基于飞秒激光泵浦的双啁啾光参量放大特性研究

Mid-infrared laser pulse has became a hot research topic in the world for its applications in molecular spectroscopy and attosecond science in recent years. However, the conventional picosecond laser pumped optical parametric chirped pulse amplification or the femtosecond laser pumped optical parametric amplification face several difficulties in producing mid-infrared laser pulse with shorter pulse duration and higher energy, due to the limitations of the damage threshold, size and gain bandwidth of nonlinear crystal. Following our own theoretical proposal, a novel dual-chirped optical parametric amplification for generation of high-energy ultrashort mid-infrared laser pulse is investigated experimentally in this program based on the high-energy Ti:Sapphire laser. By chirping both pump and seed pulses in an optimized way, the high-energy pump pulses can be employed without exceeding the damage threshold of the nonlinear crystals, and then the broadband output mid-infrared pulse with relative high conversion efficiency can be obtained. Moreover, the approaches for compensation of chirped induced phase mismatching, optimizing gain bandwidth and conversion efficiency, minimizing B-integral and suppressing quantum noise will be explored. In this way the output beam quality of the output mid-infrared laser pulse can be further improved.

中红外激光脉冲因在分子光谱学以及阿秒科学等方面的重要应用而成为了近年来国内外研究的热点问题。然而由于非线性晶体损伤阈值、晶体尺寸、增益谱宽等因素的限制，采用长脉宽低强度的皮秒激光泵浦的光参量啁啾脉冲放大以及短脉宽高强度飞秒激光泵浦的光参量放大技术在获得脉冲宽度更短、能量更高的中红外激光脉冲方面都面临着若干困难。本项目将在前期理论研究的基础上，开展基于高能量Ti:Sapphire激光器的双啁啾光参量放大产生高能量超短中红外激光脉冲的实验研究。通过将泵浦光和种子光啁啾展宽到合适的脉冲宽度，可以在使用高能量的飞秒泵浦源时保持强度低于晶体的损伤阈值，同时获得较宽的增益谱宽和较高的转化效率。通过对双啁啾光参量放大过程的进一步理论和实验分析，探索补偿啁啾引起的相位失配、优化增益谱宽和转化效率、减小B积分以及抑制量子噪声的手段,从而进一步提高输出光束质量。

中红外激光脉冲因在分子光谱学以及阿秒科学等方面的重要应用而成为了近年来国内外研究的热点问题。其中中红外激光脉冲的宽度，即光谱范围，以及脉冲能量是进一步拓展其应用的关键。本项目通过对光参量放大过程中的相位匹配特性，B 积分以抑制量子噪声的研究，提出了若干产生宽谱带高能量中红外激光脉冲的新方案。采用紧凑的双非线性晶体的群速度失配补偿方案，基于共线光参量放大技术在实验上在1300纳米中心波长获得了超过200纳米的增益带宽，对应的光周期数少于4个。本项目在实施过程中，项目组在物理、光学类的国际重要期刊上发表相关SCI论文5，其中包括Opt. Express 4篇，Phys. Rev. A 1篇，申请国家发明专利3项，共参加国内外主流,会议5人次，做报告5次。此外，通过与日本理化学研究所开展合作实验研究，在J. Opt.上发表论文1篇，加强了与国际同行间的学术合作交流。3年中，7名研究生参与到项目中，2人获得硕士学位。