Spectral Characteristics of Terahertz Quantum Cascade Lasers

Terahertz quantum cascade lasers (THz QCLs) are prospective radiation sources for high-resolution gas spectroscopy. A wide range of operating frequencies (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 a new generation of gas spectrometers for biomedical and environmental applications. The article discusses the possibilities of controlling the spectral characteristics of THz QCLs by changing the operating temperature and parameters of the injection current pulses: amplitude, duration, and repetition rate. For the first time, the study of energy transfer between longitudinal Fabry — Perot modes in THz QCLs with a change in the duty cycle of injection current pulses has been carried out.