基于双损耗调制的低重频高稳定亚纳秒锁模脉冲激光特性及频率变换特性研究

All solid-state lasers with low repetition rate(several KHz), sub- nanosecond pulsed width, high stability and high peak power have wide applications in the fields of laser measurement, nonlinear optics, biological medicine and so on. By using single-loss modulation technology of Q-switching or Q-switching and mode-locking or continue wave mode-locking,it is difficult to obtain these kinds of short pulse lasers. Based on the advantages of the active modulation with low repetition and high stability, as well as the the passively Q-switching mode-locking with sub-nanosecond pulse width and high peak power,by using the mixed crystals with broader fluoresence linewidth as laser medium, this item will explore the dual-loss-modulation technology i.e. both the active electro-optic Q-switching- - the passive mode-locking of the saturable absorbers, to realize one mode-locking pulse run with mixed crystal in an Q-switched envelope of the double Q-switched mode-locked laser, the runs of intra-cavity frequency-doubled green laser and the optical parameter oscillating eye-safe laser; study the generation mechanism of the sub-nanosecond mode-locking pulses with low repetition rate, high peak power and high stability based on dual loss modulation, probe the new method to generate these kinds of mode-locking pulse lasers; reveal the basic generation principle of these kinds of mode-locking pulses based on dual-loss-modulaton; investagate their optical nonlinear frequency conversion characteristics. From the abovementioned studies, the law basis of the sub- nanosecond mode-locking pulse laser with low repetion rate, high peak power and high stability will be presented.

全固态、低重频（几KHz）、高稳定、高峰值功率的亚纳秒脉冲在激光测量、非线性光学、生物医学等领域具有广阔的应用。通常单一损耗调制的调Q、调Q锁模、连续锁模技术，难以获得这类短脉冲激光。依据主动调制重复率低、稳定性强和被动调Q锁模亚纳秒脉宽、高峰值功率的特点，利用荧光谱线较宽的钒酸类混合晶体作激活介质，本项目拟基于电光调Q- - 饱和吸收体被动锁模的双损耗调制技术，实现混合晶体主被动双调Q锁模每个调Q包络仅有一个锁模脉冲激光运转及内腔倍频锁模脉冲绿激光运转和光学参量振荡人眼安全锁模脉冲激光运转，探索双损耗调制产生低重频、高稳定、高峰值功率的亚纳秒锁模脉冲激光的机理，探究产生这类锁模脉冲激光的新方法，揭示基于双损耗调制技术产生这类锁模脉冲激光的基本原理，研究这类锁模脉冲激光的非线性光学频率变换特性。通过此项目的理论和实验研究，为低重频、高稳定、高峰值功率的亚纳秒锁模脉冲激光的实现提供规律性依据。

本项目基于主被动双损耗调制，从理论和实验上系统地研究了低重频高稳定亚纳秒锁模脉冲激光特性和频率变化特性，实现了电光主动——饱和吸收体（Cr4+:YAG、GaAs、SESAM、碳纳米管、石墨烯、WS2、黑磷等）被动双调Q锁模1.06μm激光运转、倍频0.53μm绿激光运转，通过优化谐振腔参数，压缩调Q包络的脉冲宽度，使每个调Q包络内只有一个锁模脉冲，脉冲宽度亚纳秒级，重复率为电光调制频率，获得了低重频、高稳定、高峰值功率亚纳秒级锁模脉冲1.06μm激光、倍频0.53μm绿激光输出。采用主动声光——饱和吸收体（Cr4+:YAG、碳纳米管）被动双损耗调制，实现了主动被动双调Q锁模1.06μm激光泵浦的KTP内腔光学参量振荡（OPO）信频光1.5μm调Q锁模稳定运转，并能获得一个调Q包络内一个锁模脉冲稳定输出。研究了主被动双损耗调制的低重频、高稳定、高峰值功率亚纳秒锁模脉冲基频1.06μm激光、KTP倍频0.53μm绿激光及1.5μm人眼安全光的运转规律和运转特性，获得了产生亚纳秒单锁模脉冲的条件及其平均输出功率、锁模脉冲宽度、锁模脉冲能量、锁模脉冲的峰值功率与泵浦功率、饱和吸收体小信号透过率、主动调制频率、激活介质受激发射截面等参量的依赖关系；理论上建立了高斯分布近似下主被动双损耗调制的调Q锁模1.06μm和内腔倍频0.53μm及内腔1.5μm光学参量振荡的耦合速率方程组，数值求解方程组获得了调Q包络的脉冲宽度与主动重复率、饱和吸收体小信号透过率、泵浦功率的依赖关系以及高稳定、高峰值功率、低重频、单锁模亚纳秒脉冲产生的条件，数值模拟与实验结果相符； 理论和实验的研究结果显示了利用双损耗调制技术是一种获得低重频、高峰值功率、高稳定亚纳秒锁模脉冲的有效方法。此外，还研究了主被动双损耗调制调Q锁模激光调Q包络重复率的依赖特性、双调Q激光泵浦的内腔光学参量振荡特性、双调Q中红外2μm波段激光特性等。理论和实验研究获得了一系列创新成果，发表标明该基金资助论文共 60篇，全部是国际SCI索引的杂志，影响因子大于3的12 篇、影响因子在2-3之间的 15篇、影响因子在1-2之间的 31篇、影响因子小于1的2 篇。此外，授权发明专利、实用新型专利各1项，培养博士生 5名，硕士生2 名。