新型中红外非线性光学材料AGGS晶体的生长与机理研究

AgGaGeS4 is a promising new nonlinear optical crystal for frequency-shifting 1.064 μm Nd∶YAG laser into the mid-infrared (2–12 μm) spectral range. It also can output mid-infrared (3.8–11 μm) spectral range pumping by 820 nm femtosecond laser, and the damage threshold is up to 170 GW/cm2. Therefore, it has great application prospect in the infrared tracking, guidance, laser anti-satellite and laser medical and other fields. In the polycrystalline synthesis process, the large vapour pressure of Sulphur easily leads the synthesis ampoule to explosion. In the single crystal growth process, due to the large super-cooling degree (86 ℃), it is hard to achieve mononuclear crystal growth by the way of geometric elimination. What’s more, it easily generates composition segregation, twin crystal, inclusions and other defects and the large vapour pressure of dissociated Sulphur easily leads the synthesis ampoule to explosion. In this project, during the process of researching impurities, defects and the reasons of the explosion in polycrystalline synthesis and crystal growth, we will put forward new principles and methods which can solve these problems, and clarify the mechanism and key control technology. Using “vapor transporting with mobile crucible in dual-temperature zone combining with the mechanical and temperature oscillation” and “directional seed crystal growth by descending double-wall crucible with rotation and timely variable temperature” new methods, high-purity and single-phase polycrystal would be synthesized, and large-size and high-quality single crystal would be obtained. At the same time, it has an important value of science and technology on the researches of the relationship between crystal structure, defects, properties with the process conditions and key control technology, and improving the quality of crystal and OPO device fabrication.

AgGaGeS4是一种性能优异的中红外高功率激光频率转换新材料，可用1.064 μm泵浦输出2－12μm宽可调激光，820 nm泵浦可在3.8－11μm获得宽可调激光，损伤阈值高达170 GW/cm2，在红外跟踪、制导、激光反卫星和激光医学等领域有重大应用前景。多晶合成时，S蒸气压很高，易发生爆炸；单晶生长时，过冷度大(86 ℃)、很难通过几何淘汰成单核生长，易出现组分偏析、孪晶、包裹等缺陷、离解出S的高蒸汽压导致爆炸等。研究多晶合成和单晶生长中杂质、缺陷和爆炸的原因，提出解决难题的新原理、新方法，阐明机理和关键控制技术；采用“移动坩埚两温区气相输运和高温熔体机械与温度振荡”和 “定向籽晶双层坩埚旋转下降和适时变温调速”的新方法，合成高纯单相多晶、生长大尺寸高质量单晶。研究晶体结构、缺陷、性能与工艺条件关系及机理和关键控制技术，提高晶体质量、制备OPO器件，具有重要的科学和技术价值

AgGaGeS4是一种性能优异的中红外高功率激光频率转换材料，可用1.064μm泵浦输出2~12μm宽可调激光，820nm泵浦可在3.8－11μm获得宽可调激光，在红外跟踪、制导、激光反卫星和激光医学等领域有重大应用前景。在合成过程中，“移动坩埚（石英安瓿）两温区气相输运和高温熔体机械与温度振荡”法有效的控制了蒸气压，防止石英安瓿爆炸，还避免了成分偏析，合成出了单相的AgGaGeS4多晶，单次合成量可达180g。在生长过程中，首先通过“自发成核籽晶回熔坩埚旋转下降”法克服了过冷度大的难题，快速获得较大尺寸的晶锭。然后对晶体的生长方向和生长界面进行研究，[100]、[010]和[001]方向的热膨胀系数在600 K时分别为1.39×10-5 K-1，6.87×10-6 K-1和1.44×10-5 K-1，在[100]、[010]和[001]方向的热导率分别为0.629，0.495和0.336W/(m K)，同时测试得到了热容随温度变化曲线。采用“定向籽晶双层坩埚旋转下降和适时变温调速”的方法生长出尺寸为Φ45mm×90mm的AgGaGeS4单晶，是目前报道的AgGaGeS4最大单晶尺寸。.生长出的AgGaGeS4晶体表现出了很好的光学性能，11.5mm厚的晶体透过率为70%左右。退火后的晶体在0.9~10 μm波段的吸收系数为0.01~0.05cm-1，2.9和4μm的吸收峰基本消除。晶体表面激光损伤阈值（1064nm，10ns）为103MW·cm-2，约为文献报道的2倍，体损伤阈值为132MW·cm-2。最终制备出激光频率转换器件。此外，我们对不同n值的AgGaGenS2(n+1)和AgGaGenSe2(n+1)晶体进行了研究，生长出Φ15mm×20~40mm的AgGaGe2S6、AgGaGe3S8、AgGaGe4S10和AgGaGe5S12晶体，以及Φ40mm×50mm的AgGaGe3Se8和Φ40mm×100mm的AgGaGe5Se12晶体。该系列晶体都具有较大的非线性光学系数，可以通过组分来调控物理化学性质，根据不同的应用环境和条件来选择更合适的晶体进行激光频率转换。.通过项目的研究，全面掌握大尺寸AgGaGeS4晶体生长机理和生长工艺，为制备四元硫族非线性光学晶体、实现高功率中红外激光频率转换提供了理论基础和技术保证，具有重要的科学和和技术价值。