Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
Not a member yet
13355 research outputs found
Sort by
Conical refraction, for annular pumping of an efficient vortex Nd:YAG laser
No full textNational Natural Science Foundation of China [61275206, 61475166]; National Science Foundation for Young Scientists of China [61405226]; Shanghai Natural Science Fund [14ZR1445200]We presented a proof-of-concept investigation upon an end-pumped and vortex Nd:YAG laser. In this laser, for the first time, the conical refraction (CR) ring of a biaxial KGd(WO4)(2) crystal was used for annular pumping. Owing to nearly 100% conversion efficiency in forming the CR ring, the Nd: YAG laser was highly efficient and emitted LG(01)-mode vortex light with 177.5 mW beam power and 65% slope efficiency. This study showed the CR ring pumping would favor the production of a compact, simple and efficient vortex laser. It is expected that, in future, the CR ring pumping technique would also facilitate the high-power vortex solid-state laser where a long gain medium is required
Cyphertext-only attack on the double random-phase encryption: experimental demonstration
No full textWe demonstrate experimentally that the traditional double random phase encoding (DPRE) technique is vulnerable to the cyphertext-only attack (COA). With the statistical ergodic property of the speckle, we show that the plaintext image can be recovered from the cyphertext alone owing to the fact that their energy spectral density functions are identical. Our result reveals the most serious security issue with the DRPE as it suggests that even the one-time-pad does not guarantee its security. This will open up new inside understanding of current optical security techniques. (C) 2017 Optical Society of Americ
Characterization method of unusual second-order-harmonic generation based on vortex transformation
No full textNational Natural Science Foundation of China [11374318, 11674312, 61775087]; Natural Science Foundation of Jiangsu province [BK20161159]; Open Fund of the State Key Laboratory of High Field Laser Physics of SIOM; 100-talents Project of Chinese Academy of SciencesWhen a few-cycle laser beam nonresonantly propagates through an inversion-symmetric medium, beyond the usual odd-order harmonics in the transmission spectra, a well-defined spectral peak at twice the incident laser central frequency is disclosed [T. Tritschler et al., Phys. Rev. Lett. 90, 217404 (2003)]. Beyond the characterization method via the rf measurement of its carrier-envelope phase dependence, here a more direct mode of characterization is proposed by means of vortex transformation where a few-cycle vortex laser is adopted instead: One can easily clarify its origin as an usual third-order harmonic that appears to be a second-order harmonic, based on the criteria that the topological charge number of harmonics is directly proportional to its harmonic order
Internal Laser Writing of High-Aspect-Ratio Microfluidic Structures in Silicate Glasses for Lab-on-a-Chip Applications
No full textNational Basic Research Program of China [2014CB921300]; National Natural Science Foundation of China [61590934, 11134010, 61327902]Femtosecond laser direct writing is unique in allowing for fabrication of 3D micro- and nanofluidic structures, thereby enabling rapid and efficient manipulation of fluidic dynamics in 3D space to realize innovative functionalities. Here, I discuss the challenges in producing fully functional and highly integrated 3D micro- and nanofluidic systems with potential applications ranging from chemical and biological analyses to investigations of nanofluidic behaviors. In particular, I review the achievements we have made in the past decade, which have led to 3D microchannels with controllable cross-sectional profiles and large aspect ratios, 3D nanofluidic channels with widths of several tens of nanometers, and smooth inner walls with roughness on the order of similar to 1 nm. Integration of the microfluidics with other functional microcomponents including microoptics and microelectrodes will also be discussed, followed by conclusions and the future perspective
Investigation of pre-pulse pumping laser for preserving temporal waveform of stimulated Raman scattering
No full textNational Science Foundation of China (NSFC) [11127901, 11134010]; Shanghai Sailing Program [15YF1413500]A modified polarized beam combination technique is proposed for preserving the temporal waveforms of stimulated Raman scattering. 1064 nm pre-pulse pumping lasers prior to the main pumping laser with a delay time are generated and injected into a Ba(NO3)(2) Raman medium to excite the crystal firstly. The influences of pre-pulse lasers with various energy levels on the temporal shapes of Raman lasers are investigated, and it is demonstrated that the temporal waveforms of the Raman laser are distorted once the energies of the pre-pulse are below and above the required energy for preserving the temporal shapes of Stokes radiation. It is also discovered that the temporal shape of the 1197 nm Raman laser cannot be perfectly preserved if the energy of the 1064 nm main laser is too low or the relative delay time is too large. Moreover, the optical conversion efficiency and Stokes laser energy obtained under pumping lasers with single and double intensity peaks are compared
Magetostatic amplifier with tunable maximum by twisted-light plasma interactions
No full textNational Natural Science Foundation of China [11605269, 11674341, 11675245]; Science Challenge Project [TZ2016005]Laser beams with Laguerre-Gaussian (LG) mode carry orbital angular momentum (OAM); however, when interacting with plasmas, the net angular momentum acquired by plasmas is basically zero after interaction. Here, we find when there exists a small magetostatic seed along the laser propagation direction, the barrier would be broken, giving rise to dramatic angular momentum transfer from LG-lasers to plasmas. Hence, the net OAM remaining in the plasmas system would continuously enhance the magetostatic field, until the corresponding Larmor frequency of electrons is comparable to the laser frequency in vacuum. Three-dimensional particle-in-cell simulations are performed to confirm our theory, producing spatial-uniform, temporal-stable and extremely-intense magetostatic fields
Automatic focusing for multisectional objects in digital holography using the structure tensor
No full textResearch Grants Council, University Grants Committee (RGC, UGC) [NSFC/RGC N_HKU714/13]Determining the axial position of the recorded object in digital holography is a crucial step for image reconstruction. When multiple discrete sections of a three-dimensional object are overlapping each other, this issue becomes more challenging. In this Letter, an autofocusing algorithm using the structure tensor and its eigenvalues is proposed. This method can extract the focal distance of each section for a multi-sectional object irrespective of whether the sections are overlapping or not. We validate the applicability of the proposed technique with synthesized and experimental data using two types of holographic systems. (C) 2017 Optical Society of Americ
Effect of hydrogen annealing on the photoluminescence properties of colour conversion glass in borosilicate glass
No full textNational Natural Science Foundation of China [51302171]; Science and Technology Commission of Shanghai Municipality [14500503300]; Natural Science Foundation of Shanghai [12ZR1430900]; Shanghai Municipal Alliance Programme [LM201547]Colour conversion glasses were prepared by cosintering borosilicate glass frits and Ce:YAG phosphors at various temperatures in the 600-900 degrees C range. The effect of hydrogen annealing on the photoluminescence (PL) of the colour conversion glasses was investigated. The relative photoluminescence (PL) intensity of the colour conversion glasses sintered at 600-800 degrees C was significantly enhanced from 4.87% to 225.61% after hydrogen annealing for 3 h. However, changes to the relative PL intensity of the colour conversion glasses sintered above 850 degrees C after hydrogen annealing were miniscule, because the corrosion of the glass matrix disturbed the YAG lattice. The findings revealed that hydrogen annealing improved the PL intensity of the colour conversion glasses only when the crystal structure of YAG was intact. (C) 2016 Published by Elsevier B.V
Influence of La/Al ratio on the structure and spectroscopy of Tm3+ doped Al2O3-La2O3-SiO2 glasses
No full textChinese National Natural Science Foundation [61405215, 61475174]Lanthanum aluminosilicate (LAS) glasses with compositions (Tm2O3)(0.8)-(Al2O3)(12-x) (La2O3)(x)-(SiO2)(87.2) (x = 0, 1.2, 4.5 mol%; La/Al = 0, 1/9, 3/5) were prepared via a sol-gel method combined with high temperature sintering. The total amount of Al2O3 and La2O3 was 12 mol%. The effect of the La/Al ratio on the structure and spectroscopic properties of Tm3+ has been studied in detail. The structure of Tm-3+ doped LAS glasses was studied via Al-27 nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The spinning sideband patterns of the Al-27 NMR spectra showed that the population of Tm3+ ions in the vicinity of Al3+ decreased with an increase in the La2O3 concentration. FTIR and Raman spectra suggest that glasses with high La/Al ratios have less interconnected glass networks. The spectroscopic properties of Tm3+ ions were investigated via the Judd-Ofelt method using the measurement of absorption and emission spectra. Both the 1.8 mu m fluorescence intensity and the relative intensity of up-conversion emission of Tm3+ ions decrease with an increase in the La/Al ratio. This indicates reduced cross relaxation between Tm3+ ions in glass with a high La/Al ratio. We conclude that the spatial distribution homogeneity of Tm3+ ions in LAS glass improves when the La/Al ratio increases. (C) 2016 Elsevier B.V. All rights reserved
Vortex Ti:Sapphire laser by using an intracavity spot-defect spatial filter
No full textNational Natural Science Foundation of China [61275206, 61475166, 61405226]; Shanghai Natural Science Fund [14ZR1445200]We demonstrated an LG(01)-mode vortex Ti:Sapphire laser by utilizing an intracavity spot defect for spatial filtering. At the 140-mu m diameter of spot defect, the power of vortex laser output reached 135 mW, and the slope efficiency of laser was 17.7%. The effects of the sizes of spot defects on the transverse laser modes and laser powers were also discussed. (C) 2017 Elsevier Ltd. All rights reserved