Evaluating the safe limit of large-aperture potassium dihydrogen phosphate crystals associated with transverse stimulated Raman scattering

We propose a process to evaluate the safe limit of large-aperture DKDP crystals associated with transverse stimulated Raman scattering (TSRS) at the wavelength of 351 nm. The DKDP crystals’ safety can be assured by controlling the intensity of TSRS-scattering light to the same order of that of Rayleigh-scattering light. We use an optical fiber sensor system to detect side-scattering light in the DKDP and compare the intensity between Raman- and Rayleigh-scattering light. By defining the threshold intensity as a condition in which the intensity ratio between transverse Raman-scattering light and Rayleigh-scattering light exceeds 1, we obtain the threshold intensity of approximately 2.6 GW/cm2 in our experiment. This method enables us to determine the TSRS threshold directly instead of measuring the TSRS gain coefficient and edge reflectivity of the crystals.