【作者】 王红英；

【导师】 赵卫；

【作者基本信息】 中国科学院研究生院（西安光学精密机械研究所） ， 光学， 2008， 博士

【摘要】 光学参量啁啾放大(OPCPA)技术将是完全替代啁啾脉冲放大(CPA)技术而产生脉宽更短、峰值功率和信噪比更高超短超强脉冲激光的新原理和新技术。本论文首先综述了OPCPA技术概念以及研究进展状况,其次利用已经研究的基本理论,进行了基于钛宝石激光器和锁模光纤激光器的OPCPA系统技术研究。本论文工作的主要内容和取得的创新结果主要有以下几个方面:1.以第Ⅰ类相位匹配的BBO放大器为例,详细研究了OPA过程的基本理论。主要涉及到耦合波方程,光参量放大晶体,相位匹配,带宽以及增益等问题。2.采用第Ⅰ类相位匹配的BBO晶体的放大传递函数方法,对光参量放大中出现的参量荧光的空间特性进行了详细的研究。结果表明参量荧光是根据强角度分布的,在某一特定的非共线角和相位匹配角下,它是以抽运光为中心,呈锥形分布;而在其它的相位匹配区域内,则呈环形分布。3.对宽带OPCPA系统的色散控制进行了详细的理论研究。首先,对色散源进行了理论分析和讨论,其次,计算和分析了OPCPA系统的色散量以及各个过程中的高阶色散对脉冲时域和频域特性的影响。理论模拟结果表明展宽器引入了非常大的色散,放大器中信号光相位变化产生的色散较大,参量晶体本身引入的色散相对较小可以忽略不计。结果还显示出输出脉冲宽度主要受二阶色散影响,而三阶和四阶色散主要影响脉冲的波形和信噪比,对频域影响很小。4.对大展宽比的(?)ffner展宽器进行了详细的理论与实验研究。首先通过光线追迹法对影响(?)ffner展宽器输出脉宽的关键参数进行了理论分析,并以此为基础,进行了详细而深入的实验研究。通过合理优化关键参数,最终将30fs的种子脉冲无色差展宽至545ps,展宽比达到18,167倍。5.进行了基于钛宝石激光器为种子源的OPCPA系统技术研究。第一级放大采用单通结构,第二级放大首次采用单脉冲双通结构,有效提高了转换效率,同时解决了OPCPA中参量荧光影响再压缩脉冲信噪比的技术难题。适用于小型化拍瓦激光装置的宽带前端预放大。放大信号光输出能量为3mJ,总增益达到3×10~7,能量稳定性为＜3%rms,光谱带宽为30nm(FWHM),压缩脉宽为82fs(FWHM)。6.首次进行了以锁模光纤激光器为种子源的OPCPA实验研究。采用两级单通光参量放大(OPA)结构,实现了基于全光纤锁模激光器的高稳定、高效率、高集成、无展宽器的OPCPA技术。放大输出能量为6mJ,总增益达4×10~6,能量稳定性为＜2%rms,光谱带宽为14nm(FWHM),采用光栅压缩器将输出的放大信号光脉冲压缩成525fs的脉冲输出。另外,采用单级双通OPA结构,在维持原有优点的同时,有效提高了转换效率,并且很好地抑制了参量荧光的影响。放大输出能量为2mJ,总增益达2×10~6,能量稳定性为＜2%rms,光谱带宽为8nm(FWHM)。更多还原

【Abstract】 A novel thesis and technique called optical parametric chirped pulse amplification（OPCPA） will be as a substitute for chirped pulse amplification（CPA）, which generates ultrashort laser pulses with high-peak powers and a high prepulse contrast ratio.This thesis first summarizes the development and level of OPCPA technology,explores key technique based on the basic theory of OPCPA,builds the OPCPA system seeded by Ti:sapphire laser and a home-made Yb³⁺-doped self-starting passively mode-locked fiber laser separately,and studies detailedly the key issue involved in the OPCPA system.We summarize the main research works and the innovative results as follows:1.A detailed basic theoretical study of the optical parametric amplification process based on the theoretical model of typeⅠphase-matched BBO optical parametric chirped pulse amplifier was detailedly investigated.The theoretical treatment includes mainly coupled wave equation for OPCPA, crystal for optical parametric amplification,phase-matching principles and phase-matching types,the bandwidth and gain of optical parametric amplifier.2.The spatial properties of parametric fluorescence based on the amplification transfer function in a typeⅠphase-matched BBO crystal were detailed studied.The numerical simulation results demonstrate that the angular distribution parametric fluorescence is first emitted in a cone in a specific phase-matching angle zone and noncollinear angle zone,then in a ring in the other phase-matching angle zone and noncollinear angle zone always centered on the pump wave direction.3.Dispersion control of a broadband optical parametric chirped pulses amplification laser system is investigated.Firstly,Dispersion source of the OPCPA system is analyzed and discussed.Secondly,using the numerical method,the theoretical model of dispersion and the effects of high-order dispersion on signal pulses are presented in broadband OPCPA laser system. The numerical simulation results demonstrate that dispersion of pulse stretcher and phase change from signal pulse in amplifier is relatively great, dispersion of parametric crystal can be ignored,and that second-order-dispersion mainly controlled the pulse duration,the pulse SNR is effected by third-order-dispersion and fourth-order-dispersion.However, change of pulse frequency from dispersion is negligible.4.Theoretical and experimental study of Large-ratio（O|¨）ffner stretcher for OPCPA laser system was presented.Firstly,the key parameters of the output pulse duration of the pulse stretcher was discussed by use of the method of numerical simulation based on the more scientific way of the ray-tracing. Secondly,an（O|¨）ffner stretcher was setup experimentally.Through appropriate optimization of the four parameters,expansion of 30 fs pulses to 545 ps with free aberration and a stretching ratio of 18,167 have been experimentally demonstrated.5.The OPCPA system seeded by Ti:sapphire laser source has been built.In this system,the single-passed architecture of the first OPA stage and double-passed architecture of the second OPA stage was demonstrated.By use of the double-passed architecture,on the one hand,this scheme efficiently increases the conversion efficiency,on the other hand,it remarkably decreases the uncompressible background arose from the parametric fluorescence.This scheme has a potential application for front-end amplification for petawatt-class laser system.The net total gain higher than 3×10⁷,single pulse energy exceeding 3 mJ with fluctuations less than 3%rms,30 nm（FWHM） amplified signal spectrum and recompressed pulse duration of 82 fs（FWHM）are achieved.6.The experimental study of the OPCPA system seed by fiber laser was demonstrated for the first time.Firstly,two stage single-passed OPA arrangement was used,high stability,great conversion efficiency,compact and omitting pulse stretcher OPCPA system was realized.A gain higher than 4.0×10⁶,single pulse energy exceeding 6 mJ with fluctuations less than 2% rms,14 nm amplified signal spectrum and recompressed pulse duration of 525 fs are achieved.Secondly,single stage double-passed OPA architecture was utilized.This scheme efficiently increases the transfer efficiency,and remarkably decreases the parametric fluorescence.The net total gain higher than 2×10⁶,single pulse energy exceeding 2 mJ with fluctuations less than 2%rms,parametric fluorescence less than 0.5%of the total output pulse energy,8 nm（FWHM）amplified signal spectrum are achieved.更多还原