We review recent advances in chemical sensing applications based on surface emitting ring quantum cascade lasers (QCLs). Such lasers can be implemented in monolithically integrated on-chip laser/detector devices forming compact gas sensors, which are based on direct absorption spectroscopy according to the Beer-Lambert law. Furthermore, we present experimental results on radio frequency modulation up to 150 MHz of surface emitting ring QCLs. This technique provides detailed insight into the modulation characteristics of such lasers. The gained knowledge facilitates the utilization of ring QCLs in combination with spectroscopic techniques, such as heterodyne phase-sensitive dispersion spectroscopy for gas detection and analysis.
quantum cascade laser; quantum cascade detector; gas sensing; radio frequency modulation; heterodyne phase-sensitive dispersion spectroscopy; gas sensing; absorption spectroscopy; chemical sensors; dispersions; electrochemical sensors; gas detectors; heterodyning; modulation; quantum cascade lasers; radio waves; semiconductor lasers; spectroscopic analysis; chemical sensing applications; direct absorption spectroscopies; modulation characteristics; phase sensitive; quantum cascade detectors; quantum cascade lasers (QCLs); frequency modulation