The terahertz (THz) quantum cascade laser (QCL), first demonstrated in 2002, is among the most promising radiation sources in the THz region owing to its high output power and broad frequency coverage from ∼1.3 to ∼5.4 ​THz and sub-terahertz, without and with assistance of external strong magnetic field. The operation of THz QCLs, however, has thus far been limited to applications below room temperature. Recent advances in THz QCL research have principally focused on optimization of quantum design, fabrication, and growth techniques to improve the maximum operating temperature of THz QCLs; these efforts culminated in a recent demonstration of pulse-mode lasing at temperature up to 250 ​K. Research interests continue to be propelled as new maximum lasing temperature record are set, heating up the race to realize room-temperature operation of THz QCLs. This paper critically reviews key achievements and milestones of quantum designs, fabrication techniques, and simulation methods applicable to the high temperature operation of THz QCLs. In addition, this paper provides a succinct summary of efforts in this field to pinpoint the remaining challenges and provide a comprehensive picture for future trends in THz QCL research.

太赫兹 (THz) 量子级联激光器 (QCL) 于 2002 年首次展示，由于其高输出功率和从 ~1.3 到 ~5.4 THz 和亚太赫兹的宽频率覆盖范围，是太赫兹区域最有前途的辐射源之一, 没有和有外部强磁场的帮助。然而，太赫兹 QCL 的操作迄今为止仅限于低于室温的应用。太赫兹 QCL 研究的最新进展主要集中在量子设计、制造和生长技术的优化上，以提高太赫兹 QCL 的最高工作温度；这些努力最终导致了最近在高达 250 K 的温度下进行脉冲模式激光的演示。随着新的最大激光温度记录的建立，研究兴趣继续得到推动，为实现 THz QCL 的室温操作而进行的竞赛升温。本文批判性地回顾了适用于太赫兹 QCL 高温操作的量子设计、制造技术和模拟方法的关键成就和里程碑。此外，本文简要总结了该领域的努力，以查明剩余的挑战，并为太赫兹 QCL 研究的未来趋势提供全面的图景。