Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Generation of square arrays of curved Bessel-like beams using continuous-phase encoding gratings
No full textNational Natural Science Foundation of China (NSFC) [61675093]We propose a scheme based on a type of continuous-phase encoding grating for the generation of multiple curved Bessel-like beams simultaneously. It is shown that multiple identical curved Bessel-like beams that diverge from a common center can be generated by overlapping a specially designed phase with a continuous-phase grating, and multiple high-order curved Bessel-like beams can be generated when another spiral phase is embedded. As an example, a 5 x 5 symmetric continuous-phase grating embedded with the special designed phase and a spiral phase is demonstrated based on a spatial light modulator. The experimental results show that 5 x 5 square arrays of bright- and dark-center curved Bessel-like beams were well generated. The proposed method provides an interesting method for obtaining simultaneously multiple curved Bessel-like beams, which should be of high interest for its promising applications in parallel optical manipulation, optical guiding, laser machining or laser surgery, particle acceleration, etc
Coherent supercontinuum in a silicate glass composite fiber with all-normal dispersion
No full textWith all-normal-dispersion fibers, highly coherent supercontinuum (SC) can be obtained, which has several applications. Traditional air-hole photonic crystal fibers encountered some limitations for such light emission. In this study, all solid composite fibers with a silica glass cladding and a yttria-alumino-silicate glass core were fabricated, which were designed for flat coherent SCs. We achieved a flat normal dispersion in this composite fiber. Flat SCs were experimentally demonstrated with different pump conditions. The simulated SC spectra coincided well with the experimental results. It also indicated that a coherent SC with more than one octave can be obtained with higher input power
Study of a grating interferometer with high optical subdivision technique
No full textDisplacement laser interferometers and grating interferometers are two main apparatus for the micron-nanometer displacement measurement over a long range. However, the laser interferometers, whose measuring scale is based on the wavelength, are very sensitive to the environment. On the contrast, the grating interferometers change the measuring scale from wavelength to grating period, which is much stable for the measurement results. But the resolution of grating interferometer is usually lower than that of laser interferometer. Therefore, further investigation is needed to improve the performance of grating interferometer. As we known, the optical subdivision is a main factor that affects the measurement resolution. In this paper, a grating interferometer with high optical subdivision is presented based on the Littrow configuration. We mainly use right angle prisms accompanied with plane mirrors to make the measuring lights diffracted by the grating scale for many times. An optical subdivision factor of 1/24 can be obtained by this technique. A main difficulty of this technique is that the grating scale should be with high diffraction efficiency. Fortunately, the measuring light is incident on the grating scale at the Littrow angle, the grating scale can be designed with very high efficiency easily in this condition. Compared with traditional grating interferometers, this kind of grating interferometer can greatly increase the measuring resolution and accuracy, which could be widely used in nanometer-scale fabrications and measurements
Three-dimensional identification card and applications
No full textThree dimensional Identification Card, with its three-dimensional personal image displayed and stored for personal identification, is supposed be the advanced version of the present two-dimensional identification card in the future [ 1]. Three dimensional Identification Card means that there are three-dimensional optical techniques are used, the personal image on ID card is displayed to be three-dimensional, so we can see three dimensional personal face. The ID card also stores the three-dimensional face information in its inside electronics chip, which might be recorded by using two-channel cameras, and it can be displayed in computer as three-dimensional images for personal identification. Three-dimensional ID card might be one interesting direction to update the present two-dimensional card in the future. Three-dimension ID card might be widely used in airport custom, entrance of hotel, school, university, as passport for on-line banking, registration of on-line game, etc..
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
High Speed Computational Ghost Imaging via Spatial Sweeping
No full textNational Natural Science Foundation of China [61327902, 61377005]; Chinese Academy of Sciences [QYZDB-SSW-JSC002]Computational ghost imaging (CGI) achieves single-pixel imaging by using a Spatial Light Modulator (SLM) to generate structured illuminations for spatially resolved information encoding. The imaging speed of CGI is limited by the modulation frequency of available SLMs, and sets back its practical applications. This paper proposes to bypass this limitation by trading off SLM's redundant spatial resolution for multiplication of the modulation frequency. Specifically, a pair of galvanic mirrors sweeping across the high resolution SLM multiply the modulation frequency within the spatial resolution gap between SLM and the final reconstruction. A proof-of-principle setup with two middle end galvanic mirrors achieves ghost imaging as fast as 42 Hz at 80 x 80-pixel resolution, 5 times faster than state-of-the-arts, and holds potential for one magnitude further multiplication by hardware upgrading. Our approach brings a significant improvement in the imaging speed of ghost imaging and pushes ghost imaging towards practical applications
Modal analysis of 1 x 3 reflective triangular gratings under normal incidence
No full textNational Natural Science Foundation of China (NSFC) [61307064, 61405214]; Ministry of Science and Technology of China (MOST) [2012YQ170004]Modal analysis of the 1 x 3 highly efficient reflective triangular grating operating in the 800 nm wavelength under normal incidence for TE polarization is presented in this Letter. The rigorous coupled wave analysis and simulated annealing algorithm are used to design this beam splitter. The reflective grating consists of a highly reflective mirror and a transmission grating on the top. The mechanism of the reflective triangular grating is clarified by the simplified modal method. Then, gratings are fabricated by direct laser writing lithography
Monocular Vision-Based Underwater Object Detection
No full textNational Natural Science Foundation of China [61501173, 61671201]; Natural Science Foundation of Jiangsu Province [BK20150824]; Fundamental Research Funds for the Central Universities [2017B01914]; Jiangsu Overseas Scholar Program for University Prominent Young & Middle-aged Teachers and PresidentsIn this paper, we propose an underwater object detection method using monocular vision sensors. In addition to commonly used visual features such as color and intensity, we investigate the potential of underwater object detection using light transmission information. The global contrast of various features is used to initially identify the region of interest (ROI), which is then filtered by the image segmentation method, producing the final underwater object detection results. We test the performance of our method with diverse underwater datasets. Samples of the datasets are acquired by a monocular camera with different qualities (such as resolution and focal length) and setups (viewing distance, viewing angle, and optical environment). It is demonstrated that our ROI detection method is necessary and can largely remove the background noise and significantly increase the accuracy of our underwater object detection method
Tapered simplified modal method for analysis of non-rectangular gratings
No full textU.S. Department of Homeland Security (DHS) [HSHQDC-13-C-B0040]The simplifiedmodal method (SMM) [Opt. Quantum Electron. 37, 309 (2005)] provides a quick, intuitive way to analyze the performance of the gratings of rectangular shapes. For non-rectangular shapes, a version of SMM has been developed [Opt. Lett. 33, 1554 (2008)], but it applies only to the Littrow-mounting incidence case and neglects reflection. Here, we use the theory of mode-coupling in a tapered waveguide to improve SMM so that it applies to non-rectangular gratings at arbitrary angles of incidence. Moreover, this new tapered simplified modal method (TSMM) allows us to properly account for reflected light and requires fewer coupled guided modes to compute the correct diffracted field than required plane wave modes in rigorous coupled wave analysis (RCWA). We present here the analytical development of the theory and numerical simulations, demonstrating the validity of the method by comparing it with RCWA and the finite difference time domain method. (C) 2016 Optical Society of Americ
Demonstration of a diode pumped Nd,Y co-doped SrF2 crystal based, high energy chirped pulse amplification laser system
No full textShanghai Sailing Program [15YF1413500]; National Natural Science Foundation of China (NSFC) [11127901, 11134010, 61422511, 51432007]We report, to the best of our knowledge, a chirped pulse amplification laser system based on the Nd,Y:SrF2 crystal for the first time. The incorporation of Y3+ nonactive ions can significantly improve laser properties of Nd:SrF2 crystal, including broader emission linewidth, larger cross-section as well as longer fluorescence lifetime. Pulse laser with 5.1 mJ (uncompressed), 3.7 mJ (compressed) energy, 1.6 ps duration at 5 Hz repetition rate is demonstrated. The results indicate that the Nd,Y:SrF2 crystal is a potential candidate with excellent laser and thermal performance for developing ultra-intense laser with high repetition rate. (C) 2016 Elsevier B.V. All rights reserved