Noncollinear optical parametric amplification in lithium triborate seeded by a cw Ti:sapphire laser

Experimental investigations of a type-I noncollinear phase-matched optical parametric amplification based on lithium triborate, which was pumped by a 5-ns second-harmonic pulses from a Q-switched Nd:YAG, seeded by a cw Ti:sapphire laser at 800 nm, was presented. The experiments generated 2-ns signal output pulses at 800 nm, the maximum signal output pulse energy reached 19 μJ, the corresponding parametric gain was 44 dB. Furthermore, the experiments demonstrate that the 65 nm-FWHM parametric fluorescence gain spectrum could also be observed. A quantitative account of the ultrabroadband parametric fluorescence gain spectrum was given with our theory. The experimental measurements are in agreement with theoretical calculations.     

Lasing dynamics study by femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy

Femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy(FNOPAS) is a versatile technique with advantages of high sensitivity, broad detection bandwidth, and intrinsic spectrum correction function. These advantages should benefit the study of coherent emission, such as measurement of lasing dynamics. In this letter,the FNOPAS was used to trace the lasing process in Rhodamine 6G(R6G) solution and organic semiconductor nano-wires.High-quality transient emission spectra and lasing dynamic traces were acquired, which demonstrates the applicability of FNOPAS in the study of lasing dynamics. Our work extends the application scope of the FNOPAS technique.     

啁啾脉冲参量放大特性的数值模拟研究

根据啁啾脉冲激光参量放大技术,数值模拟了光参量放大在啁啾脉冲放大中的应用。研究啁啾脉冲参量放大增益及时间特性,特别是在大信号注入与小信号注入两种有代表意义的情况下,详细地分析了群速度失配、相位失配对放大过程的影响。研究了泵浦光脉冲与信号光脉冲的时间同步要求,讨论了放大系统的稳定性。     

啁啾脉冲参量放大特性的数值模拟研究

 根据啁啾脉冲激光参量放大技术,数值模拟了光参量放大在啁啾脉冲放大中的应用。研究啁啾脉冲参量放大增益及时间特性,特别是在大信号注入与小信号注入两种有代表意义的情况下,详细地分析了群速度失配、相位失配对放大过程的影响。研究了泵浦光脉冲与信号光脉冲的时间同步要求,讨论了放大系统的稳定性。     

具有腔内光放大的单共振光参量振荡器

推导了描述稳态运行，具有腔内光放大的环形腔单共振光参量振荡器(ICOASRO)的功率特性的高斯光束理论.在这种结构的单共振光参量振荡器(SRO)中，适当地选择光放大器的参数，可以很大程度地降低单共振光参量振荡器的抽运阈值.在平均场近似下无二阶非线性交叉耦合作用的具有腔内光放大的环形腔单共振光参量振荡器的工作范围分成四个工作区域，且存在最小的单共振光参量振荡器的抽运阈值.文中的分析考虑了作为光放大器的激光增益介质的端面抽运特性，考虑了一般化单共振光参量振荡器的特性. 关键词： 单共振光参量振荡器 光放大 阈值     

基于荧光非共线光参量放大光谱技术的溶剂化动力学研究中的光谱矫正

利用荧光非共线光参量放大光谱技术测量了DCM染料乙醇溶液的溶剂化动力学过程. 实验结果表明,瞬态荧光光谱经过光谱矫正后,可以产生准确的溶剂化相关函数以及溶剂化过程中瞬态光谱峰值频率移动. 本文的工作表明荧光非共线光参量放大光谱技术有益同时关注荧光强度动力学以及光谱谱型演化的研究领域.     

光参量啁啾脉冲放大增益特性研究

 通过对非线性三波耦合方程组进行数值求解，研究了光参量放大的增益特性及饱和放大特性。给出了泵浦光、信号光参数对参量增益的影响及其与晶体饱和长度的关系。且OPA具有传统CPA系统所不具有的优点，将有可能取代传统的CPA系统而作为超短超强激光系统的新型前端。     

光参量啁啾脉冲放大增益特性研究

通过对非线性三波耦合方程组进行数值求解,研究了光参量放大的增益特性及饱和放大特性。给出了泵浦光、信号光参数对参量增益的影响及其与晶体饱和长度的关系。且OPA具有传统CPA系统所不具有的优点,将有可能取代传统的CPA系统而作为超短超强激光系统的新型前端。     

Femtosecond two-photon photoemission at 150 kHz utilizing two noncollinear optical parametric amplifiers for measuring ultrafast electron dynamics

An improved setup for femtosecond two-photon photoemission spectroscopy (TR-2PPE) is presented. Two noncollinear optical parametric amplifiers (NOPA) were operated simultaneously at a repetition rate of 150 kHz. The frequencies of the NOPA outputs were tuned such that subsequent second harmonic generation (SHG) provided the two different ultraviolet wavelengths required for the pump and probe pulse. The width of the crosscorrelation function (CC) for pump and probe pulse was sub-30 fs (FWHM).The performance of this assembly was tested by measuring the lifetime of image potential states (IS) on Cu(111) and Ag(111) surfaces. We present here for the first time lifetimes of the IS that were determined directly from the measured decay of the 2PPE signal.This revised version was published online in August 2005 with a corrected cover date.     

Amplification of fluorescence using collinear picosecond optical parametric amplification at degeneracy

We demonstrate the output characteristic of broadband parametric amplification of incoherent light pulses in a 355-nm pumped degenerate picosecond optical parametric amplification with either saturated or unsaturated amplification.The optical parametric amplifier is seeded by the fluorescence generated in a solution of pyridine-1 dye in ethanol.With the saturated amplification,we can obtain high energy incoherent light pulses,whose full width at half maximum bandwidth varies from 16 nm to 53 nm for the different phase matching angles near degeneracy.Moreover,the unsaturated bandwidth of the amplified pulses fits well to the calculated result at degeneracy.Selecting s-polarized fluorescence with a Glan-Taylor prism,the maximum bandwidth of the amplified fluorescence is found to be 59 nm for a purely s-polarized seed.The maximum output energy is 0.67 mJ for the optical parametric amplifier.By using an optical filter and compressor,the generated high energy incoherent light has great potential as the incoherent pump,signal or idler wave of a parametric down-conversion process,so that a wave with a high degree of coherence can be generated from an incoherent pump light.     

BBOⅠ类相位匹配非共线参量产生中的群速自匹配

利用重复频率为1kHz的钛宝石激光的倍频蓝光抽运Ⅰ类相位匹配的偏硼酸钡(BBO)晶体，获得了可见光区的非共线参量超荧光.给出了最强光强处参量超荧光的非共线角，波长随相位匹配角的变化.理论计算了在参量超荧光中三波的群速失配随非共线角和相位匹配角的变化规律.结果表明，Ⅰ类非共线相位匹配的参量超荧光关于抽运光中心对称.并且沿光强最强的参量超荧光方向三波的群速失配最小，有效互作用长度最大，即参量超荧光的强度角分布是三波的相速和群速自匹配的结果.该理论和实验研究为减小飞秒光参量放大中三波的群速失配提供了一个理想的几何模型，为获得高增益、窄脉冲宽度的参量光输出提供了理论依据和实验验证. 关键词： 群速自匹配 参量超荧光 非共线相位匹配 飞秒光参量放大     

基于光纤光参量放大的异步双波长全光再生技术研究

本文提出了一种新型的多波长全光再生方案,利用相位时钟光纤光参量放大,并采用相邻信道偏振正交的方法,实现对由异步信源产生的双波长信号全光再生.理论分析了参量放大中的增益饱和现象用于幅度噪声抑制,以及利用相位时钟及后续色散实现对信号定时的机理.在这个基础上,对两个独立信源产生的异步双波长10Gbit/s信号进行再生实验,实验表明该方案有效的抑制了基于多波长3R再生系统中信道间的四波混频与交叉相位调制等非线性干扰.系统在单波长和双波长情况下分别将两路信号信噪比改善了至少6.5dB与4.5dB.误码率测试结果说明,与背对背测试结果相比,无论是在单波长还是双波长条件下,两路波长的信号经过再生后都实现了约2dB的接收机功率代价的改善.     

色散效应对光学参量放大器量子起伏特性的影响

解析求解了包含色散、损耗和抽运吃空的含时的Fokker-Planck方程,通过数值计算首先获得了色散时简并参量放大(DOPA)系统的光压缩特性.研究结果表明：色散效应是由非线性极化率从χ″增大到χ″/{1+σ²/}/+2而引起的.随着色散效应的逐渐增大,压缩曲线的形状基本相同,且整体向左收缩,最大压缩趋近于线性理论的结果1/(1+μ).还获得了色散时非简并参量放大(NOPA)系统的光纠缠特性.研究发现：当σ给定,随着抽运参数μ的增大,相应的相位变化也增大,非线性极化率的极性发生多次变化,极性为正阶段的增益大部分被极性为负阶段的衰减所抵消,净增益不大,压缩也不大,最小均方差V₁的值逐渐减小,且整体向右移动,接近于线性理论的结果1/(1+μ).     

色散效应对光学参量放大器量子起伏特性的影响

解析求解了包含色散、损耗和抽运吃空的含时的Fokker-Planck方程,通过数值计算首先获得了色散时简并参量放大(DOPA)系统的光压缩特性.研究结果表明：色散效应是由非线性极化率从χ″增大到χ″/{1+σ²/}/+2而引起的.随着色散效应的逐渐增大,压缩曲线的形状基本相同,且整体向左收缩,最大压缩趋近于线性理论的结果1/(1+μ).还获得了色散时非简并参量放大(NOPA)系统的光纠缠特性.研究发现：当σ给定,随着抽运参数μ的增大,相应的相位变化也增大,非线性极化率的极性发生多次变化,极性为正阶段的增益大部分被极性为负阶段的衰减所抵消,净增益不大,压缩也不大,最小均方差V₁的值逐渐减小,且整体向右移动,接近于线性理论的结果1/(1+μ). 关键词： 色散 量子起伏 光学参量放大器     

基于预啁啾控制的极宽带光参量放大

在以飞秒钛宝石放大系统的倍频光为抽运光和超连续白光为信号光的光参量放大中,针对抽运光的宽带特点,分析了一种新的极宽带相位匹配方法.结果表明,10nm的抽运光带宽可得到近400nm的相位匹配带宽,若抽运光带宽达到20nm,相位匹配带宽就能达到近600nm.零色散波长为800nm的光子晶体光纤产生的超连续谱经光纤传输后为二次啁啾,宽带抽运光经棱镜对展宽具有线性啁啾,满足了极宽带相位匹配方法所需要的光谱分布.理论计算了对输入脉冲进行预啁啾控制应选择的光纤长度和棱镜对在光路中的插入量,为实现极宽带光参量放大提供了 关键词： 啁啾 极宽带相位匹配 光参量放大 光子晶体光纤     

Optical parametric chirped pulse amplification based on photonic crystal fibre

A compact two-stage optical parametric chirped pulse amplifier based on photonic crystal fibre is demonstrated.A 1064-nm soliton pulse is obtained in a home-made photonic crystal fibre (PCF) with femtosecond pulse pumping and then amplified to 2 mJ in an Nd:YAG regenerative amplifier.After the amplified pulses pass through the LBO crystal,the 532-nm double-frequency light with an energy of 0.8 mJ and a duration of over 100 ps at 10-Hz repetition rate is generated as a pump source in the following two-stage optical parametric amplification (OPA).The 850-nm chirped signal light gain from the stretcher is 1.5×10 4 in the first-stage OPA while it is 120 in the second-stage OPA.The total signal gain of optical parametric chirped pulse amplification (OPCPA) can reach 1.8×10 6.     

光参量啁啾脉冲放大过程中脉冲特性理论研究

 通过数值求解非线性三波耦合方程组,并利用色散致啁啾引起的瞬时频率与时间的关系,模拟了啁啾脉冲在光参量放大过程中的脉冲波形和频谱形状的变化关系,以及通过压缩器的脉冲形状。模拟结果表明：啁啾脉冲在光参量放大过程中的时域宽度和频谱有很小程度的加宽,但基本上不影响放大后脉冲的压缩及信噪比。     

光参量啁啾脉冲放大过程中脉冲特性理论研究

通过数值求解非线性三波耦合方程组,并利用色散致啁啾引起的瞬时频率与时间的关系,模拟了啁啾脉冲在光参量放大过程中的脉冲波形和频谱形状的变化关系,以及通过压缩器的脉冲形状。模拟结果表明：啁啾脉冲在光参量放大过程中的时域宽度和频谱有很小程度的加宽,但基本上不影响放大后脉冲的压缩及信噪比。     

基于准相位匹配晶体的宽带可调谐光参量放大过程研究

系统分析了基于准相位匹配晶体的光参量放大过程中极化周期和非共线结构对信号光调谐带宽的影响.提出了最大极化周期的概念,用于描述非共线相位匹配和群速度匹配同时满足时晶体的极化周期所能达到的最大值,给出了用于计算不同温度下周期极化铌酸锂晶体的最大极化周期的数学公式,并确定了宽带可调谐光参量放大过程应使用的最佳非共线结构.当采用此非共线结构时,通过将晶体的极化周期设定为最大极化周期可以在相对最大的波长范围内实现信号光的调谐放大输出.在此基础上提出了一个用于最大化光参量放大过程的信号光调谐带宽、确定工作温度等最佳工作参数以及简化实验操作方法的可行性方案.最后对最大极化周期和非共线结构对光参量放大的参量带宽的影响进行了研究. 关键词： 光参量放大 极化周期 非共线结构 带宽     

Femtosecond noncollinear and collinear parametric generation and amplification in BBO crystal

Measurements of intensity and frequency noise of an injection-locked 5-W Nd:YAG laser are presented and compared with the predictions of models. We show that the output of the injection-locked laser has very low levels of noise, and that the measurements support the predictions of the models. Thus these models can confidently be used to predict the performance of high-power, injection-locked lasers being developed for gravity wave detection. Received: 31 January 2000 / Revised version: 18 March 2000 / Published online: 16 June 2000