Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Mid-infrared spectroscopy of novel Er3+ doped indium modified chalcogenide glasses
No full textNational Natural Science Foundation of China [NSFC 51572081]In this work Er3+ doped chalcogenide glasses structurally modified by indium (In-ChG) was prepared. The mid-infrared spectroscopic properties and solubility of Er3+ in In-ChG was investigated and compared with those of gallium modified glasses (Ga-ChG). Thermal stability, mid-infrared (MIR) photoluminescence (PL), absorption spectra of both Ga-ChG and In-ChG were characterized and compared in parallel. Both the obtained MIR absorption and emission cross sections of In-ChG are higher than those of Ga-ChG. The theoretical branching ratio and decay lifetimes of I-4(11/2)-4I(13/2) transition calculated from Judd-Ofelt theory were compared with those obtained from experiments. The tested and calculated lifetime is similar and it indicates high radiative quantum efficiency. Raman spectra reveal the fact that In-ChG possess lower phonon energy than that of Ga-ChG, which might possibly give rise to the improved MIR emission. Er3+ doped In-ChG chalcogenide glass is a potential material for MIR fiber laser application. (C) 2017 Elsevier B.V. All rights reserved
33 W continuous-wave single-frequency green laser by frequency doubling of a single-mode YDFA
No full textA high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier (YDFA) is developed. A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm, corresponding to an optical conversion efficiency of 58%. An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation. A 33.2Wlaser at 532 nm is obtained with a 45W incident 1064 nm fundamental laser, corresponding to a conversion efficiency of 74%
Q-switching Yb3+: YAG lasers based on plasmon resonance nonlinearities of Cu2-xSe@Cu2-xS nanorods
No full textNatural Science Foundation of Shandong Province [ZR.2016FM08]; Key Scientific Research Program of Beijing City [Kz201110005010]Copper(II) chalcogenide nanocrystals, including Cu2-xY (Y = S, Se, and Te), have an intense localized surface plasmon resonance (LSPR) band in the near-infrared (NIR) region. In this research, colloidal Cu2-xSe@Cu2-xS nanorods were synthesized using the organometallic colloidal and cation-exchange methods. The dynamics of LSPR were investigated using ultrafast laser pulses via pump-probe experiments in the NIR region. Investigation of the transient absorption spectra revealed an LSPR spectral band from approximately 850 to 1350 nm, with a center wavelength of 1030 nm. The kinetics of the recovering plasmon maximum, probed at the peak wavelength of 1030 nm, exhibited a strong nonlinear response for plasmonic absorption, with a modulation depth exceeding 25% in the transmitted signal under a pump fluence of 3.97 mJ/cm(2). The ultrafast nonlinear optical properties of these plasmonic nanoparticles could be used as excellent saturable absorbers (SAs) in ultrafast lasers. A compact passively Q-switched Yb3+: YAG microchip laser with a Cu2-xSe@Cu2-xS SA was investigated. Furthermore, a maximum average output power of 187 mW was obtained, with a pulse energy of 4.11 mu J, pulse duration of 8.5 mu s, and repetition rate of 45.45 KHz at a pump power of 8.7 W
Real-time intravascular photoacoustic-ultrasound imaging of lipid-laden plaque in human coronary artery at 16 frames per second
No full textAHA Postdoctoral Fellowship; IUPUI Graduate Student Imaging Research Fellowship; [R01HL125385]Intravascular photoacoustic-ultrasound (IVPA-US) imaging is an emerging hybrid modality for the detection of lipid-laden plaques, as it provides simultaneous morphological and lipid-specific chemical information of an artery wall. Real-time imaging and display at video-rate speed are critical for clinical utility of the IVPA-US imaging technology. Here, we demonstrate a portable IVPA-US system capable of imaging at up to 25 frames per second in real-time display mode. This unprecedented imaging speed was achieved by concurrent innovations in excitation laser source, rotary joint assembly, 1 mm IVPA-US catheter size, differentiated A-line strategy, and real-time image processing and display algorithms. Spatial resolution, chemical specificity, and capability for imaging highly dynamic objects were evaluated by phantoms to characterize system performance. An imaging speed of 16 frames per second was determined to be adequate to suppress motion artifacts from cardiac pulsation for in vivo applications. The translational capability of this system for the detection of lipid-laden plaques was validated by ex vivo imaging of an atherosclerotic human coronary artery at 16 frames per second, which showed strong correlation to gold-standard histopathology. Thus, this high-speed IVPA-US imaging system presents significant advances in the translational intravascular and other endoscopic applications
Generalized non-separable two-dimensional Dammann encoding method
No full textWe generalize for the first time, to the best of our knowledge, the Dammann encoding method into non separable two-dimensional (2D) structures for designing various pure-phase Dammann encoding gratings (DEGs). For examples, three types of non-separable 2D DEGs, including non-separable binary Dammann vortex gratings, non-separable binary distorted Dammann gratings, and non-separable continuous-phase cubic gratings, are designed theoretically and demonstrated experimentally. Correspondingly, it is shown that 2D square arrays of optical vortices with topological charges proportional to the diffraction orders, focus spots shifting along both transversal and axial directions with equal spacings, and Airy-like beams with controllable orientation for each beam, are generated in symmetry or asymmetry by these three DEGs, respectively. Also, it is shown that a more complex-shaped array of modulated beams could be achieved by this non-separable 2D Dammann encoding method, which will be a big challenge for those conventional separable 2D Dammann encoding gratings. Furthermore, the diffractive efficiency of the gratings can be improved around 10% when the non-separable structure is applied, compared with their conventional separable counterparts. Such improvement in the efficiency should be of high significance for some specific applications. (C) 2016 Elsevier B.V. All rights reserved
Interferometric rotating point spread function
No full textChina Postdoctoral Science Foundation [2015M580356]; National Natural Science Foundation of China [61377005, 61327902]; Chinese Academy of Sciences [QYZDB-SSW-JSC002]Rotating point spread functions (PSF), such as the double helix (DH) PSF, are widely used in localization-based super-resolution imaging because of their large working depth range. In this article, we propose an interferometric DH PSF (iDH PSF) using two opposed objective lenses as in the 4Pi microscope. In the proposed iDH PSF, the super-resolution in the axial PSF is transferred to the azimuthal rotation. Moreover, we design an iDH PSF whose imaging range reaches 3 mu m, which is roughly 3 times as much as that which can be obtained by using other interferometric localization-based super-resolution imaging methods
Phase problems in optical imaging
No full textNational Natural Science Foundation of China [61377005, 61327902]; Chinese Academy of Sciences [QYZDB-SSW-JSC002]Because the phase contains more information about the field compared to the amplitude, measurement of the phase is encountered in many branches of modern science and engineering. Direct measurement of the phase is difficult in the visible regime of the electromagnetic wave. One must employ computational techniques to calculate the phase from the captured intensity. In this paper, we provide a review of our recent work on iterative phase retrieval techniques and their applications in optical imaging
Polarization phase-shifting lateral shearing interferometer with two polarization beam splitter plates
No full textInternational Science & Technology Cooperation Program of China [2016YFE0110600]; International Science & Technology Cooperation Program of Shanghai [16520710500]; Youth Innovation Promotion Association CASWe proposed a compact and simple polarization phase-shifting lateral shearing interferometer using two polarization beam splitter plates (PBSP). This interferometer is composed of two PBSP, a quarter-wave plate, an analyzer and a CCD camera. With the two PBSP positioned in appropriate spatial positions, optical path difference compensation is achieved, which allows for the implement of aplanatic and common-path shearing interferometer. Therefore, the system possesses significant advantages of simple structure, compact and strong anti-interference ability. The effectiveness of the interferometer is demonstrated by simulations and experiments
Understanding Enhanced Upconversion Luminescence in Oxyfluoride Glass-Ceramics Based on Local Structure Characterizations and Molecular Dynamics Simulations
No full textNational Natural Science Foundation of China [61475047, 11504323]; State Key Laboratory of Precision Spectroscopy (East China Normal University); State Key Laboratory of High Field Laser Physics (Shanghai Institute of Optics and Fine Mechanics); Science and Technology Department of Zhejiang Province [2015C31045]; Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques; South China University of TechnologyIn this Article, large enhancement in upconversion (UC) luminescence was verified in a transparent aluminosilicate glass-ceramics (GCs) containing CaF2 nanocrystals (NCs) codoped with Era(3+) and Yb3+ ions. On the basis of the joint spectroscopic and structural characterizations, we suggest that the precipitation of fluoride NCs is correlated with the preexistence of the fluoride-rich domains in the as-melt glass, which is supported by scanning transmission electron microscopy (STEM) and reproduced by molecular dynamics (MD) simulation. The precipitation of the fluoride NCs starts from a phase-separated as-melt glass consisting of fluorine-rich and oxygen-rich domains, while the spatial distribution of rare earth (RE) ions and the vibration energies of the bonds connecting RE ions remain almost unchanged after crystallization. In the GCs, both the fluoride domain and the oxygen-containing polyhedrons surrounding RE ions experience significant ordering, which may affect the UC emission for both glasses and GCs. We therefore attribute the enhanced UC emissions of the GCs to the long-range structural ordering and the change of site symmetry surrounding RE ions, rather than the preference of RE ions in migrating from fluoride-rich phase to the fluoride NCs. Our results may have strong implications for a better understanding of the enhanced UC emission in similar oxyfluoride GCs
Thermal stability and reliability studies of (Sr, Ca) AlSiN3:Eu2+ phosphors for LED application
No full textNational Nature Science Foundation of China [51302171]; Science and Technology Commission of Shanghai Municipality (CN) [14500503300]; Shanghai Municipal Alliance Program [Lm201547]; Shanghai Cooperative Project [ShanghaiCXY-2013-61]; Jiashan County Technology Program [20141316]In this paper, the thermal stability and reliability properties of (Sr, Ca) AlSiN3:0.05Eu(2+) phosphors prepared by solid-state reaction in 1.1 MPa N-2 atmosphere were studied. The internal quantum efficiency of (Sr, Ca) AlSiN3:0.05Eu(2+) could reach as high as about 92% after Sr ions replacing Ca upon excitation in blue light range (450-470 nm). As the temperature increased from 300 to 500 K, PL intensity of SrxCa1-xAlSiN3:0.05Eu(2+) phosphor decreases by 66.24, 27.87 and 16.66% of the initial PL intensity for x = 0.2, 0.5 and 0.8, respectively. The relative PL intensity of SrxCa1-xAlSiN3:0.05Eu(2+) phosphor decrease to 98.67% from 96.87% as x increased to 0.8 from 0.2 after storing into an ambient condition of 120 A degrees C for 1 h and -40 A degrees C for 1 h by turns for five times. Reliability test results show that, with x value is from 0.2 to 0.8, the relative PL intensity of SrxCa1-xAlSiN3:0.05Eu(2+) phosphor is from 95.87 to 86.51% after the ambient condition of 85 A degrees C/RH 85% for the exposure time of 168 h, from 99.86 to 92.45% after soaking the phosphors into boiled water for 3 h. It can be summarized that the addition of Sr increased the thermal stability largely and deteriorates the reliability of the phosphors slightly. And the reactivity of phosphor with water is the main reason for reducing the reliability of the phosphors