A novel technique for the measurement of low optical absorption coefficients of the massive crystal boules of an arbitrary shape is proposed. It is based on the concept of equivalent temperature of the crystal interacting with laser radiation. Optical absorption coefficient of the LBO boule was measured. The accuracy of the method was theoretically estimated.
We propose a novel technique for measuring the surface temperature distribution of optical elements interacting with high power laser radiation. This technique is based on measuring the temperature sensitive piezoelectric resonance frequencies of nonlinear-optical crystals that are transparent at involved laser radiation wavelengths. Using small thermoresonators made of lithium niobate (LiNbO3) crystals the kinetics of the surface temperature distribution of the silica lens heated by 11W CW laser radiation at 1064 nm was measured. Modeling of the experiment results reveal the optical absorption coefficient of the lens to be 6×10<sup>-5</sup> cm<sup>-1</sup>.