Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Facile Syntheses of Ba-2[B4O7(OH)(2)] and Na[B5O7(OH)(2)](H2O) Borate Salts Exhibiting Nonlinear Optical Activity in the Ultraviolet
No full textNational Natural Science Foundation of China [51432006, 50925207, 51172100]; Ministry of Science and Technology of China [2011DFG52970]; Ministry of Education of China for the Changjiang Innovation Research Team [IRT13R24]; Ministry of Education; State Administration of Foreign Experts Affairs [B13025]; 100 Talents Program of CAS; Australian Research CouncilTwo novel noncentrosymmetric metal borates, Ba-2[B4O7(OH)(2)] (1) and Na[B5O7(OH)(2)](H2O) (2), have been obtained by hydrothermal and surfactant-thermal means. Compound 1 consists of novel one-dimensional borate chains formed by B3O9 and B3O8 rings, assembled into a three-dimensional (3D) framework by Ba2+ cations. The structure of 2 exhibits double-helical chains constructed from B5O10 primary building units, which are interconnected via Na+ cations and H-bonding interactions to generate a 3D framework. Second-harmonic-generation (SHG) measurements show that 1 shows a phase-matching powder SHG response of similar to 2.2 x KH2PO4 (KDP), while 2 exhibits a weak SHG response. The cutoff edges of 1 and 2 are similar to 242 and similar to 221 nm, respectively, which suggests that they are potential ultraviolet nonlinear optical (NLO) materials. Band structures and NLO properties have also been theoretically studied
Low-dose and fast grating-based x-ray phase-contrast imaging
No full textNational Research and Development Project for Key Scientific Instruments [CZBZDYZ20140002]; National Natural Science Foundation of China [11535015, 11305173, 11375225, 61705246]; Fundamental Research Funds for the Central Universities [WK2310000065]; Chinese Academy of Sciences and The World Academy of Sciences (CAS-TWAS) President's Fellowship programX-ray phase-contrast imaging has experienced rapid development over the last few decades, and, in this technology, the phase modulation strategy of phase stepping (PS) is used most widely to measure the sample's phase signal. However, because of its discontinuous nature, PS has the defects of worse mechanical stability and high exposure dose, which greatly hinder its wide use in dynamic phase measurement and potential clinical applications. We demonstrate preliminary research on the use of integrating-bucket (IB) phase modulation method to retrieve the phase information in grating-based x-ray phase-contrast imaging. Experimental results show that our proposed method can be well employed to extract the differential phase-contrast image, compared with the commonly used PS strategy, the advantage of the IB phase modulation technique is that fast measurement and low dose are promising. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License
Q-switching of waveguide lasers based on graphene/WS2 van der Waals heterostructure
No full text111 Project of China [B13029]; Strategic Priority Research Program of CAS [XDB16030700]; Key Research Program of Frontier Science of CAS [QYZDB-SSW-JSC041]; National Natural Science Foundation of China (NSFC) [11274203, 61522510]; STCSM Excellent Academic Leader of Shanghai [17XD1403900]We report on the operation of passively Q-switched waveguide lasers at 1 mu m wavelength based on a graphene/WS2 heterostructure as a saturable absorber (SA). The gain medium is a crystalline Nd:YVO4 cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 mW and slope efficiency of 37%. In comparison with the systems based on single WS2 or graphene SA, the lasing Q-switched by a graphene/WS2 heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promising applications of van der Waals heterostructures for ultrafast photonic devices
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
Extreme case of Faraday effect: magnetic splitting of ultrashort laser pulses in plasmas
No full textNational Basic Research Program of China [2013CBA01504]; National Natural Science Foundation of China (NSFC) [11129503, 11374210, 11405108, 11421064, 11675108]; National 1000 Youth Talent Project of China; Leverhulme TrustThe Faraday effect, caused by a magnetic-field-induced change in the optical properties, takes place in a vast variety of systems from a single atomic layer of graphenes to huge galaxies. Currently it plays a pivotal role in many applications such as the manipulation of light and the probing of magnetic fields and materials' properties. Basically, this effect causes a polarization rotation of light during its propagation along the magnetic field in a medium. Here, we report an extreme case of the Faraday effect where a linearly polarized ultrashort laser pulse splits in time into two circularly polarized pulses of opposite handedness during its propagation in a highly magnetized plasma. This offers a new degree of freedom for manipulating ultrashort and ultrahigh-power laser pulses. Together with the technologies of ultra-strong magnetic fields, it may pave the way for novel optical devices such as magnetized plasma polarizers. In addition, it may offer a powerful means to measure strong magnetic fields in laser-produced plasmas
Monolithic integration of a lithium niobate microresonator with a free-standing waveguide using femtosecond laser assisted ion beam writing
No full textNational Basic Research Program of China (Program 973) [2014CB921300]; Natural National Science Foundation of China (NSFC) [61505231, 61405220, 61327902, 61590934]; Fundamental Research Funds for the Central Universities and the Open Fund of the State Key Laboratory on Integrated Optoelectronics [IOSKL2015KF34]We demonstrated integrating a high quality factor lithium niobate microdisk resonator with a free-standing membrane waveguide. Our technique is based on femtosecond laser direct writing which produces the pre-structure, followed by focused ion beam milling which reduces the surface roughness of sidewall of the fabricated structure to nanometer scale. Efficient light coupling between the integrated waveguide and microdisk was achieved, and the quality factor of the microresonator was measured as high as 1.67 x 10(5)
Soliton dynamics for trapped Bose-Einstein condensate with higher-order interaction
No full textNational Natural Science Foundation (NSF) of China [11791240178, 11547024, 11674338]We model the three-dimensional (3D) trapped Bose-Einstein condensate with the Gross-Pitaevskii equation (GPE) incorporating higher-order nonlinear interaction effects. Based on the F-expansion method and self-similar approach, we analytically derive the exact soliton solutions of the 3D GPE, identifying the oscillatory mode under certain experimental settings. The oscillatory kinetic parameter values we obtained coincide very well with those reported in previous work, which is based on the variational approach, showing the applicability of the theoretical treatment presented in this work. (C) 2017 Author(s)
Bond-Selective Imaging of Cells by Mid-Infrared Photothermal Microscopy in High Wavenumber Region
No full textKeck Foundation Science and Engineering grant; UCAS Joint Ph.D. Training Program [UCAS [2015]37]Using a visible beam to probe the thermal effect induced by infrared absorption, mid-infrared photothermal (MIP) microscopy allows bond-selective chemical imaging at submicron spatial resolution. Current MIP microscopes cannot reach the high wavenumber region due to the limited tunability of the existing quantum cascade laser source. We extend the spectral range of MIP microscopy by difference frequency generation (DFG) from two chirped femtosecond pulses. Flexible wavelength tuning in both C-D and C-H regions was achieved with mid-infrared power up to 22.1 mW and spectral width of 29.3 cm(-1). Distribution of fatty acid in live human lung cancer cells was revealed by MIP imaging of the C-D bond at 2192 cm(-1)
Characterization of ultrashort pulses by time-frequency conversion and temporal magnification based on four-wave mixing at 1 mu m
No full textNational Natural Science Foundation of China (NSFC) [11604350, 61205103, 61405211]In order to characterize ultrashort pulses in real time at 1 mu m wavelength, a temporal imaging structure based on the four-wave mixing effect in highly nonlinear fibers is implemented and analyzed both theoretically and experimentally. It is found that both time-frequency transfer and the temporal magnification process can be realized approximately in one structure. The pulse widths of the signal laser measured by the time-frequency transfer and the temporal magnification process are 3.2 ps and 3.1 ps, respectively, which are nearly the same and are in agreement with the result of the autocorrelator. The temporal magnification factor is 33, and the temporal resolution is 380 fs. The method based on the temporal magnification process is inherently real time and single shot, which makes it suitable for applications in the measurement of high-power ultrashort pulses. The four-wave mixing time lens promises future applications in the characterization of the single-shot high-power short laser. (C) 2017 Optical Society of Americ
Compensation for the setup instability in ptychographic imaging
No full textNational Natural Science Foundation of China [61675215]The high-frequency vibration of the imaging system degrades the quality of the reconstruction of ptychography by acting as a low-pass filter on ideal diffraction patterns. In this study, we demonstrate that by subtracting the deliberately blurred diffraction patterns from the recorded patterns and adding the properly amplified subtraction to the original data, the high-frequency components lost by the vibration of the setup can be recovered, and thus the image quality can be distinctly improved. Because no prior knowledge regarding the vibrating properties of the imaging system is needed, the proposed method is general and simple and has applications in several research fields