新型中红外光栅分布反馈量子级联激光器

The mid-infrared grating distributed feedback quantum cascade laser are becoming very attractive for numbers of applications, such as environmental pollution monitoring, high-resolution spectroscopy and medical diagnosis. At present, the key factor for further applications of the mid-infrared grating distributed feedback quantum cascade laser is the device performance. In particular, the two fatal drawbacks including the high waveguide loss of surface grating and low extracted efficiency of buried grating is still an open topic. The two important parameters including low threshold and high power can not be achieved simultaneously in the mid-infrared grating distributed feedback quantum cascade laser. The project will promote the study on high performance mid-infrared grating distributed feedback quantum cascade laser based on the novel porous grating and sampled grating. The corresponding relations between grating coupling coefficient, modal loss and threshold gain will be investigated by analysis of the novel porous grating and sampled grating. In addition, the key physic factor for device performance will be explored. Proper grating coupling coefficient will be obtained while maintaining a low waveguide loss. The material quality and thermal management will be improved. And then the low threshold and high power mid-infrared grating distributed feedback quantum cascade laser are achieved simultaneously by matching the novel porous grating and sampled grating structures.

中红外光栅分布反馈量子级联激光器在环境污染监测、高分辨率光谱、医疗诊断等方面有重要的应用前景。目前，限制中红外光栅分布反馈量子级联激光器深入应用的主要因素是不完备的器件性能。其中，表面光栅引入的高波导损耗和掩埋光栅产生的低抽取效率这两个关键科学问题还没有得到解决，低阈值和高功率这两个极为重要的技术参数在光栅分布反馈量子级联激光器上还没有实现真正意义上的统一。本项目基于前期的工作基础通过引入新型的多孔光栅和采样光栅结构开展高性能中红外分布反馈量子级联激光器的研究。通过对新型多孔光栅和采样光栅结构的分析，研究光栅耦合系数、模式损耗、阈值增益之间的对应关系，探索影响光栅器件性能的关键物理因素，研制低波导损耗和适度耦合系数的表面多孔光栅和掩埋采样光栅。通过完善量子级联激光材料质量、配合新型的多孔光栅和采样光栅结构并采用良好的热管理技术实现低阈值和高功率兼得的中红外光栅分布反馈量子级联激光器。

中红外光栅分布反馈量子级联激光器在环境污染监测、高分辨率光谱、医疗诊断等方面有重要的应用前景。本项目基于前期的工作基础注入了新的物理思想实现了低阈值、高功率工作的单模量子级联激光器。（1）发展了量子级联激光材料的可控制备理论，实现了高质量的量子级联激光材料制备。X射线衍射显示外延材料的零级峰与InP衬底峰完全的重合，卫星峰超过了60级且半高宽仅为11-13弧秒。（2）研制了深刻蚀的表面金属/InP光栅单模器件，激射波长4.7微米，对于镀有高反射膜的4毫米长、13微米脊宽的激光器室温连续输出功率超过了1W，阈值电流密度为1.13kA/cm2。采用电化学腐蚀结合全息曝光技术研制出了新型的多孔InP光栅分布反馈量子级联激光器，激射波长7.6微米，多孔器件比起原来的金属/InP光栅结构波导损耗降低了0.6cm-1，输出功率提高了50%。制作了掩埋的二级光栅衬底发射量子级联激光器并实现了高温连续工作，随后为了实现低的光束发散角，将多孔的InP技术制作在出光衬底面上实现了脊宽方向远场发散角的校准，获得了腔长方向0.12°，脊宽方向0.29°的小发散角器件。（3）研制了低损耗的掩埋采样光栅分布反馈量子级联激光器，通过改变采样占空比降低了光栅耦合系数，通过使用4mm长的腔获得了室温连续输出功率大于600mW，阈值电流密度仅为0.8 kA/cm2的高性能器件。