Free-running deep-UV dual-comb spectroscopy

Abstract We demonstrate dual-comb spectroscopy in the deep UV at 257 nm with an etalon, supported by molecular spectroscopy of iodine at 515 nm. Our free-running thin-disk oscillator provides an average power of 25 W at 1030 nm that is frequency doubled and quadrupled to generate up to 15 W in green and 1.5 W in deep UV. The peak and average power levels in the deep UV generated from the thin-disk oscillator are one order of magnitude higher than in previous systems. The compact frequency conversion setup enables parallel dual-comb spectroscopy in the spectral bands. We use a self-referenced digital correction scheme to achieve a high signal-to-noise ratio (SNR) via coherent interferogram averaging. In the deep UV, our 62 MHz oscillator achieves a SNR of 69 dB at GHz resolution within a 1 s measurement time, covering a spectral span of 2 THz. Our free-running system presents a straightforward solution for precise deep UV dual-comb spectroscopy.