Supercontinuum generation and optical damage of sapphire and YAG at high repetition ratesOptics Letters
- Robertas Grigutis, Gintaras Tamosauskas, Vytautas Jukna, Alex Risos, and Audrius Dubietis
- received 05/12/2020; accepted 07/05/2020; posted 07/06/2020; Doc. ID 397481
- Abstract: We experimentally investigated supercontinuum generation and evolution of the optical damage in sapphire and YAG crystals with 180 fs, 1035 nm pulses from an amplified Yb:KGW laser with variable repetition rates, in tight and loose focusing conditions. We demonstrate that the extinction of supercontinuum spectrum always correlates with an occurrence of third harmonic diffraction, which thus readily serves as an indication of the onset of in-bulk optical damage. Damage-related structural changes of the nonlinear material are also justified by an increased intensity and large red-shift of crystal luminescence spectrum corresponding to F center emission. The supercontinuum spectrum in sapphire starts shrinking on the time scale of seconds to minutes by varying the focusing condition from thigh to loose at laser repetition rate of 200 kHz, whereas YAG crystal produces stable performance for several hours at least.