Broadband near-ultraviolet dual comb spectroscopy

Abstract

The highly energetic photons of ultraviolet light drive electronic, vibrational and rotational transitions in virtually all atomic or molecular species. This radiation is thus a prime tool for strongly selective spectroscopic fingerprinting and real-time environmental monitoring if broad spectral coverage, short acquisition times and high spectral resolution can be achieved – requirements that are in mutual competition in traditional applications. As a novel concept with intrinsic potency in all three aspects, here we introduce ultraviolet dual comb spectroscopy using two broadband ultraviolet frequency combs centered at 871 THz (343 nm central wavelength) and covering a spectral bandwidth of 35.7 THz. We demonstrate the potential of the novel spectroscopy platform by acquiring fully state-resolved absorption spectra of formaldehyde, a prototype molecule with high relevance for laser spectroscopy and environmental sciences, with acquisition times as short as 100 µs and an averaged spectral resolution of 50 GHz and perform element-selective real-time tracking of gas concentration changes. To our knowledge, this is the first realization of dual comb spectroscopy in the ultraviolet spectral region and the first tool to allow for a real-time monitoring of the trinity of rotational, vibrational and electronic excitations in molecular species of major earth-atmospheric relevance.