Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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iPrivacy: Image Privacy Protection by Identifying Sensitive Objects via Deep Multi-Task Learning
No full textNational Science Foundation [1651166-CNS, 1651455-CNS]; National Natural Science Foundation of China [61622205]; Zhejiang Provincial Natural Science Foundation of China [LR15F020002]To achieve automatic recommendation of privacy settings for image sharing, a new tool called iPrivacy (image privacy) is developed for releasing the burden from users on setting the privacy preferences when they share their images for special moments. Specifically, this paper consists of the following contributions: 1) massive social images and their privacy settings are leveraged to learn the object-privacy relatedness effectively and identify a set of privacy-sensitive object classes automatically; 2) a deep multi-task learning algorithm is developed to jointly learn more representative deep convolutional neural networks and more discriminative tree classifier, so that we can achieve fast and accurate detection of large numbers of privacy-sensitive object classes; 3) automatic recommendation of privacy settings for image sharing can be achieved by detecting the underlying privacy-sensitive objects from the images being shared, recognizing their classes, and identifying their privacy settings according to the object-privacy relatedness; and 4) one simple solution for image privacy protection is provided by blurring the privacy-sensitive objects automatically. We have conducted extensive experimental studies on real-world images and the results have demonstrated both the efficiency and effectiveness of our proposed approach
Stably dispersed metallophthalocyanine noncovalently bonded to multiwalled carbon nanotubes for ammonia sensing at room temperature
No full textNational Natural Science Foundation of China [51202061, 51002046]; Natural Science Foundation for the Returned Overseas Scholars of Heilongjiang Province [LC2012CO2]; Natural Science of Heilongjiang Province [B201308]; Research Fund of Heilongjiang Provincial Education Department [12511377, 12521399]; Postdoctoral Science-Research Developmental Foundation of Heilongjiang Province [LBH-Q11015]; Innovative Talents Program for the Returned Overseas Scholars of Harbin [2012RFLXG031]; Opening Project Foundation of Key Laboratory of Functional Inorganic Material Chemistry (Heilongjiang University),Herein, a series of tetra-alpha-isopentyloxyphthalocyanine copper, nickle, lead (CuPc-3, NiPc-3, PbPc-3) have been successfully bonded on the surface of acidified multi-walled carbon nanotubes (MWCNTs) by using a solution self-assembly method based on pi-pi stacking interaction facile reaction. The obtained MPc-3/MWCNTs (M = Cu, Ni, and Pb) hybrids display good dispersibility in DMF, which is beneficial to construct uniform sensing devices. The MPc-3/MWCNTs sensors exhibit excellent sensing performance, in terms of sensitivity, reversibility, reproducibility, selectivity and stability, especially CuPc-3/MWCNTs sensor in detail, the response is about 40.5% (80 ppm), the limit of detection is as low as 75 ppb, and the recovery time is about as fast as 180 s at room temperature. The enhanced NH3-sensing performance is mainly due to the synergistic effect between MPc-3 and MWCNTs, e.g. the stronger adsorption interaction of MPc3 with NH3, the high electrical conductivity of MWCNTs, and the fast charge transfer between MPc-3 and MWCNTs. The systematic study developed here provides a valid way to fabricate high-efficient NH3 sensors. (C) 2017 Elsevier B.V. All rights reserved
5 W output power from a double-clad hybrid fiber with Yb-doped phosphate core and silicate cladding
No full textNatural Science Foundation of Shanghai [17ZR1434000]; Youth Innovation Promotion Association of the Chinese Academy of Sciences; National Natural Science Foundation of China (NSFC) [61405215, 61505232]; National High Technology Research and Development Program of China [2016YFB0402201]; China Postdoctoral Science Foundation [2016M601653]; Key Technologies R and D Program of Jiangsu [BE2014001, BE2016005]For the first time, to the best of our knowledge, we report on the realization of a laser from a Yb-doped phosphate core/silicate cladding double-clad hybrid fiber. 5 W output power was extracted with 14.6% slope efficiency and a laser spectrum of a 1027 nm central wavelength from a 20 cm long single-mode fiber with a similar to 10 mu m core diameter in a 20%-4% laser cavity. The laser efficiency can be significantly enhanced by correspondingly adjusting and optimizing the laser oscillator
Effect of B2O3 content on structure and spectroscopic properties of neodymium-doped calcium aluminate glasses
No full textNd2O3-doped calcium aluminate glasses was synthesized with the following compositions: (100 - x)(33Al(2)O(3)-62CaO-2MgO-3BaO)-xB(2)O(3)-0.5Nd(2)O(3) (x = 0, 2.5, 5, 7.5, 10). The Raman, absorption, and emission spectra were measured to characterize the structure and spectroscopic properties of these glasses. The glass thermal stability was studied using differential scanning calorimetry (DSC) tests. Both the Raman spectra and DSC results indicated a decrease in the non-bridging oxygens (NBOs) in the [AlO4](-) network with an increase in the B2O3 content. The J-O intensity parameter Omega(2), covalency degree of the Nd-O bond, and emission bandwidth of the Nd3+ ions decreased with the B2O3 content. The stimulated emission cross-section and optical gain property increased with an increase in the B2O3 content. The tunable gain property and broadband emission feature of the Nd3+-doped CaO-Al2O3-B2O3MgO-BaO calcium aluminate glass suggested a potential application to a high-energy ultra-short-pulse laser. (C) 2017 Elsevier B.V. All rights reserved
Double-pulse single-longitudinal-mode operation of injection-seeded laser using intracavity phase modulator
No full textNatural Science Foundation of China [61475170, 61505230]; Scientific Innovation Fund of Chinese Academy of Sciences [CXJJ-16S014]A single-longitudinal-mode (SLM) double-pulse injection-seeded neodymium-doped yttrium aluminium garnet (Nd:YAG) laser was established utilizing an RbTiOPO4 electro-optic crystal to modulate the optical path of the slave resonator for generating a resonance condition. The Q-switcher was fired twice during every pump period. This enabled the laser to emit a pair of SLM laser pulses with a time separation of 200 mu s. Each pulse had a pulse energy of 13 mJ at 50-Hz repetition rate, pulse duration of 20 +/- 0.5 ns, and linewidth of 30 +/- 0.3 MHz (within 2 min). The beam quality factor of M-2 was <1.22. A frequency jitter of 1.4 MHz was obtained within 2 min. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE
Calibration of photoelastic modulator using direct current component
No full textInternational Science & Technology Cooperation Program of China [2016YFE0110600]; International Science & Technology Cooperation Program of Shanghai [16520710500]; Youth Innovation Promotion Association CASA method of calibrating the photoelastic modulator (PEM) using direct current component is proposed. The laser beam passes through a polarizer, the PEM to be calibrated and is then split into two sub-beams by a Wollaston prism. The two sub-beams are then detected by two detectors. The small peak retardation is independent of the fluctuation of the initial intensity. The calibration setup is compact. In experiments, a PEM was calibrated and the calibration error was less than 0.008 rad when the peak retardation changed in the range of 0.1 lambda-0.5 lambda
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
Optimal defocus selection based on normed Fourier transform for digital fringe pattern profilometry
No full textNational Natural Science Foundation of China (NSFC) [61474129]; World Academy of Sciences (TWAS); Chinese Academy of Sciences (CAS)Owing to gamma-effect robustness and high-speed imaging capabilities, projector defocusing of binary-coded fringe patterns is by far the most widely used and effective technique in generating sinusoidal fringe patterns for three-dimensional optical topography measurement with digital fringe projection techniques. However, this technique is not trouble-free. It is borne with uncertainty and challenges mainly because it remains somewhat difficult to quantify and ascertain the level of defocus required for desired fidelity in sinuousness of the projected fringe pattern. Too much or too little defocusing will affect the sinuosity accuracy of fringe patterns and consequently jeopardize the quality of the measurement results. In this paper, by combining intrinsic phase spectral sensitivities and normed Fourier transform, a method to quantify the amount of defocus and subsequently select the optimal degree of sinuosity for generating digital sinusoidal fringe patterns with projector defocusing for fringe pattern optical three-dimensional profilometry is proposed. Numerical simulations plus experiments give evidence of the feasibility and validity of the proposed method in enabling an improved digital binary defocusing technique for optical phase-shift profilometry using the digital fringe projection technique
Tailoring femtosecond 1.5-mu m Bessel beams for manufacturing high-aspect-ratio through-silicon vias
No full textNational Natural Science Foundation of China [61327902, 11134010]; National Basic Research Program of China [2014CB921300]Three-dimensional integrated circuits (3D ICs) are an attractive replacement for conventional 2D ICs as high-performance, low-power-consumption, and small-footprint microelectronic devices. However, one of the major remaining challenges is the manufacture of high-aspect-ratio through-silicon vias (TSVs), which is a crucial technology for the assembly of 3D Si ICs. Here, we present the fabrication of high-quality TSVs using a femtosecond (fs) 1.5-mu m Bessel beam. To eliminate the severe ablation caused by the sidelobes of a conventional Bessel beam, a fs Bessel beam is tailored using a specially designed binary phase plate. We demonstrate that the tailored fs Bessel beam can be used to fabricate a 2D array of approximately circle divide 10-mu m TSVs on a 100-mu m-thick Si substrate without any sidelobe damage, suggesting potential application in the 3D assembly of 3D Si ICs
Attosecond chirp effect on the transient absorption spectrum of laser-dressed helium atom
No full textNational Natural Science Foundation of China [61690223, 11561121002, 61521093, 11127901, 11227902, 11404356, 11574332]; Strategic Priority Research Program of the Chinese Academy of Sciences [XDB16]; Shanghai Commission of Science and Technology Sailing Project [14YF1406000]; Shanghai Institute of Optics and Fine Mechanics Specialized Research Fund [1401561J00]; Youth Innovation Promotion Association CASWe theoretically investigate the attosecond transient absorption spectrum of helium atom in the presence of an infrared-dressed laser pulse upon scanning their relative delay, with the particular emphasis on the chirp effect of the attosecond pulse. By numerically solving the fully three-dimensional time-dependent Schrdinger equation, we identify the attoscecond chirp can induce the temporal shift of the absorption spectrogram along the delay axis. Additionally, it is found that the extent of the temporal shift is dependent on both the position of the absorption line and the infrared pulse wavelength, which is well confirmed and reproduced by a three-level model. Moreover, we demonstrate that the observed features can be quantitatively explained in terms of the indirect two-photon absorption processes through some virtual states. This effect might provide a way to measure the chirp of attosecond pulse in an all-optical way. (C) 2017 Optical Society of Americ