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A flat-field soft X-ray spectrometer for X-ray absorption spectroscopy measurement of warm dense matter
摘要： A flat-field soft X-ray spectrograph operating in the spectral range of 250–1240 eV was designed and built for warm dense matter and high-energy density plasma physics. It employs a grazing incidence toroidal mirror as a focusing optic, an aberration-corrected variable line spacing concave grating with 2400 lines/mm as a dispersive element, and a charge coupled device as an X-ray detector. The dispersion and energy resolution are calibrated with a high-power laser-produced plasma and X-ray free electron laser sources. A resolving power over 370 was achieved over the entire spectral range. A super broadband spectrum in the range of 250–1000 eV was measured from the laser-produced bismuth plasma. The signal-to-noise of 130 was obtained with an average of 10 pulses. These results demonstrate the capability of the spectrograph for single laser shot based experiments for warm dense matter and high energy density plasma research.
关键词： soft x-ray spectrometer,laser plasma,warm dense matter,x-ray spectroscopy,high power laser
更新于2025-09-23 15:23:52
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Suppression of amplitude modulation induced by polarization mode dispersion using a multi-degree-of-freedom fiber filter
摘要： Polarization mode dispersion (PMD) in ?bers for high-power lasers can induce signi?cant frequency modulation to amplitude modulation (FM-to-AM) conversion. However, existing techniques are not suf?ciently ?exible to achieve ef?cient compensation for such FM-to-AM conversion. By analyzing the nonuniform transmission spectrum caused by PMD, we found that the large-scale envelope of the transmission spectrum has more serious impacts on the amount of AM. In order to suppress the PMD-induced FM-to-AM conversion, we propose a novel tunable spectral ?lter with multiple degrees of freedom based on a half-wave plate, a nematic liquid crystal, and an axis-rotated polarization-maintaining ?ber. Peak wavelength, free spectral range (FSR), and modulation depth of the ?lter are decoupled and can be controlled independently, which is veri?ed through both simulations and experiments. The ?lter is utilized to compensate for the PMD-induced FM-to-AM conversion in the front end of a high-power laser facility. The results indicate that, for a pulse with phase-modulation frequency of 22.82 GHz, the FM-to-AM conversion could be reduced from 18% to 3.2% within a short time and maintained below 6.5% for 3 h. The proposed ?lter is also promising for other applications that require ?exible spectral control such as high-speed channel selection in optical communication networks.
关键词： laser facility,laser systems,optimization,high-power laser,laser facility and engineering,advanced laser technology and applications,?ber laser and applications,modeling,design
更新于2025-09-23 15:21:01
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Development of low vacuum laser welding technique using an aerodynamic window; ??o????a?????????¨???????????§??°?￠?????????????????o???￥???è??é????o;
摘要： In order to realize deep laser welding, conceptual application of a supersonic jet as an aerodynamic window was investigated. Detailed characteristics of the supersonic jet as the aerodynamic window were studied experimentally. Flow field of the supersonic jet was examined based on the schlieren flow visualization technique. As compared to a free-vortex flow design applied to the aerodynamic window nozzle, in the case of supersonic jet, oblique shock waves were captured both at the nozzle exit edge and the shear layer on the aerodynamic window. The velocity field under the condition that the shock-expansion wave was formed in the aerodynamic window was measured by the PIV (Particle Image Velocimetry) system (Koncerto II, Seika Digital Image Corp.). Both the vorticity magnitude and angular momentum were analyzed. Level of the vorticity magnitude in the core region of the supersonic jet was smaller by one-order than that in the shear layer in the region corresponding to the passage of laser-light (θ = 30 to 40° and r = 23.8 to 27.1 mm). The radial and circumferential velocity product in this region was similar to that observed under the free-vortex condition. In addition to the measurement mentioned above, pressure behavior was investigated using a multi-pressure measuring system (Scanivalve Corp. ZOC33). When the reservoir pressure was set at 800 kPa and diffuser width as 30.0mm, cavity pressure was reduced to 10.0 kPa. Under this reduced pressure environment, penetration depth increased by 2.6 times compared to penetration depth under atmospheric pressure environment. The effectiveness of the supersonic free-vortex aerodynamic window system tested in the high power laser welding manufacturing has been proven by the present study.
关键词： PIV,Aerodynamic window,High power laser welding,Flow visualization,Supersonic flow,Schlieren
更新于2025-09-23 15:21:01
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Efficient and Higha??Brightness Broad Area Laser Diodes Designed for Higha??Temperature Operation
摘要： Efficient and High-Brightness Broad Area Laser Diodes Designed for High-Temperature Operation. Advantages of semiconductor laser diodes as efficient high-power laser light sources applicable at elevated ambient temperatures. Semiconductor laser diodes, manufactured as single emitters or laser bars, are highly desired light sources for direct material processing as well as optical pumping of fiber and solid-state lasers. Laser diodes feature high optical output power and efficiency, long lifetimes, low maintenance and consequently low cost of ownership. To improve the usability and extend the application spectrum of high-power laser diodes, relaxed cooling requirements – without compromise in laser performance and lifetime – are required. Therefore, great development efforts are made, both in externally and internally funded research projects, to push the maximum permissible operating temperature of such semiconductor laser diodes to higher levels.
关键词： efficiency,semiconductor laser diodes,high-power laser,brightness,high-temperature operation
更新于2025-09-23 15:19:57
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Thermal design for the package of high-power single-emitter laser diodes
摘要： An analytical three-dimensional thermal model is employed to perform the thermal design for the package of high-power single-emitter laser diodes. Thermal design curves for the heat sink and submount are presented in detail, for laser diodes subjected to several convective heat transfer conditions on the bottom of the heat sink. An effective heat spreading angle is proposed to characterize thermal design for the heat sink. A differential heat spreading angle is proposed to clearly manifest heat flow in the packages. Full width and length at 90% energy are introduced to reveal the requirement of submount width and length, respectively. The impact of coefficient of thermal expansion (CTE)-matched sandwiched submount on total heat dissipation is studied. Special discussion is presented for a commercial F-Mount laser diode, and it is found that current heat sink design leads to a 27.4% increase in thermal resistance relative to a free lateral diffusion package.
关键词： Thermal resistance,Heat spreading angle,Submount,Heat sink,Thermal design,High-power laser diodes
更新于2025-09-23 15:19:57
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[Laser Institute of America ICALEO?? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18a??22, 2015)] International Congress on Applications of Lasers & Electro-Optics - New generation of high power reflective focusing optics (HPRFO)
摘要： As the high power laser market continues to grow, so does the need for robust optical solutions that can withstand the inherently harsh environment of laser welding. EWI continues to push the design envelope for high power optics that are capable of withstanding 20 kW or more of laser power for extended periods of time. A second version of EWI’s high power reflective focusing optics, referred to as HPRFO2, incorporates a patented aero window for internal protection of critical components, improved process effluent protection, and a revised beam delivery path. Long focal lengths separate the critical optics from the harsh welding environment without compromising the focal spot size. The previously published results of version one of the HPRFO exhibited minimal focal shift, unmatched by commercially available optics. In this work a production hardened version was designed and tested. Key attributes, which proved successful in version one of the HPRFO, were incorporated in the new design along with changes resulting from lessons learned. Shallower fold angles (compared to original HPRFO) for the asymmetric aspheric mirrors, adaptable effluent management solutions and better thermal management were included in the new design. Initial testing of the HPRFO2 demonstrated promising results and robustness unrivaled by commercially available optics.
关键词： HPRFO,reflective focusing optics,high power laser,thermal management,aero window
更新于2025-09-23 15:19:57
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Wavelength stabilized high pulse power 48 emitter laser bars for automotive LiDAR application
摘要： Diode lasers generating optical pulses with high peak power and lengths in the nanosecond range are key components for LiDAR (Light Detection and Ranging) systems, e.g., for autonomous driving and object detection. We present here an internally wavelength stabilized distributed Bragg reflector (DBR) broad area (BA) laser bar with 48 emitters. The vertical structure based on AlGaAs (confinement and cladding layers) and InGaAs (active quantum well) is specifically optimized for wavelength-stabilized pulsed operation applying a surface Bragg grating with high reflectivity. The bar is electrically driven by a new in-house developed high-speed driver based on GaN transistors providing current pulses with amplitudes of up to 1000 A and a repetition frequency of 10 kHz. The generated 4 ns to 10 ns long optical pulses are nearly rectangular shaped and reach a pulse peak power in excess of 600 Watts at 25°C. The optical spectrum with a centre wavelength of about 900 nm has a width of 0.15 nm (FWHM) with a side mode suppression ratio > 30 dB.
关键词： nanosecond pulses,high power,laser bar,DBR laser
更新于2025-09-19 17:13:59
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Bremsstrahlung emission from high power laser interactions with constrained targets for industrial radiography
摘要： Laser–solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging. A bright, energetic X-ray pulse can be driven from a small source, making it ideal for high resolution X-ray radiography. By limiting the lateral dimensions of the target we are able to con?ne the region over which X-rays are produced, enabling imaging with enhanced resolution and contrast. Using constrained targets we demonstrate experimentally a (20 ± 3) μm X-ray source, improving the image quality compared to unconstrained foil targets. Modelling demonstrates that a larger sheath ?eld envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target, driving a brighter source of X-rays.
关键词： high power laser,bremsstrahlung,nondestructive imaging,X-ray,radiography
更新于2025-09-19 17:13:59
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Single-shot electrons and protons time-resolved detection from high-intensity laser–solid matter interactions at SPARC_LAB
摘要： Laser–plasma interactions have been studied in detail over the past twenty years, as they show great potential for the next generation of particle accelerators. The interaction between an ultra-intense laser and a solid-state target produces a huge amount of particles: electrons and photons (X-rays and γ-rays) at early stages of the process, with protons and ions following them. At SPARC LAB Test Facility we have set up two diagnostic lines to perform simultaneous temporally resolved measurements on both electrons and protons.
关键词： high power laser,TNSA,electron diagnostics,proton diagnostics,single-shot diagnostics,time-of-flight detector
更新于2025-09-19 17:13:59
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Experimental study on cooling of high-power laser diode arrays using hybrid microchannel and slot jet array heat sink
摘要： In this study, a hybrid microchannel and slot jet array heat sink is designed and fabricated to achieve a better thermal performance of the high-power laser diode arrays. A standard commercial laser bar with wavelength of 808 nm is packaged on the heat sink and experiments are performed to assess the cooling performance of the hybrid heat sink. In the experiments, the forward voltage method is used to measure the chip temperature and the structure function method is applied to obtain the thermal resistance of the heat sink. Using the deionized water as coolant, the heat sink deals with a heat flux of up to 506 W/cm2 and the thermal resistance of the heat sink is only 0.23 K/W when the flow rate is 0.8 L/min (The average jet velocity is 13.3 m/s). The optical power can be up to 135.5 W corresponding to the wall plug efficiency of 64.2%. Compared with the published solutions related to cooling similar laser chips, the thermal resistance reduces by over 15%, indicating that this hybrid heat sink is an interesting solution to improve the cooling of the high-power laser diode arrays.
关键词： High-power laser diode array,Cooling,Forward voltage method,Thermal resistance,Optical power
更新于2025-09-16 10:30:52