Browsing by Author "Kuittinen, Markku"

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    Sapphire-based resonant waveguide-grating mirrors : advancing their intra-cavity power density capability
    (2023) Bashir, Danish; Boubekraoui, Ayoub; Mourkioti, Georgia; Li, Fangfang; Karvinen, Petri; Kuittinen, Markku; Mackenzie, Jacob. I.; Graf, Thomas; Abdou Ahmed, Marwan
    We report on the design, fabrication, and implementation of a single-layer resonant waveguide-grating (RWG) mirror on a sapphire substrate. Our goal is to enhance these optics capability to withstand high intra-cavity power densities by exploiting the superior thermal properties of sapphire. The RWG was implemented as an intra-cavity folding mirror in an Yb:YAG thin-disk laser to generate linearly polarized and spectrally stabilized radiation. A linearly polarized output power of 191 W with an optical efficiency of 39% was obtained in multi-mode operation. This corresponds to a power density of 52 kW/cm 2 on the RWG, for which the increase of its surface temperature was measured to be 12 K, which resulted in a 46-fold reduction of the surface temperature rise dependence on the intra-cavity power density with respect to what has been reported for a RWG on a fused silica substrate. In near fundamental-mode operation, a linearly polarized emission with an output power of 90 W, an optical efficiency of 30%, and a spectral bandwidth of 28 pm FWHM was obtained.