Ultraviolet dual comb spectroscopy (Invited Paper)

Although the development of ultraviolet (UV) frequency combs has been accomplished 20 years ago [1, 2], it was only very recently that the ultraviolet spectral region has been conquered by dual comb spectroscopy (DCS) [3-7]. DCS combines broad spectral coverage with frequency comb precision, fast measurement speeds and high spectral resolution. However, as frequency combs mainly emit in the infrared region, frequency up-conversion into the UV is still required for UV DCS. This makes UV DCS challenging: the conversion efficiency scales with pulse energy and hence increases with shrinking pulse repetition rates. On the other hand, DCS favors high repetition rates for stable conditions during the pulse interferometry. In this conference contribution, the most recent projects of the Coherent Sensing Group at TU Graz aiming at UV frequency comb generation and DCS will be presented. The efforts advancing dual comb spectroscopy include different comb systems with different repetition rates and the extension into the vacuum ultraviolet via nonlinear methods such as high harmonic generation. Intermediate steps recently enabled dual comb spectroscopy in real time and in the field for atmospheric sensing of nitrogen dioxide with an unprecedented temporal resolution of one second [8, 9]. References: [1] C. Gohle et al., “A frequency comb in the extreme ultraviolet", Nature 436, 234 (2005). [2] R. Jason Jones et al., Phys. Rev. Lett. 94, 193201 (2005). [3] B. Xu et al., “Near-ultraviolet photon-counting dual-comb spectroscopy”. Nature 627, 289 (2024). [4] K. F. Chang et al. „Multi-harmonic near-infrared–ultraviolet dual-comb spectrometer”, Opt Lett 49, 1684 (2024). [5] J. J. McCauley et al., “Dual-comb spectroscopy in the deep ultraviolet. Optica 11, 460 (2024). [6] A., Muraviev et al., Optica 11, 1486 (2024). [7] L., Fürst et al. “Broadband near-ultraviolet dual comb spectroscopy”. Optica 11, 471 (2024). [8] A. Eber et al., “Streaming self-corrected dual-comb spectrometer”, Optics Letters, 33, 35314 (2025). [9] A. Eber et al., Coherent field sensing of nitrogen dioxide. Opt Express 32, 6575 (2024). [10] A. Eber et al., NIR/VIS DCS comparing high and low repetition rate regimes, arXiv:2509.02159 (2025).