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Investigation of high power laser coatings

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光学精密工程 2005年第4期13卷 471-479页

作者： SHAO Jian-da FAN Zheng-xiu R＆D center for optical Thin Film coating Technology Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China

High laser-induced damage threshold and large aperture were focuses on the studies of high power laser coatings. This paper reports the research activities at our center. Several measures were developed for evaluating characters of laser damage, including determination of laser induced damage threshold and detection of absorption based on surface thermal lensing technique. Defect was deemed to be the initial source of laser damage, and was the main factor restricting the laser damage resistance of optical coatings. The contribution of several kinds of typical defects to laser damage was analyzed, and some deposition measures were adopted to control and eliminate the origin of defect. Furthermore, some post-treatment methods were also employed to alleviate the influence of the defect and to improve the laser damage resistance. Correction mask was introduced to improve the thickness uniformity, and the thickness uniformity can be amended to less than 1% in the range of Φ650 mm. Preliminary investigation related to surface deformation was also conducted.

关键词：激光涂覆技术 LIDT 吸收能力激光器

A Spectroscopic Ellipsometry Study of TiO2 Thin Films Prepared by dc Reactive Magnetron Sputtering： Annealing Temperature Effect

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Chinese Physics Letters 2007年第6期24卷 1505-1508页

作者： Mati Horprathum Pongpan Chindaudom Pichet Limsuwan Department of Physics Faculty of Science King Mongkut's University of Technology Thonburi Bangkok 10140 Thailand optical coating Laboratory National Electronics and Computer Technology Center Pathumthani 12120 Thailand

TiO2 thin films are obtained by dc reactive magnetron sputtering. A target of titanium （99.995%） and a mixture of argon and oxygen gases are used to deposit TiO2 films on to silicon wafers （100）. The crystalline structure of deposited and annealed film are deduced by variable-angle spectroscopic ellipsometry （VASE） and supported by x-ray diffractometry. The optical properties of the films are examined by VASE. Measurements of ellipsometry are performed in the spectral range O. 72-3.55 e V at incident angle 75^o. Several SE models, categorized by physical and optical models, are proposed based on the ＇simpler better＇ rule and curve-fits, which are generated and compared to the experimental data using the regression analysis. It has been found that the triple-layer physical model together with the Cody-Lorentz dispersion model offer the most convincing result. The as-deposited films are found to be inhomogeneous and amorphous, whereas the annealed films present the phase transition to anatase and rutile structures. The refractive index of TiO2 thin films increases with annealing temperature. A more detailed analysis further reveals that thickness of the top sub-layer increases, whereas the region of the bottom amorphous sub-layer shrinks when the films are annealed at 300℃.

关键词： PHOTOCATALYTIC ACTIVITY MODEL

Plasmon-phonon coupling in graphene-hyperbolic bilayer heterostructures

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Chinese Physics B 2016年第11期25卷 324-332页

作者：尹格元军姜玮朱剑飞马云贵 State Key Laboratory of Modern optical Instrumentation Center for Optical and Electromagnetic ResearchCollege of Optical Science and Engineering Zhejiang University

Polar dielectrics are important optical materials enabling the subwavelength manipulation of light in infrared due to their capability to excite phonon *** practice,it is highly desired to actively modify these hyperbolic phonon polaritons（HPPs） to optimize or tune the response of the *** this work,we investigate the plasmonic material,a monolayer graphene,and study its hybrid structure with three kinds of hyperbolic thin films grown on SiO_2 *** inter-mode hybridization and their tunability have been thoroughly clarified from both the band dispersions and the mode patterns numerically calculated through a transfer matrix *** results show that these hybrid multilayer structures are of strong potentials for applications in plasmonic waveguides,modulators and detectors in infrared.

关键词： hyperbolic phonon desired clarified multilayer Polar enabling manipulation infinite optimize

Silicon nanophotonics for on-chip light manipulation

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Chinese Physics B 2018年第10期27卷 46-57页

作者： Jingshu Guo Daoxin Dai center for optical and Electromagnetic Research State Key Laboratory for Modern Optical InstrumentationCollege of Optical Science and EngineeringZhejiang UniversityHangzhou 310058China

The field of silicon nanophotonics has attracted considerable attention in the past decade because of its unique advantages,including complementary metal–oxide–semiconductor（CMOS） compatibility and the ability to achieve an ultra-high integration density. In particular, silicon nanophotonic integrated devices for on-chip light manipulation have been developed successfully and have played very import roles in various applications. In this paper, we review the recent progress of silicon nanophotonic devices for on-chip light manipulation, including the static type and the dynamic type. Static onchip light manipulation focuses on polarization/mode manipulation, as well as light nanofocusing, while dynamic on-chip light manipulation focuses on optical modulation/switching. The challenges and prospects of high-performance silicon nanophotonic integrated devices for on-chip light manipulation are discussed.

关键词： silicon nanophotonics polarization mode manipulation nanoplasmonics optical modulator optical switch.

Investigations of range accuracy for long-range three-dimensional active imaging

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Chinese Optics Letters 2011年第6期9卷 48-50页

作者：张秀达严惠民周琴 State Key Laboratory of Modern optical Instrument National Engineering Research Center for Optical Instrument Optical Engineering Department Zhejiang University

Distance resolutions and noises are analyzed experimentally for long-range three-dimensional （3D） active imaging systems that have signal-to-noise ratios （SNRs） more optimal than 30：1. Findings indicate that the photon shot noise primarily determines the SNR. However, the active imaging method, which has a relatively low SNR, generates a relatively high distance resolution. To explain this phenomenon, a theory in which the distance resolution of 3D active imaging systems is determined by both the photon shot noise and the subinterval width is developed. Theoretical and experimental results differ by less than 4%.

关键词： Imaging systems Photons Shot noise Signal to noise ratio

Recovery schemes for different distributed connection management in generalized multi-protocol label switching networks

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Chinese Optics Letters 2007年第3期5卷 142-145页

作者：王璨纪越峰 optical Communication center Beijing University of Posts and Telecommunications

As the wavelength division multiplexing （WDM） technology matures and the demands for bandwidth increase, survivability becomes more and more important in generalized multi-protocol label switching （GMPLS） controlled intelligent optical networks （IONs）. There are great interests to study the performance of restorability under one certain connection management strategy. And studies in the problem of providing recovery from link failures under two different resource reservation schemes, forward reservation protocols （FRPs） and backward reservation protocols （BRPs）, are presented. They are examined from the point of view of connection blocking probability, restorability and average recovery time. The two different connection management schemes and the survey of different recovery schemes are first presented. The performance of these recovery strategies is analyzed and compared both through theoretical analysis and simulation results. The main stressed idea is that using BRPs gives the best performance in terms of restorability and blocking Drobability in restorable GMPLS networks.

关键词： Bandwidth Blocking probability Fiber optic networks Network protocols Wavelength division multiplexing

Improved partial response maximum likelihood method combining modulation code for signal waveform modulation multi-level disc

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Chinese Physics B 2014年第10期23卷 213-219页

作者：王鹤群裴京潘龙法 optical Memory National Engineering Research center Tsinghua University

In this paper, we describe an improved adaptive partial response maximum likelihood （PRML） method combining modulation code tbr signal waveform modulation multi-level disc. This improved adaptive PRML method employs partial response equalizer and adaptive viterbi detector combining modulation code. Compared with the traditional adaptive PRML detector, the improved PRML detector additionally employs illogical sequence detector and corrector. Illogical sequence detector and corrector can aw）id the appearance of illogical sequences effectively, which do not follow the law of modulation code for signal waveform modulation multi-level disc, and obtain the correct sequences. We implement the improved PRML detector using a DSP and an FPGA chip. The experimental results show good performance. The higher efficient and lower complexity can be obtained by using the improved PRML method than by using the previous PRML method. Meanwhile, resource utilization of the improved PRML detector is not changed, but the bit error rate （BER） is reduced by more than 20%.

关键词： multi-level disc signal waveform modulation viterbi detector partial response maximum likeli-hood

Effect of structural parameters of Gaussian repaired pit on light intensity distribution inside KH_2PO_4 crystal

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Chinese Physics B 2014年第8期23卷 540-547页

作者：肖勇陈明君程健廖威王海军李明全 center for Precision Engineering Harbin Institute of Technology Chengdu Fine optical Engineering Research center

KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage threshold, affecting the crystal service life. In this paper, Gaussian repaired pit is used to replace the crystal surface micro-defects, in order to improve the laser damage resistance of the KDP crystal with surface micro-defects. At first, the physical model of Gaussian repaired pit is built by Fourier model method, and the accuracy of the method is analyzed. It is found that the calculation error can be reduced by increasing the product of the width-period ratio and the truncation constant of the repaired pit. The calculation results about the physical model of Gaussian repaired pit show that the light intensity distribution within the crystal is symmetrical, and there are evidently enhanced light intensity regions in the crystal. Meanwhile, the maximum relative intensity inside the KDP crystal decreases gradually with the increase of the width of the Gaussian repaired pit. Secondly, the Gaussian repaired pits with different widths and the same depth of 20 μm are processed by micro-milling. Their surfaces are very smooth and present the ductile cutting state under the microscope. Finally, the laser damage threshold of the Gaussian repaired pits on the surface of the KDP crystal sample is measured by a 3 ω, 6-ns laser. The results showthat the maximum threshold of the Gaussian repaired pits is 3.12 J/cm2, which is 60% higher than the threshold of initial damage point, and the laser damage threshold increases with the increase of the width of the Gaussian repaired pit.

关键词： KH2PO4 Gaussian repaired pit Fourier modal method laser damage threshold

Mechanism of micro-waviness induced KH_2PO_4 crystal laser damage and the corresponding vibration source

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Chinese Physics B 2012年第5期21卷 34-42页

作者：李明全陈明君安晨辉周炼程健肖勇姜伟 center for Precision Engineering Harbin Institute of Technology Chengdu Fine optical Engineering Research center

The low laser induced damage threshold of the KH2PO4 crystal seriously restricts the output power of inertial confinement *** micro-waviness on the KH2PO4 surface processed by single point diamond turning has a significant influence on the damage *** this paper,the influence of micro-waviness on the damage threshold of the KH2PO4 crystal and the chief sources introducing the micro-waviness are analysed based on the combination of the Fourier modal theory and the power spectrum density *** results indicate that among the sub-wavinesses with different characteristic spatial frequencies there exists the most dangerous frequency which greatly reduces the damage threshold,although it may not occupy the largest proportion in the original *** experimental damage threshold is basically consistent with the theoretical *** the processing parameters used,the leading frequency of micro-waviness which causes the damage threshold to decrease is between 350-1 μm-1 and 30-1 μm-1,especially between 90-1 μm-1 and 200-1 μ*** on the classification study of the time frequencies of microwaviness,we find that the axial vibration of the spindle is the chief source introducing the micro-waviness,nearly all the leading frequencies are related to the practical spindle frequency（about 6.68 Hz,400 r/min） and a special middle frequency（between 1.029 Hz and 1.143 Hz）.

关键词： laser induced damage threshold micro-waviness Fourier modal theory power spectrum density