Mid-IR Optical Frequency Comb

Lasers have transformed our daily lives, with applications ranging from optical communication and medical procedures to material processing. In particular, ultrafast lasers with ultrashort pulse durations have revolutionized nonlinear optics, micromachining, and enabled the study of physical processes at attosecond time scales. Additionally, frequency-stabilized ultrafast lasers, known as optical frequency combs, directly link optical frequencies and radio-frequencies, making them ideal tools for optical metrology and spectroscopy. Molecular species can be uniquely identified by measuring their wavelength-resolved absorption. This measurement then provides an absorption spectrum of the molecular species. One of the spectral regions with the strongest absorption cross- sections is the mid-IR region of the electromagnetic spectrum, ranging from 2.5 m to 20 m. Notably, visible light ranges from 0.4 m to 0.8 m. An important group of gas species that shows strong absorption features in the mid-IR spectral region around 2.8 m are greenhouse gases (GHGs), particularly nitrous oxide, which is among the most significant GHGs after methane and carbon dioxide. Nitrous oxide, commonly known as laughing gas, is introduced to the atmosphere primarily through fertilizer usage. The MIRO project targets the research and development of ultrafast mid-IR frequency combs. The laser will operate at 2.8 m and be stable enough for open-air spectroscopy, as required for the detection of N2O and other GHGs. One of the main goals is to facilitate access to stable light sources at wavelengths close to the absorption features for nitrous oxide. To this end, we are working on a novel laser concept that leverages newly developed, more robust fiber technology in the mid-IR spectral region. The inherent stability and robustness of the developed laser will ultimately enable open-air dual-comb spectroscopy of N2O outside protected laboratory environments.