Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Tunable photoluminescence of CsPbBr3 perovskite quantum dots for light emitting diodes application
No full textNational Natural Science Foundation of China [61520106012, 61574024, 61475169]; Fundamental Research Funds for the Central Universities [106112015CDJZR125511, 106112015CDJXY120001, 106112016CDJCR121222]; SRF [0210002409003]; Advanced and Fundamental Research Funds of Chongqing [cstc2015jcyjA1055, cstc2015jcjA90007]; Chinese Academy SciencesAll-inorganic cesium lead halide (CsPbBr3) perovskite quantum dots (QDs), as one kind of promising materials, have attracted considerable attention in optoelectronic applications. Herein, we synthesized the colloidal CsPbBr3 QDs with tunable photoluminescence (PL) (493-531 nm) by adjusting the reaction temperatures, which revealed narrow emission bandwidths of about 25 nm. The average diameters of the QDs could be adjusted from 7.1 to 12.3 nm as the temperature increased from 100 degrees C to 180 degrees C. Moreover, the radiative lifetimes of CsPbBr3 QDs were measured to be similar to 2 ns, and the single QD fluorescence intensity time trace results demonstrated its suppressed blinking emission. Moreover, green light emitting diodes by using CsPbBr3 QDs tasted on blue LED chips were further fabricated, which provided potential applications in the field of display and lighting technology
Optomechanically induced transparency in a spinning resonator
No full textNational Natural Science Foundation of China (NSFC) [11474087, 91536107]; Key Research Program of Frontier Science of Chinese Academy of Sciences (CAS) [QYZDY-SSW-SLH009]; National Key R&D Program of China [2016YFA0301504]We study optomechanically induced transparency in a spinning microresonator. We find that in the presence of rotation-induced Sagnac frequency shift, both the transmission rate and the group delay of the signal are strongly affected, leading to a Fano-like spectrum of transparency. In particular, tuning the rotary speed leads to the emergence of nonreciprocal optical sidebands. This indicates a promising new way to control hybrid light - sound devices with spinning resonators
Performance analysis of ghost imaging lidar in background light environment
No full textNational Natural Science Foundation of China (NSFC) [61571427]; Ministry of Science and Technology of the People's Republic of China (MOST) [2013AA122901]; Youth Innovation Promotion Association of Chinese Academy of Sciences [2013162]The effect of background light on the imaging quality of three typical ghost imaging (GI) lidar systems (namely narrow pulsed GI lidar, heterodyne GI lidar, and pulse-compression GI lidar via coherent detection) is investigated. By computing the signal-to-noise ratio (SNR) of fluctuation-correlation GI, our analytical results, which are backed up by numerical simulations, demonstrate that pulse-compression GI lidar via coherent detection has the strongest capacity against background light, whereas the reconstruction quality of narrow pulsed GI lidar is the most vulnerable to background light. The relationship between the peak SNR of the reconstruction image and sigma (namely, the signal power to background power ratio) for the three GI lidar systems is also presented, and the results accord with the curve of SNR-sigma
Recent improvements on the pulsed optically pumped rubidium clock at SIOM
No full textNational Natural Science Foundation of China [91536220, 11504393]We report the recent progress of our pulsed optically pumped ( POP) vapor cell rubidium clock with dispersive detection. A new compact physics package is made. A rubidium cell with a high precision buffer gases mixing ratio is obtained, and the temperature controlling system is renovated to reduce fractional frequency sensitivity to temperature variation. The resolution of the servo control voltage is also optimized. With these improvements, a clock frequency stability of 3.53 x 10(-13) at 1 s is obtained, and a fractional frequency stability of 4.91 x 10(-15) is achieved at an average time of tau = 2000 s
Superexchange-mediated magnetization dynamics with ultracold alkaline-earth atoms in an optical lattice
No full textNational Key Research and Development Program of China [2016YFA0301504]Superexchange and inter-orbital spin-exchange interactions are key ingredients for understanding (orbital) quantum magnetism in strongly correlated systems and have been realized in ultracold atomic gases. Here we study the spin dynamics of ultracold alkaline-earth atoms in an optical lattice when the two exchange interactions coexist. In the superexchange interaction dominating regime, we find that the time-resolved spin imbalance shows a remarkable modulated oscillation, which can be attributed to the interplay between local and nonlocal quantum mechanical exchange mechanisms. Moreover, the filling of the long-lived excited atoms affects the collapse and revival of the magnetization dynamics. These observations can be realized in state-dependent optical lattices combined with the state-of-the-art advances in optical lattice clock spectroscopy
Mitigation of beam sampling grating damage induced by upstream flaws in the final optics assembly
No full textCollaboration on Advance Key Techniques for Inertial Fusion Energy [2012DFG62040]; National Natural Science Foundation of China [11104296]The high fluence performance of high-power laser systems is set by optical damage, especially in the final optics assembly (FOA). The flaws on the frequency converter surface can cause optical intensity intensification and, therefore, damage the downstream optical elements, such as the beam sampling grating (BSG), which is an important component in the FOA. Mitigation of BSG damage caused by flaws is discussed. Physical models are established to simulate the optical field enhancement on BSG modulated by the upstream flaw, considering both the linear and nonlinear propagation effects. Numerical calculations suggest that it is important to place the BSG in a properly selected position to mitigate the laser-induced damage. Furthermore, strict controls of flaw size, modulation depth, distance between frequency converter and focusing lens, and the thickness of the focusing lens are also significant to mitigate the BSG damage. The results obtained could also give some suggestions for damage mitigation of optical components and the layout design of the final optics assembly. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE
Modeling of ablation threshold dependence on pulse duration for dielectrics with ultrashort pulsed laser
No full textOpen Research Fund of State Key Laboratory of Pulsed Power Laser Technology, Electronic Engineering Institute [SKL2014KF05]; Fund of Key Laboratory of High Power Laser and Physics, Chinese Academy of Sciences [CXJJ-16S040]We present a numerical model of plasma formation in ultrafast laser ablation on the dielectrics surface. Ablation threshold dependence on pulse duration is predicted with the model and the numerical results for water agrees well with the experimental data for pulse duration from 140 fs to 10 ps. Influences of parameters and approximations of photo- and avalanche-ionization on the ablation threshold prediction are analyzed in detail for various pulse lengths. The calculated ablation threshold is strongly dependent on electron collision time for all the pulse durations. The complete photoionization model is preferred for pulses shorter than 1 ps rather than the multiphoton ionization approximations. The transition time of inverse bremsstrahlung absorption needs to be considered when pulses are shorter than 5 ps and it can also ensure the avalanche ionization (AI) coefficient consistent with that in multiple rate equations (MREs) for pulses shorter than 300 fs. The threshold electron density for AI is only crucial for longer pulses. It is reasonable to ignore the recombination loss for pulses shorter than 100 fs. In addition to thermal transport and hydrodynamics, neglecting the threshold density for AI and recombination could also contribute to the disagreements between the numerical and the experimental results for longer pulses. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE
Ptychographic phase microscope based on high-speed modulation on the illumination beam
No full textChinese Academy of Sciences (CAS) [902012312D1100101]; CAS [29201431151100301]A type of ptychography-based phase microscope was developed by integrating a spatial light modulator (SLM) into a commercial wide-field light microscope. By displaying a moving pattern on the SLM to change the sample illumination and record the diffraction intensities formed, both the modulus and phase of the transmission function of the sample could be accurately reconstructed with formulas similar to those of common ptychography. Compared with other kinds of phase microscopes, the developed microscope has several advantages, including its simple structure, high immunity to coherent noise, and low requirement for quality optics. In addition, defects in the illumination beam are also removed from the reconstructed image. Further, this microscope's fast data acquisition ability makes it highly suitable for many applications where highly accurate quantitative phase imaging is important, such as in living cells or other fragile biological samples that cannot sustain continuous imaging over a long period of time. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE
CsPbBr3 perovskite quantum dots: saturable absorption properties and passively Q-switched visible lasers
No full textNational Natural Science Foundation of China (NSFC) [61378074, 61475173]; Youth Innovation Promotion Association Chinese Academy of Sciences (CAS)This work presents the saturable absorption (SA) properties of CsPbBr3 perovskite quantum dots (QDs). The perovskite QDs show excellent SA performance with a nonlinear absorption coefficient of -35 x 10(-2) cm/GW and a figure of merit of 3.7 x 10(-14) esu cm. Further, their use as saturable absorbers in a passively Q-switched visible solid-state laser for the generation of soliton pulses is demonstrated. These results demonstrate the potential for the perovskite QDs to act as saturable absorbers
Effect of erbium concentration on optical properties of Er:YLF laser crystals
No full textNational Natural Science Foundation of China [51302283, 51502321]Four Er-doped LiYF4 crystals with different Er-concentrations were grown by Czochralski method. The laser crystals were characterized by measurements of ICP-AES, XRD, absorption spectra, up-conversion fluorescence spectra, near-infrared (NIR) and mid-infrared (Mid-IR) fluorescence spectra, as well as luminescence decays. It was found that the heavily 15 at% Er-doped YLF crystal is more proper in up conversion or similar to 3 mu m laser applications; while the 5 at% Er-doped YLF is a better candidate for 1.5 mu m lasers within these four crystals. (C) 2016 Elsevier B.V. All rights reserved