Quantitative evaluation of DUV-induced absorption in CsLiB ₆ O ₁₀ under focused-beam irradiation

We demonstrate a numerical approach to simultaneously determine linear and two-photon absorption coefficients in CsLiB 6 O 10 (CLBO) crystals under focused 221 nm irradiation. By analyzing transmittance through thick samples, we obtained intrinsic values of α = 0.047 /cm and β = 1.93 cm/GW. Furthermore, by scanning the crystal along the focused beam axis, we spatially resolved the photo-induced absorption coefficient, which reached a peak of 1.47 /cm at the beam waist. This enhancement, scaled with the square of the pump intensity, indicated that defect formation is driven by two-photon absorption. This method provides a useful approach for investigating deep-ultraviolet optical degradation mechanisms.