Fe2+:ZnSe晶体的移动加热器法生长及机理研究

Fe2+:ZnSe crystals have been considered as the most effective laser medium to obtain 3~5μm mid-infrared lasers with high performance and wide turning range due to its broadly tunable range, big absorption and emission cross-sections, high quantum efficiency, low excited state absorption, etc. However, it is usually hard to obtain uniform doped Fe2+:ZnSe crystals with large volume and high optical quality. Here, the accelerated crucible rotation technique (ACRT) is introduced in the traveling heater method (THM) growth process of Fe2+:ZnSe crystals to regulate the heat and mass transfer. The effects of ACRT on the growth interfaces and inclusions are studied during the crystal growth. Then, the relationships among the growth conditions, doping ways, doping efficiency and profile are revealed. In addition, the effects of the sample size, inclusions, doping concentration and uniformity on laser output properties are investigated. On this basis, we’ll illuminate the regulation mechanism of inclusions and the dopant distribution in THM growth process of Fe2+:ZnSe crystals, and obtain uniform doped Fe2+:ZnSe crystals with large volume and high optical quality, in turn providing the gain medium material with excellent performance for the mid-infrared laser.

Fe2+:ZnSe晶体具有宽的调谐范围、大的吸收和发射截面、高的量子效率、低的激发态吸收等特性，是实现高性能、宽调谐中红外（3～5μm）激光输出的最具前景的激光介质之一。制备掺杂均匀、浓度精确可控的大尺寸高光学质量的Fe2+:ZnSe晶体是目前限制其发展的关键因素。针对此问题，本项目提出采用移动加热器法（THM）生长Fe2+:ZnSe晶体，通过引入ACRT技术调控THM过程中的传热传质，研究ACRT对生长界面形貌、夹杂相的影响规律；揭示生长条件、掺杂方式、掺杂效率及其分布的内在关联；探索Fe2+:ZnSe晶体尺寸、夹杂相、掺杂浓度及其均匀性对激光输出性能的影响。在此基础上，阐明THM生长Fe2+:ZnSe晶体过程中夹杂相、掺杂元素的调控机制，从而成功获得掺杂均匀、浓度精确可控的大尺寸（直径15mm长50mm）高光学质量的Fe2+:ZnSe晶体，为中红外激光器提供性能优异的增益介质材料。

3～5 μm波段的激光源处于大气传输窗口，在人眼安全雷达、激光医疗、环境监测、空间通讯和激光对抗等领域均具有广阔的应用前景，是国内外激光领域的研究热点。Fe2+:ZnSe晶体因其优异的光学性能，被认为是最有应用前景的中红外（3～5μm）激光增益介质材料之一。本项目将坩埚加速旋转技术（ACRT）与移动加热器法（THM）结合，研究了Fe2+:ZnSe/ZnSe晶体的低温（900-1050℃）生长技术，揭示了生长参数（生长温度、生长速率、熔区长度以及ACRT参数）对Fe2+:ZnSe/ZnSe晶体生长的影响规律，成功获得一套适合生长厘米级高光学品质Fe2+:ZnSe/ZnSe单晶的最佳工艺。分析了不同生长条件下淬火的生长界面形貌，揭示生长界面形貌、生长参数以及夹杂相之间的内在关系，掌握了生长界面形貌和减少甚至消除夹杂相的调控机制。通过优化ACRT最大转速至15rpm，生长界面由凹变为微凸，显著减少了晶体中的夹杂相，其尺寸小于50μm，密度仅为7.03×102cm-2。对Fe2+:ZnSe/ZnSe晶体中夹杂相的研究发现，以PbCl2作为溶剂，生长的ZnSe多晶中存在PbCl2和ZnCl2两种夹杂相，且ZnCl2夹杂相仅在晶界上被观察到。以SnSe作为溶剂，生长的Fe2+:ZnSe单晶中也观察到溶剂SnSe和六方结构的ZnSe两种类型的夹杂相。探索了ZnSe晶体的退火改性，发现退火后晶体内部夹杂相尺寸显著减少甚至消失，红外透过率由30%提升到75%，禁带宽度由2.54eV提高到2.67eV，表明退火处理是进一步消除ZnSe晶体中夹杂相和改善光电性能的有效途径。性能测试结果表明，THM生长Fe2+:ZnSe/ZnSe单晶的摇摆曲线半峰宽仅为22arcsec，位错腐蚀坑密度为（1-2）×105cm-2，红外透过率高达70%以上，说明生长的单晶具有高的结晶质量和光学品质，这将为中红外激光器提供性能优异的增益介质材料。发表相关SCI论文5篇，申请发明专利1项。