In this paper, we present a detailed investigation of three types of tapered distributed feedback (DFB) quantum cascade lasers (QCLs) emitting at $7.2~\mu \text{m}$ . The sampling gratings with different sampling duty cycles were fabricated by holographic lithography combined with the conventional optical photolithography. High output power of more than 550mW with excellent beam quality was achieved in continuous-wave operation at 293K for a 2.5-mm-long DFB-QCL with sampling duty cycles of 0.25 and 0.5 in the tapered region and uniform region, respectively. Stable single-mode emission with a side-mode suppression ratio above 25dB was obtained in the temperature range of 283-318K. The demonstrated tapered DFB QCL structure with asymmetric coupling coefficient can effectively achieve high performance with low fabrication cost, which is beneficial for many applications.

中文翻译：

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高功率锥形采样光栅分布式反馈量子级联激光器

在本文中，我们详细研究了以 $7.2~\mu\text{m}$ 发射的三种类型的锥形分布式反馈 (DFB) 量子级联激光器 (QCL)。采用全息光刻与常规光学光刻相结合的方法制作了不同采样占空比的采样光栅。对于 2.5 毫米长的 DFB-QCL，在锥形区域和均匀区域的采样占空比分别为 0.25 和 0.5，在 293K 的连续波操作中实现了超过 550mW 的高输出功率和出色的光束质量。在283-318K的温度范围内获得了边模抑制比高于25dB的稳定单模发射。所展示的具有非对称耦合系数的锥形 DFB QCL 结构可以以较低的制造成本有效地实现高性能，