Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Research on High Accuracy Sub-Aperture Stitching Algorithm for Flat Optics
No full text对平面子孔径拼接累积误差的理论分析及数值仿真表明,参考镜面形的拼接重叠区域的局部斜率差和直流偏差是产生累积误差的原因。为了提高大口径平面光学元件子孔径拼接检测精度,提出一种简单有效的可以减小子孔径拼接测量累积误差的方法,该方法采用第4项和第6项泽尼克像差拟合一个假设的准参考镜面形,再从每个子孔径测量结果中减去,最后拼接合成全口径面形。对450 mmX60 mm的平面镜进行了8个子孔径的拼接检测,去除准参考镜面形前后,拼接测量结果与Zygo公司24英寸(600 mm)口径干涉仪检测结果的偏差峰谷(PV)值从国家自然科学基金; 中国科学院青年创新促进会Theoretical analysis and numerical simulation on the error accumulation in sub-aperture stitching for flat optics show that the slope and piston difference of the surface figure of the reference flat in the overlap region lead to error accumulation. In order to improve the measurement accuracy of the stitching interferometer for large aperture flat optics, a simple and effective method is proposed to reduce the accumulated error of the sub-aperture stitching measurements. The 4th and 6th Zernike aberration are used to synthesize the virtual reference flat. Sub-apertures with the virtual reference surface figure removed are stitched together to obtain a full aperture surface figure. A flat mirror with aperture of 450 mm X 60 mm is tested by 8 sub-apertures. The deviation between the stitching result and the test result of a Zygo 24 inch (600 mm) interferometer peak-valley (PV) value is reduced from A/7 to A/100 after removing the virtual reference surface figure. The flatness of the virtual reference surface is 0.02 lambda (PV value), which is comparable to the real figure of the reference flat. The influence of removing of virtual reference surface on the measurement results of each sub-aperture can also be ignored. Experimental results show that the accumulated error is controlled effectively and the measurement accuracy is evidently improved by the proposed method
Source Mask Optimization Based on Dynamic Fitness Function
No full text提出了一种基于动态适应度函数的光刻机光源掩模优化方法(SMO)。动态适应度函数方法在遗传算法优化过程中采用动态适应度函数模拟真实光刻工艺条件误差对光刻结果的影响,得到对光刻工艺条件误差不敏感的优化光源和优化掩模。该方法无需优化权重系数,即可获得与权重优化后的加权适应度函数方法相近的工艺宽容度。典型逻辑图形的仿真实验表明,曝光剂量误差为15%时,动态适应度函数方法得到的优化光源和优化掩模的可用焦深达到200 nm,与加权适应度函数方法的优化效果相当。动态适应度函数方法也可用于降低SMO的优化光源和掩模对其他国家自然科学基金A dynamic source mask optimization (SMO) method is developed. The dynamic SMO method uses a dynamic fitness function in genetic algorithm to simulate the process variations in real lithography process. So the imaging quality of the optimized source and mask is not sensitive to the process errors. The dynamic SMO method can get similar result as the conventional weighted SMO method without the necessity of weighting coefficient optimization. Simulation results show that the dynamic method can get a usable defocus of 200 nm when the dose error is 15%. This is comparable with the optimized result of the weighted method. The dynamic SMO method can be also used to make the optimized source and mask less sensitive to other process errors, such as coma errors
Fabrication of microresonators of high Q/V ratios using femtosecond laser micromachining
No full textWe report on fabrication of on-chip lithium niobate (LN) microresonators with high Q/V ratio by femtosecond laser micromachining. A Purcell-factor of 2.8x10(3) is obtained in a microdisk with a diameter of 6.42 mu m
Focal spot effects on the generation of proton beams during target normal sheath acceleration
No full text973 Program [2011CB808104]; National Natural Science Foundation of China [11335013, 11125526, 11305236, 11575274]; International S&T Cooperation Program of China [2011DFA11300]; Shanghai Natural Science Foundation [13ZR1463300]Focal spot effects on the generation of proton beams are investigated by a high-intensity high-contrast laser irradiating on solid foil in target normal sheath acceleration experiments. Different spot size, transverse shape, and intensity of the laser are obtained by appropriately using deformable mirrors and parabolic mirrors. Experiments show that the maximum proton energy is mainly determined by the laser intensity if the focal spot size is not seriously changed. Compared with the previous experimental results, the optimum foil thickness d(o) is scaled by the laser intensity I as d(o) similar to I-0.33. The corresponding theoretical estimation is carried out as d(o) similar to I-0.25 for ultra-high intensity laser systems with similar contrast. MULTI and particle-in-cell simulations are used to interpret the experimental results
High-Brightness High-Energy Electron Beams from a Laser Wakefield Accelerator via Energy Chirp Control
No full textNational Natural Science Foundation of China [11127901, 11425418, 61521093, 11304271, 11205228, 11505263]; State Key Laboratory Program of Chinese Ministry of Science and Technology; Youth Innovation Promotion Association CAS; [XDB16]By designing a structured gas density profile between the dual-stage gas jets to manipulate electron seeding and energy chirp reversal for compressing the energy spread, we have experimentally produced high-brightness high-energy electron beams from a cascaded laser wakefield accelerator with peak energies in the range of 200-600 MeV, 0.4%-1.2% rms energy spread, 10-80 pC charge, and similar to 0.2 mrad rms divergence. The maximum six-dimensional brightness B-6D,B-n is estimated as similar to 6.5 x 10(15) A/m(2)/0.1%, which is very close to the typical brightness of e beams from state-of-the-art linac drivers. These high-brightness high-energy e beams may lead to the realization of compact monoenergetic gamma-ray and intense coherent x-ray radiation sources
Laser-induced periodic surface structures on 6H-SiC single crystals using temporally delayed femtosecond laser double-pulse trains
No full textNational Natural Science Foundation of China [61205128, 60908007, 11374316]; Research Foundation for Advanced Talents of Jiangsu University [09 JDG022]; Shanghai Municipal Natural Science Foundation [13ZR1414800]In this paper, a time-delay-adjustable double-pulse train with 800-nm wavelength, 200-fs pulse duration and a repetition rate of 1 kHz, produced by a collinear two-beam optical system like a Mach-Zehnder interferometer, was employed for irradiation of 6H-SiC crystal. The dependence of the induced structures on time delay of double-pulse train for parallel-polarization configuration was studied. The results show that as the time delay of collinear parallel-polarization dual-pulse train increased, the induced near-subwavelength ripples (NSWRs) turn from irregular rippled pattern to regularly periodic pattern and have their grooves much deepened. The characteristics timescale for this transition is about 6.24 ps. Besides, the areas of NSWR were found to decay exponentially for time delay from 0 to 1.24 ps and then slowly increase for time delay from 1.24 to 14.24 ps. Analysis shows that multi-photon ionization effect, grating-assisted surface plasmon coupling effect, and timely intervene of second pulse in a certain physical stage experienced by 6H-SiC excited upon first pulse irradiation may contribute to the transition of morphology details
Megahertz-level, high-power picosecond Nd:LuVO4 regenerative amplifier free of period doubling
No full textNational Science Foundation of China [11504394, 61521093, 61378030]We report on a high repetition rate, high-power picosecond Nd:LuVO4 regenerative amplifier. Period doubling caused energy instability was eliminated at megahertz-level repetition rate with the modified seeding source. A multi-pass cell was used to improve the seed pulse energy to achieve complete suppression of the onset of bifurcation. At a maximum repetition rate of 1.43 MHz, the system produced 7.0-ps-long pulses with an average output power of 25.1 W, corresponding to a pulse energy of 17.6 mu J. At 100 kHz, the pulse energy increased to 205 mu J with an average power of 20.5 W. Moreover, the injected pulses with pulse duration of 5.1 ps broadened to 8.9 ps because of gain narrowing in the amplifier. (C) 2016 Optical Society of Americ
Room temperature single-photon emission and lasing for all-inorganic colloidal perovskite quantum dots
No full textNational Natural Science Foundation of China [61475169, 61520106012, 61574024]; Fundamental Research Funds for the Central Universities [106112015CDJXY120001]; Hundred Young Talents Plan at Chongqing University [0210001104430]; SRF for ROCS, SEM [02100024Recent reports regarding metal halide semiconductors of perovskite nanocrystal structures have presented us a promising future on their optoelectronic applications such as laser and light harvesting devices. In this paper, all-inorganic perovskites CsPbX3 (X=Cl, Br and I) quantum dots (QDs) with tunable fluorescence from 400 nm to 700 nm were prepared by a facile hot-injection method. Besides, random lasing with coherent feedback was observed in films of CsPbX3 QDs. Under 400 nm optical excitation at room temperature, sharp lasing peaks emission at around 427 nm, 527 nm and 539 nm with low pump thresholds intensity were achieved by halide substitution. The dynamic fluorescence from one single quantum dot also was detailed investigated. These results demonstrated that all-inorganic perovskites could be used as low-threshold and wavelength-tunable gain materials for lasing application at room temperature. (C) 2016 Elsevier Ltd. All rights reserved
Spectroscopic analysis of high electric field enhanced ionization in laser filaments in air for corona guiding
No full textsupported in part by National Natural Science Foundation of China; the National 973 Project of China; the Chinese Academy of Sciences and the State Key Laboratory of High Field Laser Physics; the 100 Talents Program of Chinese Academy of Sciences, and theWe report on a systematic experimental study on the fluorescence spectra produced from a femtosecond laser filament in air under a high electric field. The electric field alone was strong enough to create corona discharge (CD). Fluorescence spectra from neutral and ionic air molecules were measured and compared with pure high-voltage CD and pure laser filamentation (FIL). Among them, high electric field assisted laser FIL produced nitrogen fluorescence more efficiently than either pure CD or pure FIL processes. The nonlinear enhancement of fluorescence from the interaction of the laser filament and corona discharging electric field resulted in a more efficient ionization along the laser filament zone, which was confirmed by the spectroscopic measurement of both ionization-induced fluorescence and plasma-scattered 800 nm laser pulses. This is believed to be the key precursor process for filament-guided discharge
A Single Folded Beam Magneto-Optical Trap System for Neutral Mercury Atoms
No full textNational Natural Science Foundation of China [91436105]; National Basic Research Program of China [2011CB921504]; Research Project of Shanghai Science and Technology Commission [09DJ1400700]Mercury is a promising candidate for the optical lattice clock, due to its low sensitivity to the blackbody radiation. We develop a single folded beam magneto-optical trap for the neutral mercury optical lattice clock, with a 253.7nm frequency quadrupled laser. Up to 1.7 x 10(6) ((202) Hg) or 1.5 x 10(6) ((199) Hg) atoms can be captured, and the atom temperature is lowered to 170 mu K ((202) Hg) or 50 mu K ((199) Hg). The cold atom signals of all six rich abundant isotopes are observed in this system