新型高效中红外晶体LiInSe2、LiGa3Te5的生长机理、缺陷与非线性光学器件研究

Mid-infrared nonlinear optical crystals with the transparency range of 3-12 μm are very important in military and civilian applications. LiInSe2 (LISe) crystal has large nonlinear optical coefficients and high laser damage threshold. It can be pumped by ~1 μm lasers and used as 10.6 μm CO2 laser second harmonic generators. LiGa3Te5 (LGT) crystal is one of the few mid-infrared crystals that the transparency cut-off edge extends to 24 μm. In this project, the polycrystal synthesis and the controlling of solid liquid interface during Bridgman growth will be investigated. The thermodynamics and dynamics of the synthesis and the growth mechanism of LISe and LGT will be obtained. The absorption and scattering induced by crystal defects can give rise to laser losses, which is the bottleneck of the applications in optical devices. The defects, impact of defects on crystal quality, and annealing process will be studied. Finally, we will investigate the nonlinear optical properties and optical devices, and the widely tunable mid-infrared lasers can be obtained. This project will be of great importance for the improvement of research in mid-infrared nonlinear optical crystals. It can also provide experimental and theoretical experience in exploring the excellent infrared materials.

3-12 μm中红外非线性光学晶体在军事和民用领域具有重要应用。LiInSe2（LISe）晶体具有大的非线性系数和高的激光损伤阈值，可采用商用1 μm激光泵浦，且能实现10.6 μm CO2激光倍频。LiGa3Te5 (LGT)晶体是为数不多的透过截止边扩展到24 μm的中红外晶体。本课题以LISe、LGT晶体为研究对象，突破高蒸汽压材料体系多晶合成、Bridgman法晶体生长固液界面控制等关键技术，获得多晶合成热力学和动力学反应机理、晶体生长机理。围绕影响红外晶体应用的关键瓶颈——缺陷吸收、散射引起的激光损耗，系统开展晶体缺陷和退火后处理等研究，揭示缺陷对晶体质量影响的基本规律。通过开展晶体的非线性光学性能与器件研究，最终实现宽带可调谐的中红外激光输出。本项目的实施对于提高我国在红外非线性光学晶体领域的研究水平具有重要的意义，为优秀红外材料的探索提供实验经验和理论指导。

3-12 μm中红外非线性光学晶体在军事和民用领域具有重要应用。本课题以LiInSe2(LISe)、LiGa3Te5(LGT)晶体为研究对象，突破高蒸汽压材料体系多晶合成等关键技术，单炉可得360 g的高纯LiInSe2多晶料。采用定向籽晶Bridgman技术，通过晶体生长固液界面控制、解决了籽晶熔接的关键技术，生长了高质量LISe晶体，晶体尺寸大于Ф25 mm × 50 mm，通过自发成核Bridgman技术生长出了厘米级LGT晶体。开展LISe晶体的非线性光学性能与器件研究，在国际上，首次通过LISe-OPA技术实现了3-5 μm及7-12 μm宽调谐皮秒激光输出。获得4 μm中红外激光单脉冲能量为433 μJ，峰值功率约为 14.3 MW，能量转换效率达2.55%，光子转换效率为9.63%；7.5 μm中红外激光单脉冲能量为170 μJ，能量转换效率达1.21%，光子转换效率为8.6%。本项目取得的成果，为长波红外激光提供了重要的基础，对于满足红外技术在军民领域的应用，促进了我国在中红外领域的发展具有重要的意义。