Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Three-dimensional edge extraction in optical scanning holography
No full textEdge extraction has found applications in various image processing fields, such as in pattern recognition. In this paper, a new method is proposed for edge extraction of three-dimensional objects in optical scanning holography (OSH). Isotropic and anisotropic edge extraction of 3D objects is simulated using spiral phase plates in OSH operating in an incoherent mode. We propose to use a delta function and a spiral phase plate as the pupil functions to realize isotropic and anisotropic edge extraction. Our computer simulations show the capability of extracting the edges of a given 3D object by spiral phase filtering in OSH
Design and Implementation of a Cloud Based Lithography Illumination Pupil Processing Application
No full textPupil parameters are important parameters to evaluate the quality of lithography illumination system. In this paper, a cloud based full-featured pupil processing application is implemented. A web browser is used for the UI (User Interface), the websocket protocol and JSON format are used for the communication between the client and the server, and the computing part is implemented in the server side, where the application integrated a variety of high quality professional libraries, such as image processing libraries libvips and ImageMagic, automatic reporting system latex, etc., to support the program. The cloud based framework takes advantage of server's superior computing power and rich software collections, and the program could run anywhere there is a modern browser due to its web UI design. Compared to the traditional way of software operation model: purchased, licensed, shipped, downloaded, installed, maintained, and upgraded, the new cloud based approach, which is no installation, easy to use and maintenance, opens up a new way. Cloud based application probably is the future of the software development
Measurement precision improvement for excimer laser pulse energy sensor based on a special finite impulse response filter
No full textIn deep ultraviolet lithographic tools, precise measurement of excimer laser pulse energy is essential. However, system noise of the energy sensor, which is used to monitor the laser pulse during exposure dose control, complicate pulse energy measurement. To improve measurement precision, a specific finite impulse response filter is proposed for signal denoising. Particularly, the convolution kernel of the specific finite impulse response filter is derived from the nonlinear fitting of the energy sensor output. Experimental results show that the measurement precision of the energy sensor improves 2-3 times with the specific finite impulse response filter. To verify the effectiveness of the energy sensor, it is used for transmittance measurement; the measurement result of a Corning 7980 witness sample is consistent with that measured by a commercial ultraviolet spectrophotometer and the measurement accuracy is 0.11% (k = 2)
Far-field outdoor experimental demonstration of down-looking synthetic aperture ladar
No full textNational Natural Science Foundation of China [61605226, 61505233]; Shanghai Astronomical Observatory, Chinese Academy of SciencesA specific system structure of down-looking synthetic aperture imaging ladar (SAIL) is given, and a far-field experiment over 6 km of down-looking SAIL under this system design is carried out. The down-looking SAIL can overcome the influence of atmospheric turbulence to a great extent. By applying this system design, it also has advantages in self-compensating phase modulation. A fine image is obtained after aligning in the orthogonal direction and phase error compensation in the travel direction based on a dominant scatterer. The achieved imaging resolutions in the two dimensions are both better than 5 cm
Mode suppression employing periodical large-small-core (PLSC) filter in strongly pumped large mode area fiber amplifier
No full textNational Key Research and Development Program [2016YFB0402201]; NSAF Foundation of National Natural Science Foundation of China [U1330134]; National Natural Science Foundation of China [61308024]; Natural Science Foundation of Shanghai [16ZR1440100, 16ZR1440200]; Key Technologies R&D Program of Jiangsu [BE2014001]Mode instability (MI) has become one of the main restrictions for further power scaling of large mode area (LMA) fiber systems. A periodical large-small-core (PLSC) filter in a strongly pumped LMA fiber amplifier based on multimode interference and self-imaging effect is proposed to suppress high order modes and improve the beam quality. An investigation on the modeling of light propagation within this filter structure is presented. Transverse mode competition and individual transverse mode power distribution in a strongly pumped fiber amplifier are theoretically analyzed. By employing this PLSC mode filter in the 30/400 strongly pumped LMA fiber amplifier, the percentage of the fundamental mode rises from 27.8% (without filter) to 95.6%, and the percentage of the high order modes correspondingly reduces from 72.2% (without filter) to 4.4%. By the modal power decomposition, the optical field pattern in free space is established and the M-2 parameter of beam quality decreases dramatically from 2.24 to 1.12 (0 relative phase) and from 3.01 to 1.28 (pi/2 relative phase). This study provides a new method to achieve high beam quality in LMA fiber amplifiers and this filter would be extended to larger mode area fiber amplifiers
Temperature insensitive high energy Q-switched Nd:YAG slab laser
No full textNational Key Research and Development Program of China [2016YFC1400902]A temperature insensitive high energy Nd:YAG Q-switched laser operating over a temperature variation range of 35 degrees C is presented. Multi-wavelength (lambda) laser diode (LD) stacks and a hexagon Nd:YAG slab with an effective absorption length of 46 mm are adopted to diminish the output energy fluctuation due to the temperature changing. A couple of crossed Porro prisms are used to form a folded laser cavity with polarization coupled output, and actively Q-switched operation is realized by using a KD*P Pockels cell. Output pulse energy of about 128 mJ is obtained over the temperature range of 10-45 degrees C, corresponding to an optical-to-optical efficiency of 14% and a slope efficiency of 21%. The pulse duration and beam divergence are around 17 ns and 2.8 mrad respectively
Depth-dependent dispersion compensation for full-depth OCT image
No full textInnovation Action Plan of Science and Technology Commission of Shanghai Municipality [15441905600]; Open Fund of Key Laboratory of Optoelectronic Information Processing of University in Guangxi [KFJJ2016-04]; National Natural Science Foundation of China [61405210]A depth-dependent dispersion compensation algorithm for enhancing the image quality of the Fourier-domain optical coherence tomography (OCT) is presented. The dispersion related with depth in the sample is considered. Using the iterative method, an analytical formula for compensating the depth-dependent dispersion in the sample is obtained. We apply depth-dependent dispersion compensation algorithm to process the phantom images and in vivo images. Using sharpness metric based on variation coefficient to compare the results processed with different dispersion compensation algorithms, we find that the depth-dependent dispersion compensation algorithm can improve image quality at full depth. (C) 2017 Optical Society of Americ
Accelerating gradient improvement from hole-boring to light-sail stage using shape-tailored laser front
No full textNational Natural Science Foundation of China [11125526, 11335013, 11575274, 11305236]; Shanghai Natural Science Foundation [13ZR1463300]The accelerating gradient of a proton beam is a crucial factor for the stable radiation pressure acceleration, because quickly accelerating protons into the relativistic region may reduce the multidimensional instability grow to a certain extent. In this letter, a shape-tailored laser is designed to accelerate the protons in a controllable high accelerating gradient in theory. Finally, a proton beam in the gigaelectronvolt range with an energy spread of similar to 2.4% is obtained in one-dimensional particle-in-cell simulations. With the future development of the high-intense laser, the ability to accelerate a high energy proton beam using a shape-tailored laser will be important for realistic proton applications, such as fast ignition for inertial confinement fusion, medical therapy, and proton imaging. Published by AIP Publishing
Comparison of high-energy multi-pass Ti:sapphire amplifiers with a different Ti-dopant concentration
No full textWe experimentally compare the output abilities of lightly and heavily doped Ti:Sapphire (Ti:S) amplifiers with diameters as large as 150 mm. Although a lightly doped Ti: S is more favorable to overcome parasitic lasing (PL) and transverse amplified spontaneous emission (TASE), the self-phase-modulation (SPM) effect becomes more pronounced when a longer crystal is used. Recompression of the amplified, stretched pulses can be seriously affected by the SPM effect. We then propose a temporal multi-pulse pump scheme to suppress PL and TASE in a thin, heavily doped Ti: S crystal. This novel temporal multi-pulse pump technique can find potential applications in 10 PW chirped-pulse amplification laser systems
Corona discharge induced snow formation in a cloud chamber
No full textNational Basic Research Program of China [2011CB808100]; Shanghai Science and Technology Talent Project [12XD1405200]; 100 Talents Program of Chinese Academy of Sciences; Shanghai Pujiang Program; Laval University, Quebec City, CanadaArtificial rainmaking is in strong demand especially in arid regions. Traditional methods of seeding various Cloud Condensation Nuclei (CCN) into the clouds are costly and not environment friendly. Possible solutions based on ionization were proposed more than 100 years ago but there is still a lack of convincing verification or evidence. In this report, we demonstrated for the first time the condensation and precipitation (or snowfall) induced by a corona discharge inside a cloud chamber. Ionic wind was found to have played a more significant role than ions as extra CCN. In comparison with another newly emerging femtosecond laser filamentation ionization method, the snow precipitation induced by the corona discharge has about 4 orders of magnitude higher wall-plug efficiency under similar conditions