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Repaired morphology of CO_(2)laser rapid ablation mitigation of fused silica and its influence on downstream light modulation

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Science China(Technological Sciences) 2022年第5期65卷 1116-1126页

作者： TAN Chao ZHAO LinJie CHEN MingJun CHENG Jian ZHANG Yu ZHANG Jiong YANG Hao YIN ZhaoYang State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin150001China Department of Mechanical Engineering National University of SingaporeSingapore117575Singapore

The threat of cascading damage to downstream components caused by the light modulation intensification of laser repaired morphology on the surface of fused silica optics cannot be ignored in high-power laser systems.This paper uses the angular spectrum diffraction theory based on the analysis of repaired surface morphology of CO_(2)laser rapid ablation mitigation to study the influence of different repaired morphologies on the downstream 355 nm laser transmission.Studies show that the arc-shaped laser processing lines on the repaired surface are formed by the residual height superposition of the material after laser scanning of two adjacent layers,and the short-pulse laser can substantially suppress the heat-affected zone of the repaired area.The offaxis ring caustic and on-axis hotspot are sequentially generated in the downstream modulated light fields of the conical repaired sites with different diameters.A secondary peak with modulation larger than 3 emerges downstream of the modulation curve.Meanwhile,the maximum modulation and the secondary peak increase with the diameter and cone angle of the repaired site,and the position of the secondary peak appears farther away from the rear surface.The modulations of three repaired sites with cone angles of 15°,20°,and 25°can finally be stabilized below 3.Overall,the downstream optics should be installed far away from the positions where the maximum modulation and the secondary peak emerge.Additionally,the maximum value and the secondary peak of the downstream light modulation of double repaired sites are larger than that of the single repaired site,and both rise as the repaired sizes increase.Thus,large-scale and large-size repairing of multiple surface damages in the same area should be avoided in the laser repairing of fused silica.

关键词： fused silica laser repairing morphology light modulation secondary peak double repaired sites

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Simulation and optimization of spatial light modulation of twisted-nematic liquid crystal display

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Chinese Optics Letters 2010年第10期8卷 960-963页

作者：马百恒姚保利严绍辉彭飞闵俊伟雷铭叶彤 State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Graduate University of the Chinese Academy of Sciences

The approaches to obtaining desired intensity or phase modulation by twisted-nematic liquid crystal display （TN-LCD） have been extensively studied based on the knowledge of the LCD＇s internal structure parameters. Generally, the TN-LCD placed between two linear polarizers （P） produces coupled intensity and phase modulation. To obtain the commonly used phase-only modulation, quarter wave plates （QWPs） are often used in front of and/or behind the LCD. Here we present a method to optimize the optical modulation properties of the TN-LCD to obtain phase-only modulation in the configuration of P-QWP-LCD-QWP-P each with proper orientation. Our method is based on the macroscopical Jones matrix descriptions for the LCD, the QWPs, and the linear polarizers. Through Jones matrix calculations, the orientations of the polarizers and QWPs can be optimized to satisfy differently desired modulation demands. In contrast to the traditional method, which requires knowledge of the LCD＇s internal structure parameters, our method simplified the complicated theory analysis and can work in the absence of information on the LCD＇s internal structure parameters, which are usually not available for the commercial products.

关键词： Crystal structure light modulation Liquid crystals Liquids Nematic liquid crystals Optical instruments Optical properties Optimization Phase modulation

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Mitigation of signal quality degradation induced by PMD using synchronous modulation

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Chinese Optics Letters 2004年第9期2卷 505-507页

作者：霍力杨彦甫娄采云姚和军宋晓旻高以智 DepartmentofElectronicEngineering TsinghuaUniversityBeijing100084

In-line synchronous modulation as a way of mitigating the signal quality degradation induced by polarization mode dispersion (PMD) was experimentally studied using 10-Gb/s return to zero signal. Bit error rate of the degraded signal and the synchronously modulated signal under the differential group delay (DGD) values of 10, 20, 34, and 70 ps was measured and compared. The experimental results showed that in-line synchronous modulation is useful to mitigate the signal quality degeneration induced by PMD. 1-dB power penalty reduction was obtained even when the PMD was as high as 70% of the bit interval. The limitation of method is also discussed.

关键词： Bit error rate Electromagnetic dispersion Interference suppression Intersymbol interference light modulation light polarization

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Laser pulse spectral shaping based on electro-optic modulation

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Chinese Optics Letters 2008年第11期6卷 841-844页

作者：王艳海王江峰姜有恩鲍岩李学春林尊琪 National Laboratory of High Power Laser Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800 College of Sciences Hebei University of Science and TechnologyShijiazhuang 050018

A new spectrum shaping method, based on electro-optic modulation, to alleviate gain narrowing in chirped pulse amplification （CPA） system, is described and numerically simulated. Near-Fourier transform-limited seed laser pulse is chirped linearly through optical stretcher. Then the chirped laser pulse is coupled into integrated waveguide electro-optic modulator driven by an aperture-coupled-stripline （ACSL） electricalwaveform generator, and the pulse shape and amplitude are shaped in time domain. Because of the direct relationship between frequency interval and time interval of the linearly chirped pulse, the laser pulse spectrum is shaped correspondingly. Spectrum-shaping examples are modeled numerically to determine the spectral resolution of this technique. The phase error introduced in this method is also discussed.

关键词： Amplification Electrooptical devices Fourier transforms Laser beams Laser fusion Laser pulses Lasers light modulation modulation Photolithography Pulse amplifiers Pulsed laser applications

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Optical reconstruction of 3D images by use of pure-phase computer-generated holograms

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Chinese Optics Letters 2009年第12期7卷 1101-1103页

作者：张浩谢敬辉刘娟王涌天 School of Optoelectronics Beijing Institute of Technology

A three-dimensional （3D） object reconstruction technique that uses pure-phase computer-generated holograms （CGHs） and a phase-only spatial light modulator （SLM） is proposed. The full parallax CGHs are generated by the point source method and the wave-oriented method without paraxial approximation. Different from conventional CGHs, the pure-phase information on the hologram plane is loaded on the SLM to reconstruct the 3D diffusive objects without considering the reference wave. This technique is more efficient in its utilization of the space-bandwidth product of the SLMs. Numerical simulations and experiments are performed, and the results show that our proposed method can reconstruct 3D diffusive objects successfully.

关键词： Bandwidth Computer generated holography Geometrical optics Holograms light modulation light modulators

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Two localized CO_2 laser treatment methods for mitigation of UV damage growth in fused silica

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Chinese Physics B 2012年第6期21卷 299-306页

作者：蒋勇向霞刘春明罗成思王海军袁晓东贺少勃任玮吕海兵郑万国祖小涛 Department of Applied Physics University of Electronic Science and Technology of China Research Center of Laser Fusion China Academy of Engineering Physics

Two methods：high-power,short-time,single-shot irradiation（Method A） and low-power,long-time,multi-shot irradiation（Method B） are investigated to mitigate the UV damage growth in fused silica by using a 10.6-μm CO2 laser.To verify the mitigation effect of the two methods,the laser induced damage thresholds（LIDTs） of the mitigated sites are tested with a 355-nm,6.4-ns Nd：YAG laser,and the light modulation of the mitigation sites are tested with a 351-nm continuous Nd：YLF laser.The mitigated damaged sites treated with the two methods have almost the same LIDTs,which can recover to the level of pristine material.Compared with Method A,Method B produces mitigated sites with low crater depth and weak light modulation.In addition,there is no raised rim or re-deposited debris formed around the crater edge for Method B.Theoretical calculation is utilized to evaluate the central temperature of the CO2 laser beam irradiated zone and the radius of the crater.It is indicated that the calculated results are consistent with the experimental results.

关键词： fused silica C02 laser mitigation light modulation damage threshold

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Optimization of computer-generated holograms for dynamic optical manipulation with uniform structured light spots

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Chinese Optics Letters 2011年第6期9卷 56-59页

作者：步敬苑光辉孙宇扬朱思伟袁小聪 Institute of Modern Optics Key Laboratory of Optoelectronic Information Science and Technology Ministry of Education of China Nankai University School of Electrical and Electronic Engineering Nanyang Technological University Nankai University Affiliated Hospital

An optimized iterative technique combining the merits of conventional Gerchber-Saxton （G-S） and adaptive-additive （A-A） algorithms to design multilevel computer-generated holograms for the creation of a desirable structured intensity pattern for multiple optical manipulation is theoretically adopted. Optical trap arrays are demonstrated with the help of liquid crystal spatial light modulator and a microscopic optical tweezer system. Additionally, continuous locked-in transport and deflection of microparticles with the generated optical lattice is proven experimentally. The proposed method possesses apparent high efficiency, high uniformity, and dynamic and reconfigurable advantages.

关键词： Holograms light modulation light modulators Liquid crystals Optimization

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Grating light modulator for projection display

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Chinese Optics Letters 2009年第2期7卷 146-148页

作者：孙吉勇黄尚廉张洁张智海朱永 The Key Laboratory for Optoelectronic Technology and System Ministry of Education of ChinaOptoelectronic Engineering Department Chongqing University

A novel grating light modulator for projection display is introduced. It consists of an upper moveable grating, a bottom mirror, and four supporting posts between them. The moveable grating and the bottom mirror compose a phase grating whose phase difference is controlled by the actuating voltage. When the phase difference is 2kπ, the grating light modulator will switch the incident light to zero-order diffraction; when the phase difference is （2k - 1）π, the grating light modulator will diffract light to first-order diffraction. A 16 × 16 modulator array is fabricated by the surface micromachining technology. The device works well when it is actuated by a voltage with 1-kHz frequency and 10-V amplitude. The fabricated grating light modulator can show blackness and brightness when controlled by the voltage. This modulator has potential applications in projection display system.

关键词： Diffraction light light modulation Micromachining Mirrors Optical projectors

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Beam steering approach for high-precision spatial light modulators

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Chinese Optics Letters 2010年第11期8卷 1085-1089页

作者：孔令讲朱颖宋艳杨建宇 School of Electronic Engineering University of Electronic Science and Technology of China

Steering accuracy is limited by the quantized phase modulation values and the number of phase pixels for spatial light modulators （SLMs）.Conventional methods of beam steering lack optimum precision.In this letter,a beam steering approach based on horizontally moving phase steps is proposed.Compared with the conventional methods,this novel method is able to reduce the maximum normalized steering error in SLM significantly by a factor proportional to the number of pixels.In addition,steering errors of high steering angles can be drastically reduced by a factor proportional to the product of the number of pixels and the quantized phase levels; the number of high-precision steering angles increases with the number of pixels or the quantized phase levels increasing.

关键词： light modulation Phase modulation Pixels

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Observation of a fused dual-fiber sensor head tips by SEM

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Chinese Optics Letters 2006年第1期4卷 8-10页

作者：王晓旭林钧岫王德和 Department of Physics Dalian University of TechnologyDalian 116024

The shape and microstructure of the fiber-optic liquid-level sensor head. which was made of two fusion- spliced multimode optical fibers, were experimentally studied by using scanning electron microscope （SEM） technology in order to optimize the performance characteristic of the fiber sensor head. The parabolic profile of the sensor head was found to be better and having length-width ratio from 1.2：1 to 1.3：1. Some other useful possibilities were proposed.

关键词： light modulation Liquid level indicators Microstructure Multimode fibers Refractive index Scanning electron microscopy

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