Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Synthesis of multifunction optical filter based on digital signal processing method
No full textNational Natural Science Foundation of China [51472258]; Innovation Program of Shanghai Municipal Education Commission [15ZZ045]By a digital signal processing method, a multifunction optical filter is synthesized. The filter is formed by a Mach-Zehnder interferometer with two cascaded double-ring resonators and a single-ring resonator on the two arms respectively. It can operate as a symmetrical interleaver, an asymmetrical interleaver with arbitrary duty cycles, a notch filter with a single notch point and a notch filter with two notch points. These four functions can be realized by choosing appropriate structural parameters. The configurable and tunable features make it useful in the future intelligent optical communication networks
Imaging process and signal-to-noise ratio improvement of enhanced self-heterodyne synthetic aperture imaging ladar
No full textNational Natural Science Foundation of China [61605226, 61505233]; Key Laboratory of Space Laser Communication and Detection Technology of Chinese Academy of SciencesThis Letter gives the general construction of an enhanced self-heterodyne synthetic aperture imaging ladar ( SAIL) system, and proposes the principle of image processing. A point target is reconstructed in the enhanced self-heterodyne SAIL as well as in down-looking SAIL experiments, and the achieved imaging resolution of the enhanced self-heterodyne SAIL is analyzed. The signal-to-noise ratio (SNR) of the point target final image in the enhanced self-heterodyne SAIL is higher than that in the down-looking SAIL. The enhanced self-heterodyne SAIL can improve the SNR of the target image in far-distance imaging, with practicality
Raman fiber lasers
No full textHigh-power fiber lasers have seen tremendous development in the last decade, with output powers exceeding multiple kilowatts from a single fiber. Ytterbium has been at the forefront as the primary rare-earth-doped gain medium owing to its inherent material advantages. However, for this reason, the lasers are largely confined to the narrow emission wavelength region of ytterbium. Power scaling at other wavelength regions has lagged significantly, and a large number of applications rely upon the diversity of emission wavelengths. Currently, Raman fiber lasers are the only known wavelength agile, scalable, high-power fiber laser technology that can span the wavelength spectrum. In this review, we address the technology of Raman fiber lasers, specifically focused on the most recent developments. We will also discuss several applications of Raman fiber lasers in laser pumping, frequency conversion, optical communications and biology
Wavelength calibration of narrowband ArF laser with iron hollow cathode lamp
No full textNational Science and Technology Major Project [2013ZX02202003]; National Key Research and Development Program [2016YFB0402201]; K. C. Wong Education Foundation; Program of Shanghai Technology Research Leader [17XD1424800]; Shanghai Sailing Program of Talented Youth in Science and Technology [17YF1421200]; Key Technologies R&D Program of Jiangsu [BE2014001, BE2016005-4]; Natural Science Foundation of Shanghai [16ZR1440100, 16ZR1440200]; NSAF Foundation of National Natural Science Foundation of China [U1330134, 61405202]Accurate and precise wavelength controlling of narrowband excimer lasers is essential for the lithography of an integrated circuit. High-precision wavelength tuning and calibration of a line-narrowed ArF laser are presented in this work. The laser spectrum is narrowed to a sub-picometer with a line narrowing system. Absolute wavelength calibration of the line-narrowed laser is performed based on the optogalvanic (OG) effect using iron hollow cathode discharge (HCD). An sccuracy of better than 0.1 pm for wavelength tuning and calibration is achieved with our homemade wavemeter
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
Monodisperse beta-NaYF4:Yb3+, Tm3+ hexagonal microplates with efficient NIR-to-NIR up-conversion emission developed via ion exchange
No full textChina: National Natural Science Foundation of China [61405215, 61505232]; Germany: Helmholtz Association's research program Science and Technology of Nanosystems (STN)Monodisperse beta-NaYF4:Yb3+, Tm3+ (NYF) hexagonal microplates with efficient near-infrared (NIR)-to-NIR up-conversion (UC) developed via a new ion-exchange modified hydrothermal method are reported. Ion exchange modification (IEM) not only significantly increases the UC intensity by up to 1000 times and prolongs the emission lifetimes of Tm3+ and Yb3+, but also enables the monodisperse morphology and size of hexagonal microplates to be maintained. A high UC quantum efficiency (QE) of 3.1% is obtained for IEM beta-NaYF4: 20%Yb3+, 1%Tm3+ when excited with 980 nm light at a power density of 10W cm(-2). The UC emission properties can be finely tailored by changing the NaF/NYF molar ratio (NYF represents lanthanide doped beta-NaYF4) and the doping concentration of Tm3+. The two photon NIR UC emission centered at B803 nm (arising from Tm3+:3H(4)-3H(6)) dominates the UC emission spectrum and high concentrations of Tm3+ favor NIR UC further. A proof-of-concept optical image of printed patterns is demonstrated to verify their applications in security. These results suggest the promising applications of the newly developed monodisperse beta-NaYF4:Yb3+, Tm3+ hexagonal microplates in security, luminescent labels, solid-state lasers, amplifiers, and biomedicine
Spectral Properties of Er3+/Tm3+ Co-Doped ZBLAN Glasses and Fibers
No full textNational Natural Science Foundation of China [51272265, 61405215]; Natural Science Foundation of Shanghai [17ZR1434000]; China Postdoctoral Science Foundation [2016M601653]A series of Er3+/Tm3+ co-doped fluoride (ZBLAN) glasses and fibers was prepared and their fluorescence spectra was measured under excitation at 793 nm and 980 nm. Correlation between the self-absorption effect of rare-earth ions and the shift of the emission peak was investigated. With the increasing length of fiber, the emission peaks red-shift when self-absorption occurs at the upper level of emission transition or blue-shift when that occurs at the lower level. As a result of the strong self-absorption effect, Er3+/Tm3+ co-doped fibersmainly yield 1390-1470, 1850-1980, and 2625-2750 nm emissions when excited at 793 nm, and 1480-1580, 1800-1980, and 2625-2750 nm emissions when excited at 980 nm. Further, a broadband emission in the range of 1410-1580 nm covering the S + C communication band was obtained by the dual-pumping scheme of 793 nm and 980 nm. Results suggest that the dual-pumping scheme would be more effective and important for an Er3+/Tm3+ co-doped fiber amplifier working in the S + C communication band
A brief review on perovskite multiferroics
No full textShanghai University of Engineering Science [2014-35]; Shanghai Municipal Education Commission [ZZgcd14009]The paper first introduces the basic physics behind perovskite multiferroics. Then the recent progress on simple, complex perovskites, and manganites are briefly reviewed. The review discloses two important directions on achievement multiferrocity in perovskite: pay with strain engineering and adjust octahedral deformation. The authors also suggest that specific issues like leakage current and characterization platforms are also very important for the study of multiferroics
Attitude-error compensation for airborne down-looking synthetic-aperture imaging lidar
No full textNational Nature Science Foundation of China (NSF) [61605226, 61505233]Target-coordinate transformation in the lidar spot of the down-looking synthetic-aperture imaging lidar (SAIL) was performed, and the attitude errors were deduced in the process of imaging, according to the principle of the airborne down-looking SAIL. The influence of the attitude errors on the imaging quality was analyzed theoretically. A compensation method for the attitude errors was proposed and theoretically verified. An airborne down-looking SAIL experiment was performed and yielded the same results. A point-by-point error-compensation method for solving the azimuthal-direction space-dependent attitude errors was also proposed
Single scan femtosecond laser transverse writing of depressed cladding waveguides enabled by three-dimensional focal field engineering
No full textNational Basic Research Program of China [2013CB921904]; National Natural Science Foundation of China (NSFC) [11474010, 61590933, 11527901]; State Key Laboratory on Integrated Optoelectronics [IOSKL2015KF36]We report single scan transverse writing of depressed cladding waveguides inside ZBLAN glass with the longitudinally oriented annular ring-shaped focal intensity distribution of the femtosecond laser. The entire region of depressed cladding at the cross section, where a negative change of refraction index is induced, can be modified simultaneously with the ring-shaped focal intensity profile. The fabricated waveguides exhibit good single guided mode