Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Highly linearly polarized white light emission from InGaN light-emitting diode with nanograting-integrated fluorescent ceramics
No full textNational Natural Science Foundation of China [61378057]; National High Technology Research and Development Program of China [2013AA031901]; project of the Priority Academic Program Development (PAPD) of Jiangsu Higher Education InstitutionsWe proposed and demonstrated a linearly polarized white light emission from an InGaN light-emitting diode with nanograting-integrated fluorescent ceramics. By incorporating a dielectric layer with low refractive index between multilayer nanogratings and a fluorescent ceramic, both high TM transmission (TMT) and high extinction ratio (ER) were effectively achieved across the entire range of white light. An ER higher than 20 dB and a TMT of 60% were obtained experimentally for a GaN/fluorescent-ceramic-integrated white LED with a multilayer grating of 150nm period. The fluorescent-ceramic-integrated structure showed possibilities of implementing a polarized white LED with high performance. (C) 2017 The Japan Society of Applied Physic
Identification of Cr valence states in Cr and Nd co-doped Lu3Al5O12 laser ceramics
No full textNational Nature Science Founds of China [61378069, 61405221]; Youth Innovation Promotion Association of CASCr and Nd co-doped laser ceramics, as the potential gain materials in inertial confinement fusion (ICF), have been widely investigated. And the study on valence states of chromium ions is important. The effects of sintering additives and annealing atmosphere on the valence state of chromium were studied in detail, and the results shown that the Cr valence states were demonstrated to be Cr2+ and Cr3+ ions in HIP-sintered Cr(0.2 at.%), Nd(0.8 at.%): LuAG laser ceramics. And the intensity of the near-infrared absorption band caused by Cr2+ ions was attenuated with the decreasing SiO2 concentration and increasing MgO amount. The near-infrared absorption could be eliminated by annealing in air. And the transformation of valence states of Cr ions in the Cr,Nd:LuAG ceramics were also confirmed by electron paramagnetic resonance and X-ray photoelectron spectroscopy
Influence of moisture absorption on the synthesis and properties of Y2O3-MgO nanocomposites
No full textNational Youth Natural Science Foundation of China [51302284, 61405221]; China Scholarship CouncilY2O3-MgO nanocomposites are appropriate materials for hypersonic infrared windows and domes because of their low emissivity and improved mechanical properties. In this study, the synthesized Y2O3-MgO nanopowders are investigated to evaluate the influence of moisture absorption on the manufacturing process and properties of the resulting nanocomposites. It is shown that MgO plays a more significant role than Y2O3 in the moisture absorption of the composite nanopowders, and the absorbed moisture leads to a lowering IR transmittance of the final Y2O3 MgO nanocomposites. A higher calcination temperature improves the resistance to moisture absorption of Y2O3 MgO nanopowders, which is beneficial for IR transmittance of the final nanocomposites. In addition, increasing the sintering temperature to 1100 degrees C during spark plasma sintering (SPS) minimizes the influence of absorbed moisture on the IR transmittance of the final nanocomposites. In the water resistance test, the Y2O3 MgO nanocomposites demonstrate severely eroded surfaces and degraded IR transmittance after water erosion, suggesting the requirement for necessary waterproof treatments on such materials in practical applications
Measurement of different types of optical loss using high-precision laser photometer
No full textNational Natural Science Foundation of China [61405219]The development of high-power laser systems requires optical components that function at peak performance. Here, a high-precision, double beam, 1064 nm laser photometer setup was developed to measure the following different forms of optical loss from Nd-glass samples: total loss, volume loss, and the residual reflection and surface loss. The double beam design and a lock-in technique were utilized to decrease the impact of light-source instabilities and signal noise, respectively. The stability of the signal was further improved by decreasing the amount of optical absorption along the light path and by increasing the detection responsivity. Paired samples were symmetrically placed to eliminate beam displacement, and a laser scattering imaging technique was used to determine the influence of surface defects on the optical performance. Using the above techniques, multiple measurements of the transmittance and reflection values of the sample were taken, which showed our transmittance measurement to be highly precise, exhibiting a relative standard deviation of less than 0.06%. Different types of optical loss were distinguished and obtained from the transmittance and reflection measurements of samples with different thicknesses. A comparison of the optical performance from test points with and without surface defects allowed us to determine the influence of surface defects on the optical performance
Optical characterization of Tm3+ in LaF3 single crystal
No full textNational Natural Science Foundation of China [51472257, 51502321]; National Key R&D Program of China [2016YFB0701002, 2016YFB1102302, 2016YFB0402105]Optical properties of a Tm-doped LaF3 single crystal have been detailed investigated as a promising material for similar to 1.84 mu m lasers for the first time. Judd-Ofelt theory was applied to analyze the absorption spectrum. With the J-O intensity parameters Omega t((t=2,4,6)), the emission probabilities, branching ratios and radiative lifetimes for the as-grown crystal were all calculated. The stimulated emission cross-section of the F-3(4) -> H-3(6) transition was obtained by using the Fuchtbauer-Ladenburg method. The gain cross-ection for similar to 1.84 mu m emission becomes positive once the population inversion level reaches 30%. The fluorescence lifetime of the F-3(4) manifold was measured to be 15.56 ms. Potential utility of the Tm:LaF3 crystal as laser active material at similar to 1.84 mu m can be expected. (C) 2017 Elsevier B.V. All rights reserved
Optically Induced Transparency and Extinction in Dispersed MoS2, MoSe2, and Graphene Nanosheets
No full textNSFC [61675217, 61522510]; Strategic Priority Research Program of CAS [XDB16030700]; Key Research Program of Frontier Science of CAS [QYZDB-SSW-JSC041]; Program of Shanghai Academic Research Leader [17XD1403900]This work reports the optically induced transparency and extinction in MoS2, MoSe2, and graphene nanosheets in N-methyl-2-pyrrolidone. It is found that the 632.8 nm continuous-wave probe light can be effectively modulated by the 532 nm nanosecond pump pulsed laser into peaks (transparency) and valleys (extinction) induced by two distinct nonlinear optical mechanismssaturable absorption and nonlinear scattering, respectively. The optical modulation depths under different pump conditions have been deduced, and the maximum value of the modulation depth can reach approximate to 7 dB. Multiple nonlinear optical mechanisms coexisting in these 2D nanomaterials make them a category of intriguing and promising candidate materials for diverse photonic applications
Polarization-independent almost-perfect absorber controlled from narrowband to broadband
No full textNational Natural Science Foundation of China [11604352, 10704079, U1630140, U1430121]; Shanghai Science and Technology Committee Program [16JC1420600]Achieving perfect absorption and controlling the absorption bandwidth are highly desirable for many applications. In this Work, we design a narrowband almost-perfect absorber by using a metal-insulator-metal thin-film stack with absorption up to 99.671% at 0.58 mu m incident Wavelength. The peak of absorption can be totally controlled by adjusting the thickness of the insulator layer. When the top metal layer is patterned by crossed grating nanostructure with optimized parameters, the absorber becomes broadband over 150nm bandwidth with average absorption exceeding 97% from 0.5 mu m to 0.65 mu m in the visible region. Both the narrowband and broadband absorbers are independent on polarization in specific incident angle range. This work opens up a promising new approach to control bandwidth of perfect absorption, which implicates many potential applications
High-speed maskless nanolithography with visible light based on photothermal localization
No full textNational Natural Science Foundation of China [51672292, 61627826, 61137002]; PAPIIT-UNAM [IN100514]; UNAMHigh-speed maskless nanolithography is experimentally achieved on AgInSbTe thin films. The lithography was carried out in air at room temperature, with a GaN diode laser (lambda = 405 nm), and on a large sample disk of diameter 120 mm. The normal width of the written features measures 46 +/- 5 nm, about 1/12 of the diffraction allowed smallest light spot, and the lithography speed reaches 6 +/- 8 m/s, tens of times faster than traditional laser writing methods. The writing resolution is instantaneously tunable by adjusting the laser power. The reason behind the significant breakthrough in terms of writing resolution and speed is found as the concentration of light induced heat. Therefore, the heat spot is far smaller than the light spot, so does the size of the written features. Such a sharp focus of heat occurs only on the selected writing material, and the phenomenon is referred as the photothermal localization response. The physics behind the effect is explained and supported with numerical simulations
Preparation and characterizations of Yb:YAG-derived silica fibers drawn by on-line feeding molten core approach
No full textNational Natural Science Foundation of China [51272262, 61405215]Three Yb:YAG transparent ceramics with Yb2O3 doping concentrations of 1, 10, and 15 at%, respectively were made into silica-clad hybrid fibers using an on-line feeding molten core approach. The diffusion of silica was mitigated such that the lowest SiO2 concentration was 36.4 wt%, and consequently, the Yb2O3 content could reach 8.93 wt% in the fiber core. The fiber core transformed from a YAG ceramic to an yttrium aluminosilicate glass, and the formation of abundant Q(2) silicate species implied that the structure of the core glass maintained some environments similar to that of YAG with Q(2)-AlO4 tetrahedra. The absorption and emission spectra of the obtained fibers were compared to those of Yb:YAG ceramics, and the self-absorption effect was analyzed in detail. All three fibers could output lasers under 940 or 970 nm pumping. The maximum output power of the Yb:YAG-derived fibers was higher than that of ceramic wafers owing to the cladding pump technology, which offered a new method to improve the application of ceramics
Statistical structure analysis of GeO2 modified Yb3+: Phosphate glasses based on Raman and FTIR study
No full textNational Natural Science Foundation of China [61177083]Structural modification of conventional Yb3+ doped phosphate glass by GeO2 was shown to significantly improve both thermal and spectroscopic properties, namely, transition temperature, coefficient of thermal expansion, effective line width, Stark splitting, and fluorescence lifetime. Raman and IR spectroscopic techniques, in conjunction with a statistical analysis method, were used to determine plausible network structure units, or "genes", which had significant effects on the properties, specifically the distributions of tetrahedron units (Ge-[4]-O-Ge-[4], Ge-[4]-O-P, P-O-P) and octahedron units (Ge-[6]-O-Ge-[6]) in the GeO2-containing glasses. The use of statistical approach enabled us to build linear mathematic functions of network structure units - property relationships, or models, and the model predictions were closely matched with the measured values. The outcome demonstrates that statistically derived results from Raman and/or IR spectra can be used to aid glass design, achieving target properties. (C) 2016 Elsevier B.V. All rights reserved