High-sensitivity measurement of residual absorption of lithium triborate crystals

Lithium triborate (LBO) crystals are used for nonlinear-optical applications, e.g. second-harmonic generation of high-power visible laser light and the generation of tunable laser light via optical parametric oscillation. However, at high light powers, residual absorption in LBO crystals leads to heating and to temperature phase mis-matching, limiting the conversion efficiency and the available output power. To enhance the capability of optical devices based on LBO crystals, high-quality crystals with low absorption coefficients are required.