

    CERN Document Server

    Bianchi, Antonio

    2015-01-01

    In this report the importance of a magnetic field mapping (B-mapping) around the HIE-ISOLDE superconducting cavities is described. In fact the cavities are not always above the HIE-ISOLDE specification, so it is important to understand the reason of their bad performances and improve them. For doing the B-mapping, the supports for three fluxgate sensors are designed and manufactured. The material of the supports is PEEK: a proper thermoplastic for the extreme operation conditions of the cavities. According to simulation of behavior of external magnetic field, an initial configuration of the sensors is proposed for the first measurements, in order to get the extent of Meissner effect around the superconducting cavities.

  2. Mechanical stability study of capture cavity II at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    McGee, M.W.; Pischalnikov, Y.; /Fermilab

    2007-06-01

    Problematic resonant conditions at both 18 Hz and 180 Hz were encountered and identified early during the commissioning of Capture Cavity II (CC2) at Fermilab. CC2 consists of an external vacuum vessel and a superconducting high gradient (close to 25 MV/m) 9-cell 1.3 GHz niobium cavity, transported from DESY for use in the A0 Photoinjector at Fermilab. An ANSYS modal finite element analysis (FEA) was performed in order to isolate the source of the resonance and directed the effort towards stabilization. Using a fast piezoelectric tuner to excite (or shake) the cavity at different frequencies (from 5 Hz to 250 Hz) at a low-range sweep for analysis purposes. Both warm (300 K) and cold (1.8 K) accelerometer measurements at the cavity were taken as the resonant ''fix'' was applied. FEA results, cultural and technical noise investigation, and stabilization techniques are discussed.

  3. Glial heterotopia of the oral cavity

    Directory of Open Access Journals (Sweden)

    Radhames E. Lizardo

    2015-07-01

    Full Text Available We report an unusual case of a glial heterotopia arising from the oral cavity of an African neonate. The patient presented with an external pedunculated oral mass which was connected to the anterior hard palate by a firm, rubbery stalk of mucosal tissue. While the mass appeared painless, it interfered with the infant's feeding and was disturbing to the parents. After a computed tomography scan excluded an intracranial connection, the mass was excised at its base and sent for biopsy. Histopathology examination confirmed glial heterotopia. Glial heterotopias should be included in the differential diagnosis of congenital masses in the oral region.

  4. Water exchange between the continental shelf and the cavity beneath Nioghalvfjerdsbræ (79 North Glacier)

    Science.gov (United States)

    Wilson, N. J.; Straneo, F.

    2015-09-01

    The mass loss at Nioghalvfjerdsbræ is primarily due to rapid submarine melting. Ocean data obtained from beneath the Nioghalvfjerdsbræ ice tongue show that melting is driven by the presence of warm (1°C) Atlantic Intermediate Water (AIW). A sill prevents AIW from entering the cavity from Dijmphna Sund, requiring that it flow into the cavity via bathymetric channels to the south at a pinned ice front. Comparison of water properties from the cavity, Dijmphna Sund, and the continental shelf support this conclusion. Overturning circulation rates inferred from observed melt rates and cavity stratification suggest an exchange flow between the cavity and the continental shelf of 38mSv, sufficient to flush cavity waters in under 1 year. These results place upper bounds on the timescales of external variability that can be transmitted to the glacier via the ice tongue cavity.

  5. Optimization of photonic crystal cavities

    DEFF Research Database (Denmark)

    Wang, Fengwen; Sigmund, Ole

    2017-01-01

    We present optimization of photonic crystal cavities. The optimization problem is formulated to maximize the Purcell factor of a photonic crystal cavity. Both topology optimization and air-hole-based shape optimization are utilized for the design process. Numerical results demonstrate...... that the Purcell factor of the photonic crystal cavity can be significantly improved through optimization....

  6. Hollow waveguide cavity ringdown spectroscopy

    Science.gov (United States)

    Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

    2012-01-01

    Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

  7. Advanced configuration of gravitational-wave interferometer on the base of "sensitive mode" in "white-light cavity"

    OpenAIRE

    Karapetyan, G. G.

    2002-01-01

    A novel conception of "sensitive mode" (SM) is proposed to apply in gravitational-wave advanced interferometer configuration. The SM is resonant oscillation of electromagnetic field in "white-light cavity", where the resonance line is broadened without decreasing cavity quality. The frequency of the SM is greatly susceptible to the change of cavity length, and the SM is established in a cavity with time constant smaller than a conventional mode. Due to these advantages the sensitivity and ban...

  8. Cavity enhanced atomic magnetometry

    CERN Document Server

    Crepaz, Herbert; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  9. Access cavity preparation.

    Science.gov (United States)

    Adams, N; Tomson, P L

    2014-03-01

    Each stage of root canal treatment should be carried out to the highest possible standard. The access cavity is arguably the most important technical stage, as subsequent preparation of the root canal(s) can be severely comprised if this is not well executed. Inadequate access can lead to canals being left untreated, poorly disinfected, difficult to shape and obturate, and may ultimately lead to the failure of the treatment. This paper highlights common features in root canal anatomy and outlines basic principles for locating root canals and producing a good access cavity. It also explores each phase of the preparation in detail and offers suggestions of instruments that have been specifically designed to overcome potential difficulties in the process. Good access design and preparation will result in an operative environment which will facilitate cleaning, shaping and obturation of the root canal system in order to maximise success.

  10. Colloquium: cavity optomechanics

    CERN Multimedia

    2011-01-01

    Monday 14 November 2011, 17:00 Ecole de Physique, Auditoire Stueckelberg Université de Genève Cavity optomechanics: controlling micro mechanical oscillators with laser light Prof. Tobias Kippenberg EPFL, Lausanne Laser light can be used to cool and to control trapped ions, atoms and molecules at the quantum level. This has lead to spectacular advances such as the most precise atomic clocks. An outstanding frontier is the control with lasers of nano- and micro-mechancial systems. Recent advances in cavity optomechanics have allowed such elementary control for the first time, enabling mechanical systems to be ground state cooled leading to readout with quantum limited sensitivity and permitting to explore new device concepts resulting from radiation pressure.  

  11. Cavity enhanced atomic magnetometry.

    Science.gov (United States)

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-10-20

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  12. Regulating multiple externalities

    DEFF Research Database (Denmark)

    Waldo, Staffan; Jensen, Frank; Nielsen, Max

    2016-01-01

    Open access is a well-known externality problem in fisheries causing excess capacity and overfishing. Due to global warming, externality problems from CO2 emissions have gained increased interest. With two externality problems, a first-best optimum can be achieved by using two regulatory instrume......Open access is a well-known externality problem in fisheries causing excess capacity and overfishing. Due to global warming, externality problems from CO2 emissions have gained increased interest. With two externality problems, a first-best optimum can be achieved by using two regulatory...

  13. 肢体延长后行全髋关节置换治疗CroweⅣ型髋关节发育不良%Treatment of Crowe type Ⅳ developmental dysplasia of the hip with total hip arthroplasty after limb-lengthing with external fixator

    Institute of Scientific and Technical Information of China (English)

    曹发奇; 杨述华; 许伟华; 叶树楠; 刘先哲; 冯勇; 张波

    2013-01-01

    Objective To retrospectively analyze the methods and clinical outcome to treat Crowe type Ⅳ developmental dysplasia of the hip (DDH) in young adults with total hip arthroplasty (THA) after limb-lengthing with external fixator.Methods From October 2007 to January 2012,12 patients with unilateral Crowe type Ⅳ DDH were treated with two-staged surgical method in our department.There were 2 males and 10 females with an average age of 25.7 years (range,18-35 years).In the first stage,the patients underwent soft tissue relaxation and iliofemoral distraction with use of an external fixator for 10-17 days.There were 1-2 cm distraction at the first time and 3-5 mm daily distraction.When the femoral head was distracted to the level of anatomical position,the second stage-THA was performed.All patients underwent uncemented prosthesis with bulk femoral head autograft for acetabular reconstruction.The acetabular cup was placed in the anatomical position in every patient.Shortening femoral osteotomies were not required.Results The mean time of first operation was 35.2±3.6 min,and hospital stay was 13.3±1.6 days.The mean time of second operation was 77.3±12.4 min,and hospital stay was 9.2±2.5 days.The average follow-up was 13.6±3.2 months,limb-length discrepancy was 5.6±1.5 cm on average preoperatively and 0.5±0.2 cm on average postoperatively.The Harris hip score was increased from 45.7±2.6 preoperatively to 92.3±3.3 postoperatively.All of the cases had acquired good hip and knee function.No patient suffered pin-site infection,hip joint infection,prosthesis loosening or deep vein thrombosis in our research.Transient nerve palsy occurred during the leg limb lengthening in 3 cases; calf skin numbness after THA occurred in 5 cases.Conclusion For the Crowe type Ⅳ DDH in young adults,normal limb length can be restored nearly and avoid nerve injury via continuously limb-lengthing with external fixator before THA.This method can get precise results,improve limb function

  14. Cavity enhanced atomic magnetometry

    OpenAIRE

    Herbert Crepaz; Li Yuan Ley; Rainer Dumke

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage...

  15. ExternE National Implementation Finland

    Energy Technology Data Exchange (ETDEWEB)

    Pingoud, K.; Maelkki, H.; Wihersaari, M.; Pirilae, P. [VTT Energy, Espoo (Finland); Hongisto, M. [Imatran Voima Oy, Vantaa (Finland); Siitonen, S. [Ekono Energy Ltd, Espoo (Finland); Johansson, M. [Finnish Environment Institute, Helsinki (Finland)

    1999-07-01

    ExternE National Implementation is a continuation of the ExternE Project, funded in part by the European Commission's Joule III Programme. This study is the result of the ExternE National Implementation Project for Finland. Three fuel cycles were selected for the Finnish study: coal, peat and wood-derived biomass, which together are responsible for about 40% of total electricity generation in Finland and about 75% of the non-nuclear fuel based generation. The estimated external costs or damages were dominated by the global warming (GW) impacts in the coal and peat fuel cycles, but knowledge of the true GW impacts is still uncertain. From among other impacts that were valued in monetary terms the human health damages due to airborne emissions dominated in all the three fuel cycles. Monetary valuation for ecosystem impacts is not possible using the ExternE methodology at present. The Meri-Pori power station representing the coal fuel cycle is one of the world's cleanest and most efficient coal-fired power plants with a condensing turbine. The coal is imported mainly from Poland. The estimated health damages were about 4 mECU/kWh, crop damages an order of magnitude lower and damages caused to building materials two orders of magnitude lower. The power stations of the peat and biomass fuel cycles are of CHP type, generating electricity and heat for the district heating systems of two cities. Their fuels are of domestic origin. The estimated health damages allocated to electricity generation were about 5 and 6 mECU/kWh, respectively. The estimates were case-specific and thus an generalisation of the results to the whole electricity generation in Finland is unrealistic. Despite the uncertainties and limitations of the methodology, it is a promising tool in the comparison of similar kinds of fuel cycles, new power plants and pollution abatement technologies and different plant locations with each other. (orig.)

  16. Cavity QED by the Numbers

    Science.gov (United States)

    Kimble, H. J.; Boca, A.; Boozer, A. D.; Bowen, W. P.; Buck, J. R.; Chou, C. W.; Duan, L.-M.; Kuzmich, A.; McKeever, J.

    2004-12-01

    Observations of cooling and trapping of N = 1,2,3,... atoms inside a small optical cavity are described. The atom-cavity system operates in a regime of strong coupling for which single photons are sufficient to saturate the atomic response. New theoretical protocols for the efficient engineering of multi-atom entanglement within the setting of cavity QED are described. By trapping a single atom within the cavity mode, a one-atom laser is experimentally realized in a regime of strong coupling. Beyond the setting of cavity QED, quantum correlations have been observed for photon pairs emitted from an atomic ensemble and with a programmable time offset.

  17. 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.

  18. Computer Aided Modeling of Human Mastoid Cavity Biomechanics Using Finite Element Analysis

    Directory of Open Access Journals (Sweden)

    Chou Yuan-Fang

    2010-01-01

    Full Text Available The aim of the present study was to analyze the human mastoid cavity on sound transmission using finite element method. Pressure distributions in the external ear canal and middle ear cavity at different frequencies were demonstrated. Our results showed that, first, blocking the aditus improves middle ear sound transmission in the 1500- to 2500-Hz range and decreases displacement in frequencies below 1000 Hz when compared with the normal ear. Second, at frequencies lower than 1000 Hz, the acoustic pressures were almost uniformly distributed in the external ear canal and middle ear cavity. At high frequencies, higher than 1000 Hz, the pressure distribution varied along the external ear canal and middle ear cavity. Third, opening the aditus, the pressures difference in dB between the middle ear cavity and external ear canal were larger than those of the closed mastoid cavity in low frequency (<1000 Hz. Finally, there was no significant difference in the acoustic pressure between the oval window and round window is noted and increased by 5 dB by blocking the aditus. These results suggest that our complete FE model including the mastoid cavity is potentially useful and can provide more information in the study of middle ear biomechanics.

  19. Crab Cavities for Linear Colliders

    Energy Technology Data Exchange (ETDEWEB)

    Burt, G.; Ambattu, P.; Carter, R.; Dexter, A.; Tahir, I.; /Cockcroft Inst. Accel. Sci. Tech. /Lancaster U.; Beard, C.; Dykes, M.; Goudket, P.; Kalinin, A.; Ma, L.; McIntosh, P.; /Daresbury; Shulte, D.; /CERN; Jones, Roger M.; /Cockcroft Inst. Accel. Sci. Tech. /Manchester U.; Bellantoni, L.; Chase, B.; Church, M.; Khabouline, T.; Latina, A.; /Fermilab; Adolphsen, C.; Li, Z.; Seryi, Andrei; /SLAC

    2011-11-08

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  20. Crab cavities for linear colliders

    CERN Document Server

    Burt, G; Carter, R; Dexter, A; Tahir, I; Beard, C; Dykes, M; Goudket, P; Kalinin, A; Ma, L; McIntosh, P; Shulte, D; Jones, Roger M; Bellantoni, L; Chase, B; Church, M; Khabouline, T; Latina, A; Adolphsen, C; Li, Z; Seryi, Andrei; Xiao, L

    2008-01-01

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  1. ASH External Web Portal (External Portal) -

    Data.gov (United States)

    Department of Transportation — The ASH External Web Portal is a web-based portal that provides single sign-on functionality, making the web portal a single location from which to be authenticated...

  2. Optical re-injection in cavity-enhanced absorption spectroscopy.

    Science.gov (United States)

    Leen, J Brian; O'Keefe, Anthony

    2014-09-01

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10(-10) cm(-1)/√Hz; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features.

  3. Optical re-injection in cavity-enhanced absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Leen, J. Brian, E-mail: b.leen@lgrinc.com; O’Keefe, Anthony [Los Gatos Research, 67 E. Evelyn Avenue, Suite 3, Mountain View, California 94041 (United States)

    2014-09-15

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10{sup −10} cm{sup −1}/√(Hz;) an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features.

  4. Waveguide-coupled cavities for energy recovery linacs

    Science.gov (United States)

    Kurennoy, S. S.; Nguyen, D. C.; Young, L. M.

    2004-08-01

    A novel scheme for energy recovery linacs used as FEL drivers is proposed. It consists of two parallel beam lines, one for electron beam acceleration and the other for the used beam that is bent after passing through a wiggler. The used beam is decelerated by the structure and feeds the cavity fields. The main feature of the scheme is that RF cavities are coupled with waveguides between these two linacs. The waveguide cut through the two beam pipes provides an efficient mechanism for energy transfer. The superconducting RF cavities in the two accelerators can be shaped differently, with an operating mode at the same frequency. This provides HOM detuning and therefore reduces the beam break-up effects. Another advantage of the proposed two-beam scheme is easy tuning of the cavity coupling by changing the waveguide length.

  5. Entanglement dynamics of two distant atoms in two detuning cavities

    Institute of Scientific and Technical Information of China (English)

    Ji Xin; L(u) Tian-Quan; Zhang Shou

    2010-01-01

    We investigate the entanglement dynamics via the concurrence of two distant atoms interacting off-resonantly with two cavity fields in Fock states, respectively. We find that the evolution of entanglement has sudden death and sudden birth phenomena, that with the increase of photon numbers in the two cavities, the alternate frequency of sudden death and sudden birth turns fast, and that the amplitude of concurrence oscillates regularly with oscillation frequency becoming slow when the cavity fields have the same photon numbers. While, the maximum of concurrence declines and the amplitude of concurrence oscillates irregularly when the two cavity fields have different photon numbers. In addition, we find the length of death time is dependent on the initial entanglement.

  6. Grid Window Tests on an 805-MHz Pillbox Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Torun, Y. [IIT, Chicago; Moretti, A. [Fermilab

    2015-06-01

    Muon ionization cooling channel designs use pillbox shaped RF cavities for improved power efficiency and fine control over phasing of individual cavities. For minimum scattering of the muon beam, the ends should be made out of a small thickness of high radiation length material. Good electrical and thermal conductivity are required to reduce power dissipation and remove the heat efficiently. Thin curved beryllium windows with TiN coating have been used successfully in the past. We have built an alternative win- dow set consisting of grids of tubes and tested these on a pillbox cavity previously used with both thin Be and thick Cu windows. The cavity was operated with a pair of grids as well as a single grid against a flat endplate.

  7. The dynamics of coupled atom and field assisted by continuous external pumping

    Energy Technology Data Exchange (ETDEWEB)

    Burlak, G.; Hernandez, J.A. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma de Morelos, Cuernavaca, Morelos (Mexico); Starostenko, O. [Departamento de Fisica, Electronica, Sistemas y Mecatronica, Universidad de las Americas, 72820 Puebla (Mexico)

    2006-07-01

    The dynamics of a coupled system comprising a two-level atom and cavity field assisted by a continuous external classical field (driving Jaynes-Cummings model) is studied. When the initial field is prepared in a coherent state, the dynamics strongly depends on the algebraic sum of both fields. If this sum is zero (the compensative case) in the system, only the vacuum Rabi oscillations occur. The results with dissipation and external field detuning from the cavity field are also discussed. (Author)

  8. Broadband Measurement of Coating Thermal Noise in Rigid Fabry-Perot Cavities

    CERN Document Server

    Chalermsongsak, Tara; Hall, Evan D; Arai, Koji; Gustafson, Eric K; Adhikari, Rana X

    2014-01-01

    We report on the relative length fluctuation of two fixed-spacer Fabry-Perot cavities with mirrors fabricated from silica/tantala dielectric coatings on fused silica substrates. By locking a laser to each cavity and reading out the beat note $\\hat{\

  9. Negative differential resistance in Josephson junctions coupled to a cavity

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Filatrella, G.; Pierro, V.

    2014-01-01

    or external – is often used. A cavity may also induce a negative differential resistance region at the lower side of the resonance frequency. We investigate the dynamics of Josephson junctions with a negative differential resistance in the quasi particle tunnel current, i.e. in the McCumber curve. We find......Regions with negative differential resistance can arise in the IV curve of Josephson junctions and this phenomenon plays an essential role for applications, in particular for THz radiation emission. For the measurement of high frequency radiation from Josephson junctions, a cavity – either internal...

  10. State-Insensitive Trapping of Single Atoms in Cavity QED

    CERN Document Server

    McKeever, J; Boozer, A D; Kuzmich, A M; Nägerl, H C; Stamper-Kurn, D M; Kimble, H J

    2002-01-01

    Single Cesium atoms are cooled and trapped inside a small optical cavity by way of a novel far-off-resonance dipole-force trap (FORT), with observed lifetimes of 2 - 3 seconds. The trapping field is provided by a TEM-00 mode of the cavity at a wavelength of 935.6 nm, and is such that the external potential for the center-of-mass motion is only weakly dependent on the atom's internal state. Continuous real time observations of single trapped atoms in a regime of strong coupling are reported, with mean duration 0.4 s and with individual events lasting ~ 1 s.

  11. RF Characterization of Niobium Films for Superconducting Cavities

    CERN Document Server

    Aull† , S; Doebert, S; Junginger, T; Ehiasarian, AP; Knobloch, J; Terenziani, G

    2013-01-01

    The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The Quadrupole Resonator modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HIPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HIPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

  12. Beam-wave interaction behavior of a 35 GHz metal PBG cavity gyrotron

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ashutosh, E-mail: asingh.rs.ece@iitbhu.ac.in [Faculty of Physical Sciences, Institute of Natural Sciences and Humanities Shri Ramswaroop Memorial University, Lucknow-Deva Road, Uttar Pradesh-225003 (India); Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005 (India); Jain, P. K. [Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005 (India)

    2014-09-15

    The RF behavior of a 35 GHz photonic band gap (PBG) cavity gyrotron operating in TE{sub 041}-like mode has been presented to demonstrate its single mode operation capability. In this PBG cavity gyrotron, the conventional tapered cylindrical cavity is replaced by a metal PBG cavity as its RF interaction structure. The beam-wave interaction behavior has been explored using time dependent multimode nonlinear analysis as well as through 3D PIC simulation. Metal PBG cavity is treated here similar to that of a conventional cylindrical cavity for the desired mode confinement. The applied DC magnetic field profile has been considered uniform along the PBG cavity length both in analysis as well as in simulation. Electrons energy and phase along the interaction length of the PBG cavity facilitates bunching mechanism as well as energy transfer phenomena from the electron beam to the RF field. The RF output power for the TE{sub 041}-like design mode as well as nearby competing modes have been estimated and found above to 100 kW in TE{sub 041}-like mode with ∼15% efficiency. Results obtained from the analysis and the PIC simulation are found in agreement within 8% variation, and also it supports the single mode operation, as the PBG cavity does not switch into other parasitic modes in considerably large range of varying DC magnetic field, contrary to the conventional cylindrical cavity interaction structure.

  13. Measuring Thermodynamic Length

    Energy Technology Data Exchange (ETDEWEB)

    Crooks, Gavin E

    2007-09-07

    Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

  14. ISR RF cavities

    CERN Multimedia

    1983-01-01

    In each ISR ring the radiofrequency cavities were installed in one 9 m long straight section. The RF system of the ISR had the main purpose to stack buckets of particles (most of the time protons)coming from the CPS and also to accelerate the stacked beam. The installed RF power per ring was 18 kW giving a peak accelerating voltage of 20 kV. The system had a very fine regulation feature allowing to lower the voltage down to 75 V in a smooth and well controlled fashion.

  15. Cavity Optomechanical Magnetometer

    CERN Document Server

    Forstner, S; Knittel, J; van Ooijen, E D; Swaim, J D; Harris, G I; Szorkovszky, A; Bowen, W P; Rubinsztein-Dunlop, H

    2011-01-01

    A cavity optomechanical magnetometer is demonstrated where the magnetic field induced expansion of a magnetostrictive material is transduced onto the physical structure of a highly compliant optical microresonator. The resulting motion is read out optically with ultra-high sensitivity. Detecting the magnetostrictive deformation of Terfenol-D with a toroidal whispering gallery mode (TWGM) resonator a peak sensitivity of 400 nT/Hz^.5 was achieved with theoretical modelling predicting that sensitivities of up to 500 fT/Hz^.5 may be possible. This chip-based magnetometer combines high-sensitivity and large dynamic range with small size and room temperature operation.

  16. Cavity optomechanical magnetometer.

    Science.gov (United States)

    Forstner, S; Prams, S; Knittel, J; van Ooijen, E D; Swaim, J D; Harris, G I; Szorkovszky, A; Bowen, W P; Rubinsztein-Dunlop, H

    2012-03-23

    A cavity optomechanical magnetometer is demonstrated. The magnetic-field-induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator and read out optically with ultrahigh sensitivity. A peak magnetic field sensitivity of 400  nT  Hz(-1/2) is achieved, with theoretical modeling predicting the possibility of sensitivities below 1  pT  Hz(-1/2). This chip-based magnetometer combines high sensitivity and large dynamic range with small size and room temperature operation.

  17. An RF input coupler for a superconducting single cell cavity

    Energy Technology Data Exchange (ETDEWEB)

    Fechner, B.; Ouchi, Nobuo; Kusano, Joichi; Mizumoto, Motoharu; Mukugi, Ken [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Krawczyk, F.

    1999-03-01

    Japan Atomic Energy Research Institute proposes a high intensity proton accelerator for the Neutron Science Project. A superconducting linac is a main option for the high energy part of the accelerator. Design and development work for the superconducting accelerating cavities (resonant frequency of 600 MHz) is in progress. Superconducting cavities have an advantage of very high accelerating efficiency because RF wall loss is very small and much of the RF power fed to the cavity is consumed for the beam acceleration. On the other hand, an RF input coupler for the superconducting cavity has to be matched to the beam loading. Therefore, estimation of coupling coefficient or external quality factor (Qext) of the RF input coupler is important for the design of the couplers. In this work, Qext`s were calculated by the electromagnetic analysis code (MAFIA) and were compared with those by the measurements. A {beta} (ratio of the particle velocity to the light velocity) = 0.5 single-cell cavity with either axial coupler or side coupler was used in this work. In the experiments, a model cavity made by copper is applied. Both 2- and 3-dimensional calculations were performed in the axial coupler geometry and the results were compared. The agreements between calculated and measured values are good and this method for calculation of Qext is confirmed to be proper for the design of the RF input couplers. (author)

  18. The ideal dimensions of a Halbach cylinder of finite length

    DEFF Research Database (Denmark)

    Bjørk, Rasmus

    2011-01-01

    but with a possible shorter length is considered. The external radius and the length of the Halbach cylinder with the smallest possible dimensions are found as a function of a desired internal radius, length of the sample volume and mean flux density. It is shown that the optimal ratio between the outer and inner...... radius of the Halbach cylinder does not depend on the length of the sample volume. Finally, the efficiency of a finite length Halbach cylinder is considered and compared with the case of a cylinder of infinite length. The most efficient dimensions for a Halbach cylinder are found and it is shown...

  19. A new awakening for accelerator cavities

    CERN Multimedia

    Katarina Anthony

    2013-01-01

    Imagine: an accelerator unbound by length; one that can bring a beam up to the TeV level in just a few hundred metres. Sounds like a dream? Perhaps not for long. At CERN’s Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE), physicists may soon be working to bring this contemporary fairy-tale to life.   The AWAKE experiment in the CNGS facility. Wherever you find a modern linear particle accelerator, you’ll find with it a lengthy series of RF accelerating cavities. Although based on technology first developed over half a century ago, RF cavities have dominated the accelerating world since their inception. However, new developments in plasma accelerator systems may soon be bringing a new player into the game. By harnessing the power of wakefields generated by beams in plasma cells, physicists may be able to produce accelerator gradients of many GV/m –  hundreds of times higher than those achieved in current RF cavities. “Plasma wakef...

  20. Nonradiating and radiating modes excited by quantum emitters in open epsilon-near-zero cavities

    CERN Document Server

    Liberal, Iñigo

    2015-01-01

    Controlling the emission and interaction properties of quantum emitters (QEs) embedded within an optical cavity is a key technique in engineering light-matter interactions at the nanoscale, as well as in the development of quantum information processing. State-of-the-art optical cavities are based on high Q photonics crystals and dielectric resonators. However, wealthier responses might be attainable with cavities carved in more exotic materials. Here, we theoretically investigate the emission and interaction properties of QEs embedded in open epsilon-near-zero (ENZ) cavities. Using analytical methods and numerical simulations, it is demonstrated that open ENZ cavities present the unique property of supporting nonradiating modes independently of the geometry of the external boundary of the cavity (shape, size, topology...). Moreover, the possibility of switching between radiating and nonradiating modes enables a dynamic control of both the emission by, and the interaction between, QEs. These phenomena provide...

  1. Multi-purpose 805 MHz Pillbox RF Cavity for Muon Acceleration Studies

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, Sergey S. [Los Alamos National Laboratory; Chan, Kwok-Chi Dominic [Los Alamos National Laboratory; Jason, Andrew [Los Alamos National Laboratory; Miyadera, Haruo [Los Alamos National Laboratory; Turchi, Peter J. [Los Alamos National Laboratory

    2011-01-01

    An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques. The cavity can operate at vacuum or under pressure to 100 atmospheres, at room temperature or in a liquid nitrogen bath at 77 K. The cavity is designed for easy assembly and disassembly with bolted construction using aluminum seals. The surfaces of the end walls of the cavity can be replaced with different materials such as copper, aluminum, beryllium, or molybdenum, and with different geometries such as shaped windows or grid structures. Different surface treatments such as electro polished, high-pressure water cleaned, and atomic layer deposition are being considered for testing. The cavity has been designed to fit inside the 5-Tesla solenoid in the MuCool Test Area at Fermilab. Current status of the cavity prepared for initial conditioning and operation in the external magnetic field is discussed.

  2. A Comprehensive study of Cavities on the Sun: Structure, Formation, and Evolution

    Science.gov (United States)

    Karna, Nishu; Zhang, Jie; Pesnell, William D.

    2016-05-01

    Coronal cavities are large-scale structures in the Sun's corona that are closely related with the long-term evolution of the magnetic field in the photosphere as well as associated with the energetic solar activity such as prominence eruptions and coronal mass ejections. They are observed as circular or elliptical-shaped relatively low-density dark regions above the solar limb in EUV, X-ray, and white-light coronal images. We used SDO/AIA limb synoptic maps, constructed from annuli above the solar limb, to systematically identify cavities. We observed 429 coronal prominence cavities between May 20, 2010 and Feb 1, 2015. We examined correlations between height, width, and length of the cavities. Based on the fitting of the shape of the cross section, we classified cavities in three types: prolate (38%), oblate (27%) and circular (35%). We found that the cavities of all shapes are common in shorter length while circular and oblate cavities are more common in the longer length. In general, we found that the overall 3-D topology of long stable cavities can be characterized as a long tube with an elliptical cross-section. Next, we investigated the pattern of cavity location and found that cavity systematically drifts towards the pole. We found that cavities form a belt by making a plot using SDO/HMI surface magnetogram similar to classical buttery diagram of sunspots, we call that the cavity belt. Our analysis showed that the cavity belts migrated towards higher latitude with time and the cavity belts disappeared after the polar magnetic field reversal. This result shows that cavity evolution provides new insight into the solar cycle. Moreover, we studied the underlying magnetic field of a circumpolar crown cavity (Mar 21, 2013- Oct 25, 2013) that was observed for several Carrington Rotations. Our results showed that the underlying polarity inversion line of cavities is formed between the trailing part of decayed active regions and the unipolar magnetic field in the

  3. Applications of cavity optomechanics

    Science.gov (United States)

    Metcalfe, Michael

    2014-09-01

    "Cavity-optomechanics" aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems.

  4. Oral cavity eumycetoma.

    Science.gov (United States)

    Nai, Gisele Alborghetti; Stuani, Maria Luiza de Toledo; Stuani, Luís Antonio Sasso

    2011-01-01

    Mycetoma is a pathological process in which eumycotic (fungal) or actinomycotic causative agents from exogenous source produce grains. It is a localized chronic and deforming infectious disease of subcutaneous tissue, skin and bones. We report the first case of eumycetoma of the oral cavity in world literature. A 43-year-old male patient, complaining of swelling and fistula in the hard palate. On examination, swelling of the anterior and middle hard palate, with fistula draining a dark liquid was observed. The panoramic radiograph showed extensive radiolucent area involving the region of teeth 21-26 and the computerized tomography showed communication with the nasal cavity, suggesting the diagnosis of periapical cyst. Surgery was performed to remove the lesion. Histopathological examination revealed purulent material with characteristic grain. Gram staining for bacteria was negative and Grocott-Gomori staining for the detection of fungi was positive, concluding the diagnosis of eumycetoma. The patient was treated with ketoconazole for nine months, and was considered cured at the end of treatment. Histopathological examination, using histochemical staining, and direct microscopic grains examination can provide the distinction between eumycetoma and actinomycetoma accurately.

  5. Oral cavity eumycetoma

    Directory of Open Access Journals (Sweden)

    Gisele Alborghetti Nai

    2011-06-01

    Full Text Available Mycetoma is a pathological process in which eumycotic (fungal or actinomycotic causative agents from exogenous source produce grains. It is a localized chronic and deforming infectious disease of subcutaneous tissue, skin and bones. We report the first case of eumycetoma of the oral cavity in world literature. CASE REPORT: A 43-year-old male patient, complaining of swelling and fistula in the hard palate. On examination, swelling of the anterior and middle hard palate, with fistula draining a dark liquid was observed. The panoramic radiograph showed extensive radiolucent area involving the region of teeth 21-26 and the computerized tomography showed communication with the nasal cavity, suggesting the diagnosis of periapical cyst. Surgery was performed to remove the lesion. Histopathological examination revealed purulent material with characteristic grain. Gram staining for bacteria was negative and Grocott-Gomori staining for the detection of fungi was positive, concluding the diagnosis of eumycetoma. The patient was treated with ketoconazole for nine months, and was considered cured at the end of treatment. CONCLUSION: Histopathological examination, using histochemical staining, and direct microscopic grains examination can provide the distinction between eumycetoma and actinomycetoma accurately.

  6. Applications of cavity optomechanics

    Energy Technology Data Exchange (ETDEWEB)

    Metcalfe, Michael [Booz Allen Hamilton, 3811 Fairfax Drive, Arlington, Virginia 22203 (United States)

    2014-09-15

    Cavity-optomechanics” aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems.

  7. Secondary emission electron gun using external primaries

    Science.gov (United States)

    Srinivasan-Rao, Triveni; Ben-Zvi, Ilan

    2009-10-13

    An electron gun for generating an electron beam is provided, which includes a secondary emitter. The secondary emitter includes a non-contaminating negative-electron-affinity (NEA) material and emitting surface. The gun includes an accelerating region which accelerates the secondaries from the emitting surface. The secondaries are emitted in response to a primary beam generated external to the accelerating region. The accelerating region may include a superconducting radio frequency (RF) cavity, and the gun may be operated in a continuous wave (CW) mode. The secondary emitter includes hydrogenated diamond. A uniform electrically conductive layer is superposed on the emitter to replenish the extracted current, preventing charging of the emitter. An encapsulated secondary emission enhanced cathode device, useful in a superconducting RF cavity, includes a housing for maintaining vacuum, a cathode, e.g., a photocathode, and the non-contaminating NEA secondary emitter with the uniform electrically conductive layer superposed thereon.

  8. Secondary emission electron gun using external primaries

    Science.gov (United States)

    Srinivasan-Rao, Triveni; Ben-Zvi, Ilan; Kewisch, Jorg; Chang, Xiangyun

    2007-06-05

    An electron gun for generating an electron beam is provided, which includes a secondary emitter. The secondary emitter includes a non-contaminating negative-electron-affinity (NEA) material and emitting surface. The gun includes an accelerating region which accelerates the secondaries from the emitting surface. The secondaries are emitted in response to a primary beam generated external to the accelerating region. The accelerating region may include a superconducting radio frequency (RF) cavity, and the gun may be operated in a continuous wave (CW) mode. The secondary emitter includes hydrogenated diamond. A uniform electrically conductive layer is superposed on the emitter to replenish the extracted current, preventing charging of the emitter. An encapsulated secondary emission enhanced cathode device, useful in a superconducting RF cavity, includes a housing for maintaining vacuum, a cathode, e.g., a photocathode, and the non-contaminating NEA secondary emitter with the uniform electrically conductive layer superposed thereon.

  9. Cavity coalescence in superplastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Stowell, M.J.; Livesey, D.W.; Ridley, N.

    1984-01-01

    An analysis of the probability distribution function of particles randomly dispersed in a solid has been applied to cavitation during superplastic deformation and a method of predicting cavity coalescence developed. Cavity size distribution data were obtained from two microduplex nickel-silver alloys deformed superplastically to various extents at elevated temperature, and compared to theoretical predictions. Excellent agreement occurred for small void sizes but the model underestimated the number of voids in the largest size groups. It is argued that the discrepancy results from a combination of effects due to non-random cavity distributions and to enhanced growth rates and incomplete spheroidization of the largest cavities.

  10. Graded-index optical fiber tweezers with long manipulation length.

    Science.gov (United States)

    Gong, Yuan; Huang, Wei; Liu, Qun-Feng; Wu, Yu; Rao, Yunjiang; Peng, Gang-Ding; Lang, Jinyi; Zhang, Ke

    2014-10-20

    Long manipulation length is critical for optical fiber tweezers to enhance the flexibility of non-contact trapping. In this paper a long manipulation distance of more than 40 μm is demonstrated experimentally by the graded-index fiber (GIF) tweezers, which is fabricated by chemically etching a GIF taper with a large cone angle of 58°. The long manipulation distance is obtained by introducing an air cavity between the lead-in single mode fiber and the GIF as well as by adjusting the laser power in the existence of a constant background flow. The influence of the cavity length and the GIF length on the light distribution and the focusing length of the GIF taper is investigated numerically, which is helpful for optimizing the parameters to perform stable optical trapping. This kind of optical fiber tweezers has advantages including low-cost, easy-to-fabricate and easy-to-use.

  11. A CAVITY RING-DOWN SPECTROSCOPY MERCURY CONTINUOUS EMISSION MONITOR

    Energy Technology Data Exchange (ETDEWEB)

    Christopher C. Carter

    2002-12-31

    SRD tested a number of different length cavities during this past quarter. Continuous transmission was observed with cavity lengths from 65 to 12 cm. The 65 cm cavity was replaced with a 39 cm cavity for work performed during this quarter. Flue gas components were tested for background absorptions and any interference with the determination of accurate mercury concentrations. Sulfur dioxide was found to absorb fairly strongly in the region of the mercury transition, but the Cavity Ring-Down (CRD) instrument was still able to detect mercury at subparts-per-billion by volume (ppb) levels. Additional flue gases tested included H{sub 2}O, CO, CO{sub 2}, NO, NO{sub 2}. None of these flue gas constituents showed any observable absorption in the ultraviolet region near the atomic mercury transition. Work was also initiated in speciation studies. In particular mercury chloride (HgCl{sub 2}) was tested. A mercury signal was detected from a gas stream containing HgCl{sub 2}. SRD was not able to determine definitively if there exists a spectral shift great enough to separate HgCl{sub 2} from elemental mercury in these initial tests.

  12. Impact of Trapped Flux and Thermal Gradients on the SRF Cavity Quality Factor

    CERN Document Server

    Kugeler, O; Knobloch, J; Aull, S

    2012-01-01

    The obtained Q0 value of a superconducting niobium cavity is known to depend on various factors like the RRR of the Niobium material, crystallinity, chemical treatment history, the high-pressure rinsing process, or effectiveness of the magnetic shielding. We have observed that spatial thermal gradients over the cavity length during cool-down appear to contribute to a degradation of Q0. Measurements were performed in the Horizontal Bi-Cavity Test Facility (HoBiCaT) at HZB on TESLA type cavities as well as on disc- and rod-shaped niobium samples equipped with thermal, electrical and magnetic diagnostics. Possible explanations for the effect are discussed.

  13. 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....

  14. External radiation surveillance

    Energy Technology Data Exchange (ETDEWEB)

    Antonio, E.J.

    1995-06-01

    This section of the 1994 Hanford Site Environmental Report describes how external radiation was measured, how surveys were performed, and the results of these measurements and surveys. External radiation exposure rates were measured at locations on and off the Hanford Site using thermoluminescent dosimeters (TLD). External radiation and contamination surveys were also performed with portable radiation survey instruments at locations on and around the Hanford Site.

  15. How the cross-sectional discontinuity between ear canal and probe affects the ear canal length estimation.

    Science.gov (United States)

    Zebian, Makram; Hensel, Johannes; Fedtke, Thomas

    2012-07-01

    Many ear canal probes both deliver and measure sound via narrow tubes. This study investigates the effect of the cross-sectional discontinuity at the interface between ear canal models and the connecting tubes of a commercially available otoacoustic emission probe on the "acoustically" estimated cavity lengths. Rigid cavities having the same length but different diameters were produced, and modeled by the finite element method. Cavities with a diameter larger than 8 mm had acoustic lengths that considerably overestimated the real geometry. A length correction was derived, which, in most applications, compensates for the measurement errors emerging from the discontinuity effects.

  16. Numerical study of natural melt convection in cylindrical cavity with hot walls and cold bottom sink

    Directory of Open Access Journals (Sweden)

    Ahmanache Abdennacer

    2013-01-01

    Full Text Available Numerical study of natural convection heat transfer and fluid flow in cylindrical cavity with hot walls and cold sink is conducted. Calculations are performed in terms of the cavity aspect ratio, the heat exchanger length and the thermo physical properties expressed via the Prandtl number and the Rayleigh number. Results are presented in the form of isotherms, streamlines, average Nusselt number and average bulk temperature for a range of Rayleigh number up to 106. It is observed that Rayleigh number and heat exchanger length influences fluid flow and heat transfer, whereas the cavity aspect ratio has no significant effects.

  17. Shock induced cavity collapse

    Science.gov (United States)

    Skidmore, Jonathan; Doyle, Hugo; Tully, Brett; Betney, Matthew; Foster, Peta; Ringrose, Tim; Ramasamy, Rohan; Parkin, James; Edwards, Tom; Hawker, Nicholas

    2016-10-01

    Results from the experimental investigation of cavity collapse driven by a strong planar shock (>6km/s) are presented. Data from high speed framing cameras, laser backlit diagnostics and time-resolved pyromety are used to validate the results of hydrodynamic front-tracking simulations. As a code validation exercise, a 2-stage light gas gun was used to accelerate a 1g Polycarbonate projectile to velocities exceeding 6km/s; impact with a PMMA target containing a gas filled void results in the formation of a strong shockwave with pressures exceeding 1Mbar. The subsequent phenomena associated with the collapse of the void and excitation of the inert gas fill are recorded and compared to simulated data. Variation of the mass density and atomic number of the gas fill is used to alter the plasma parameters furthering the extent of the code validation.

  18. A Scanning Cavity Microscope

    CERN Document Server

    Mader, Matthias; Hänsch, Theodor W; Hunger, David

    2014-01-01

    Imaging of the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1700-fold signal enhancement compared to diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross section of gold nanoparticles with a sensitivity below 1 nm2, we show a method to improve spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for opt...

  19. 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.

  20. Heat Transfer Characteristics of Hydrate Slurries Transported by Visco-Elastic Fluid in a Cavity

    Science.gov (United States)

    Nakamura, Ryoichi; Yamada, Sayaka; Suzuki, Hiroshi; Komoda, Yoshiyuki; Usui, Hiromoto

    A two dimentional numerical study has been performed to investigate on heat transfer characteristics of a hydrate slurry transported by a visco-elastic fluid flowing between parallel plates with a one-sided cavity. In this study, the cavity length was changed in three steps, while the rib height and rib length were kept constant. Heat flux on the solid wall was set at 20,000W•m-2. The concentration of hydrate particles at inlet was set at 5wt%. From the results, it is found that hydrate particles dispersed with Newtonian fluid (water) flows over the cavity without penetration. On the other hand, hydrate particles dispersed with visco-elastic fluid are observed effectively to penetrate into the cavity and sweep the bottom of cavity by Barus effect. This causes effective heat transfer from the bottom wall of the cavity. Heat transfer difference was observed that the cavity length was changed. Consequently, there exists the optimum geometry for the heat transfer enhancement in a cavity by using Barus effect.

  1. Frequency Tuning for a DQW Crab Cavity

    CERN Document Server

    Verdú-Andrés, Silvia; Ben-Zvi, Ilan; Calaga, Rama; Capatina, Ofelia; Leuxe, Raphael; Skaritka, John; Wu, Qiong; Xiao, Binping; Zanoni, Carlo

    2016-01-01

    The nominal operating frequency for the HL-LHC crab cavities is 400.79 MHz within a bandwidth of ±60kHz. Attaining the required cavity tune implies a good understanding of all the processes that influence the cavity frequency from the moment when the cavity parts are being fabricated until the cavity is installed and under operation. Different tuning options will be available for the DQW crab cavity of LHC. This paper details the different steps in the cavity fabrication and preparation that may introduce a shift in the cavity frequency and introduces the different tuning methods foreseen to bring the cavity frequency to meet the specifications.

  2. Interpreting debris from satellite disruption in external galaxies

    NARCIS (Netherlands)

    Johnston, KV; Sackett, PD; Bullock, JS

    2001-01-01

    We examine the detectability and interpretation of debris trails caused by satellite disruption in external galaxies using semianalytic approximations for the dependence of streamer length, width, and surface brightness on satellite and primary galaxy characteristics. The semianalytic method is test

  3. Quantum entanglement purification in cavities

    CERN Document Server

    Romero, J L; Saavedra, C; Retamal, J C

    2002-01-01

    A physical implementation of an entanglement purification protocol is studied using a cavity quantum electrodynamic based proposal, where, the quantum information is stored in quantum field sates inside cavities. Also a procedure is given for quantifying the degree of entanglement between quantum fields. (Author)

  4. Quench studies of ILC cavities

    Energy Technology Data Exchange (ETDEWEB)

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari; Dai, Jin

    2011-07-01

    Quench limits accelerating gradient in SRF cavities to a gradient lower than theoretically expected for superconducting niobium. Identification of the quenching site with thermometry and OST, optical inspection, and replica of the culprit is an ongoing effort at Jefferson Lab aimed at better understanding of this limiting phenomenon. In this contribution we present our finding with several SRF cavities that were limited by quench.

  5. Superconducting cavity model for LEP

    CERN Multimedia

    1979-01-01

    A superconducting cavity model is being prepared for testing in a vertical cryostat.At the top of the assembly jig is H.Preis while A.Scharding adjusts some diagnostic equipment to the cavity. See also photo 7912501X.

  6. LEP radio-frequency cavity

    CERN Multimedia

    1991-01-01

    One of the copper radio-frequency accelerating cavities installed for the first phase of LEP (1989-1995). Bunches of electrons and positrons circulated in LEP in opposite directions and were accelerated in eight different sets of 16 cavities (situated on either side of the four experiments), gaining 400 million volts of accelerating power per turn.

  7. Single and Coupled Nanobeam Cavities

    DEFF Research Database (Denmark)

    Ivinskaya, Aliaksandra; Lavrinenko, Andrei; Shyroki, Dzmitry M.

    2013-01-01

    for analysis and design of photonic crystal devices, such as 2D ring resonators for filters, single and coupled nanobeam cavities, birefringence in photonic crystal cavities, threshold analysis in photonic crystal lasers, gap solitons in photonic crystals, novel photonic atolls, dynamic characteristics...

  8. Heat flux reduction mechanism induced by a combinational opposing jet and cavity concept in supersonic flows

    Science.gov (United States)

    Huang, Wei; Jiang, Yan-ping; Yan, Li; Liu, Jun

    2016-04-01

    The thermal protection on the surface of hypersonic vehicles attracts an increasing attention worldwide, especially when the vehicle enters the atmosphere at high speed. In the current study, the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Menter's shear stress transport (SST) model have been employed to investigate the heat flux reduction mechanism induced by the variations of the cavity configuration, the jet pressure ratio and the injectant molecular weight in the combinational opposing jet and cavity concept. The length of the cavity is set to be 6 mm, 8 mm and 10 mm in order to make sure that the cavity configuration is the "open" cavity, and the jet pressure ratio is set to be 0.4, 0.6 and 0.8 in order to make sure that the flow field is steady. The injectant is set to be nitrogen and helium. The obtained results show that the aft angle of the cavity only has a slight impact on the heat flux reduction, and the heat flux peak decreases with the decrease of the length of the cavity. The design of the thermal protection system for the hypersonic blunt body is a multi-objective design exploration problem, and the heat flux distribution depends on the jet pressure ratio, the aft wall of the cavity and the injectant molecular weight. The heat flux peak decreases with the increase of the jet pressure ratio when the aft angle of the cavity is large enough, and this value is 45°.

  9. Flow Tones in a Pipeline-Cavity System: Effect of Pipe Asymmetry

    Energy Technology Data Exchange (ETDEWEB)

    D. Erdem; D. Rockwell; P.L. Oshkai; M. Pollack

    2001-02-28

    Flow tones in a pipeline-cavity system are characterized in terms of unsteady pressure within the cavity and along the pipe. The reference case corresponds to equal lengths of pipe connected to the inlet and outlet ends of the cavity. Varying degrees of asymmetry of this pipe arrangement are investigated. The asymmetry is achieved by an extension of variable length, which is added to the pipe at the cavity outlet. An extension length as small as a few percent of the acoustic wavelength of the resonant mode can yield a substantial reduction in the pressure amplitude of the flow tone. This amplitude decrease occurs in a similar fashion within both the cavity and the pipe resonator, which indicates that it is a global phenomenon. Furthermore, the decrease of pressure amplitude is closely correlated with a decrease of the Q (quality)-factor of the predominant spectral component of pressure. At a sufficiently large value of extension length, however, the overall form of the pressure spectrum recovers to the form that exists at zero length of the extension. Further insight is provided by variation of the inflow velocity at selected values of extension length. Irrespective of its value, both the magnitude and frequency of the peak pressure exhibit a sequence of resonant-like states. moreover, the maximum attainable magnitude of the peak pressure decreases with increasing extension length.

  10. Flow Tones in a Pipeline-Cavity System: Effect of Pipe Asymmetry

    Energy Technology Data Exchange (ETDEWEB)

    D. Erdem; D. rockwell; P. Oshkai; M. Pollack

    2002-05-29

    Flow tones in a pipeline-cavity system are characterized in terms of unsteady pressure within the cavity and along the pipe. The reference case corresponds to equal lengths of pipe connected to the inlet and outlet ends of the cavity. Varying degrees of asymmetry of this pipe arrangement are investigated. The asymmetry is achieved by an extension of variable length, which is added to the pipe at the cavity outlet. An extension length as small as a few percent of the acoustic wavelength of the resonant mode can yield a substantial reduction in the pressure amplitude of the flow tone. This amplitude decrease occurs in a similar fashion within both the cavity and the pipe resonator, which indicates that it is a global phenomenon. Furthermore, the decrease of pressure amplitude is closely correlated with a decrease of the Q (quality)-factor of the predominant spectral component of pressure. At a sufficiently large value of extension length, however, the overall form of the pressure spectrum recovers to the form that exists at zero length of the extension. Further insight is provided by variation of the inflow velocity at selected values of extension length. Irrespective of its value, both the magnitude and frequency of the peak pressure exhibit a sequence of resonant-like states. Moreover, the maximum attainable magnitude of the peak pressure decreases with increasing extension length.

  11. Mechanical Properties of Niobium Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Dhakal, Pashupati [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Matalevich, Joseph R. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Myneni, Ganapati Rao [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  12. Predicting Length of Psychiatric Hospital Stay in Children and Adolescents.

    Science.gov (United States)

    Leininger, Michele; Stephenson, Laura A.

    Length of stay in psychiatric inpatient units has received increasing attention with the external pressures for treatment cost-effectiveness and evidence that longer hospital stays do not appear to have significant advantages over shorter hospital stays. This study examined the relationship between length of psychiatric hospital stay and…

  13. Operation of the 56 MHz superconducting RF cavity in RHIC during run 14

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Q. [Brookhaven National Lab. (BNL), Upton, NY (United States); Belomestnykh, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); Ben-Zvi, I. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hayes, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Mernick, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Severino, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zaltsman, A. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-09-11

    A 56 MHz superconducting RF cavity was designed and installed in the Relativistic Heavy Ion Collider (RHIC). It is the first superconducting quarter wave resonator (QWR) operating in a high-energy storage ring. We discuss herein the cavity operation with Au+Au collisions, and with asymmetrical Au+He3 collisions. The cavity is a storage cavity, meaning that it becomes active only at the energy of experiment, after the acceleration cycle is completed. With the cavity at 300 kV, an improvement in luminosity was detected from direct measurements, and the bunch length has been reduced. The uniqueness of the QWR demands an innovative design of the higher order mode dampers with high-pass filters, and a distinctive fundamental mode damper that enables the cavity to be bypassed during the acceleration stage.

  14. A Lamb wave source based on the resonant cavity of phononic-crystal plates.

    Science.gov (United States)

    Sun, Jia-Hong; Wu, Tsung-Tsong

    2009-01-01

    In this paper, we propose a Lamb wave source that is based on the resonant cavity of a phononic-crystal plate. The phononic-crystal plate is composed of tungsten cylinders that form square lattices in a silicon plate, and the resonant cavity is created by arranging defects inside the periodic structure. The dispersion, transmission, and displacement of Lamb waves are analyzed by the finite-difference time-domain (FDTD) method. The eigenmodes inside the cavities of the phononic-crystal plate are identified as resonant modes. The fundamental and higher order resonant modes, which vary with the length of cavities, are calculated. By exciting the specific resonant mode in an asymmetric cavity, the 232.40 MHz flexural Lamb wave has a magnified amplitude of 78 times larger than the normal one. Thus, the cavity on the tungsten/silicon phononic-crystal plate may serve as a source element in a microscale acoustic wave device.

  15. Cavity optomechanical spring sensing of single molecules

    Science.gov (United States)

    Yu, Wenyan; Jiang, Wei C.; Lin, Qiang; Lu, Tao

    2016-07-01

    Label-free bio-sensing is a critical functionality underlying a variety of health- and security-related applications. Micro-/nano-photonic devices are well suited for this purpose and have emerged as promising platforms in recent years. Here we propose and demonstrate an approach that utilizes the optical spring effect in a high-Q coherent optomechanical oscillator to dramatically enhance the sensing resolution by orders of magnitude compared with conventional approaches, allowing us to detect single bovine serum albumin proteins with a molecular weight of 66 kDa at a signal-to-noise ratio of 16.8. The unique optical spring sensing approach opens up a distinctive avenue that not only enables biomolecule sensing and recognition at individual level, but is also of great promise for broad physical sensing applications that rely on sensitive detection of optical cavity resonance shift to probe external physical parameters.

  16. Minimum Length - Maximum Velocity

    CERN Document Server

    Panes, Boris

    2011-01-01

    We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example we can predict the ratio between the minimum lengths in space and time using the results from OPERA about superluminal neutrinos.

  17. Localization transition in the presence of cavity backaction

    Science.gov (United States)

    Rojan, Katharina; Kraus, Rebecca; Fogarty, Thomás; Habibian, Hessam; Minguzzi, Anna; Morigi, Giovanna

    2016-07-01

    We study the localization transition of an atom confined by an external optical lattice in a high-finesse cavity. The atom-cavity coupling yields an effective secondary lattice potential, whose wavelength is incommensurate with the periodicity of the optical lattice. The cavity lattice can induce localization of the atomic wave function analogously to the Aubry-André localization transition. Starting from the master equation for the cavity and the atom we perform a mapping of the system dynamics to a Hubbard Hamiltonian, which can be reduced to the Harper's Hamiltonian in appropriate limits. We evaluate the phase diagram for the atom's ground state and show that the transition between extended and localized wave function is controlled by the strength of the cavity nonlinearity, which determines the size of the localized region and the behavior of the Lyapunov exponent. The Lyapunov exponent, in particular, exhibits resonancelike behavior in correspondence with the optomechanical resonances. Finally we discuss the experimental feasibility of these predictions.

  18. Superconducting Accelerating Cavity Pressure Sensitivity Analysis and Stiffening

    Energy Technology Data Exchange (ETDEWEB)

    Rodnizki, J [Soreq NRC, Yavne, Israel; Ben Aliz, Y [Soreq NRC, Yavne, Israel; Grin, A [Soreq NRC, Yavne, Israel; Horvitz, Z [Soreq NRC, Yavne, Israel; Perry, A [Soreq NRC, Yavne, Israel; Weissman, L [Soreq NRC, Yavne, Israel; Davis, G Kirk [JLAB; Delayen, Jean R. [Old Dominion Universtiy

    2014-12-01

    The Soreq Applied Research Accelerator Facility (SARAF) design is based on a 40 MeV 5 mA light ions superconducting RF linac. Phase-I of SARAF delivers up to 2 mA CW proton beams in an energy range of 1.5 - 4.0 MeV. The maximum beam power that we have reached is 5.7 kW. Today, the main limiting factor to reach higher ion energy and beam power is related to the HWR sensitivity to the liquid helium coolant pressure fluctuations. The HWR sensitivity to helium pressure is about 60 Hz/mbar. The cavities had been designed, a decade ago, to be soft in order to enable tuning of their novel shape. However, the cavities turned out to be too soft. In this work we found that increasing the rigidity of the cavities in the vicinity of the external drift tubes may reduce the cavity sensitivity by a factor of three. A preliminary design to increase the cavity rigidity is presented.

  19. Cavity Microwave Searches for Cosmological Axions

    Energy Technology Data Exchange (ETDEWEB)

    Carosi, G; van Bibber, K

    2007-01-22

    This chapter will cover the search for dark matter axions based on microwave cavity experiments proposed by Pierre Sikivie. We will start with a brief overview of halo dark matter and the axion as a candidate. The principle of resonant conversion of axions in an external magnetic field will be described as well as practical considerations in optimizing the experiment as a signal-to-noise problem. A major focus of this chapter will be the two complementary strategies for ultra-low noise detection of the microwave photons--the 'photon-as-wave' approach (i.e. conventional heterojunction amplifiers and soon to be quantum-limited SQUID devices), and 'photon-as-particle' (i.e. Rydberg-atom single-quantum detection). Experimental results will be presented; these experiments have already reached well into the range of sensitivity to exclude plausible axion models, for limited ranges of mass. The section will conclude with a discussion of future plans and challenges for the microwave cavity experiment.

  20. New Developments of Broadband Cavity Enhanced Spectroscopic Techniques

    Science.gov (United States)

    Walsh, A.; Zhao, D.; Linnartz, H.; Ubachs, W.

    2013-06-01

    In recent years, cavity enhanced spectroscopic techniques, such as cavity ring-down spectroscopy (CRDS), cavity enhanced absorption spectroscopy (CEAS), and broadband cavity enhanced absorption spectroscopy (BBCEAS), have been widely employed as ultra-sensitive methods for the measurement of weak absorptions and in the real-time detection of trace species. In this contribution, we introduce two new cavity enhanced spectroscopic concepts: a) Optomechanical shutter modulated BBCEAS, a variant of BBCEAS capable of measuring optical absorption in pulsed systems with typically low duty cycles. In conventional BBCEAS applications, the latter substantially reduces the signal-to-noise ratio (S/N), consequently also reducing the detection sensitivity. To overcome this, we incorporate a fast optomechanical shutter as a time gate, modulating the detection scheme of BBCEAS and increasing the effective duty cycle reaches a value close to unity. This extends the applications of BBCEAS into pulsed samples and also in time-resolved studies. b) Cavity enhanced self-absorption spectroscopy (CESAS), a new spectroscopic concept capable of studying light emitting matter (plasma, flames, combustion samples) simultaneously in absorption and emission. In CESAS, a sample (plasma, flame or combustion source) is located in an optically stable cavity consisting of two high reflectivity mirrors, and here it acts both as light source and absorbing medium. A high detection sensitivity of weak absorption is reached without the need of an external light source, such as a laser or broadband lamp. The performance is illustrated by the first CESAS result on a supersonically expanding hydrocarbon plasma. We expect CESAS to become a generally applicable analytical tool for real time and in situ diagnostics. A. Walsh, D. Zhao, W. Ubachs, H. Linnartz, J. Phys. Chem. A, {dx.doi.org/10.1021/jp310392n}, in press, 2013. A. Walsh, D. Zhao, H. Linnartz Rev. Sci. Instrum. {84}(2), 021608 2013. A. Walsh, D. Zhao

  1. Telomere length and depression

    DEFF Research Database (Denmark)

    Wium-Andersen, Marie Kim; Ørsted, David Dynnes; Rode, Line

    2016-01-01

    BACKGROUND: Depression has been cross-sectionally associated with short telomeres as a measure of biological age. However, the direction and nature of the association is currently unclear. AIMS: We examined whether short telomere length is associated with depression cross-sectionally as well...... as prospectively and genetically. METHOD: Telomere length and three polymorphisms, TERT, TERC and OBFC1, were measured in 67 306 individuals aged 20-100 years from the Danish general population and associated with register-based attendance at hospital for depression and purchase of antidepressant medication....... RESULTS: Attendance at hospital for depression was associated with short telomere length cross-sectionally, but not prospectively. Further, purchase of antidepressant medication was not associated with short telomere length cross-sectionally or prospectively. Mean follow-up was 7.6 years (range 0...

  2. Myofilament length dependent activation

    Energy Technology Data Exchange (ETDEWEB)

    de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

    2010-05-25

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  3. Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers.

    Science.gov (United States)

    Mullavey, Adam J; Slagmolen, Bram J J; Miller, John; Evans, Matthew; Fritschel, Peter; Sigg, Daniel; Waldman, Sam J; Shaddock, Daniel A; McClelland, David E

    2012-01-02

    Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.

  4. Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers

    CERN Document Server

    Mullavey, Adam J; Miller, John; Evans, Matthew; Fritschel, Peter; Sigg, Daniel; Waldman, Sam J; Shaddock, Daniel A; McClelland, David E

    2011-01-01

    Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.

  5. A Characteristic Particle Length

    CERN Document Server

    Roberts, Mark D

    2015-01-01

    It is argued that there are characteristic intervals associated with any particle that can be derived without reference to the speed of light $c$. Such intervals are inferred from zeros of wavefunctions which are solutions to the Schr\\"odinger equation. The characteristic length is $\\ell=\\beta^2\\hbar^2/(8Gm^3)$, where $\\beta=3.8\\dots$; this length might lead to observational effects on objects the size of a virus.

  6. Continuous Pump Assisted Conditional Synthesis of Nonclassical States in a Dispersive Cavity QED

    Institute of Scientific and Technical Information of China (English)

    GUOJian-Hong

    2003-01-01

    The interaction of N identical atoms with both a quantized cavity field and an external classical pumping field with the fields being degenerate in frequency, is studied in the regime where the atoms and fields are highly detuned. This dispersive interaction can be used to generate coherent states for the cavity field. By preparing the injected atoms in a superposition of the bare atomic states, various types of Schroedinger-cat-like states may be generated.

  7. Equilibrium CO bond lengths

    Science.gov (United States)

    Demaison, Jean; Császár, Attila G.

    2012-09-01

    Based on a sample of 38 molecules, 47 accurate equilibrium CO bond lengths have been collected and analyzed. These ultimate experimental (reEX), semiexperimental (reSE), and Born-Oppenheimer (reBO) equilibrium structures are compared to reBO estimates from two lower-level techniques of electronic structure theory, MP2(FC)/cc-pVQZ and B3LYP/6-311+G(3df,2pd). A linear relationship is found between the best equilibrium bond lengths and their MP2 or B3LYP estimates. These (and similar) linear relationships permit to estimate the CO bond length with an accuracy of 0.002 Å within the full range of 1.10-1.43 Å, corresponding to single, double, and triple CO bonds, for a large number of molecules. The variation of the CO bond length is qualitatively explained using the Atoms in Molecules method. In particular, a nice correlation is found between the CO bond length and the bond critical point density and it appears that the CO bond is at the same time covalent and ionic. Conditions which permit the computation of an accurate ab initio Born-Oppenheimer equilibrium structure are discussed. In particular, the core-core and core-valence correlation is investigated and it is shown to roughly increase with the bond length.

  8. Slot-coupled CW standing wave accelerating cavity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shaoheng; Rimmer, Robert; Wang, Haipeng

    2017-05-16

    A slot-coupled CW standing wave multi-cell accelerating cavity. To achieve high efficiency graded beta acceleration, each cell in the multi-cell cavity may include different cell lengths. Alternatively, to achieve high efficiency with acceleration for particles with beta equal to 1, each cell in the multi-cell cavity may include the same cell design. Coupling between the cells is achieved with a plurality of axially aligned kidney-shaped slots on the wall between cells. The slot-coupling method makes the design very compact. The shape of the cell, including the slots and the cone, are optimized to maximize the power efficiency and minimize the peak power density on the surface. The slots are non-resonant, thereby enabling shorter slots and less power loss.

  9. [Fast and accurate extraction of ring-down time in cavity ring-down spectroscopy].

    Science.gov (United States)

    Wang, Dan; Hu, Ren-Zhi; Xie, Pin-Hua; Qin, Min; Ling, Liu-Yi; Duan, Jun

    2014-10-01

    Research is conducted to accurate and efficient algorithms for extracting ring-down time (r) in cavity ring-down spectroscopy (CRDS) which is used to measure NO3 radical in the atmosphere. Fast and accurate extraction of ring-down time guarantees more precise and higher speed of measurement. In this research, five kinds of commonly used algorithms are selected to extract ring-down time which respectively are fast Fourier transform (FFT) algorithm, discrete Fourier transform (DFT) algorithm, linear regression of the sum (LRS) algorithm, Levenberg-Marquardt (LM) algorithm and least squares (LS) algorithm. Simulated ring-down signals with various amplitude levels of white noises are fitted by using five kinds of the above-mentioned algorithms, and comparison and analysis is conducted to the fitting results of five kinds of algorithms from four respects: the vulnerability to noises, the accuracy and precision of the fitting, the speed of the fitting and preferable fitting ring-down signal waveform length The research results show that Levenberg-Marquardt algorithm and linear regression of the sum algorithm are able to provide more precise results and prove to have higher noises immunity, and by comparison, the fitting speed of Leven- berg-Marquardt algorithm turns out to be slower. In addition, by analysis of simulated ring-down signals, five to ten times of ring-down time is selected to be the best fitting waveform length because in this case, standard deviation of fitting results of five kinds of algorithms proves to be the minimum. External modulation diode laser and cavity which consists of two high reflectivity mirrors are used to construct a cavity ring-down spectroscopy detection system. According to our experimental conditions, in which the noise level is 0.2%, linear regression of the sum algorithm and Levenberg-Marquardt algorithm are selected to process experimental data. The experimental results show that the accuracy and precision of linear regression of

  10. Atom-assisted quadrature squeezing of a mechanical oscillator inside a dispersive cavity

    Science.gov (United States)

    Biswas, Asoka; Chauhan, Anil Kumar

    2016-05-01

    Measurement of position of a mesoscopic harmonic oscillator below standard quantum limit in cavity optomechanics has seen a growing interest in recent times. If the oscillator is suspended inside the cavity (with both the mirrors fixed) at a position where the cavity frequency becomes extremum (a membrane-in-the-middle setup), large squeezing can be achieved by conditional measurement of thermal photons; however the cavity decay degrades such squeezing. Here we propose an atom-cavity-oscillator hybrid scheme, in which the effect of cavity decay is eliminated via dispersive coupling of the cavity mode. The atom in Λ configuration is considered to be trapped on either side of the membrane inside the cavity. We show that a considerable amount of squeezing (far beyond the 3 dB limit) can be achieved that is not affected by spontaneous emission of the atom. The squeezing depends upon the initial preparation of the atomic states. Further, the external classical fields, that drive the atomic transition and the cavity mode, control the degree of squeezing and can also lead to a strong effective atom-oscillator coupling. Effect of thermal phonon bath on squeezing is studied in terms of the squeezing spectrum. The results are supported by the detailed analytical calculations.

  11. The ideal dimensions of a Halbach cylinder of finite length

    CERN Document Server

    Bjørk, R

    2014-01-01

    In this paper the smallest or optimal dimensions of a Halbach cylinder of a finite length for a given sample volume and desired flux density are determined using numerical modeling and parameter variation. A sample volume that is centered in and shaped as the Halbach cylinder bore but with a possible shorter length is considered. The external radius and the length of the Halbach cylinder with the smallest possible dimensions are found as a function of a desired internal radius, length of the sample volume and mean flux density. It is shown that the optimal ratio between the outer and inner radius of the Halbach cylinder does not depend on the length of the sample volume. Finally, the efficiency of a finite length Halbach cylinder is considered and compared with the case of a cylinder of infinite length. The most efficient dimensions for a Halbach cylinder are found and it is shown that the efficiency increases slowly with the length of the cylinder.

  12. Externally Verifiable Oblivious RAM

    Directory of Open Access Journals (Sweden)

    Gancher Joshua

    2017-04-01

    Full Text Available We present the idea of externally verifiable oblivious RAM (ORAM. Our goal is to allow a client and server carrying out an ORAM protocol to have disputes adjudicated by a third party, allowing for the enforcement of penalties against an unreliable or malicious server. We give a security definition that guarantees protection not only against a malicious server but also against a client making false accusations. We then give modifications of the Path ORAM [15] and Ring ORAM [9] protocols that meet this security definition. These protocols both have the same asymptotic runtimes as the semi-honest original versions and require the external verifier to be involved only when the client or server deviates from the protocol. Finally, we implement externally verified ORAM, along with an automated cryptocurrency contract to use as the external verifier.

  13. External Beam Therapy (EBT)

    Science.gov (United States)

    ... Esophageal Cancer Treatment Head and Neck Cancer Treatment Lung Cancer Treatment Prostate Cancer Treatment Brain Tumor Treatment Why is ... Radiation Oncology) Breast Cancer Treatment Esophageal Cancer Treatment Lung Cancer Treatment Images related to External Beam Therapy (EBT) Sponsored ...

  14. MALIGNANT EXTERNAL OTITIS

    OpenAIRE

    Massoud Moghaddam

    1993-01-01

    Two case reports of malignant external otitis in the elderly diabetics and their complications and management with regard to our experience at Amir Alam Hospital, Department of ENT will be discussed here.

  15. Checklists for external validity

    DEFF Research Database (Denmark)

    Dyrvig, Anne-Kirstine; Kidholm, Kristian; Gerke, Oke;

    2014-01-01

    RATIONALE, AIMS AND OBJECTIVES: The quality of the current literature on external validity varies considerably. An improved checklist with validated items on external validity would aid decision-makers in judging similarities among circumstances when transferring evidence from a study setting...... to an implementation setting. In this paper, currently available checklists on external validity are identified, assessed and used as a basis for proposing a new improved instrument. METHOD: A systematic literature review was carried out in Pubmed, Embase and Cinahl on English-language papers without time restrictions....... The retrieved checklist items were assessed for (i) the methodology used in primary literature, justifying inclusion of each item; and (ii) the number of times each item appeared in checklists. RESULTS: Fifteen papers were identified, presenting a total of 21 checklists for external validity, yielding a total...

  16. Observation of Stable Low Surface Resistance in Large-Grain Niobium SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Huang, Shichun [Institute of Modern Physics (IMP)/Chinese Academy of Sciences (CAS), Lanzhou (China)

    2016-05-01

    Low surface resistance, or high unloaded quality factor (Q0), superconducting radio frequency (SRF) cavities are being pursued actively nowadays as their application in large-scale CW SRF accelerators can save capital and operational cost in cryogenics. There are different options in realization of such cavities. One of them is the large-grain (LG) niobium cavity. In this contribution, we present new experimental results in evaluation of LG niobium cavities cooled down in the presence of an external magnetic field. High Q0 values are achieved even with an ambient magnetic field of up to 100 mG. More over, it is observed that these high Q0 values are super-robust against repeated quench, literally not affected at all after the cavity being deliberately quenched for hundreds of times in the presence of an ambient magnetic field of up to 200 mG.

  17. Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

    Energy Technology Data Exchange (ETDEWEB)

    Freemire, Ben [IIT, Chicago; Bowring, Daniel [Fermilab; Kochemirovskiy, Alexey [Chicago U.; Moretti, Alfred [Fermilab; Peterson, David [Fermilab; Tollestrup, Alvin [Fermilab; Torun, Yagmur [IIT, Chicago; Yonehara, Katsuya [Fermilab

    2016-06-01

    Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% alumina ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.

  18. Photon-Induced Spin-Orbit Coupling in Ultracold Atoms inside Optical Cavity

    Directory of Open Access Journals (Sweden)

    Lin Dong

    2015-05-01

    Full Text Available We consider an atom inside a ring cavity, where a plane-wave cavity field together with an external coherent laser beam induces a two-photon Raman transition between two hyperfine ground states of the atom. This cavity-assisted Raman transition induces effective coupling between atom’s internal degrees of freedom and its center-of-mass motion. In the meantime, atomic dynamics exerts a back-action to cavity photons. We investigate the properties of this system by adopting a mean-field and a full quantum approach, and show that the interplay between the atomic dynamics and the cavity field gives rise to intriguing nonlinear phenomena.

  19. The measurement of the transfer function for the Spoke cavities of C-ADS project

    CERN Document Server

    Huang, Xue-Fang; Wang, Guang-Wei; Wang, Shao-Zhe; Zheng, Xiang; Wang, Qun-Yao; Liu, Rong; Lin, Hai-Ying; Wang, Mu-Yuan

    2016-01-01

    The spoke cavities mounted in the China Accelerator Driven sub-critical System (C-ADS) have high quality factor(Q) and very small bandwidth, making them very sensitive to mechanical perturbations whether external or self-induced. The transfer function is used to characterize the response of the cavity eigen frequency to the perturbations. This paper describes a method to measure the transfer function of a spoke cavity. The measured Lorentz transfer function shows there are 206 Hz and 311 Hz mechanical eigenmodes in the cavities of C-ADS, and the measured piezo fast tuner transfer function shows there are 12 mechanical eigenmodes from 0 to 500 Hz. These results will play important roles when designing a corresponding cavity control system.

  20. An equivalent circuit model and power calculations for the APS SPX crab cavities.

    Energy Technology Data Exchange (ETDEWEB)

    Berenc, T. (Accelerator Systems Division (APS))

    2012-03-21

    An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarized TM110 dipole-mode cavity is developed and minimum radio-frequency (rf) generator requirements are calculated for the Advanced Photon Source (APS) short-pulse x-ray (SPX) superconducting rf (SRF) crab cavities. A beam-loaded circuit model for polarized TM110 mode crab cavities was derived. The single-cavity minimum steady-state required generator power has been determined for the APS SPX crab cavities for a storage ring current of 200mA DC current as a function of external Q for various vertical offsets including beam tilt and uncontrollable detuning. Calculations to aid machine protection considerations were given.

  1. Migration with fiscal externalities.

    Science.gov (United States)

    Hercowitz, Z; Pines, D

    1991-11-01

    "This paper analyses the distribution of a country's population among regions when migration involves fiscal externalities. The main question addressed is whether a decentralized decision making [by] regional governments can produce an optimal population distribution...or a centralized intervention is indispensable, as argued before in the literature.... It turns out that, while with costless mobility the fiscal externality is fully internalized by voluntary interregional transfers, with costly mobility, centrally coordinated transfers still remain indispensable for achieving the socially optimal allocation."

  2. Sen cycles and externalities

    OpenAIRE

    Piggins, Ashley; Salerno, Gillian

    2016-01-01

    It has long been understood that externalities of some kind are responsible for Sen’s (1970) theorem on the impossibility of a Paretian liberal. However, Saari and Petron (2006) show that for any social preference cycle generated by combining the weak Pareto principle and individual decisiveness, every decisive individual must suffer at least one strong negative externality. We show that this fundamental result only holds when individual preferences are strict. Building on their contribution,...

  3. High reflected cubic cavity as long path absorption cell for infrared gas sensing

    Science.gov (United States)

    Yu, Jia; Gao, Qiang; Zhang, Zhiguo

    2014-10-01

    One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

  4. Vibration insensitive optical ring cavity

    Institute of Scientific and Technical Information of China (English)

    Miao Jin; Jiang Yan-Yi; Fang Su; Bi Zhi-Yi; Ma Long-Sheng

    2009-01-01

    The mounting configuration of an optical ring cavity is optimized for vibration insensitivity by finite element analysis. A minimum response to vertical accelerations is found by simulations made for different supporting positions.

  5. Niobium LEP 2 accelerating cavities

    CERN Multimedia

    An accelerating cavity from LEP. This could be cut open to show the layer of niobium on the inside. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment. These challenging requirements pushed European industry to new achievements. 256 of these cavities were used in an upgrade of the LEP accelerator to double the energy of the particle beams.

  6. SRF Cavity Fabrication and Materials

    CERN Document Server

    Singer, W

    2014-07-17

    The technological and metallurgical requirements of material for highgradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10μg/g. The hydrogen content should be kept below 2μg/g to prevent degradation of the Q-value under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Defects may be detected by quality control methods such as eddy current scanning and identified by a number of special methods. Conventional and alternative cavity fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and Electron-Beam Welding (EBW). The welding of half-cells is a delicate...

  7. Development of Fundamental Power Coupler for C-ADS Superconducting Elliptical cavities

    CERN Document Server

    Gu, Kui-Xiang; Pan, Wei-Min; Huang, Tong-Ming; Ma, Qiang; Meng, Fan-Bo

    2016-01-01

    5-cell elliptical cavities are chosen for the main linac of China Accelerator Driven sub-critical System in the medium energy section. Each cavity is driven by one fundamental power coupler delivering RF power up to 150 kW. A single window, coaxial type coupler satisfying high power requirements, class 10 clean room assembly with cavity and low heat load simultaneously was designed. This paper gives the details of RF design, external Q calculation and thermal analysis as well as multipacting simulations of the coupler.

  8. An all-optical buffer based on temporal cavity solitons operating at 10 Gb/s

    CERN Document Server

    Jang, Jae K; Schröder, Jochen; Eggleton, Benjamin J; Murdoch, Stuart G; Coen, Stéphane

    2016-01-01

    We demonstrate the operation of an all-optical buffer based on temporal cavity solitons stored in a nonlinear passive fiber ring resonator. Unwanted acoustic interactions between neighboring solitons are suppressed by modulating the phase of the external laser driving the cavity. A new locking scheme is presented that allows the buffer to operate with an arbitrarily large number of cavity solitons in the loop. Experimentally, we are able to demonstrate the storage of 4536 bits of data, written all-optically into the fiber ring at 10 Gb/s, for 1 minute.

  9. Longitudinal and transversal flow over a cavity containing a second immiscible fluid

    CERN Document Server

    Schönecker, Clarissa

    2012-01-01

    An analytical solution for the flow field of a shear flow over a rectangular cavity containing a second immiscible fluid is derived. While flow of a single-phase fluid over a cavity is a standard case investigated in fluid dynamics, flow over a cavity which is filled with a second immiscible fluid, has received little attention. The flow filed inside the cavity is considered to define a boundary condition for the outer flow which takes the form of a Navier slip condition with locally varying slip length. The slip-length function is determined from the related problem of lid-driven cavity flow. Based on the Stokes equations and complex analysis it is then possible to derive a closed analytical expression for the flow field over the cavity for both the transversal and the longitudinal case. The result is a comparatively simple function, which displays the dependence of the flow field on the cavity geometry and the medium filling the cavity. The analytically computed flow field agrees well with results obtained ...

  10. Effective emissivity of a blackbody cavity formed by two coaxial tubes.

    Science.gov (United States)

    Mei, Guohui; Zhang, Jiu; Zhao, Shumao; Xie, Zhi

    2014-04-10

    A blackbody cavity is developed for continuously measuring the temperature of molten steel, which consists of a cylindrical outer tube with a flat bottom, a coaxial inner tube, and an aperture diaphragm. The ray-tracing approach based on the Monte Carlo method was applied to calculate the effective emissivity for the isothermal cavity with the diffuse walls. And the dependences of the effective emissivity on the inner tube relative length were calculated for various inner tube radii, outer tube lengths, and wall emissivities. Results indicate that the effective emissivity usually has a maximum corresponding to the inner tube relative length, which can be explained by the impact of the inner tube relative length on the probability of the rays absorbed after two reflections. Thus, these results are helpful to the optimal design of the blackbody cavity.

  11. Sterility of the uterine cavity

    DEFF Research Database (Denmark)

    Møller, Birger R.; Kristiansen, Frank V.; Thorsen, Poul

    1995-01-01

    from the same sites. Nearly a quarter of all the patients harbored one or more microorganisms in the uterus, mostly Gardnerella vaginalis, Enterobacter and Streptococcus agalactiae. We found that in a significant number of cases, the uterine cavity is colonized with potentially pathogenic organisms...... which may play a causative role in endometritis. The results indicate that inflammation of the uterine cavity should be evaluated by hysteroscopic examination before hysterectomy is undertaken in patients with persistent irregular vaginal bleeding. Udgivelsesdato: 1995-Mar...

  12. LEP Radio Frequency Copper Cavity

    CERN Multimedia

    The pulse of a particle accelerator. 128 of these radio frequency cavities were positioned around CERN's 27-kilometre LEP ring to accelerate electrons and positrons. The acceleration was produced by microwave electric oscillations at 352 MHz. The electrons and positrons were grouped into bunches, like beads on a string, and the copper sphere at the top stored the microwave energy between the passage of individual bunches. This made for valuable energy savings as it reduced the heat generated in the cavity.

  13. Imaging of the oral cavity.

    Science.gov (United States)

    Meesa, Indu Rekha; Srinivasan, Ashok

    2015-01-01

    The oral cavity is a challenging area in head and neck imaging because of its complex anatomy and the numerous pathophysiologies that involve its contents. This challenge is further compounded by the ubiquitous artifacts that arise from the dental amalgam, which compromise image quality. In this article, the anatomy of the oral cavity is discussed in brief, followed by a description of the imaging technique and some common pathologic abnormalities.

  14. Active Control of Open Cavities

    Science.gov (United States)

    UKeiley, Lawrence

    2010-01-01

    Open loop edge blowing was demonstrated as an effective method for reducing the broad band and tonal components of the fluctuating surface pressure in open cavities. Closed loop has been successfully applied to low Mach number open cavities. Need to push actuators that are viable for closed loop control in bandwidth and output. Need a better understanding of the effects of control on the flow through detailed measurements so better actuation strategies can be developed.

  15. Pressure and kinetic energy transport across the cavity mouth in resonating cavities.

    Science.gov (United States)

    Bailey, Peter Roger; Abbá, Antonella; Tordella, Daniela

    2013-01-01

    Basic properties of the incompressible fluid motion in a rectangular cavity located along one wall of a plane channel are considered. For Mach numbers of the order of 1×10(-3) and using the incompressible formulation, we look for observable properties that can be associated with acoustic emission, which is normally observed in this kind of flow beyond a critical value of Reynolds number. The focus is put on the energy dynamics, in particular on the accumulation of energy in the cavity which takes place in the form of pressure and kinetic energy. By increasing the external forcing, we observe that the pressure flow into the cavity increases very rapidly, then peaks. However, the flow of kinetic energy, which is many orders of magnitude lower than that of the pressure, slowly but continuously grows. This leads to the pressure-kinetic energy flows ratio reaching an asymptotic state around the value 1000 for the channel bulk speed Reynolds number. It is interesting to note that beyond this threshold when the channel flow is highly unsteady-a sort of coarse turbulent flow-a sequence of high and low pressure spots is seen to depart from the downward cavity step in the statistically averaged field. The set of spots forms a steady spatial structure, a sort of damped standing wave stretching along the spanwise direction. The line joining the centers of the spots has an inclination similar to the normal to the fronts of density or pressure waves, which are observed to propagate from the downstream cavity edge in compressible cavity flows (at Mach numbers of 1×10(2) to 1×10(3), larger than those considered here). The wavelength of the standing wave is of the order of 1/8 the cavity depth and observed at the channel bulk Reynolds number, Re~2900. In this condition, the measure of the maximum pressure differences in the cavity field shows values of the order of 1×10(-1) Pa. We interpret the presence of this sort of wave as the fingerprint of the noise emission spots which

  16. Spontaneous external gallbladder perforation

    Energy Technology Data Exchange (ETDEWEB)

    Noeldge, G.; Wimmer, B.; Kirchner, R.

    1981-04-01

    Spontaneous perforation of the gallbladder is one complication of cholelithiasis. There is a greater occurence of free perforation in the peritoneal cavity with bilary pertonitis, followed by the perforation into the stomach, small intestine and colon. A single case of the nowadays rare spontaneous perforation in and through the abdominal wall will be reported. Spontaneous gallbladder perforation appears nearly asymptomatic in its clinical course because of absent biliary peritonitis.

  17. TESLA superconducting RF cavity development

    Energy Technology Data Exchange (ETDEWEB)

    Koepke, K. [Fermi National Accelerator Lab., Batavia, IL (United States); TESLA Collaboration

    1995-05-01

    The TESLA collaboration has made steady progress since its first official meeting at Cornell in 1990. The infrastructure necessary to assemble and test superconducting rf cavities has been installed at the TESLA Test Facility (TTF) at DESY. 5-cell, 1.3 GHz cavities have been fabricated and have reached accelerating fields of 25 MV/m. Full sized 9-cell copper cavities of TESLA geometry have been measured to verify the higher order modes present and to evaluate HOM coupling designs. The design of the TESLA 9-cell cavity has been finalized and industry has started delivery. Two prototype 9-cell niobium cavities in their first tests have reached accelerating fields of 10 MV/m and 15 MV/m in a vertical dewar after high peak power (HPP) conditioning. The first 12 m TESLA cryomodule that will house 8 9-cell cavities is scheduled to be delivered in Spring 1995. A design report for the TTF is in progress. The TTF test linac is scheduled to be commissioned in 1996/1997. (orig.).

  18. 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.

  19. 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.

  20. Design of an L-band normally conducting RF gun cavity for high peak and average RF power

    Science.gov (United States)

    Paramonov, V.; Philipp, S.; Rybakov, I.; Skassyrskaya, A.; Stephan, F.

    2017-05-01

    To provide high quality electron bunches for linear accelerators used in free electron lasers and particle colliders, RF gun cavities operate with extreme electric fields, resulting in a high pulsed RF power. The main L-band superconducting linacs of such facilities also require a long RF pulse length, resulting in a high average dissipated RF power in the gun cavity. The newly developed cavity based on the proven advantages of the existing DESY RF gun cavities, underwent significant changes. The shape of the cells is optimized to reduce the maximal surface electric field and RF loss power. Furthermore, the cavity is equipped with an RF probe to measure the field amplitude and phase. The elaborated cooling circuit design results in a lower temperature rise on the cavity RF surface and permits higher dissipated RF power. The paper presents the main solutions and results of the cavity design.

  1. 流场中填充吸声材料夹层板结构与声腔的耦合特性%Performance of Vibro-acoustic Coupling of the Sandwich Structure with Absorptive Material and Cavity in External Convected Fluids

    Institute of Scientific and Technical Information of China (English)

    宁少武; 史治宇; 李晓松

    2016-01-01

    采用等效流体模拟吸声材料,建立外部流场作用下填充吸声材料夹层板结构与封闭空间声场的声振耦合模型,应用波动分析方法研究结构的声透射性能,分析入射声波入射角和方位角、流场流速和流向、夹层板几何尺寸和声腔深度等参数对填充吸声材料夹层板结构声振耦合特性的影响。计算分析表明吸声材料提高了结构的隔声性能;结构的隔声性能随着面板厚度和夹层厚度的增加而提高,且“板-等效流体-板”共振频率向低频移动;随着入射角、方位角、马赫数和空腔深度的变化改变了结构的隔声性能,驻波衰减频率和驻波共振频率随入射角和方位角的增大向高频移动,随空腔深度的增加向低频移动,顺流入射时随马赫数的增加向低频移动,而逆流入射时则移向高频。%An equivalent fluid model is employed to characterize the absorption of sound in the sound absorptive material. A vibro-acoustic coupling model of the sandwich structure with absorptive material and cavity in convected fluids is developed. The performance of sound transmission is obtained by employing the wave approach. The effects factors of vibro-acoustic responses which were researched include incident elevation angles and azimuch angles, the velocity and direction of convected flow, the geometrical dimensions of the double panels and the depth of the cavity. Studies have shown that the insulation of an structure with absorption than air is improved; sound transmission loss increases with the thickness of the up and low panel and the gap increase and the panel- equivalent fluid-panel resonance shift to lower frequencies; the parametric variation of incident elevation angles and azimuch angles, Mach number and the depth of the cavity changed the performance of sound Transmission of the structure; standing-wave attenuation frequency and standing-wave resonance frequency shift to higher

  2. Laser frequency stabilisation via quasi-monolithic, unequal arm-length Mach-Zehnder interferometer with balanced DC readout

    CERN Document Server

    Gerberding, Oliver; Mehmet, Moritz; Danzmann, Karsten; Heinzel, Gerhard

    2016-01-01

    Low frequency high precision laser interferometry is subject to excess laser frequency noise coupling via arm-length differences which is commonly mitigated by locking the frequency to a stable reference system. This is crucial to achieve picometer level sensitivities in the 0.1 mHz to 1 Hz regime, where laser frequency noise is usually high and couples into the measurement phase via arm-length mismatches in the interferometers. Here we describe the results achieved by frequency stabilising an external cavity diode laser to a quasi-monolithic unequal arm-length Mach-Zehnder interferometer read out at mid-fringe via balanced detection. This stabilisation scheme has been found to be an elegant solution combining a minimal number of optical components, no additional laser modulations and relatively low frequency noise levels. The Mach-Zehnder interferometer has been designed and constructed to minimise the influence of thermal couplings and to reduce undesired stray light using the optical simulation tool IfoCAD...

  3. Polishing Difficult-To-Reach Cavities

    Science.gov (United States)

    Malinzak, R. Michael; Booth, Gary N.

    1990-01-01

    Springy abrasive tool used to finish surfaces of narrow cavities made by electrical-discharge machining. Robot arm moves vibrator around perimeters of cavities, polishing walls of cavities as it does so. Tool needed because such cavities inaccessible or at least difficult to reach with most surface-finishing tools.

  4. Simultaneous measurement of temperature and refractive index using focused ion beam milled Fabry-Perot cavities in optical fiber micro-tips.

    Science.gov (United States)

    André, Ricardo M; Warren-Smith, Stephen C; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Zibaii, M I; Latifi, H; Marques, Manuel B; Bartelt, Hartmut; Frazão, Orlando

    2016-06-27

    Optical fiber micro-tips are promising devices for sensing applications in small volume and difficult to access locations, such as biological and biomedical settings. The tapered fiber tips are prepared by dynamic chemical etching, reducing the size from 125 μm to just a few μm. Focused ion beam milling is then used to create cavity structures on the tapered fiber tips. Two different Fabry-Perot micro-cavities have been prepared and characterized: a solid silica cavity created by milling two thin slots and a gap cavity. A third multi-cavity structure is fabricated by combining the concepts of solid silica cavity and gap cavity. This micro-tip structure is analyzed using a fast Fourier transform method to demultiplex the signals of each cavity. Simultaneous measurement of temperature and external refractive index is then demonstrated, presenting sensitivities of - 15.8 pm/K and -1316 nm/RIU, respectively.

  5. Evaluation of cavity wall adaptation of bulk esthetic materials to restore class II cavities in primary molars.

    Science.gov (United States)

    Gaintantzopoulou, Maria D; Gopinath, Vellore K; Zinelis, Spiros

    2017-05-01

    The purpose of the study was to assess the cavity wall adaptation and gap formation of a bulk fill composite resin and reinforced conventional glass ionomer cement and a resin-modified glass ionomer cement in class II restorations on primary molars. Standardized class II slot cavity preparations were prepared in exfoliating primary molars. Teeth were restored with one of the three tested materials (n = 10): SonicFill bulk fill composite resin (SF), EQUIA Fil conventional reinforced glass ionomer cement (EQF), and Vitremer resin-reinforced glass ionomer cement (VT). Cavity wall adaptation of the restorations was investigated by computerized X-ray micro-tomography and the percentage void volume fraction (%VVF) was calculated. Same specimens were sectioned and the interfaces were evaluated by reflection optical microscopy to measure the percentage linear length (%LD) of the interfacial gaps. Samples were further evaluated by environmental scanning electron microscopy (ESEM). EQF and SF showed significantly lower %VVF and %LD values than VT (p materials showed good cavity wall adaptation. Short operating time and good cavity wall adaptation are advantages of the materials in restorative and pediatric dentistry, especially while working on children with limited attention span.

  6. Environmental external effects from wind power based on the EU ExternE methodology

    DEFF Research Database (Denmark)

    Ibsen, Liselotte Schleisner; Nielsen, Per Sieverts

    1998-01-01

    The European Commission has launched a major study project, ExternE, to develop a methodology to quantify externalities. A “National Implementation Phase”, was started under the Joule II programme with the purpose of implementing the ExternE methodology in all member states. The main objective...

  7. Theoretical analysis of transmission characteristics for all fiber, multi-cavity Fabry-Perot filters based on fiber Bragg gratings

    Institute of Scientific and Technical Information of China (English)

    XU OU; LU ShaoHua; DONG XiaoWei; LI Bin; NING TiGang; JIAN ShuiSheng

    2008-01-01

    The characteristics of transmission spectra for the all fiber, multi-cavity FabryPerot (FP) configuration based on fiber Bragg gratings (FBG) are theoretically analyzed and modeled. The general transmission matrix function for the structure with any number of cavities is derived, and explicit expression of the power trans-mission coefficient for symmetrical two-cavity FP is presented. The general condi-tions for flat-top single resonant peak at the central wavelength in FBG stop band are derived and verified in the numerical simulation section. The transmission peaks of single-cavity and two-cavity FP structures are compared and discussed, and results show that compared to the single-cavity FP, flatness of the top and steepness at the edge of transmission peak can be improved by introducing one more cavity. The resonant transmission peak properties of two-cavity structure are investigated in detail for various values of cavity length and FBGs with different reflection characteristics, and the design guidelines for transmission-type filters are presented. The results show that the steepness of peak slope can be improved by increase of FBG reflectivities, and these kinds of filters can be used as nar-row-band single-channel selectors and multi-channel wavelength de-multiplexing by properly choosing the length of cavities and reflectivities of FBGs.

  8. Three dimensional color Doppler transvaginal ultrasound morphologic features of uterine septum and residual cavity in women with reproductive failure

    Directory of Open Access Journals (Sweden)

    Somayya M. Sadek

    2015-03-01

    Conclusion: 3D US plays a valuable role in the assessment of morphologic characters of uterine septum and the calculation of the residual cavity volume. Septal length followed by width is a significant variable that affects reproductive outcome.

  9. Single atoms on demand for cavity QED experiments

    Energy Technology Data Exchange (ETDEWEB)

    Dotsenko, I.

    2007-09-06

    cavity and their coupling to the cavity mode. The strong coupling manifests itself in a strong reduction of the cavity transmission probed by a weak external laser. The atoms remain trapped and coupled to the cavity mode for several seconds until we move them out of the cavity for final analysis of their number and position. (orig.)

  10. Mappability and Read Length

    Directory of Open Access Journals (Sweden)

    Wentian eLi

    2014-11-01

    Full Text Available Power-law distributions are the main functional form forthe distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size offragments and reads may prevent an unique alignment of repeatsequences to the reference sequence. Repeats in the human genome canbe as long as $10^4$ bases, or $10^5-10^6$ bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of $10^3$ bases.With the read length of exactly 1000 bases, slightly more than 1% of theassembled genome, and slightly less than 1% of the 1kbreads, are unmappable, excluding the unassembled portion of the humangenome (8% in GRCh37. The slow decay (long tail ofthe power-law function implies a diminishing return in convertingunmappable regions/reads to become mappable with the increase of theread length, with the understanding that increasing read length willalways move towards the direction of 100% mappability.

  11. Telomere Length and Mortality

    DEFF Research Database (Denmark)

    Kimura, Masayuki; Hjelmborg, Jacob V B; Gardner, Jeffrey P

    2008-01-01

    telomeres predicted the death of the first co-twin better than the mTRFL did (mTRFL: 0.56, 95% confidence interval (CI): 0.49, 0.63; mTRFL(50): 0.59, 95% CI: 0.52, 0.66; mTRFL(25): 0.59, 95% CI: 0.52, 0.66; MTRFL: 0.60, 95% CI: 0.53, 0.67). The telomere-mortality association was stronger in years 3-4 than......Leukocyte telomere length, representing the mean length of all telomeres in leukocytes, is ostensibly a bioindicator of human aging. The authors hypothesized that shorter telomeres might forecast imminent mortality in elderly people better than leukocyte telomere length. They performed mortality...... analysis in 548 same-sex Danish twins (274 pairs) aged 73-94 years, of whom 204 pairs experienced the death of one or both co-twins during 9-10 years of follow-up (1997-2007). From the terminal restriction fragment length (TRFL) distribution, the authors obtained the mean TRFL (mTRFL) and the mean values...

  12. Fabrication of elliptical SRF cavities

    Science.gov (United States)

    Singer, W.

    2017-03-01

    The technological and metallurgical requirements of material for high-gradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10 μg g-1. The hydrogen content should be kept below 2 μg g-1 to prevent degradation of the quality factor (Q-value) under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Traditional and alternative cavity mechanical fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and electron beam welding. The welding of half-cells is a delicate procedure, requiring intermediate cleaning steps and a careful choice of weld parameters to achieve full penetration of the joints. A challenge for a welded construction is the tight mechanical and electrical tolerances. These can be maintained by a combination of mechanical and radio-frequency measurements on half-cells and by careful tracking of weld shrinkage. The main aspects of quality assurance and quality management are mentioned. The experiences of 800 cavities produced for the European XFEL are presented. Another cavity fabrication approach is slicing discs from the ingot and producing cavities by deep drawing and electron beam welding. Accelerating gradients at the level of 35-45 MV m-1 can be achieved by applying electrochemical polishing treatment. The single-crystal option (grain boundary free) is discussed. It seems that in this case, high performance can be achieved by a simplified treatment procedure. Fabrication of the elliptical resonators from a seamless pipe as an alternative is briefly described. This technology has yielded good

  13. 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.

  14. Externality or sustainability economics?

    Energy Technology Data Exchange (ETDEWEB)

    Bergh, Jeroen C.J.M. van den [ICREA, Barcelona (Spain); Department of Economics and Economic History and Institute for Environmental Science and Technology, Universitat Autonoma de Barcelona (Spain)

    2010-09-15

    In an effort to develop 'sustainability economics' Baumgaertner and Quaas (2010) neglect the central concept of environmental economics-'environmental externality'. This note proposes a possible connection between the concepts of environmental externality and sustainability. In addition, attention is asked for other aspects of 'sustainability economics', namely the distinction weak/strong sustainability, spatial sustainability and sustainable trade, distinctive sustainability policy, and the ideas of early 'sustainability economists'. I argue that both sustainability and externalities reflect a systems perspective and propose that effective sustainability solutions require that more attention is given to system feedbacks, notably other-regarding preferences and social interactions, and energy and environmental rebound. The case of climate change and policy is used to illustrate particular statements. As a conclusion, a list of 20 insights and suggestions for research is offered. (author)

  15. Investigation of Multiscale Non-equilibrium Flow Dynamics Under External Force Field

    CERN Document Server

    Xiao, Tianbai

    2016-01-01

    The multiple scale non-equilibrium gaseous flow behavior under external force field is investigated. Both theoretical analysis based on the kinetic model equation and numerical study are presented to demonstrate the dynamic effect of external force on the flow evolution, especially on the non-equilibrium heat flux. The current numerical experiment is based on the well-balanced unified gas-kinetic scheme (UGKS), which presents accurate solutions in the whole flow regime from the continuum Navier-Stokes solution to the transition and free molecular ones. The heat conduction in the non-equilibrium regime due to the external forcing term is quantitatively investigated. In the lid-driven cavity flow study, due to the external force field the density distribution inside cavity gets stratified and a multiscale non-equilibrium flow transport appears in a single gas dynamic system. With the increment of external forcing term, the flow topological structure changes dramatically, and the temperature gradient, shearing s...

  16. Nonradiating and radiating modes excited by quantum emitters in open epsilon-near-zero cavities.

    Science.gov (United States)

    Liberal, Iñigo; Engheta, Nader

    2016-10-01

    Controlling the emission and interaction properties of quantum emitters (QEs) embedded within an optical cavity is a key technique in engineering light-matter interactions at the nanoscale, as well as in the development of quantum information processing. State-of-the-art optical cavities are based on high quality factor photonic crystals and dielectric resonators. However, wealthier responses might be attainable with cavities carved in more exotic materials. We theoretically investigate the emission and interaction properties of QEs embedded in open epsilon-near-zero (ENZ) cavities. Using analytical methods and numerical simulations, we demonstrate that open ENZ cavities present the unique property of supporting nonradiating modes independently of the geometry of the external boundary of the cavity (shape, size, topology, etc.). Moreover, the possibility of switching between radiating and nonradiating modes enables a dynamic control of the emission by, and the interaction between, QEs. These phenomena provide unprecedented degrees of freedom in controlling and trapping fields within optical cavities, as well as in the design of cavity opto- and acoustomechanical systems.

  17. Study of Nb-Cu 1.3 GHz SRF cavity resonators for future particle accelerators

    CERN Document Server

    Amelin, Kirill

    2017-01-01

    Niobium-coated superconducting radio-frequency cavities have a number of advantages over cavities made from bulk niobium. Cavities coated with high-power impulse magnetron sputtering are tested at CERN in order to optimize the coating and study the Q-slope that limits the performance. To accurately measure the quality factor as a function of accelerating field, it is important to have good matching between an input antenna and a cavity impedance. To improve the matching, a variable coupler that changes the length of the antenna can be used. We have shown that the Q-factor of the input antenna can be changed between $10^7-10^{11}$ by moving the antenna, which should allow to achieve critical coupling with a cavity. This technology could be used in future measurements, so that reflections are always minimized.

  18. On the electrostatic equilibrium of charges and cavities in a conductor

    CERN Document Server

    Pathak, Aritro

    2016-01-01

    We consider a charged conductor of arbitrary shape, in electrostatic equilibrium, with one or more cavities inside it, and with fixed charges placed outside the conductors and inside the cavities. The field inside a particular cavity is then only due to charges within that cavity itself and to the surface charge induced on the surface of the same cavity. A similar statement holds for the exterior of the conductor. Although this is an elementary property of conductors, it is not a trivial statement, as explained in this article. Undergraduate texts in electrodynamics do not discuss at length or provide a complete argument for an important problem such as this. Two simple and complete proofs are provided in this note with the help of the standard electrostatic uniqueness theorems.

  19. Beam-beam effects under the influence of external noise

    CERN Document Server

    Ohmi, K.

    2014-01-01

    Fast external noise, which gives fluctuation into the beam orbit, is discussed in connection with beam-beam effects. Phase noise from crab cavities and detection devices (position monitor) and kicker noise from the bunch by bunch feedback system are the sources. Beam-beam collisions with fast orbit fluctuations with turn by turn or multi-turn correlations, cause emittance growth and luminosity degradation. We discuss the tolerance of the noise amplitude for LHC and HL-LHC.

  20. Capture and release of a conditional state of a cavity QED system by quantum feedback.

    Science.gov (United States)

    Smith, W P; Reiner, J E; Orozco, L A; Kuhr, S; Wiseman, H M

    2002-09-23

    Detection of a single photon escaping an optical cavity QED system prepares a nonclassical state of the electromagnetic field. The evolution of the state can be modified by changing the drive of the cavity. For the appropriate feedback, the conditional state can be captured (stabilized) and then released. This is observed by a conditional intensity measurement that shows suppression of vacuum Rabi oscillations for the length of the feedback pulse and their subsequent return.

  1. Design of radio-frequency cavities and Tera-Hertz electron injectors for advanced applications

    Energy Technology Data Exchange (ETDEWEB)

    Seyedfakhari, Seyedmoein

    2016-06-15

    Design of three accelerator components including a buncher cavity for REGAE, a normal conducting cavity for arrival time stabilization at FLASH and ultra-fast guns for the AXSIS project is presented in this thesis. Using RF cavities caused a revolution in accelerators and made it possible to generate high energy particle beams. In advanced accelerators, cavities are not only used to increase the particle energy but they are also widely used to improve the beam quality and additionally for beam diagnostic purposes. In the present dissertation, such applications are discussed. First, design of a buncher cavity which compresses the bunch at the REGAE facility is presented. The design pursues improving the mode separation of the cavity. The simulation result illustrates that the difference between the operating mode and its adjacent mode has been increased from 2 MHz for the existing cavity to 9.5 MHz for the new design. In the second part, a normal conducting cavity is discussed, which will be used to regulate the arrival time ofthe bunches at FLASH and at the European XFEL. The designed cavity is able to correct the arrival time jitter of ± 150 fs in order to provide femtosecond precision synchronization between the electron beam and the external laser pulses. Thermal, wakefield and multipacting simulations have also been performed for the designed cavity in order to evaluate its operation efficiency. In advanced accelerators however RF cavities should be replaced by novel structures to accelerate the particles in shorter distances using higher operating frequency. To this end, ultra-fast guns are designed which will be discussed in the last part of this work. The designed guns accelerate the electrons from their rest mass up to 2 MeV using a single cycle THz signal with a total energy of 2 mJ.

  2. Flow through the nasal cavity of the spiny dogfish, Squalus acanthias

    Science.gov (United States)

    Timm-Davis, L. L.; Fish, F. E.

    2015-12-01

    The nasal cavity of spiny dogfish is a blind capsule with no internal connection to the oral cavity. Water is envisioned to flow through the cavity in a smooth, continuous flow pattern; however, this assumption is based on previous descriptions of the morphology of the olfactory cavity. No experimentation on the flow through the internal nasal cavity has been reported. Morphology of the head of the spiny dogfish ( Squalus acanthias) does not suggest a close external connection between the oral and nasal systems. However, dye visualization showed that there was flow through the nasal apparatus and from the excurrent nostril to the mouth when respiratory flows were simulated. The hydrodynamic flow through the nasal cavity was observed from flow tank experiments. The dorsum of the nasal cavity of shark heads from dead animals was exposed by dissection and a glass plate was glued over of the exposed cavity. When the head was placed in a flow, dye was observed to be drawn passively into the cavity showing a complex, three-dimensional hydrodynamic flow. Dye entered the incurrent nostril, flowed through the nasal lamellae, crossed over and under the nasal valve, and circulated around the nasal valve before exiting the excurrent nostril. When the nasal valve was removed, the dye became stagnant and back flowed out through the incurrent nostril. The single nasal valve has a hydrodynamic function that organizes a coherent flow of water through the cavity without disruption. The results suggest that the morphology of the nasal apparatus in concert with respiratory flow and ambient flows from active swimming can be used to draw water through the olfactory cavity of the shark.

  3. RRR Characteristics for SRF Cavities

    CERN Document Server

    Jung, Yoochul; Joung, Mijoung

    2015-01-01

    The first heavy ion accelerator is being constructed by the rare isotope science project (RISP) launched by the Institute of Basic Science (IBS) in South Korea. Four different types of superconducting cavities were designed, and prototypes were fabricated such as a quarter wave resonator (QWR), a half wave resonator (HWR) and a single spoke resonator (SSR). One of the critical factors determining performances of the superconducting cavities is a residual resistance ratio (RRR). The RRR values essentially represent how much niobium is pure and how fast niobium can transmit heat as well. In general, the RRR degrades during electron beam welding due to the impurity incorporation. Thus it is important to maintain RRR above a certain value at which a niobium cavity shows target performance. In this study, RRR degradation related with electron beam welding conditions, for example, welding power, welding speed, and vacuum level will be discussed.

  4. Stochastic Control - External Models

    DEFF Research Database (Denmark)

    Poulsen, Niels Kjølstad

    2005-01-01

    This note is devoted to control of stochastic systems described in discrete time. We are concerned with external descriptions or transfer function model, where we have a dynamic model for the input output relation only (i.e.. no direct internal information). The methods are based on LTI systems...

  5. Productivity Change and Externalities

    DEFF Research Database (Denmark)

    Kravtsova, Victoria

    2014-01-01

    firms and the economy as a whole. The approach used in the current research accounts for different internal as well as external factors that individual firms face and evaluates the effect on changes in productivity, technology as well as the efficiency of domestic firms. The empirical analysis focuses...... change in different types of firms and sectors of the economy...

  6. Multiple external root resorption.

    Science.gov (United States)

    Yusof, W Z; Ghazali, M N

    1989-04-01

    Presented is an unusual case of multiple external root resorption. Although the cause of this resorption was not determined, several possibilities are presented. Trauma from occlusion, periodontal and pulpal inflammation, and resorption of idiopathic origin are all discussed as possible causes.

  7. Relativistic length agony continued

    Directory of Open Access Journals (Sweden)

    Redžić D.V.

    2014-01-01

    Full Text Available We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redžić 2008b, we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the ‘pole in a barn’ paradox. [Projekat Ministarstva nauke Republike Srbije, br. 171028

  8. Ground Wood Fiber Length Distributions

    OpenAIRE

    Lauri Ilmari Salminen; Sari Liukkonen; Alava, Mikko J.

    2014-01-01

    This study considers ground wood fiber length distributions arising from pilot grindings. The empirical fiber length distributions appear to be independent of wood fiber length as well as feeding velocity. In terms of mathematics the fiber fragment distributions of ground wood pulp combine an exponential distribution for high-length fragments and a power-law distribution for smaller lengths. This implies that the fiber length distribution is influenced by the stone surface. A fragmentation-ba...

  9. A study of resonant-cavity and fiberglass-filled parallel baffles as duct silencers. [for wind tunnels

    Science.gov (United States)

    Soderman, P. T.

    1982-01-01

    Acoustical performance and pressure drop were measured for two types of splitters designed to attenuate sound propagating in ducts - resonant-cavity baffles and fiberglass-filled baffles. Arrays of four baffles were evaluated in the 7- by 10-foot wind tunnel number 1 at Ames Research Center at flow speeds from 0 to 41 m/sec. The baffles were 2.1 m high, 305 to 406 mm thick, and 3.1 to 4.4 m long. Emphasis was on measurements of silencer insertion loss as affected by variations of such parameters as baffle length, baffle thickness, perforated skin geometry, cavity size and shape, cavity damping, wind speed, and acoustic field directivity. An analytical method for predicting silencer performance is described and compared with measurements. With the addition of cavity damping in the form of 25-mm foam linings, the insertion loss above 250 Hz of the resonant-cavity baffles was improved 2 to 7 db compared with the undamped baffles; the loss became equal to or greater than the insertion loss of comparable size fiberglass baffles at frequencies above 250 Hz. Variations of cavity size and shape showed that a series of cavities with triangular cross-sections (i.e., variable depth) were superior to cavities with rectangular cross sections (i.e., constant depth). In wind, the undamped, resonant-cavity baffles generated loud cavity-resonance tones; the tones could be eliminated by cavity damping.

  10. 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...

  11. Enhanced Sensitivity in a Superluminal Single Mode DPAL Cavity at Room Temperature

    Science.gov (United States)

    Abi-Salloum, Tony; Yablon, Joshua; Tseng, Shih; Shahriar, Selim

    2012-06-01

    The note beat between two counter-propagating beams in a cavity is used to measure the effective change of the length of the cavity or interferometer for applications such as optical gyroscopes, vibrometers, and gravitational wave detectors. We show in this talk how a superluminal single mode laser cavity can enhance the measured note beat dramatically. We consider the inhomogeneous broadening case and study the dependence of the enhancement factor on few key parameters. We also show how Diode Pump Alkali Lasers (DPAL) are excellent candidates for such devices. Using a Rubidium based DPAL, we study the characteristics of these lasers and their effect on the proposed enhanced sensitivity.

  12. Cavity Optical Pulse Extraction: ultra-short pulse generation as seeded Hawking radiation.

    Science.gov (United States)

    Eilenberger, Falk; Kabakova, Irina V; de Sterke, C Martijn; Eggleton, Benjamin J; Pertsch, Thomas

    2013-01-01

    We show that light trapped in an optical cavity can be extracted from that cavity in an ultrashort burst by means of a trigger pulse. We find a simple analytic description of this process and show that while the extracted pulse inherits its pulse length from that of the trigger pulse, its wavelength can be completely different. Cavity Optical Pulse Extraction is thus well suited for the development of ultrashort laser sources in new wavelength ranges. We discuss similarities between this process and the generation of Hawking radiation at the optical analogue of an event horizon with extremely high Hawking temperature. Our analytic predictions are confirmed by thorough numerical simulations.

  13. Protein dynamics: hydration and cavities

    Directory of Open Access Journals (Sweden)

    K. Heremans

    2005-08-01

    Full Text Available The temperature-pressure behavior of proteins seems to be unique among the biological macromolecules. Thermodynamic as well as kinetic data show the typical elliptical stability diagram. This may be extended by assuming that the unfolded state gives rise to volume and enthalpy-driven liquid-liquid transitions. A molecular interpretation follows from the temperature and the pressure dependence of the hydration and cavities. We suggest that positron annihilation spectroscopy can provide additional quantitative evidence for the contributions of cavities to the dynamics of proteins. Only mature amyloid fibrils that form from unfolded proteins are very resistant to pressure treatment.

  14. A micropillar for cavity optomechanics

    CERN Document Server

    Kuhn, A G; Ducloux, O; Chartier, C; Traon, O Le; Briant, T; Cohadon, P -F; Heidmann, A; Michel, C; Pinard, L; Flaminio, R

    2011-01-01

    We present a new micromechanical resonator designed for cavity optomechanics. We have used a micropillar geometry to obtain a high-frequency mechanical resonance with a low effective mass and a very high quality factor. We have coated a 60-$\\mu$m diameter low-loss dielectric mirror on top of the pillar and are planning to use this micromirror as part of a high-finesse Fabry-Perot cavity, to laser cool the resonator down to its quantum ground state and to monitor its quantum position fluctuations by quantum-limited optical interferometry.

  15. Influence of the Vapor Cavity Depth on Liquid Flow through a Microchannel Exhibiting Superhydrophobic Walls

    Science.gov (United States)

    Maynes, Daniel; Jeffs, Kevin; Woolford, Brady; Webb, Brent

    2007-11-01

    We report results of an analytical and experimental investigation of laminar flow in a parallel-plate microchannel with superhydrophobic walls. The walls are fabricated with hydrophobically coated micro-ribs and cavities that are oriented parallel to the flow direction and are modeled in an idealized fashion, with the shape of the liquid-vapor meniscus approximated as flat. An analytical model of the flow in the vapor cavity is employed and coupled with a numerical model of the liquid flow. The numerical predictions show that the effective slip length and the reduction in the classical friction factor-Reynolds number product increase with increasing relative cavity width and depth, and decreasing relative micro-rib/cavity module length. Comparisons are also made between the zero shear interface model and the liquid-vapor cavity coupled model. The results illustrate that the zero shear interface model under-predicts the overall flow resistance. Further, the deviation between the two models was found to be significantly larger for increasing values of both the relative rib/cavity module width and the cavity fraction. The trends in the frictional pressure drop predictions are in good agreement with experimental measurements made at similar conditions and a generalized expression for predicting the friction factor is proposed.

  16. Pericardial cavity chemotherapy combined with external high frequency thermotherapy in the treatment of malignant pericardial effusion caused by lung cancer%心包腔化疗联合体外高频热疗治疗肺癌伴心包积液

    Institute of Scientific and Technical Information of China (English)

    张江灵; 赖灿辉; 陈少谊; 郑维斌; 陈云萍

    2013-01-01

    Objective To evaluate the efficacy of cisplatin chemotherapy combined with external high frequency thermotherapy in the treatment of patients with malignant pericardial effusion caused by lung cancer. Methods All of the patients were treated with intra-cavitary paracentesis and drainage at first, and then they were injected with 60 mg of cisplatin and 10 mg of dexamethasone on the first and eighth days. Then they were divided into the group A ( n = 30 ) and the group B ( n = 33 ). After the eighth days, the group A were given external high frequency thermotherapy additionally every 3 days. Results The clinical objective response was 90% ( 70% CR and 20% PR ) in the group A, and the clinical objective response was 75. 8% ( 51. 5% CR and 24. 2% PR ) in the group B. The difference of the total effective rate between the two groups was significant ( P < 0. 05 ). Conclusion On the basis of intracavitary injection of cisplatin chemotherapy, the external high frequency thermotherapy can significantly improve the curative effect in treatment of malignant pericardial effusion caused by lung cancer.%目的 探讨心包腔灌注顺铂化疗联合体外高频热疗治疗肺癌伴恶性心包积液的疗效.方法 63例患者分成甲组30例、乙组33例,甲组先行心包腔穿刺引流,再向心包腔内灌注顺铂60 mg+地塞米松10 mg,第1、8天.第8天灌注药物后即拔除引流管,然后行心包区域体外深部热疗,隔3天1次,共热疗2次.乙组除不进行热疗外,其余治疗均与甲组相同.结果 甲组CR21例、PR6例、NC3例,总有效率90.0%;乙组CR17例、PR8例、NC8例,总有效率75.8%,P<0.05.结论 心包腔灌注顺铂治疗肺癌伴恶性心包积液有效,在此基础上联合体外高频热疗可以提高疗效.

  17. Comb mode filtering silver mirror cavity for spectroscopic distance measurement

    Science.gov (United States)

    Šmíd, R.; Hänsel, A.; Pravdová, L.; Sobota, J.; Číp, O.; Bhattacharya, N.

    2016-09-01

    In this work we present a design of an external optical cavity based on Fabry-Perot etalons applied to a 100 MHz Er-doped fiber optical frequency comb working at 1560 nm to increase its repetition frequency. A Fabry-Perot cavity is constructed based on a transportable cage system with two silver mirrors in plano-concave geometry including the mode-matching lenses, fiber coupled collimation package and detection unit. The system enables full 3D angle mirror tilting and x-y off axis movement as well as distance between the mirrors. We demonstrate the increase of repetition frequency by direct measurement of the beat frequency and spectrally by using the virtually imaged phased array images.

  18. Multimode Strong Coupling in Superconducting Cavity Piezo-electromechanics

    CERN Document Server

    Han, Xu; Tang, Hong X

    2016-01-01

    High frequency mechanical resonators subjected to low thermal phonon occupancy are easier to be prepared to the ground state by direct cryogenic cooling. Their extreme stiffness, however, poses a significant challenge for external interrogations. Here we demonstrate a superconducting cavity piezo-electromechanical system in which multiple modes of a bulk acoustic resonator oscillating at $10\\,\\textrm{GHz}$ are coupled to a planar microwave superconducting resonator with a cooperativity exceeding $2\\times10^{3}$, deep in the strong coupling regime. By implementation of the non-contact coupling scheme to reduce mechanical dissipation, the system exhibits excellent coherence characterized by a frequency-quality factor product of $7.5\\times10^{15}\\,\\textrm{Hz}$. Interesting dynamics of temporal oscillations of the microwave energy is observed, implying the coherent conversion between phonons and photons. The demonstrated high frequency cavity piezo-electromechanics is compatible with superconducting qubits, repre...

  19. Resonant cavity light-emitting diodes: modeling, design, and optimization

    Science.gov (United States)

    Dumitrescu, Mihail M.; Sipila, Pekko; Vilokkinen, Ville; Toikkanen, L.; Melanen, Petri; Saarinen, Mika J.; Orsila, Seppo; Savolainen, Pekka; Toivonen, Mika; Pessa, Markus

    2000-02-01

    Monolithic top emitting resonant cavity light-emitting diodes operating in the 650 and 880 nm ranges have been prepared using solid-source molecular beam epitaxy growth. Transfer matrix based modeling together with a self- consistent model have been sued to optimize the devices' performances. The design of the layer structure and doping profile was assisted by computer simulations that enabled many device improvements. Among the most significant ones intermediate-composition barrier-reduction layers were introduced in the DBR mirrors for improving the I-V characteristics and the cavity and mirrors were detuned aiming at maximum extraction efficiency. The fabricated devices showed line widths below 15 nm, CW light power output of 8 and 22.5 mW, and external quantum efficiencies of 3 percent and 14.1 percent in the 650 nm and 880 nm ranges, respectively - while the simulations indicate significant performance improvement possibilities.

  20. Entanglement swapping between atom and cavity and generation of entangled state of cavity fields

    Institute of Scientific and Technical Information of China (English)

    Chen Ai-Xi; Deng Li

    2007-01-01

    This paper proposes a scheme where entanglement swapping between atom and cavity can be realized. A-type three-level atoms interacting resonantly with cavity field are considered. By detecting atom and cavity field, it realizes entanglement swapping between atom and cavity. It uses the technique of entanglement swapping to generate an entangled state of two cavity fields by measuring on atoms. It discusses the experimental feasibility of the proposed scheme and application of entangled state of cavity fields.

  1. Drum silencer with shallow cavity filled with helium.

    Science.gov (United States)

    Choy, Y S; Huang, Lixi

    2003-09-01

    The motivation of this study is twofold: (a) to produce a flow-through silencer with zero pressure loss for pressure-critical applications, and (b) to tackle low frequency noise with limited sideway space using cavities filled with helium. The work represents a further development of our recently conceived device of a drum-like silencer with conventional air cavity [Huang, J. Acoust. Soc. Am. 112, 2014-2025 (2002); Choy and Huang, ibid. 112, 2026-2035 (2002)]. Theoretical predictions are validated by experimental data. The new silencer consists of two highly tensioned membranes lining part of a duct, and each membrane is backed by a cavity filled with helium. For a typical configuration of a duct with height h, membrane length L = 7h, cavity depth h = 0.2h, and tension T = 0.52rho0c0(2)h2, where rho0 and c0 are the ambient density and speed of sound in air, respectively, the transmission loss has a continuous stop band of TL > 6.35 dB for frequency 0.03c0/h to 0.064c0/h, which is much better than traditional duct lining. In addition to the mechanisms at work for drum silencers with air cavity, the low density of helium reduces the masslike reactance of the cavity on the second in vacuo mode of membrane vibration. The reduction greatly enhances the membrane response at this mode, which is found to be critical for achieving a broadband performance in the low-frequency regime.

  2. On cavity modification of stimulated Raman scattering

    CERN Document Server

    Matsko, A B; Letargat, R J; Ilchenko, V S; Maleki, L

    2003-01-01

    We study theoretically stimulated Raman scattering (SRS) in a nonlinear dielectric microcavity and compare SRS thresholds for the cavity and the bulk material it is made of. We show that cavity SRS enhancement results solely from the intensity build up in the cavity and from the differences of the SRS dynamics in free and confined space. There is no significant modification of the Raman gain due to cavity QED effects. We show that the SRS threshold depends significantly on the nature of the dominating cavity decay as well as on the coupling technique with the cavity used for SRS measurements.

  3. Theoretical and experimental investigation of the mode-spacing of fiber Bragg grating Fabry-Perot cavity

    Institute of Scientific and Technical Information of China (English)

    Wenhua Ren; Peilin Tao; Zhongwei Tan; Yan Liu; Shuisheng Jian

    2009-01-01

    The mode-spacing of the fiber Bragg grating Fabry-Perot(FBG F-P)cavity is calculated by using the effective cavity length which contains the effective length of the FBG.The expression of the effective length,defined by using the phase-time delay,is obtained and simplified as a function of the peak reflectivity at the Bragg wavelength,the band edges,and the first zero-reflectivity wavelength.The effective length is discussed from the energy penetration depth point of view.Three FBG F-P cavities are fabricated in order to validate the effective length approach.The experimental data fits well with the theoretical predictions.The limitation of this method is also pointed out and the improved approach is proposed.

  4. 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.

  5. A Bloch modal approach for engineering waveguide and cavity modes in two-dimensional photonic crystals

    DEFF Research Database (Denmark)

    de Lasson, Jakob Rosenkrantz; Kristensen, Philip Trøst; Mørk, Jesper;

    2014-01-01

    uses no external excitation and determines the quasi-normal modes as unity eigenvalues of the cavity roundtrip matrix. We demonstrate the method and the quasi-normal modes for two types of two-dimensional photonic crystal structures, and discuss the quasi-normal mode eld distributions and Q...

  6. discouraged by queue length

    Directory of Open Access Journals (Sweden)

    P. R. Parthasarathy

    2001-01-01

    Full Text Available The transient solution is obtained analytically using continued fractions for a state-dependent birth-death queue in which potential customers are discouraged by the queue length. This queueing system is then compared with the well-known infinite server queueing system which has the same steady state solution as the model under consideration, whereas their transient solutions are different. A natural measure of speed of convergence of the mean number in the system to its stationarity is also computed.

  7. 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.

  8. A STUDY OF FERRITE CAVITY.

    Energy Technology Data Exchange (ETDEWEB)

    ZHAO, Y.

    2002-04-19

    This note addresses the general concerns for the design of a ferrite cavity. The parameters are specified for the RCMS, for which the frequency ramp is in the range of 1.27 MHz to 6.44 MHz, or a ratio of 1:5.

  9. 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...

  10. A 200 MHz prebunching cavity

    CERN Multimedia

    1977-01-01

    This cavity was installed in the PS ring and proved very efficient in providing a modulation on the PS beam before it is injected into the SPS machine. Moreover it allowed longitudinal instabilities studies at high intensities. Roberto Cappi stands on the left.

  11. "Grinding" cavities in polyurethane foam

    Science.gov (United States)

    Brower, J. R.; Davey, R. E.; Dixon, W. F.; Robb, P. H.; Zebus, P. P.

    1980-01-01

    Grinding tool installed on conventional milling machine cuts precise cavities in foam blocks. Method is well suited for prototype or midsize production runs and can be adapted to computer control for mass production. Method saves time and materials compared to bonding or hot wire techniques.

  12. 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...

  13. ExternE transport methodology for external cost evaluation of air pollution

    DEFF Research Database (Denmark)

    Jensen, S. S.; Berkowicz, R.; Brandt, J.

    The report describes how the human exposure estimates based on NERI's human exposure modelling system (AirGIS) can improve the Danish data used for exposure factors in the ExternE Transport methodology. Initially, a brief description of the ExternE Tranport methodology is given and it is summaris...

  14. Magnetospheric ULF waves driven by external sources

    CERN Document Server

    Agapitov, Oleksiy

    2015-01-01

    The multi-spacecraft missions (Cluster and THEMIS) observations allowed to collect large data base for Ultra Low Frequency (ULF) waves properties, their localization, and sources. Mainly here we focused on these recent results. Studying of the source and characteristics of ULF waves can help in the understanding of the interaction and energy transport from solar wind to the magnetosphere. Here we present peculiarities of ULF waves generated by different solar wind phenomenon: surface magnetopause instability, magnetosphere cavity modes and solar wind dynamic pressure sudden impulses (SI) penetration into the magnetosphere. Permanent observations of ULF waves involve existence of the permanent source and, as the previous studies showed, the contributions to Pc4-Pc5 ULF wave power from the external sources are larger than the contribution from internal magnetosphere sources. The Kelvin-Helmholtz instability (KHI) can generate on the magnetosphere flanks classical ULF resonant waves with spatially localized ampl...

  15. The External Mind

    DEFF Research Database (Denmark)

    The External Mind: an Introduction by Riccardo Fusaroli, Claudio Paolucci pp. 3-31 The sign of the Hand: Symbolic Practices and the Extended Mind by Massimiliano Cappuccio, Michael Wheeler pp. 33-55 The Overextended Mind by Shaun Gallagher pp. 57-68 The "External Mind": Semiotics, Pragmatism......, Extended Mind and Distributed Cognition by Claudio Paolucci pp. 69-96 The Social Horizon of Embodied Language and Material Symbols by Riccardo Fusaroli pp. 97-123 Semiotics and Theories of Situated/Distributed Action and Cognition: a Dialogue and Many Intersections by Tommaso Granelli pp. 125-167 Building...... Action in Public Environments with Diverse Semiotic Resources by Charles Goodwin pp. 169-182 How Marking in Dance Constitutes Thinking with the Body by David Kirsh pp. 183-214 Ambiguous Coordination: Collaboration in Informal Science Education Research by Ivan Rosero, Robert Lecusay, Michael Cole pp. 215-240...

  16. External-Memory Multimaps

    CERN Document Server

    Angelino, Elaine; Mitzenmacher, Michael; Thaler, Justin

    2011-01-01

    Many data structures support dictionaries, also known as maps or associative arrays, which store and manage a set of key-value pairs. A \\emph{multimap} is generalization that allows multiple values to be associated with the same key. For example, the inverted file data structure that is used prevalently in the infrastructure supporting search engines is a type of multimap, where words are used as keys and document pointers are used as values. We study the multimap abstract data type and how it can be implemented efficiently online in external memory frameworks, with constant expected I/O performance. The key technique used to achieve our results is a combination of cuckoo hashing using buckets that hold multiple items with a multiqueue implementation to cope with varying numbers of values per key. Our external-memory results are for the standard two-level memory model.

  17. Development of a compact cylindrical reaction cavity for a microwave dielectric heating system.

    Science.gov (United States)

    Kim, Myungsik; Kim, Kwangsoo

    2012-03-01

    This paper describes a compact reaction cavity for a microwave-assisted synthesis system. The microwave dielectric heating is a key technology to improve synthesizing yield, however, the large size of the microwave generation and reaction parts in an all-in-one system is a major obstacle when applying the technique to various systems, of which the installation space is limited. For this particular problem, a compact stand-alone cylindrical reaction cavity was developed in the current study. A microwave excited from a monopole probe, which is inserted into the side of the cavity, is transferred to a reaction mixture through the upper hole of the cavity. The cavity is miniaturized by filling it with an alumina ceramic dielectric. Fine-tuning of the resonance frequency becomes available by controlling the length of the inserted screw between the probe and the upper hole. The physical properties of the cavity were simulated using high frequency structural simulator (HFSS) and the produced cavity was tested using an Agilent E8357A network analyzer. The test results show that the developed cavity is able to send enough energy to various solvents.

  18. Thermal analysis of optical reference cavities for low sensitivity to environmental temperature fluctuations.

    Science.gov (United States)

    Dai, Xiaojiao; Jiang, Yanyi; Hang, Chao; Bi, Zhiyi; Ma, Longsheng

    2015-02-23

    The temperature stability of optical reference cavities is significant in state-of-the-art ultra-stable narrow-linewidth laser systems. In this paper, the thermal time constant and thermal sensitivity of reference cavities are analyzed when reference cavities respond to environmental perturbations via heat transfer of thermal conduction and thermal radiation separately. The analysis as well as simulation results indicate that a reference cavity enclosed in multiple layers of thermal shields with larger mass, higher thermal capacity and lower emissivity is found to have a larger thermal time constant and thus a smaller sensitivity to environmental temperature perturbations. The design of thermal shields for reference cavities may vary according to experimentally achievable temperature stability and the coefficient of thermal expansion of reference cavities. A temperature fluctuation-induced length instability of reference cavities as low as 6 × 10(-16) on a day timescale can be achieved if a two-layer thermal shield is inserted between a cavity with the coefficient of thermal expansion of 1 × 10(-10) /K and an outer vacuum chamber with temperature fluctuation amplitude of 1 mK and period of 24 hours.

  19. Far-from-equilibrium measurements of thermodynamic length

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Edward H.; Crooks, Gavin E.

    2008-11-05

    Thermodynamic length is a path function that generalizes the notion of length to the surface of thermodynamic states. Here, we show how to measure thermodynamic length in far-from-equilibrium experiments using the work fluctuation relations. For these microscopic systems, it proves necessary to define the thermodynamic length in terms of the Fisher information. Consequently, the thermodynamic length can be directly related to the magnitude of fluctuations about equilibrium. The work fluctuation relations link the work and the free energy change during an external perturbation on a system. We use this result to determine equilibrium averages at intermediate points of the protocol in which the system is out-of-equilibrium. This allows us to extend Bennett's method to determine the potential of mean force, as well as the thermodynamic length, in single molecule experiments.

  20. Single Cavity Trapped Vortex Combustor Dynamics – Part-1: Experiments

    Directory of Open Access Journals (Sweden)

    Atul Singhal

    2011-03-01

    Full Text Available In the present work, a water-cooled, modular, atmospheric pressure Trapped Vortex Combustor (TVC test rig is designed and fabricated for reacting and non-reacting flow experiments. The unique features of this rig consist of a continuously variable length-to-depth ratio (L/D of the cavity and optical access through quartz plates provided on three sides for visualization. Flame stabilization in the single cavity TVC was successfully achieved with methane as fuel and the range of flow conditions for stable operation were identified. From these, a few cases were selected for detailed experimentation. Reacting flow experiments for the selected cases indicated that reducing L/D ratio and increasing cavity-air velocity favour stable combustion. The pressure drop across the single cavity TVC is observed to be lower as compared to conventional combustors. Temperatures are measured at the exit using thermocouples and corrected for radiative losses. Species concentrations are measured at the exit using an exhaust gas analyzer. The combustion efficiency is observed to be around 97-99 % and the pattern factor is observed to be in the range of 0.08 to 0.13. High-speed imaging made possible by the optical access indicates that the overall combustion is fairly steady, and there is no vortex shedding downstream.