Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Influence of synthesis conditions on the properties of Y2O3-MgO nanopowders and sintered nanocomposites
No full textNational Youth Natural Science Foundation of China [51302284, 61405221]; China Scholarship CouncilIn this study, a citrate-nitrate combustion method was applied to synthesize composite Y2O3-MgO nanopowders. In order to optimize the synthesis condition to support sufficient combustion, the molar ratio of citric acid to nitrate (c/n molar ratio) used in the reaction mixtures was varied between 0.17 and 0.34. Nanopowders with an average particle size of 17 nm were achieved. The properties of these nanopowders indicated that the higher molar ratios decreased the unreacted organic components and increased the amount of carbide on the surface of the oxides, which helped to inhibit the formation of carbonate groups. The amount of carbonate groups was reduced with the increasing c/n molar ratio. Y2O3-MgO nanocomposites fabricated through hot-isostatic-pressing sintering showed a uniform distribution of Y2O3 and MgO grains, which had an average size of similar to 180 nm. In addition, the absorption peaks at 1410 and 1511 cm(-1) disappeared until the c/n molar ratio reached 0.28. A high average infrared transmittance of 83% in the range of 4000-1667 cm(-1) (2.5-6 mu m) was obtained in the nanocomposites. (C) 2017 Elsevier Ltd. All rights reserved
Laser-induced Damage of 355 nm High-reflective Mirror Caused by Nanoscale Defect
No full textNational Natural Science Foundation of China [11174208]; NSAF [U1430121]; Shenzhen Basic Research Project [JCYJ20150529164656098, ZDSY20170228105421966]Al2O3/SiO2 multilayer high-reflective (HR) mirrors at 355 nm were prepared by electron beam evaporation, and post-irradiated with Ar/O mixture plasma. The surface defect density, reflective spectra, and laser-induced damage characteristics were measured using optical microscopy, spectrophotometry, a damage testing system, and scanning electron microscopy (SEM), respectively. The results indicated that moderate-time of irradiation enhanced the laser-induced damage threshold (LIDT) of the mirror, but prolonged irradiation produced surface defects, resulting in LIDT degradation. LIDT of the mirrors initially increased and subsequently decreased with the plasma processing time. SEM damage morphologies of the mirrors revealed that nanoscale absorbing defects in sub-layers was one of the key factors limiting the improvement of LIDT in 355 nm HR mirror
Optical surfacing via linear ion source
No full textYouth Innovation Promotion Association of the Chinese Academy of SciencesWe present a concept of surface decomposition extended from double Fourier series to nonnegative sinusoidal wave surfaces, on the basis of which linear ion sources apply to the ultra-precision fabrication of complex surfaces and diffractive optics. The modified Fourier series, or sinusoidal wave surfaces, build a relationship between the fabrication process of optical surfaces and the surface characterization based on power spectral density (PSD) analysis. Also, we demonstrate that the one-dimensional scanning of linear ion source is applicable to the removal of mid-spatial frequency (MSF) errors caused by small-tool polishing in raster scan mode as well as the fabrication of beam sampling grating of high diffractive uniformity without a post-processing procedure. The simulation results show that optical fabrication with linear ion source is feasible and even of higher output efficiency compared with the conventional approach. (C) 2017 Elsevier B.V. All rights reserved
Structure, chemical state and photocatalytic activity of TiO2-x nanostructured thin films by glancing angle deposition technique
No full textNational Natural Science Foundation of China [21376154]; State Key Program of National Natural Science of China [11535010]Nonstoichiometric titanium dioxide nanostructured thin film (TNF) has attracted a range of interest in the green energy field. In this paper, we introduce the glancing angle deposition (GLAD) technique to produce the amorphous TNFs with discrete nanoscale columnar structures. In order to improve the crystallinity and/or gain the Ti3+ doped states, amorphous TNFs were annealed at 400 C-omicron in air or H-2. XRD, SEM, AFM, XPS and PL were used to characterize the crystallization structure morphology, chemical state, PL properties of the TNFs with different annealing conditions. Photocatalytic activities of the samples were reflected by decolorization experiments of methylene blue (MB) solution irradiated by the simulated sunlight light of AM 1.5 G. The photocatalytic activity of amorphous TNF is higher than that of conventional TiO2 thin film, indicating the prominent properties of nanostructures. Compared with annealing in air, the photocatalytic activity of TiO2-x nanostructures annealed in hydrogen is further increased and higher. The results demonstrated that Ti3+ and oxygen vacancies were beneficial and played the dominant role for the enhancement of photocatalytic activity. (C) 2017 Published by Elsevier B.V
Transition from isolated submicrometer pits to integral ablation of HfO2 and SiO2 films under subpicosecond irradiation
No full textNational Natural Science Foundation of China, China [61308021]Damage behavior of HfO2 and SiO2 films under subpicosecond irradiation is investigated experimentally and theoretically in this work. The typical damage phenomenon is the transition from isolated submicrometer pits to integral ablation at transitive threshold. The experimental damage thresholds for both coatings are consistent with the theoretical calculation. The rate equation considering the feedback effect of electron number density is applied to calculate the deposited energy density, which illustrates the evolution of damage morphology
Wide angle and broadband perfect absorber with compact multilayer structures
No full textWe design and numerically investigate a wide angle and broadband perfect absorber with compact multilayer structures. The proposed structure is composed of three stacks of semiconductor films and one metal layer. The absorber presents a broadband absorption between 450 nm and 700 nm with an average absorption above 99.2%. For oblique incidence, the absorber shows an average absorption about 90% for a wide range of incident angles from 0 to 60 with p polarization and s polarization. The electrical field intensity distributions are also studied to disclose the broadband absorption mechanism. This designed broadband absorber appears to have very promising applications in solar thermal energy harvesting, thermal emitters and detection
A study on one-step laser nanopatterning onto copper-hydrazone-complex thin films and its mechanism
No full textNational Natural Science Foundation of China [51672292, 61627826, 61137002]Semiconductor diode-based laser patterning with visible light has been extensively applied to the fabrication of arbitrary structures. However, recently, the technique has faced a great challenge because it cannot meet nanoscale-resolved patterning fabrication due to the optical diffraction limit, which is an inherent drawback in the field of optics. To attack the question, copper(II)-hydrazone-complex (CuL2) thin films are used as laser patterning materials. Under the heating of a writing laser spot, one-step laser nanopatterning on the CuL2 thin films is obtained. The convex-type and concave-type pattern structures are directly written without wet-etching and developing processes. The minimum pattern feature size is about 31 nm, which is far smaller than the diffraction limit and only similar to 1/20 the writing spot size. Analysis indicates that the laser nanopatterning originates from obvious photothermal localization responses to the writing spot. Compared with common organic resists, the exposure dose of CuL2 is several orders higher than that of the polymer; thus CuL2 thin film materials are suitable for maskless direct laser writing lithography. This work also provides an effective method for one-step nanopatternings through diode-based laser writing at visible light wavelengths
Effect of PbO on the spectral and thermo-optical properties of Nd3+-doped phosphate laser glass
No full textChinese National Natural Science Foundation [61405215]Nd3+-doped P2O5-K2O-Al2O3-BaO-PbO phosphate glasses with various PbO/BaO ratios were synthesized using the melt quenching technique. Raman, absorption, and emission spectra were measured to investigate the effects of PbO/BaO ratios on the structures and spectroscopic properties of the glasses. The emission cross-sections of the Nd3+-doped phosphate glasses were calculated using the Judd-Ofelt theory, and were found to increase from 4.37 x 10(-20) to 4.50 x 10(-20) cm(2) as the PbO/BaO ratio increased. In addition, thermo-optical properties were measured using an interferometric technique. The thermooptical coefficients, which were -1.49 x 10(-6), -1.65 x 10(-6), and -1.64 x 10(-6) K-1, respectively, were all largely negative values. The thermal expansion coefficients of the three glass samples varied within a small range. The results showed that increasing the PbO/BaO ratio of phosphate glasses can improve the laser properties while maintaining their good thermo-optical properties. (C) 2017 Elsevier B.V. All rights reserved
Ion-redistribution induced efficient upconversion in beta-NaYF4:20%Yb3+, 2%Er3+ microcrystals with well controlled morphology and size
No full textNational Natural Science Foundation of China (NSFC) [61405215, 61505232]We develop an efficient green upconversion (UC) beta-NaYF4:20%Yb3+,2% Er3+ microcrystal with well controlled morphology and size by hydrothermal method using two different chelating agents of CIT and EDTA-2Na via a simple ion-exchange reaction. Importantly, the UC emission efficiency of newly developed CIT and EDTA-2Na beta-NaYF4:20%Yb3+,2%Er3+ microcrystals is almost as strong as that of commercial counterpart by solid-state method. A proof-of-concept beta-NaYF4:20%Yb3+,2% Er3+ microcrystal waveguide is demonstrated to extend their applications in modern micro-optoelectronics. The local ion-redistribution process during the ion-exchange reaction, which effectively disperses the locally clustered Yb3+, accounts for the enormously enhanced UC emission in beta-NaYF4:20%Yb3+,2%Er3+ microcrystals. (C) 2016 Optical Society of Americ
Research and development of neodymium phosphate laser glass for high power laser application
No full textNeodymium phosphate laser glass is a key optical element for high-power laser facility. In this work, the latest research and development of neodymium phosphate laser glass at the Shanghai Institute of Optics and Fine Mechanics (SIOM), China, is addressed. Neodymium phosphate laser glasses, N31, N41, NAP2, and NAP4, for high peak power and high average power applications have been developed. The properties of these glasses are presented and compared to those of other commercial neodymium phosphate laser glass from the Schott and Hoya companies and the Vavilov State Optical Institute (GOI), Russia. Continuous melting and edge cladding are the two key fabrication techniques that are used for the mass production of neodymium phosphate laser glass slabs. These techniques for the fabrication of large aperture N31 neodymium phosphate laser glass slabs with low stress birefringence and residual reflectivity have been developed by us The effect of acid etching on the microstructure, optical transmission, and mechanical properties of NAP2 glass is also discussed. (C) 2016 Elsevier B.V. All rights reserved