新型的全固态Ho:BaY2F8中红外激光器动力学及输出特性研究

The new generation of infrared guided weapons that mostly adopts the mid-infrared and far-infrared detectors, avoids the peak emission wavelength range of the infrared decoy projectile and the jammer, while the atmospheric attenuation and the ground molestation are weak as well, thus it has the most popular application. To countermeasure this very kind of infrared guided weapon with focal plane detector, laser directional jamming in the far-infrared domain is acknowledged as the most effective approach. Currently optical parametric oscillator with multiple pump stages is the main method to generate the mid-infrared solid-state laser, however suffering from low output efficiency, poor beam equality and degraded reliability. This project put forward an all-solid-state laser based on Ho:BaY2F8 crystal to directly produce the mid-infrared output. Compared with the traditional laser gain medium, Ho:BaY2F8 demonstrates an upper-level lifetime much shorter than the lower-level lifetime. Research on the dynamic characteristic of the all-solid-state laser based on Ho:BaY2F8, which has not been reported, as well as the efficient pump method are of great importance. In addition, to overcome the weak point of large quantum defect and serious thermal effect of all-solid-state mid-wavelength laser, this project presents a new method of controlling the output mode of the laser with large quantum defect, taking advantage of the combinative effects of gain-guiding and thermal-induced refractive index guiding effects.

新一代的红外制导武器大多采用了中波和长波红外探测器，避开了红外诱饵弹和干扰机的峰值发射波段，同时大气衰减和地面干扰也较弱，应用最为广泛。中波红外激光定向干扰则被认为是对抗这类红外焦平面阵列探测器制导武器的最有效手段，目前，产生中波红外固体激光的方法主要是光学参量振荡的方法，采用多级泵浦的方式，中波红外激光输出效率低、光束质量恶化、可靠性降低等缺点。本项目提出了基于Ho:BaY2F8晶体的全固态激光方法直接实现中红外输出。与传统激光晶体相比，Ho:BaY2F8晶体中波输出激光上能级寿命比激光下能级寿命短很多，此类晶体的全固态激光输出动力学特性研究还未见报道，研究针对该类激光器的动力学特性及有效泵浦方法意义重大。同时，针对全固态中波激光器量子亏损大，热效应严重等特点，本项目还提出了利用增益折射率导引和热致折射率导引效应控制该类量子亏损大激光输出模式新方法。

本项目针对直接泵浦Ho:BYF中红外固体激光器及2μm激光展开了系统深入研究。理论方面，首先建立了889nm泵浦Ho:BYF激光器模型，对直接泵浦3.9μm 输出Ho:BYF激光器动力学特性进行了详细分析；其次建立了考虑泵浦光空间分布与频谱分布、晶体基态再吸收效应与能量共振转移效应的2μm钬激光器动力学模型，准确描述宽光谱、差光束质量半导体激光泵浦钬激光器与窄线宽、高光束质量铥光纤激光泵浦钬激光器特性。实验方面，首先研究了Ho:BYF晶体中波输出特性，采用889nm激光泵浦，获得了5.61mJ的3.9μm中红外激光输出；其次研究了铥光纤激光器级联泵浦Ho:YAG晶体的连续工作与调Q脉冲工作特点，利用TDFL泵浦Ho：YAG晶体，获得了38.6W的连续激光器输出，结合声光调Q技术，获得了最高12.8mJ、1kHz、25ns的脉冲激光输出，同时首次获得了Cr:CdSe被动调Q脉冲运转特性，实现了约1.8mJ、685Hz、15.4ns的脉冲激光输出；最后，还研究了1.9um光纤耦合LD直接泵浦Ho:YLF激光器，在“峰”泵浦情况下，报道了最高量子斜效率达89.2%、输出功率1.63W的紧凑型钬激光系统，而在“翼”泵浦情况下，实现了泵浦偏振不敏感的钬激光系统，最大连续输出功率接近1.44W。本项目在执行过程中，在国内外重要光学期刊上已发表论文8篇，其中7篇被SCI收录，申请发明专利2项，培养了3名博士研究生与1名硕士研究生。