作为一种新型半导体激光器，量子级联激光器因其独特的子带间跃迁机制，具有高速响应、高非线性、输出波长大范围可调等特点。近年来随着输出光功率和电光转化效率等性能指标的快速提升，量子级联激光器已成为中红外至太赫兹波段（波长约为3~300 μm）的主流激光光源，在大气污染监控、气体检测、太赫兹成像、生物医疗以及空间光通信等领域具有重要科学意义和应用价值。本文阐释了量子级联激光器的发展历程以及工作原理；分别重点讨论了中红外量子级联激光器在高效率、大功率、波长可调谐以及片上传感的应用等方面的研究进展，并对基于中红外量子级联激光器差频太赫兹光源和光频梳的发展进行叙述，最后进行了简要总结与展望。

基于锑化物的带间级联激光器同时具有带间跃迁的高增益和级联结构的高量子效率，是中红外波段重要的相干光源，其功耗低于其它中红外半导体激光器，因而单模带间级联激光器在基于激光吸收光谱技术的高分辨气体检测和化学传感等领域具有很大的优势。目前利用Bragg光栅实现波长选择的单模分布反馈带间级联激光器已经实现商品化，但是，与同样有源区结构的Fabry-Pérot腔带间级联激光器最高600 mW的出光功率相比，单模功率最高55 mW，损耗较大。对几种不同结构的分布反馈带间级联激光器的性能进行对比分析，探讨这类单模中红外激光器损耗的主要来源以及改进思路。此外，介绍了垂直腔面发射和光子晶体带间级联激光器的进展，并与分布反馈带间级联激光器的性能进行比较，讨论其优缺点及适用的场景。

We demonstrated an electrically pumped InP-based microcavity laser operating in continuous-wave mode. The active region is designed with antimony surfactants to enhance the gain at 2 μm, and a selective electrical isolation scheme is used to secure continuous-wave operation for the microcavity laser at room temperature. The lasers were fabricated as a notched elliptical resonator, resulting in a highly unidirectional far-field profile with an in-plane beam divergence of less than 2°. Single-mode emission was obtained over the entire dynamic range, and the laser frequencies were tuned linearly with the pumping current. Overall, these directional lasers pave the way for portable and highly integrated on-chip sensing applications.

We report on the design and fabrication of a dual-wavelength switchable quantum cascade laser (QCL) by optimizing the design of a homogeneous active region and combining superposed distributed feedback gratings. Coaxial, single-mode emissions at two different wavelengths were achieved only through adjusting the bias voltage. Room temperature continuous-wave operation with output powers of above 30 mW and 75 mW was realized for single-mode emission at 7.61 µm and 7.06 µm, respectively. The simplified fabrication process and easy wavelength control of our designed dual-wavelength QCL make it very attractive for developing miniature multi-species gas sensing systems.

带间级联激光器有源区内部的物理机制复杂，尚未得到充分研究。优化了电子注入区结构，通过减小InAs/AlSb啁啾超晶格中InAs量子阱的厚度促进电子向光增益区的注入，在较低的电子注入区掺杂浓度下满足了光增益区电子数和空穴数基本相等的注入平衡条件，降低了有源区中自由载流子吸收和杂质散射造成的光损耗。采用该有源区结构的带间级联激光器实现了较好的室温激射性能，腔长4 mm、脊宽20 μm且腔面未镀膜器件的阈值电流为200 mA，单腔面出光功率为55 mW。通过分析2~5 mm不同腔长器件的电压-电流-光功率性能，得到器件的波导损耗仅为3 cm^-1，有源区载流子寿命为0.7 ns。

We demonstrate GaSb-based interband cascade lasers (ICLs) emitting around 3.65 µm, which exhibit a room-temperature continuous-wave (CW) output power above 100 mW. Cavity-length analysis showed that the laser structure has a low internal loss of 3cm-1 while maintaining a total internal quantum efficiency greater than one. After 6400 h CW operation at 25°C, the threshold current of the laser increased by 3%, and the output power decreased by 7%, indicating good reliability of the device.

量子级联探测器是一种光伏型的子带间跃迁红外探测器，通过厚度渐变的啁啾量子阱中台阶状的子带分布，产生内建电场，使得有源区中的光生载流子定向输运，器件工作时无需外加偏压，避免了暗电流噪声的产生，能够实现室温长波红外响应。由于子带间跃迁吸收系数小、具有偏振选择性，量子级联探测器目前存在响应率低、对正入射响应无响应、探测率对温度敏感等问题。针对这些问题，本文介绍三种新型量子级联探测器有源区的设计，包括量子点/阱耦合、束缚-微带斜跃迁和小能量台阶有源区，在中波、长波和甚长波波段展现出优良的器件性能。