Investigation of absorbtion of high-power laser radiation in lithium triborate crystals

Problem formulating. Nonlinear-optical crystals are widely used for the conversion of laser radiation wavelengths. In the case of conversion of high-power laser radiation the optical quality of crystals plays a crucial role. In particular it is characterized by optical absorption coefficients. Crystals that are used for frequency conversion of laser radiation have a certain geometry and are cut from large crystal boules. Consequently, a preliminary spatial diagnostics of optical quality of crystal boules before its processing is an urgent task.

Goal. Measurements of optical absorption coefficients of nonlinear-optical lithium triborate LiB3O5 (LBO) crystal boules in different spatial regions.

Result. The spatial distribution of the optical absorption coefficients of LBO boule was investigated using the piezoelectric resonance laser calorimetry. The optical absorption coefficients of LBO boule were measured in different spatial regions under the effect of continuous laser radiation at 2 μm wavelength (10 W optical power). The optical absorption coefficients of the LBO boule varied in the range from 0.26 cm–1 to 1.72 cm–1.

Practical meaning. We have demonstrated the possibility of the spatial diagnostics of the optical quality of nonlinear-optical crystal boules.