Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Method of pupil shaping for off-axis illumination in optical lithography
No full textOff-axis illumination is one of the key resolution enhancement technologies in projection lithography systems. Phase type diffractive optical elements are adopted by most of the lithography machine manufacturers to realize off-axis illumination. In this paper, a method of pupil shaping for off-axis illumination in optical lithography is introduced which contains a zoom beam expander, circularly symmetric diffractive optical elements, and a Fourier lens. The method could produce the required illumination pattern for off-axis illumination at the pupil plane. Compared with the conventional method of off-axis illumination, the method in this paper could eliminate deterioration of the pupil thoroughly and reduces the difficulty of the optical design of the zoom lens. Based on this method, several circularly symmetric diffractive optical elements are designed for experiments, and a remarkable improvement in eliminating deterioration of the pupil is observed compared with the conventional method. (C) 2016 Optical Society of America
Nonsubsampled contourlet transform method for optical fringe pattern analysis in profilometry and interferometry
No full textNational Natural Science Foundation of China (NSFC) [61205102, 61275207, 61474129, 61405210]A method based on a nonsubsampled contourlet transform, which is an overcomplete transform with multiresolution, directionality, and shift-invariance properties, is proposed to extract the fundamental frequency component of an optical fringe pattern in profilometry and interferometry. The nonsubsampled contourlet transform method overcomes the disadvantages of the original contourlet transform method, which lacks the shift-invariance property. Besides, it improves the frequency selectivity. A strategy is developed to automatically determine the optimal decomposition scale for removing the background intensity and suppressing the noise of the fringe pattern. The proposed method is precise, effective, and possesses a strong noise immune ability. Simulations and experiments verify the validity, and show the superiorities of the proposed method. (C) 2016 Optical Society of Americ
Radial period extraction method employing frequency measurement for quantitative collimation testing
No full textNational Natural Sciences Foundation of China (NSFC) [61205102, 61275207, 61474129, 61405210]A radial period extraction method employing frequency measurement is proposed for quantitative collimation testing using spiral gratings. The radial period of the difference-frequency fringe is treated as a measure of the collimation condition. A frequency measurement technique based on wavelet transform and a statistical approach is presented to extract the radial period directly from the amplitude-transmittance spiral fringe. A basic constraint to set the parameters of the wavelet is introduced. Strict mathematical demonstration is given. The method outperforms methods employing phase measurement in terms of precision, stability and noise immune ability. (C) 2015 Published by Elsevier B.V
A facile method to fabricate superamphiphobic polytetrafluoroethylene surface by femtosecond laser pulses
No full textNational Natural Science Foundation of China [61178024, 11374316]; National Basic Research Program of China [2011CB808103]We report a simple method to fabricate superamphiphobic polytetrafluoroethylene (PTFE) surfaces by femtosecond laser direct irradiation. After femtosecond laser direct writing, a dual-scale composite structure combined a groove-like microstructure with a lamellar submicron structure forms on the PTFE surface, enhancing its hydrophobic properties with a contact angle increasing from 109 degrees to 156.88 degrees, as well as exhibiting transition from intrinsic oleophilicity to superoleophobicity. Meanwhile, the wett-ability of the surface can be tuned by changing the roughness and the interval between two adjacent micro-grooves. Furthermore, we also explain the relationship between the interval width and the contact angle using the Cassie-Baxter model. (C) 2015 Elsevier B.V. All rights reserved
Broadband spectrographic method for precision alignment of compression gratings
No full textNational Basic Research Program of China [2011CB808101]; National Natural Science Foundation of China (NSFC) [11304296, 61078037, 11127901, 11134010, 61205208, 11204328]Previous research on achieving the alignment of compression gratings has mainly focused on the parallelism of the gratings. We propose a promising method to achieve parallelism and especially accurately adjust the grating to its optimum working angle to achieve dispersion compensation. A spectrometer and a precisely adjustable mirror pair are cooperatively used to measure the wavelength of the light diffracted by the grating, satisfying the Littrow condition. Meanwhile, the tiny slit of the spectrometer can decrease the grating-tip and in-plane rotation error during the alignment procedure. Using this technique, the residual phase of the compressed pulse is optimized and the compressed pulse duration is 25.4 fs, which is 1.06 times that of the Fourier-transform-limited compressed pulse. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE
Compact design for two-dimensional electronic spectroscopy
No full textNational Natural Science Foundation of China (NSFC) [61178006, 11274327, 61527821, 11420101003, 11274232, 61308068]; Shanghai Committee of Science and Technology [13ZR1463000]; Open Fund of the State Key Laboratory of High Field Laser Physics (Shanghai InWe present a passively phase-stabilized two-dimensional electronic spectroscopy (2DES) with a compact size, and the ease of implementation and maintenance. Our design relies on a mask beam-splitter with four holes to form non-collinear box geometry, and a homebuilt stacked retroreflector, which introduces the phase-locked pulse sequence, remedying the instability of commonly used translation stages. The minimized size of the setup suppresses the influences of optical path-length fluctuations during measurements, improving the phase stability and precise timing of pulse sequences. In our 2DES, only few conventional optical components are used, which make this sophisticated instrumentation convenient to establish and particularly easy to conduct alignment. In data analysis, the self-referencing spectral interferometry (SRSI) method is first introduced to extract the complex-valued signal from spectral interferometry in 2DES. The alternative algorithm achieves the improvement of the signal-to-noise ratio (SNR) and considerable reduction of data acquisition time. The new setup is suitable over a tunable range of spectroscopic wavelength, from ultraviolet (UV) to the near-infrared (NIR) regime, and for ultra-broadband bandwidth, few-cycle laser pulses
Excitonic and vibrational coherence in artificial photosynthetic systems studied by negative-time ultrafast laser spectroscopy
No full text100 Talents Program of CAS; National Natural Science Foundation of China [61475169, 61521093, 11127901]Quantum coherences between excitonic states are believed to have a substantial impact on excitation energy transfer in photosynthetic systems. Here, the excitonic and vibrational coherence relaxation dynamics of artificially synthetic chlorosomes are studied by a sub 7 fs negative-time-delay laser spectroscopy at room temperature. The results provide direct evidence for the quantum coherence of the excitonic dephasing time of 23 +/- 1 fs at physiologically relevant temperatures, which is significant in the initial step of energy transfer in chlorosome or chlorosome-like photosynthetic systems. Meanwhile, coherent molecular vibrations in the excited state are also detected without the effect of wave-packet motion in the ground state, which shows that the excited state wave-packet motion contributes greatly to the vibrational modes of similar to 150 and similar to 1340 cm(-1) in artificial chlorosome systems
Temporal contrast improvement based on the self-diffraction process with a cylinder mirror
No full textNational Natural Science Foundation of China (NSFC) [61178006, 11274327, 61521093, 61527821]; Chinese Academy of Sciences [YZ201538]A cylinder reflective mirror was used to increase incident pulse energy to multi-millijoules in the research of temporal contrast enhancement based on a self-diffraction (SD) process. A 170 mu J first-order SD pulse with temporal contrast improved by 4 orders of magnitude was obtained when incident pulse energy was 5.1 mJ. In order to improve energy-conversion efficiency, a 67/33 beam splitter was used to replace the original 50/50 one. A 265 mu J first-order SD signal was achieved without damage of the glass plate at 3.7 mJ input pulse energy with an energy-conversion efficiency of about 7.1%. The generated SD pulse is expected to be used as the seed of high-contrast and high-power laser systems
Transverse writing of three-dimensional tubular optical waveguides in glass with a slit-shaped femtosecond laser beam
No full textNational Basic Research Program of China [2014CB921300]; National Natural Science Foundation of China [61590934, 11134010, 61327902]; Youth Innovation Promotion Association of Chinese Academy of SciencesWe report on fabrication of tubular optical waveguides buried in ZBLAN glass based on transverse femtosecond laser direct writing. Irradiation in ZBLAN with focused femtosecond laser pulses leads to decrease of refractive index in the modified region. Tubular optical waveguides of variable mode areas are fabricated by forming the four sides of the cladding with slit-shaped femtosecond laser pulses, ensuring single mode waveguiding with a mode field dimension as small as similar to 4 mu m
Effective development of Faraday rotator based on the highly transparent Tb2.96Pr0.04Ga5O12 single crystal
No full textNature Science Foundation of China [51472257]Highly transparent Tb2.96Pr0.04Ga5O12 single crystal was grown by the Czochralski (Cz) method. X-ray powder diffraction was carried out, and lattice parameters were calculated, which showed that the single crystal belongs to cubic crystal system. The full width at half maximum of the rocking curve for the crystal was about 28 arcsec that showed the high crystallinity of the crystal. The optical and magneto-optical properties of Tb2.96Pr0.04Ga5O12 are analyzed in detailed. The grown crystal exhibited a very high transmittance, particularly in the visible region. Measurements of the Faraday rotation and Verdet constant spectrum at different temperatures were investigated at VIS-NIR region. The increase in Verdet constant and magneto-optical figure of merit compared to that of TGG shows the superior characteristics of Tb2.96Pr0.04Ga5O12 compared to TGG, indicating that it has great potential to meet the increasing demand for magneto-optical devices in the VIS-NIR region