Tuning of the Spectral Characteristics of Terahertz Quantum-Cascade Lasers

Abstract—Terahertz quantum-cascade lasers (THz QCLs) are promising radiation sources for high-resolution gas spectroscopy. A wide operating-frequency band (from 1.2 to 5.4 THz), a narrow generation line (up to 10 kHz), the ability to operate on several radiative transitions (two-color lasers, generation of frequency combs) and other unique characteristics of THz QCLs make it possible to create gas spectrometers of a new generation for biomedical and environmental applications. In this paper, we consider the possibility of controlling the spectral characteristics of THz QCLs by changing the operating temperature and injection-current pulse parameters: amplitude, duration, and repetition rate. The energy transfer between longitudinal Fabry–Perot modes in THz QCLs is studied for the first time with a change in the duty cycle of the injection-current pulse cycle.