基于Tm:YAG、Ho:YAG键合晶体的共谐振腔、同带泵浦2.1um高功率激光器研究

Mid-infrared lasers are important in fields such as environmental monitoring, medical treatment, and photo-electronic countermeasure. Especially, wavelength aound 2.1μm from Ho laser is away enough from cutoff sides of the famous Mid-infrared non-linear crystals such as ZnGeP2 and LiInSe2 with low absorption losses, which is an important OPO pump source for generating high power 3~12 μm Mid-infrared lasers. For the urgent requirement of a high-efficient and miniaturized Ho laser, in this submitted application we propose a novel Ho laser mechanism, which is an co-cavity in-band pumped Ho laser with the Ho:YAG gain medium diffusion-bonded with a Tm:YAG gain medium. In this mechanism, efficient Tm laser could be generated from the 785 nm LD and confined intra-cavity, where the 2.02 μm wavelength is within the absorption side-band of Ho:YAG crystal with small quantum defect (＜5%). Hence, efficient high-power Ho laser could be generated from a single bulk composite gain medium directly pumped by a normal 785 nm LD at room-temperature. Compared with other existed Ho laser mechanisms, the Tm/Ho composite laser is more accessible, compact, and efficient. Before this submission，we have verified the robustness of this novel mechanism in preliminary experiment. Furthermore, we prepare to carry out researches about the Tm/Ho composite laser in illustrating the dual-wavelength phenomenon at low lasing power where the Tm laser goes from strong to weak and to vanished, and in thermal effects and laser stability when scaling up the Ho laser power, and so on. With the above researches, we try to explore an effective route for a compact room-temperature normal LD pumped Ho laser with high-power and high-efficiency.

中红外激光在环境监测、医疗、光电对抗等领域有重要应用价值，特别是2.1μm激光，因波长避开非线性晶体ZnGeP2和LiInSe2等的截止吸收边，是3~12μm OPO的重要泵浦源。本课题拟发展一种新型便捷的2.1μm激光实现方式，直接采用785nm LD泵浦，通过Tm:YAG与Ho:YAG晶体键合并采用共腔、同带泵浦机制来获取高效Ho激光输出。我们新提出的Tm/Ho键合激光器在窄线宽LD泵浦和Tm离子间交叉弛豫下，能够高效地产生禁锢于腔内的2.02μm激光并与Ho:YAG的次吸收带相匹配，具有小于5%的量子亏损，从而可实现高效的室温Ho激光输出。项目组在前期已对该机制进行了初步的实验论证，基于此，我们将研究同腔共振下Tm激光与Ho激光此消彼长、由强变弱到消失的物理现象和机理，以及高功率运行下的热效应管理等问题，探索出一条可实现高功率、小型化、常温制冷、常规LD泵浦2.1μm激光的有效路径。

中红外激光在环境监测、医疗、光电对抗等领域有重要应用价值，特别是 2.1 μm 激光，因波长避开非线性晶体ZnGeP2 和OP:GaAs 等的截止吸收边，是3~12 μm OPO 的重要泵浦源。本项目旨在研究并完善一种新型便捷的2.1 μm 激光实现机制，通过将掺Tm 与掺Ho 键合晶体键合为单块增益介质，可在常温条件下实现常规波长LD 泵浦的高功率的2.1 μm 激光输出。项目从Tm/Ho 键合机制的可靠性论证、调Q 脉冲机制研究、可变波长输出现象、高功率2.1μm激光实现，及新型Tm/Ho 键合增益介质探索等五个方面展开系统性研究。在常规 808 nm 和785 nm LD 泵浦下论证了Tm/Ho 键合机制具有近40 nm 宽的LD 泵浦波长范围；通过改变Tm/Ho 键合增益介质的工作温度，激光最高输出功率从9℃时的1.8 W 下降到27 ℃时的1.65 W，降幅为8%，斜效率稳定在41%附近，论证了Tm/Ho 键合机制的宽工作温度范围和高温度可靠性；通过构建复合谐振腔，将腔内Tm 激光和Ho 激光进行光谱分离，成功抑制了Tm/Ho 键合机制固有的自脉冲过程，首次从该机制上分别实现了稳定的被动调Q 和主动调Q 脉冲输出；通过改变耦合输出镜的镀膜规格，实现Tm 激光和Ho 激光可相互切换的变波长Tm/Ho 键合激光输出；在J委科技委项目支持下，进一步开发可实现百瓦级Ho激光输出的Tm/Ho键合激光系统，超出既定的50W Ho激光功率目标；从腔内泵浦 Ho 激光机制入手，开展基于钒酸盐晶体、氟化物晶体、以及YAP 基质的新型Tm/Ho 键合增益介质体系探索，均实现了常规800 nm LD泵浦下的高效率室温Ho 激光输出。在Opto-electronic Advances，Optics Letters， Optics Express，和Optics and Laser Technology等重要光学杂志上累计发表通讯作者论文20篇（高于既定5篇SCI论文的预期成果），申请发明专利4项，1项获得授权，培养博士后1人（已出站），研究生1人（已毕业），在读博士研究生4人。