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Shaping of few-cycle laser pulses via a subwavelength structure

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Chinese Physics B 2013年第9期22卷 450-455页

作者：郭亮谢小涛詹志明 Department of Physics Northwest University School of Physics and Information Engineering Jianghan University

We theoretically investigate the propagation of few-cycle laser pulses in resonant two-level dense media with a sub- wavelength structure, which is described by the full Maxwell-Bloch equations without the frame of slowly varying envelope and rotating wave approximations. The input pulses can be shaped into shorter ones with a single or less than one optical cycle. The effect of the parameters of the subwavelength structure and laser pulses is studied. Our study shows that the media with a subwavelength structure can significantly shape the few-cycle pulses into a subcycle pulse, even for the case of chirp pulses as input fields. This suggests that such subwavelength structures have potential application in the shaping of few-cycle laser pulses.

关键词： ultrashort pulses coherent propagation self-induced transparency

Coherent population transfer with chirped few-cycle laser pulses in an excited-doublet four-level system

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Chinese Optics Letters 2005年第8期3卷 435-437页

作者：杨玮枫龚尚庆钮月萍徐至展 State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Graduate School of the Chinese Academy of Sciences Beijing 100039 The behavior of population transfer in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored

The behavior of population transfcr in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.

关键词： Electron transitions Laser pulses Pulsed laser applications ultrashort pulses

Generation of the numerator=2 rational harmonic mode-locked pulses in fiber ring lasers

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Chinese Optics Letters 2004年第9期2卷 534-535页

作者：汪平河詹黎叶庆好夏宇兴 InstituteofOpticsandPhotonics NationalLaboratoryonFiberOpticCommunicationNetworks&AdvancedOpticalCommunicationSystemsShanghaiJiaoTongUniversityShanghai200240

In conventional rational harmonic mode-locking, optical pulse trains with the repetition rate of (pn+1)f_c are generated when the modulation frequency of the in-cavity modulator is set at f_m = (n+1/p)f_c, where n and p are both integers, f_c is the fundamental cavity frequency. In this paper, we report that rational harmonic mode locking phenomenon takes place in the fiber lasers when the modulation frequency is set at f_m =(n+2/p)f_c. The pulse generations are experimentally demonstrated when the numerator of the rational corresponds to 2 in 5th and 7th order rational harmonic mode-locking.

关键词： Fiber lasers Light modulation Ring lasers ultrashort pulses

Interaction of intense laser pulses with atomic clusters at different gas densities

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Chinese Optics Letters 2004年第9期2卷 497-499页

作者：李邵辉王成刘建胜王向欣李儒新倪国权徐至展 DepartmentofPhysics ShantouUniversityShantou515063 LaboratoryforHighIntensityOptics ShanghaiInstituteofOpticsandFineMechanicsChineseAcademyofSciencesShanghai201800

The interaction of intense femtosecond laser pulses with rare gas clusters was studied experimentally, the time-of-flight spectra of ions from exploding clusters at different gas densities have been measured. It is found that while the relative components of ions in low and high energy of the ion energy spectrum decrease with the increase of the gas density, the average ion energies are the same for different gas densities, which indicates that the effect of gas density on laser-cluster interaction is not important under our experimental conditions.

关键词： Atoms Density of gases ultrashort pulses

A global model of intensity autocorrelation to determine laser pulse duration

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Chinese Physics B 2024年第5期33卷 446-451页

作者：彭雨菲刘励强洪丽红李志远 School of Physics and Optoelectronics South China University of TechnologyGuangzhou 510640China

We present a new global model of collinear autocorrelation based on second harmonic generation *** model is rigorously derived from the nonlinear coupled wave equation specific to the autocorrelation measurement configuration,without requiring a specific form of the incident pulse function.A rigorous solution of the nonlinear coupled wave equation is obtained in the time domain and expressed in a general analytical *** global model fully accounts for the nonlinear interaction and propagation effects within nonlinear crystals,which are not captured by the classical local *** assess the performance of the global model compared to the classic local model,we investigate the autocorrelation signals obtained from both models for different incident pulse waveforms and different full-widthes at half-maximum(FWHMs).When the incident pulse waveform is Lorentzian with an FWHM of 200 fs,the global model predicts an autocorrelation signal FWHM of 399.9 fs,while the classic local model predicts an FWHM of 331.4 *** difference between the two models is 68.6 fs,corresponding to an error of 17.2%.Similarly,for a sech-type incident pulse with an FWHM of 200 fs,the global model predicts an autocorrelation signal FWHM of 343.9 fs,while the local model predicts an FWHM of 308.8 *** difference between the two models is 35.1 fs,with an error of 10.2%.We further examine the behavior of the models for Lorentzian pulses with FWHMs of 100 fs,200 fs and 500 *** differences between the global and local models are 17.1 fs,68.6 fs and 86.0 fs,respectively,with errors approximately around 17%.These comparative analyses clearly demonstrate the superior accuracy of the global model in intensity autocorrelation modeling.

关键词： intensity autocorrelation global model ultrashort pulses pulse-width measurement

Automatic mode-locking fiber lasers: progress and perspectives

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Science China(Information Sciences) 2020年第6期63卷 119-142页

作者： Guoqing PU Li ZHANG Weisheng HU Lilin YI State Key Lab of Advanced Communication Systems and Networks Shanghai Institute for Advanced Communication and Data Science Shanghai Jiao Tong University

Polarization control in nonlinear polarization rotation based mode-locked fiber lasers is a longterm challenge. Suffering from the polarization drifts induced by environmental disturbances, nonlinear polarization rotation based mode-locked fiber lasers is difficult in continuously operating under the desired pulsation regime thereby substantially hindering their utilizations. The appearance of automatic modelocking techniques brings the light in addressing this challenge. Combining with various algorithms and electrical polarization control, automatic mode-locking techniques resolve the dilemma of nonlinear polarization rotation based mode-locked fiber lasers. We review the research progress of automatic mode-locking techniques in detail. Furthermore, we comment on the perspectives and potential applications of automatic mode-locking techniques.

关键词： nonlinear polarization rotation ultrashort pulses automatic mode-locking electrical polarization control optimization algorithms machine learning time stretch

Design of chirped Mo/Si multilayer mirror in the extreme ultraviolet region

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Chinese Optics Letters 2008年第4期6卷 310-312页

作者：陈锐王风丽王占山 Institute of Precision Optical Engineering Tongji University Shanghai 200092

The chirped Mo/Si multilayer mirror in the extreme ultraviolet region is designed to obtain sub-femtosecond pulses from high-order harmonics. Numerical simulations of temporal profile of the pulses are made for superposition of incident high-order harmonics and that of reflected ones by the chirped multilayer mirror. The normal incidence reflectivity and chirp in the wavelength range of 12.5 - 16.5 nm are 6.7% =k 0.5% and -3617 ± 171 as^2, respectively. Simulation results indicate that the designed chirped multilayer mirror can be used for producing 104-as pulses.

关键词： Computer simulation Light reflection Mirrors Multilayer films ultrashort pulses

Narrow-linewidth single-polarization frequency-modulated Er-doped fiber ring laser

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Chinese Optics Letters 2008年第11期6卷 845-847页

作者：欧攀贾豫东曹彬张春熹胡姝玲冯迪 School of Instrument Science and Opto-Electronics Engineering Beihang UniversityBeijing 100083

We demonstrate a 1550-nm narrow-linewidth fiber ring laser with stable single polarization by using single-mode Er-doped fiber as active fiber and saturable absorber. A polarization-maintaining circulator is used to acquire single-polarization laser light with the degree of polarization of 99.8%--99.9%. The linewidth measured using a delayed self-heterodyne method is less than 0.5 kHz. Frequency of the fiber laser can be modulated by driving the waveguide phase modulator with proper voltage. A Mach-Zehnder interferometer with the optical path difference between two arms of about 36 km is used to study the long-distance coherent detection of the fiber laser for frequency-modulated continuous-wave application.

关键词： Erbium Fiber lasers Fibers Frequency modulation Lasers Linewidth Polarization Ring lasers Semiconductor quantum wells ultrashort pulses

Performance testing of log pile photonic crystal fast-fabricated by direct femtosecond laser writing

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Chinese Optics Letters 2008年第11期6卷 864-867页

作者：杨海峰周明戴娟狄建科赵恩兰 Photonics Fabrication Science Center Jiangsu UniversityZhenjiang 212013

Great efforts has been made on fabricating photonic crystals （PCs） with photonic band gaps （PBGs） during the past decade. Three-dimensional （3D） log pile PC was fabricated fast by direct femtosecond laser writing in ORMOCER. Qualitative analysis of the errors of PC was investigated using the Image Pro Plus. Surface qualities such as bending, distortion, and surface roughness were shown, and the band gap in the infrared wavelength region was observed. Meanwhile, the theory was experimentally verified that the center of PBG diminishes as the crystal lattice period reduces. Therefore, it is possible to fabricate PCs whose band gap range is from the near-infrared to visible wave band.

关键词： Crystal atomic structure Crystallography Energy gap Gallium alloys Microcomputers Photonic band gap Photonics Piles Pulsed laser applications Silicon on insulator technology Surface roughness Three dimensional ultrashort pulses