Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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228 nm pulse duration dependence in the photodissociation of H-2(+)
No full textNSF of China [11604349]We theoretically investigate the pulse duration dependence in the laser-induced dissociation of the molecular ion H-2(+) The simulation results show that the dissociation ratio can be split up into three regions with increasing duration of the external laser pulse, with a central wavelength of 228 nm, as a result of the electron capture of the vibrationally highly excited H-2(+) With the coupled equations of the 1 s sigma(g) and 2p sigma(u) states one can find that the pulse duration dependence in the photodissociation of H-2(+) is due to the different responses of the molecular dipole to the evolution time of the ultraviolet laser pulse
A High-Energy, 100 Hz, Picosecond Laser for OPCPA Pumping
No full textNational Science Foundation of China (NSFC) [11127901, 11134010]; Shanghai Sailing Program [15YF1413500]; Strategic Priority Research Program of the Chinese Academy of Sciences [XDB1603]; International S&T Cooperation Program of China [2016YFE0119300]A high-energy diode-pumped picosecond laser system centered at 1064 nm for optical parametric chirped pulse amplifier (OPCPA) pumping was demonstrated. The laser system was based on a master oscillator power amplifier configuration, which contained an Nd: YVO4 mode-locked seed laser, an LD-pumped Nd: YAG regenerative amplifier, and two double-pass amplifiers. A reflecting volume Bragg grating with a 0.1 nm reflective bandwidth was used in the regenerative amplifier for spectrum narrowing and pulse broadening to suit the pulse duration of the optical parametric amplifier (OPA) process. Laser pulses with an energy of 316.5 mJ and a pulse duration of 50 ps were obtained at a 100 Hz repetition rate. A top-hat beam distribution and a 0.53% energy stability (RMS) were achieved in this system
Broadband optical parametric chirped pulse amplification in K3B6O10Br crystal near 800 nm
No full textNational Natural Science Funding of China [NSFC 61378030, NSFC 61521093, NSFC 51425206]Broadband optical parametric chirped pulse amplification (OPCPA) of the K3B6O10Br (KBOB) crystal at a central wavelength of 800 nm has been demonstrated for the first time. Using type-1 non-collinear phase matching, a 52 nm FWHM bandwidth was achieved around 800 nm. The 0.25 mJ signal was amplified to 23.92 mJ at the pump intensity of 2.1 GW cm(-2). The energy gain was 95.68. After compression, 15.31 mJ to 31.9 fs pulses were obtained. The results confirm that KBOB crystal is a potential alternative for efficient, broadband OPCPA near 800 nm
Effective mass dependence in laser-induced absorption of ZnO pumped by mid-infrared laser pulse
No full textNational Natural Science Foundation of China [11127901, 61221064, 11134010, 11227902, 11222439, 11274325]; 973 Project [2011CB808103]The time-resolved laser-induced absorption below the band edge in a ZnO sample is observed in the presence of a strong mid-infrared (MIR) pulse. The laser-induced absorption increases with the pump intensity, but it is different in two directions ([1100] and [1120] direction). The simulation results demonstrate that this phenomenon is primarily caused by the direction dependence of the reduced effective mass of electron and hole. For smaller reduced effective mass, the number of multi-photon ionization channel becomes larger, the probe photons are more likely to be absorbed and the absorption coefficients is larger, so lower pump intensity is needed for absorption saturation. (C) 2015 Elsevier B.V. All rights reserved
Electron localization of H-2(+) in a dc electric field
No full textNational Natural Science Foundation of China [11127901, 61521093, 11134010, 11227902, 11222439, 11274325]; National Basic Research Program of China [2011CB808103]A dc electric field is utilized to steer the electron motion after the molecular ion H-2(+) is excited by an ultrashort ultraviolet laser pulse. The numerical simulation shows that the electron localization distribution and the dissociation control ratio are dependent on the polarization direction and amplitude of the dc electric field. Most electrons of the dissociation state move opposite to the dc electric field and stabilize at the dressed-up potential well, for the dressed-down well is occupied by the electrons of the 1s sigma(g) state
Energetic radially polarized few-cycle pulse compression in gas-filled hollow-core fiber
No full textNational Natural Science Foundation of China (NSFC) [61205208]; Strategic Priority Research Program of the Chinese Academy of Sciences [XDB1603]; International S&T Cooperation Program of China [2016YFE0119300]The compression of high-energy, radially polarized pulses in a gas-filled hollow-core fiber (HCF) is theoretically studied. The simulation results indicate that a 40-fs input pulse can be compressed to a full-width at half-maximum of less than 9 fs when the pulse energy reaches 7.0 mJ with a transmission efficiency of more than 67% after propagating through a 1-m-long, 500-mu m diameter HCF filled with neon. Furthermore, the spatio-temporal intensity distributions of the compressed pulses with different initial input energies are studied, and the numerical results indicate that the spatio-temporal intensity distributions are more uniform for lower input pulse energies
Exploring novel target structures for manipulating relativistic laser-plasma interaction
No full textAFOSR Basic Research Initiative (BRI) [FA9550-14-1-0085]; DFG (Germany) [Trnsregio TR18]The improved laser-to-pedestal contrast ratio enabled by current high-power laser pulse cleaning techniques allows the fine features of the target survive before the main laser pulse arrives. We propose to introduce the nano-fabrication technologies into laser-plasma interaction to explore the novel effects of micro-structures. We found out that not only laser-driven particle sources but also the laser pulse itself can be manipulated by specifically designed micro-cylinder and -tube targets, respectively. The proposal was supported by full-3D particle-in-cell simulations and successful proof-of-principle experiments for the first time. We believe this would open a way to manipulate relativistic laser-plasma interaction at the micro-size level
Fabrication of high-Q microresonators in dielectric materials using a femtosecond laser: Principle and applications
No full textNational Basic Research Program of China [2014CB921300]; National Natural Science Foundation of China (NSFC) [61275205, 11174305, 61505231]; Open Fund of the State Key Laboratory on Integrated Optoelectronics [IOSKL2015KF34]Femtosecond laser micromachining has been a promising technique for fabricating three-dimensional (3D) micro/nano-structures in various kinds of dielectric materials with unprecedented spatial resolutions as well as flexibility in terms of the geometry and the materials can be processed. This unique capability opens opportunities for fabrication of 3D high-quality (Q) microresonators, which are one of the key elements in modern photonic applications. Here, we review the recent progress in fabrication of high-Q microresonators on glass and crystalline substrates by employing femtosecond laser direct writing. We demonstrate the applications of the fabricated microresonators in generating low-threshold lasers, high-sensitivity chemical sensing and nonlinear optical wavelength conversion. (C) 2016 Elsevier B.V. All rights reserved
Fluorescence Dynamics of LicT Protein by Time-Resolved Spectroscopy
No full text使用时间分辨荧光方法,结合紫外吸收光谱和稳态荧光光谱技术,测量了LicT蛋白中色氨酸残基的荧光动力学特性,进而对LicT蛋白质激活前后的局部微环境和结构变化进行了研究。LicT蛋白质的激活态使得有关糖类利用的基因转录过程继续进行,促进机体新陈代谢。通过色氨酸残基的荧光发射和寿命的差异判断出激活型蛋白AC 141和野生型蛋白Q 22不同的结构性质和微环境差异。在此基础上,通过衰减相关光谱(DAS)和时间分辨发射光谱(TRES)阐释了两种蛋白色氨酸残基和溶剂的相互作用,说明了激活型AC 141的比野生型Q 22的结构更加紧密。此外,TRES还说明了蛋白中的色氨酸残基存在连续光谱弛豫过程。各向异性结果则对残基和整个蛋白的构象运动进行了阐述,说明了色氨酸残基在蛋白质体系内有独立的局部运动,且在激活型蛋白中该运动更加强烈。In this paper, the fluorescence dynamics of tryptophan residues in LicT protein is investigated by time-resolved fluorescence method combined with UV absorption and steady-state fluorescence spectroscopy. The local microenvironment and structural changes of LicT protein before and after activation are studied. The activated LicT protein AC 141 prevents the antitermination of gene transcription involved in carbohydrate utilization to accelerate the body's metabolism. The structural properties and microenvironment of activated protein AC 141 and wild-type protein Q 22 were determined by different fluorescence emissions and lifetimes of tryptophan residues. The interaction between tryptophan residues and solvent is elucidated by decay associated spectroscopy (DAS) and time-resolved emission spectra (TRES), indicating that upon activation, the structure of AC 141 is more compact than that of wild-type Q 22. In addition, TRES also showed that tryptophan residues in the protein had a continuous spectral relaxation process. Anisotropy results illustrated the conformational motions of residues and whole proteins, suggesting that tryptophan residues had independent local motions in the protein system, and that the motions were more intense in the activated protein
Intense keV IAP generation by orthogonally polarized multicycle midinfrared two-color laser fields
No full textNational Natural Science Foundation of China [11127901, 61521093, 11134010, 11227902, 11574332, 1151101142, 61690223, 11274325]; Chinese Academy of Sciences [XDB16]; Youth Innovation Promotion Association of Chinese Academy of SciencesWe theoretically investigate the attosecond pulse generation in an orthogonal multicycle midinfrared two-color laser field. It is demonstrated that multiple continuum-like humps, which consist of about twenty orders of harmonics and an intensity of about one order higher than the adjacent normal harmonics, are generated when longer wavelength driving fields are used. By filtering these humps, intense isolated attosecond pulses (IAPs) are directly generated without any phase compensation. Our proposal provides a simple technique to generate intense IAPs with various central photon energies covering the multi-keV spectral regime by using multicycle midinfrared driving pulses with high pump energy in the experiment