飞秒激光产生与放大技术

介绍了飞秒激光的发展和相关的应用。重点讨论了产生飞秒激光脉冲的几种方法;激光脉冲色散的物理机制及补偿方法;获得变换极限脉冲的条件等。还介绍了超短超强激光脉冲的放大与压缩技术,获得高功率窄脉冲的基本条件和啁啾脉冲放大原理;详细地讨论了基于非线性效应实现高信噪比、宽光谱、高效率脉冲放大的光参量啁啾脉冲放大技术,在飞秒激光脉冲放大中的应用和发展前景。最后还阐述了阿秒光脉冲产生与测量的新技术。     

Matched photonic bandgap fibre and fibre Bragg grating dispersion for all-in-fibre stretch pulse amplification

Kilowatt peak power pulses with pulse durations of approximately 1.5 ps within 5% of transform limit using an all-fibre stretch pulse amplification system are demonstrated. Efficient high-quality stretch pulse amplification is achieved using a matched chirped fibre Bragg grating and low nonlinearity photonic-bandgap hollow-core fibre. The nearly ideal recompression highlights the robustness of ultra-short picosecond pulses to group delay ripple in chirped fibre gratings.     

Low-noise amplification of high-power pulses in multimode fibers

Low-noise amplification of high-power pulses in multimode erbium/ytterbium-doped fibers is demonstrated. The use of multimode fiber amplifiers allows to overcome the peak power limitations of single-mode amplifiers. As a result femtosecond pulses can be efficiently amplified to peak powers >50 kW in a high-power chirped pulse amplification system using chirped PPLN for frequency-doubling. With an average power level of 1.2 W at the fundamental wavelength of 1.55-μm average powers up to 420 mW are generated at 775 mm     

Multi-terawatt femtosecond Cr:LiSAF laser

We discuss the design of a Cr:LiSAF laser system capable of generating ultrashort, 90-fs Fourier-transform limited pulses with a peak power of 8 TW. Using chirped pulse amplification and flashlamp-pumped Cr:LiSAF amplifiers this system incorporates a regenerative amplifier and three additional double-pass amplifiers with increasing aperture up to 25 mm. The temporal performance as well as the spatial beam quality are discussed in detail. We discuss extension of this system to the Petawatt power level     

可调谐超短中红外激光脉冲的参变产生与放大及其最新进展

介绍了基于非线性光学参变过程产生和放大中红外可调谐超短激光脉冲的主要方法,比较了参变振荡、差频产生、光学参变放大和啁啾脉冲光学参变放大等4种产生与放大方法的技术特点,重点评述了最近10年来国内外利用光学参变放大和啁啾脉冲光学参变放大实现大增益宽带和高峰值功率输出的最新进展.探讨了获得更高能量/功率和更短脉冲(更大带宽)...     

高功率飞秒脉冲光纤激光系统

基础科学研究和超精细工业加工领域的发展迫切需要高重复频率、高功率的飞秒脉冲激光。采用啁啾脉冲放大技术,以掺镱双包层光子晶体光纤作为增益介质,搭建了高平均功率飞秒脉冲光纤激光系统。系统包括被动锁模振荡器、脉冲展宽器、单模光纤预放大器、光子晶体光纤功率放大器和脉冲压缩器5部分。实验上获得了重复频率40 MHz、平均功率150 W、脉冲宽度273 fs的超短脉冲输出。整个系统置于3 m×1.5 m的光学平台上,通过模块化和集成化的改进,该系统体积有望大幅度减小,为科学研究和工业应用提供有力工具。     

Dispersion control in a 100-kHz-repetition-rate 35-fs Ti:sapphire regenerative amplifier system

Presents a 100-kHz femtosecond amplifier system delivering pulses with a duration of 35 fs and an energy of 7 /spl mu/J. The system does not include a stretcher, since the large amount of dispersion accumulated during the amplification process is sufficient to prevent self-focusing. Compensation in approximately all orders is achieved through a combination of a prism compressor, chirped mirrors, and a liquid-crystal modulator, allowing the amplified pulses to be shortened to nearly the bandwidth limit.     

单模光纤中啁啾脉冲的分裂机制

采用分步傅里叶算法数值求解非线性薛定谔方程,分析了单模光纤中不同情形下皮秒量级啁啾脉冲的分裂机制。结果表明,对于较短的脉冲(10 ps),啁啾脉冲分裂从高阶孤子压缩导致的脉冲塌陷开始;对于较长的脉冲(200 ps),脉冲分裂主要由调制不稳定性导致;对于介于两者之间的脉冲(50 ps),噪声使得脉冲分裂机制从高阶孤子压缩转向调制不稳定性。初始正、负啁啾能分别加速和延缓短脉冲分裂,而初始啁啾对长脉冲分裂影响很小。初始啁啾对脉冲分裂的影响与其分裂机制密切相关。     

Impact of the second order dispersion on compensation of SPM in an adaptive pulse pre-shaping quasi-CPA system

A model of quasi-CPA (chirped pulse amplification) system, in which the input is the transform-limited Gaussian pulses, is set up numerically to investigate the impact of the second order dispersion on the adaptive compensation of self-phase modulation (SPM) effect. The adaptive phase pre-shaping controlled by differential evolution algorithm is introduced to the input pulse before amplification and recompression. With maximizing the peak power of the output pulse, the simulation results show th...     

The detection of chirped radar signals by means of electron spin echoes

The application of the electron spin echo phenomenon to the detection of chirped microwave pulses is considered. The attainable time resolution is determined by the width of the paramagnetic resonance line, and the length of the received waveform is limited by the phase memory time of the spin packets in the active material. Pulse compressions of 1000:1 appear to be feasible. A typical device of this kind would require to be operated at liquid helium temperatures. It could be adapted so that in itself it provided maser amplification of the compressed pulses.     

采用啁啾光纤光栅补偿带啁啾的超高斯脉冲在光纤中传输的色散

利用啁啾光纤光栅,对带啁啾的超高斯脉冲的色散补偿特性进行了理论分析和数值模拟。数值模拟结果表明,光脉冲在普通单模光纤中传输了一定距离后,由于色散的作用,脉冲发生展宽,超高斯脉冲比高斯脉冲展得更宽。若初始脉冲含有啁啾,展宽后的脉冲还出现小调制。用啁啾光纤光栅进行色散补偿后,高斯型脉冲能够较好的恢复初始脉冲形状,带啁啾的超高斯脉冲的脉宽可恢复到接近初始脉冲的宽度,但脉冲形状发生了畸变,并出现了旁瓣,脉冲峰值功率与超高斯脉冲阶数和啁啾参数有关。     

啁啾高斯脉冲在光纤中传输的脉冲展宽研究

通过求解非线性薛定谔方程,研究了线性光纤中色散导致的具有初始频率啁啾的高斯脉冲展宽的详细物理过程。得到高斯脉冲在光纤中色散所致的脉冲展宽的特性,啁啾因子对脉冲展宽的影响,并讨论了光纤色散对不同宽度脉）中的影响,对色散补偿等技术的研究具有一定的参考价值。     

啁啾脉冲激光放大器输出光束时间特性的理论和数值模拟

利用分布傅里叶变换对描述啁啾脉冲放大的非线性薛定谔方程进行求解 ,研究了在钕玻璃和钛宝石这两种增益介质中 ,自相位调制、增益变窄和增益饱和这三种非线性效应对放大啁啾脉冲输出特性的影响 ,具体给出了在不同放大介质中 ,它们对放大脉冲的影响程度和影响结果。重点阐明了自相位调制对放大啁啾脉冲的影响 ,及其与另外两种非线性效应的内在联系     

A novel technique for suppression of parasitic superfluorescence in backward Raman amplifiers

The major parasitic modes of backward Raman amplifiers are different forms of superfluorescent forward Raman scattering. It is shown that spatial, and/or temporal variation of the Raman frequency in the scattering medium can inhibit amplification of spontaneously scattered light by creating off-resonant conditions in the forward direction. If the frequencies of the optical pulses are properly varied in time (the pulses are chirped), the required resonance condition for amplification of a counterpropagating Stokes wave can be maintained throughout the medium. Raman transition frequencies can be varied in an atomic vapor by application of a magnetic field via the Zeeman effect. The use of thallium (T1) metal vapors for scattering XeCl or KrF excimer laser radiation is considered as a particular example.     

High-energy femtosecond pulses from an ytterbium-doped fiber laser with a new cavity design

A new architecture which is based on the chirped pulse amplification scheme is proposed to increase the pulse energy of the mode-locked fiber laser. The idea was applied to a passively mode-locked laser using an ytterbium (Yb/sup 3+/)-doped double-clad silica fiber. Mode-locking was achieved by nonlinear polarization evolution associated to frequency-shifted feedback technique for self-starting. A compressor and a stretcher, based on diffraction gratings, permitted us to manage the dispersion and to reduce the pulse power in the fiber. The laser delivered chirped pulses at 1050 nm with 11.8-nJ energy at a 9.3-MHz repetition rate (110-mW average power) which were subsequently compressed to 196-fs duration.     

Multipulse operation and limits of the Kerr-lens mode-locking stability

Numerical analysis in combination with experimental data for Cr/sup 2+/:ZnSe and Ti:sapphire lasers reveal the following main mechanisms of multiple-pulse generation for Kerr-lens mode-locked solid-state lasers: 1) continuum amplification due to a spectral loss growth for ultrashort or chirped pulses and 2) a bounded perturbation rise for high-energy pulses. The role of such laser parameters as gain saturation and relaxation, saturable and unsaturable loss, self-phase modulation, Kerr-lensing, and pump intensity is analyzed. This analysis provides basic directions for single-pulse stability enhancement and for multiple-pulse generation control.     

10-GHz 1.3-ps pulse generation using chirped soliton compression in a Raman gain medium

The authors demonstrate a novel pulse compression technique that is capable of producing high-quality 1.3-ps pulses at a repetition rate of 10 GHz. The technique begins with 20-ps pulses carved by a commercially available external modulator and achieves up to 15-fold compression using a combination of phase modulation and distributed Raman amplification. Unlike adiabatic soliton compression, the scheme takes advantage of an exact solution to the nonlinear Schrodinger equation for chirped soliton evolution. As such, high-quality low-pedestal compressed pulses can be produced in a shorter span of fiber than would be needed for adiabatic compression. Because the system uses external modulation, the source is inherently tunable. Furthermore, the degree of pulse compression can be adjusted by varying the amount of Raman gain and phase modulation.     

极紫外啁啾多层膜反射镜产生亚飞秒脉冲

超短超强激光与稀有气体相互作用产生高次谐波获取亚飞秒脉冲是近年来超短超快光学的研究热点之一.具有谐波选择和啁啾补偿作用的极紫外啁啾多层膜反射镜是产生亚飞秒脉冲的有效元件.阐述了运用极紫外啁啾多层膜反射镜由高次谐波得到哑飞秒脉冲的机制,计算了特定实验条件下高次谐波产生过程中的啁啾,利用遗传算法完成了极紫外啁啾多层膜反射镜的设计,模拟分析了其产生亚飞秒脉冲的作用.结果表明,所设计极紫外啁啾多层膜反射镜能够获得半峰全宽为132 as的脉冲.     

飞秒激光脉冲技术的发展和应用

飞秒脉冲固体激光技术是９０年代以一发展起来的新的技术热点,运用所谓克尔透镜锁模原理以及色散补偿技术,人们可以轻易地从振荡器中获取小于１０飞秒的光脉冲。与此同时,掣波脉冲放大已经把脉冲的峰值功率提高到兆兆瓦水平。这些进步又推动了飞秒光脉冲的应用。本文简要地回顾了飞秒脉冲技术的发展过程和现状,以及某些应用。     

Simultaneous mode selection and pulse compression of gain-switchedpulses from a Fabry-Perot laser using a 40-mm chirped optical fibergrating

Simultaneous pulse compression and mode selection of gain-switched pulses from a Fabry-Perot semiconductor laser are demonstrated using a chirped optical fiber Bragg grating, which has transformed initially chirped 60-ps pulses from an inexpensive multimode laser into a train of 12-ps single-mode pulses with a side-mode suppression ratio of 15.2 dB