Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Structure and Upconversion Luminescence of Er3+, Yb3+ Codoped CaNb2O6 Thin Films by Pulsed Laser Deposition
No full textNational Nature Science Foundation of China [11474104, 51372092]; China Postdoctoral Science Foundation [2012M511801]Er3+, Yb3+ codoped CaNb2O6 thin films have been successfully prepared on Si(100) substrates by pulsed laser deposition. The effects of the substrate temperature on the crystallinity, morphology, and emission characteristics of Er3+, Yb3+ codoped CaNb2O6 films were studied. Results show that the substrate temperature during growth of Er3+, Yb3+ codoped CaNb2O6 films affects the film's grain size and hence influences the upconversion luminescence properties. The grain size of Er3+, Yb3+ codoped CaNb2O6 films increases with the increasing substrate temperature. Upconversion luminescence of the Er3+, Yb3+ codoped CaNb2O6 films is enhanced by increasing the grain size of the films
Enhanced light scattering effect of wrinkled transparent conductive ITO thin film
No full textNational Key Research Program of China [2016YFA0200403]; CAS Strategy Pilot Program [XDA 09020300]; National Natural Science Foundation of China [10974037, 61405223]Indium tin oxide (ITO) plays an important role due to its high transparency and high conductivity in various optoelectronic thin-film devices. However, ITO has the drawback of mechanical fragility, limiting its development. Wrinkling has been considered a powerful tool for improving the flexibility and surface properties of thin films, but wrinkled ITO has not been reported so far. In this work, we fabricate uniform wrinkles on ITO and systematically study the properties of the wrinkled ITO in optics, electrics and mechanics. The wrinkled ITO shows a high optical transmittance and also a high haze value due to a remarkable wrinkle-induced enhancement of light scattering, which is beneficial for solar cells and lightemitting diodes. Our experimental results also indicate that wrinkles can effectively improve the mechanical bending performance of ITO without compromising the crystallization and electrical conductivity
Synthesis and luminescent behavior of Dy:Y3Ga5O12 phosphor for UV induced white LEDs
No full textChina Postdoctoral Science Foundation [2016M592466]; Natural Science Foundation of Shanghai [15ZR1444700]; Guangdong Yang Fan ProjectThe synthesis, X-ray diffraction (XRD) pattern, excitation spectrum, emission spectra and decay times were studied for the first time to our best knowledge. The Dy:Y3Ga5O12 (Dy:YGG) phosphors with Dy3+ ions concentration of 0.5%, 1%,3%, 5% and 10% were prepared by sol-gel method. The XRD patterns show that the phosphors possess perfect YGG phase. The average particle size of the Dy:YGG phosphors was calculated to be about 40 nm. The strongest excitation peak was 353 nm, which is favorable to ultra violet (UV) induced white light-emitting diodes (LEDs). Three emission bands centered at 480 nm, 580 nm and 672 nm could be observed under excitation of 353 nm. The yellow-to-blue integrated intensity ratios (Y/B) were 1.4-1.7 for the Dy3+ ions concentrations from 0.5 to 5%. The optimum Dy3+ concentration is 3%, and the corresponding 1931 Commission International de I'Eclairage (CIE) coordinates is (x=0.37, y = 0.38). The results show that Dy:YGG phosphors can be a good candidate for UV-excitation warm-yellowish-white LEDs. (C) 2017 Published by Elsevier GmbH
Impact of tellurium on glass transition and crystallization in the Ge-Se-Te-Bi system
No full textShanghai Leading Academic Discipline Project [B502]; Shanghai Key Laboratory Project [08DZ2230500]; National Natural Science Foundation of China [NSFC 51572081, 51572082]Samples with compositions of Ge(20)Se(67-x)Te(x)Bin (x=0, 5, 10, 15 and 20 mol%) were prepared and characterized by XRD, Raman spectroscopy and DSC. XRD patterns and Raman spectra present consistent evidences of glass transition and crystallization in association with the variation of the structure network due to the substitution of Te for Se. Precipitation of thermoelectric (TE) crystals experiences an evolution from Bi2Se2Te (BST) to Bi2SeTe2 (BTS) phases with the increasing Te content. Based on DSC data performed at five heating rates, crystallization kinetics is analyzed by using Kissinger's relation, Ozawa model and Augis-Bennett approximation. Different methods show the identical evaluations of characteristic activation energies (E-c), while additional parameters of frequency factor (K-0) and Avrami exponent (n) are available with AB method. In particular, calculated E-c and K-o demonstrate that with the substitution of Se by Te the crystallization process of the target TE BST crystal phase is much enhanced while that of the undesired GeSe2 phase is slightly hindered
Mechanism of cluster dissolution of Yb-doped high-silica lanthanum aluminosilicate glass: Investigation by spectroscopic and structural characterization
No full textChinese National Natural Science Foundation [61405215, 61475174]To investigate clusters of Yb ions and the effectiveness of lanthanum co-doping in dispersing and isolating Yb ions in silica glass, Yb-doped high-silica lanthanum aluminosilicate (LAS) glass with compositions Yb2O3-Al2O3-La2O3-SiO2 was prepared by the solegel method combined with high temperature sintering. The glass structure and spectroscopic properties of Yb-doped high-silica LAS glass were studied in detail to explore the mechanism of cluster dissolution. Al-27 and Si-29 solid-state nuclear magnetic resonance (SSNMR) spectra were introduced to study the spatial distribution of the Yb ions in the glass. The spinning sideband patterns of the Al-27 and Si-29 NMR spectra showed that part of the Yb3+ ions in the vicinity of aluminium atoms transferred to Si ions with increasing La2O3 concentration. The results of two-dimensional hyperfine sublevel correlation (2D-HYSCORE) electron paramagnetic resonance (EPR) spectroscopy led to the conclusion that the vicinity of Yb3+ ions are mostly aluminum atoms for glass doped with Al and aluminum and silicon atoms for glass co-doped with Al and La. It was also found that Yb clusters exist in the form of Yb-O-Yb bonds in high-concentration Yb-doped silica glass and that co-doping with La can replace these bonds with Yb-O-La linkages to reduce the number of Yb3+ pairs. The fluorescence intensity and fluorescence lifetime of Yb increase steadily with increasing La2O3 concentration, which also indicates that the addition of La in silica glass can dissolve the Yb clusters. The results show that co-doping high-silica LAS glasses with La3+ ions is an ideal way to increase Yb solubility and decrease clustering. (C) 2016 Elsevier B.V. All rights reserved
Nearly-octave wavelength tuning of a continuous wave fiber laser
No full textThe wavelength tunability of conventional fiber lasers are limited by the bandwidth of gain spectrum and the tunability of feedback mechanism. Here a fiber laser which is continuously tunable from 1 to 1.9 mu m is reported. It is a random distributed feedback Raman fiber laser, pumped by a tunable Yb doped fiber laser. The ultra-wide wavelength tunability is enabled by the unique property of random distributed feedback Raman fiber laser that both stimulated Raman scattering gain and Rayleigh scattering feedback are available at any wavelength. The dispersion property of the gain fiber is used to control the spectral purity of the laser output
Thermal Tunable Narrow Linewidth External Cavity Laser With Thermal Enhanced FBG
No full textNational Natural Science Foundation of China [61405218, 61535014]; Shanghai Natural Science Foundation [14ZR1445100]We demonstrated a mode-hop-free external cavity laser (ECL) design incorporating a semiconductor gain chip and a fiber Bragg grating (FBG) with enhanced thermal sensitivity. The compact ECL features a narrow linewidth of 35 kHz and a high linear thermal tuning velocity of 65 pm/degrees C (8.125 GHz/degrees C), which is six times higher than that of normal FBG-based ECLs
Modal wavefront reconstruction based on Zernike polynomials for lateral shearing interferometry
No full textNational Natural Science Foundation of China (NSFC) [61405210, 61275207, 61474129]; Natural Science Foundation of Shanghai [14ZR1444900]The Zernike-polynomials-based modal reconstruction method is an important wavefront reconstruction method for lateral shearing interferometry. There are four typical Zernike-polynomial-based modal reconstruction methods: the Rimmer-Wyant method, the elliptical orthogonal transformation method, the numerical orthogonal transformation method (NOT), and the difference Zernike polynomial fitting method (DZF). In a previous paper [Appl. Opt. 51, 5028 (2012)], the overall performances of these four methods were comprehensively compared with each other. The conclusions showed that NOT and DZF have the highest reconstruction accuracies among these four methods. In addition, it was shown that the performance of NOT is identical to that of DZF; however, the reason behind this was not known until now, to our knowledge. In the present paper, we present a strictly mathematical proof for this highly significant result. (C) 2016 Optical Society of Americ
228 nm pulse duration dependence in the photodissociation of H-2(+)
No full textNSF of China [11604349]We theoretically investigate the pulse duration dependence in the laser-induced dissociation of the molecular ion H-2(+) The simulation results show that the dissociation ratio can be split up into three regions with increasing duration of the external laser pulse, with a central wavelength of 228 nm, as a result of the electron capture of the vibrationally highly excited H-2(+) With the coupled equations of the 1 s sigma(g) and 2p sigma(u) states one can find that the pulse duration dependence in the photodissociation of H-2(+) is due to the different responses of the molecular dipole to the evolution time of the ultraviolet laser pulse
Astigmatism transfer phenomena in the optical parametric amplification process
No full textCAS; National Natural Science Foundation of China [61475169, 61521093, 11127901]; Youth Innovation Promotion Association CASWe numerically and experimentally investigate the astigmatism transfer phenomena in femtosecond optical parametric amplification (OPA). We model the OPA process based on the coupled second-order three-wave nonlinear propagation equations. The numerical and experimental results support that the input pump pulse astigmatism can be transferred into the idler pulse but not the signal pulse, and the idler pulse astigmatism originating from spatial walk-off is less than the idler pulse astigmatism received from the pump. Thus, we can provide a clear understanding of astigmatism transfer mechanisms in the OPA process, and make better use of broadband tunable OPA sources