Towards fully passive deep UV Dual-Comb Spectroscopy

Dual-Comb Spectroscopy (DCS) offers superior acquisition speed, mechanical stability and spectral resolution in comparison to traditional Fourier transform spectroscopy [1] . Recently we developed a high power, fully passive DCS system based on two Kerr-lens mode-locked Yb:YAG oscillators in close proximity, sharing most of the cavity optics ( figure 1a ). The dual-comb interferometer of our fully passive system shows a high coherence time. The average and peak powers that are an order of magnitude higher than in previous works [2] . Here we frequency double its output beams via second-harmonic generation (SHG) to reach the green region at 515 nm and we compare the performance with that of the fundamental version operating at 1030 nm. The DCS performance in green is comparable to the fundamental wavelength showing similar signal-to-noise ratio (SNR) and spectral resolution. This is the crucial step towards DCS experiments in the UV spectral range, which has been poorly investigated until today [3] .