Optical frequency comb spectroscopy has proven an indispensable tool for high-resolution spectroscopy. QCL frequency combs offer the possibility to explore the mid-infrared spectral range. However, they suffer from large repetition frequencies which make them seemingly unsuitable for high resolution spectroscopy. We present three measurement modes overcoming this limitation. The rapid-sweep technique allows to retrieve the full high-resolution spectrum in 6ms, the step-sweep technique allows for high-resolution spectroscopy with spectral resolution <5e-4 cm-1. As a last technique we present the time-resolved step-sweep approach enabling high-resolution spectra of sub-millisecond-lived samples. It was assessed in a study of cold gases in supersonic beams.
A compact broadband atmospheric gas spectrometer has been developed in the framework of the EU-H2020 FLAIR project. The system is composed of a mid-IR 2-4um broadband supercontinuum source, a temperature controlled 10- meter-long multipass-cell for light-gas interaction, a diffraction grating, and an uncooled PbSe-on-CMOS matrix detector recording absorption spectra. The detection limit has been measured at sub-ppm level on methane under laboratory conditions. We also present 2 successful field measurement campaigns aboard airborne platforms: a hot-air airship for controlled methane release experiments, and a helicopter tracking ship exhaust fumes abroad the coastline of Denmark, with special emphasis on methane detection.