中红外激光有着广泛的应用前景，而量子级联激光器以其体积小，重量轻，效率高等优点，已成为中红外波段一种重要的新型激光光源。受限于器件发热等因素，单只量子级联激光器的发光功率有限，为了满足实际应用，采用外腔激光合束的方法提高发光功率是一种有效的途径。同偏振合束、光谱合束方法相比，外腔相干合束具有光束质量好，合束效率高，单一波长工作等优点，是理想的中波红外合束方案。本项目拟对基于达曼光栅的相干合束进行研究，围绕达曼光栅设计与制备、中红外光学介质膜设计与制备等方面开展理论与实验研究，实现3-5 微米波长功率高于3瓦的激光输出，合束效率高于60%，光束质量因子优于5。

Mid-infrared (MIR) lasers have demonstrated the extensive applications in many fields. Quantum cascade lasers (QCLs), as a new kind of MIR laser, had shown the potential applications due to their merits of high efficiency, small volume, electrical driving and room temperature operation. However, single QCL is limited in output power because the serious self-heating effect and narrow cavity. External-cavity beam combination is an effective method to solve this issue. Compared with the polarization beam combination and spectrum beam combination methods, coherent beam combination (CBC) is an ideal scheme which has advantages such as good beam quality, high efficiency and single wavelength output. This project aims to study the CBC based on Dammann grating, which is planned to be carried out by the theoretical and experimental investigations of Dammann grating and MIR coating, etc. The module of QCL with the output power of 3W operating at 3-5μm wavelength is expected to be achieved, the corresponding power efficiency and beam quality factor are respectively better than 60% and 5.