大尺寸远红外非线性晶体CdSe生长及器件制作

Cadmium selenide (CdSe) crystal is one of the most promising nonlinear materials for optical parametric oscillation (OPO)to generate a far-infrared waveband (8~12μm)laser output. Solid-state lasers based on CdSe crystal possess excellent properties such as high power, small size, easy to carry, and so on. These outstanding properties lead to the important applications of CdSe crystal in the fields of optoelectronic countermeasure, medical apparatus and remote sensing. However, there have been some awful problems such as high melting point, deviation from stoichiometry of composition, and stress-induced cracking during CdSe growth. So it is very difficult to grow crack-free large-size CdSe single crystals for high-power laser applications.. The research contents of this project include the preparation of masses of high-purity CdSe polycrystalline materials by Two-temperature technique, the growth of high-optical quality single crystals with large dimensions by Vertical Bridgman technique, the relationship study of defect structures and optical performances, and the fabrication of CdSe-OPO devices. And the key technologies about the polycrystalline synthesis, the single crystal growth and the fabrication of OPO devices will be obtained. The above-mentioned problems such as deviation from stoichiometry of composition and stress-induced cracking in large-size crystal growth can be solved. In order to significantly reduce optical absorption coefficient and obtain the high power far-infrared laser output, the subsequent treatment technologies for the as-growth crystals including constant-temperature thermal annealing and high-energy electron irradiation technology will also be studied.. Expected objectives: CdSe single crystals with dimension of φ(40~50)×90mm can be successfully grown, and devices with the typically dimension of 10×10×50mm can be fabricated. Up to 10W laser output is achieved at 8~12μm waveband through the optical parametric oscillation. These results will fill the domestic blank.

硒化镉（CdSe）晶体是目前通过OPO技术产生远波8~12μm激光输出的最好非线性材料之一，以CdSe晶体为基质的全固态激光器具有功率高、体积小、携带方便等优点，在光电对抗、医疗器械及遥感探测等领域具有重要应用。由于存在熔点高、组分易偏析、单晶生长开裂等缺点，大尺寸单晶生长异常困难，国内无满足工程应用的晶体。. 本项目主要研究双温区法合成大批量高纯CdSe多晶、垂直布里奇曼法生长大尺寸高品质单晶、缺陷结构与性能关系及OPO器件制作等关键技术和相关理论，重点解决多晶合成偏离化学计量比和大尺寸单晶生长开裂难题。探索恒温热退火和高能电子辐照技术对生长态晶体改性的后处理技术，进一步降低透光波段吸收系数，最终实现高功率远波红外激光输出。. 项目完成时晶体尺寸达到φ(40~50)×90mm，器件尺寸10×10×50mm，激光输出功率达到10W，填补国内空白。

硒化镉（CdSe）晶体是目前通过OPO技术产生远波8-12μm激光输出的最好非线性材料之一，以CdSe晶体为基质的全固态激光器具有功率高、体积小、携带方便等优点，在光电对抗、医疗器械及遥感探测等领域具有重要应用。.采用倾斜双温区方法，将反应原料分置不同温区，有效降低了反应器内的压力，解决了反应器因压力高炸裂的原因，合成出高纯CdSe多晶原料，单次合成量达到300g。采用底部籽晶垂直布里奇曼法生长出直径50mm的大尺寸单晶，对坩埚提拉速度、长晶界面温度梯度以及坩埚旋转进行模拟探究，得出生长速率为0.5mm/h时可获得接近平的固液生长界面，固液生长界面稳定性是生长大尺寸单晶的关键因素。采用X射线形貌术对缺陷结构进行了识别，主要存在三种类型位错：数量较少的螺型位错，{110}<110>和{010}<100>滑移体系中的两种刃型位错，平均位错密度Nd =4×103cm–2。II类相位匹配CdSe晶体元件采用短波谐振U形腔：当输入功率增加至8.1W时，长波10.81μm激光输出功率148mW，斜率效率为5.54%，泵浦阈值为<2.715mJ/mm2。考虑CdSe晶体小的走离效应，进一步采用长的CdSe晶体降低OPO振荡阈值，可以获得更高功率的长波8-12μm激光输出。