Abstract

Deep ultraviolet (UV) and extreme ultraviolet (XUV) spectral regions are of high interest for precision spectroscopy and metrology applications. For example, the 1S-2S transition of He⁺ ions requires a coherent deep UV source of around 60.8 nm. Another appealing application is the possibility of creating ultra-precise nuclear clocks based on the transition at approximately 150 nm in Thorium-229 [1]. However, until now, no CW lasers are available in that region. One of the most straightforward approaches is frequency up-conversion via high harmonic generation in a gas jet driven by an existing near-infrared laser. An ideal starting point can be a homebuilt carrier-envelope phase (CEP) stabilized thin-disk oscillator, delivering 110 MW output peak power at a repetition rate of 14 MHz [2]. In order to generate XUV frequency combs via high harmonic generation (typically < 10^-6) the laser must be CEP- and repetition-rate stabilized [3]. In this work, the first steps towards stabilization with an intra-cavity acousto-optic modulator were performed.

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