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Effects of spot size on the operation mode of Ga As photoconductive semiconductor switch employing extrinsic photoconductivity

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Plasma Science and Technology 2024年第5期26卷 91-99页

作者：韦金红李嵩陈红曾凡正贾成林付泽斌葛行军钱宝良 College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073People’s Republic of China

To guide the illuminating design to improve the on-state performances of gallium arsenide(GaAs)photoconductive semiconductor switch(PCSS),the effect of spot size on the operation mode of GaAsPCSS based on a semi-insulating wafer with a thickness of 1 mm,triggered by a 1064-nm extrinsic laser beam with the rectangular spot,has been investigated experimentally.It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes,and then significantly boosts the PCSS toward different operation modes.On this basis,a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms.Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching,while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching,which have been proved by comparing the domain evolutions under different spot sizes.

关键词： GaAs PCSS operation mode spot size on-state performances two-channel model domain evolution

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High-Efficiency Dynamic Scanning Strategy for Powder Bed Fusion by Controlling Temperature Field of the Heat-Affected Zone

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 203-214页

作者： Xiaokang Huang Xiaoyong Tian Qi Zhong Shunwen He Cunbao Huo Yi Cao Zhiqiang Tong Dichen Li State Key Laboratory of Manufacturing Systems Engineering Xi’an Jiaotong UniversityXian 710049China

Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature field using an infrared thermal imager has been established and integrated into a four-laser PBF equipment with a working area of 2000 mm×2000 mm.The heat-affected zone(HAZ)temperature field has been controlled by adjusting the scanning speed dynamically.Simultaneously,the relationship among spot size,HAZ temperature,and part performance has been established.The fluctuation of the HAZ temperature in four-laser scanning areas was decreased from 30.85℃to 17.41℃.Thus,the consistency of the sintering performance of the produced large component has been improved.Based on the controllable temperature field,a dynamically adjusting strategy for laser spot size was proposed,by which the fabrication efficiency was improved up to 65.38%.The current research results were of great significance to the further industrial applications of large-scale PBF equipment.

关键词： Powder bed fusion Efficiency Large-scale spot size Heat-affected zone(HAZ)

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spot size measurement of a flash-radiography source using the pinhole imaging method

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Chinese Physics C 2016年第7期40卷 124-128页

作者：王毅李勤陈楠程晋明谢宇彤刘云龙龙全红 Key Laboratory of Pulsed Power Institute of Fluid Physics China Academy of Engineering Physics

The spot size of the X-ray source is a key parameter of a flash-radiography facility, and is usually quoted as an evaluation of the resolving power. The pinhole imaging technique is applied to measure the spot size of the Dragon-I linear induction accelerator, by which a two-dimensional spatial distribution of the source spot is obtained. Experimental measurements are performed to measure the spot image when the transportation and focusing of the electron beam are tuned by adjusting the currents of solenoids in the downstream section. The spot size of full-width at half maximum and that defined from the spatial frequency at half peak value of the modulation transfer function are calculated and discussed.

关键词： spot size X-ray source pinhole linear induction accelerator

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Experimental comparison of various techniques for spot size measurement of high-energy X-ray sources

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Chinese Physics C 2016年第8期40卷 136-141页

作者：王毅李勤陈楠程晋明李成刚李洪龙全红石金水邓建军 Key Laboratory of Pulsed Power Institute of Fluid PhysicsChina Academy of Engineering Physics

In flash-radiography experiments, the quality of the acquired image strongly depends on the focal size of the X-ray source spot. A variety of techniques based on imaging of the pinhole, the slit and the rollbar are adopted to measure the focal spot size of the Dragon-I linear induction accelerator. The image of the pinhole provides a two-dimensional distribution of the X-ray spot, while those of the slit and the rollbar give a line-spread distribution and an edge-spread distribution, respectively. The spot size characterized by the full-width at half-maximum and that characterized by the LANL definition are calculated for comparison.

关键词： linear induction accelerator spot size pinhole slit rollbar

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Analyze PDL and WDL in micro-optical components

Analyze PDL and WDL in micro-optical components

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全国第十三次光纤通信暨第十四届集成光学学术会议

作者： ZHANG bo(1), LIU wen(1,2), CHEN long(1) (1. Accelink Technologies Co., Ltd, Wuhan Research Institute of Post and Telecommunications, Wuhan, 430074, China 2.Wuhan National Laboratory For Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China )

The PDL and WDL of micro-optical components are analyzed in this paper. When the input light with different wavelength pass through an aperture, it will produce corresponding spot sizes which will bring different loss, so Insertion Loss (IL) and WDL are influenced. When the input light is split inside the components and the splitting ratio is polarization dependent, because of the drift and asymmetry between the aperture and spot centre, divisive optical pulses will have different loss and the PDL will be influenced.

关键词： Wavelength Dependent Loss （WDL） Polarization Dependent Loss （PDL） spot size drift asymmetry

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