A new criterion for determining optical damage of nonlinear optical crystals, based on the use of an RF oscillator circuit

A criterion is proposed for determining laser breakdown in nonlinear optical crystals, based on measuring the absorption coefficient of optical radiation. A possibility of using a Pierce oscillator is demonstrated to determine the optical absorption coefficient in real time. The proposed criterion is applied to find the optical damage threshold of a lithium niobate crystal, which is 500 mJ/cm², taking into account the self-focusing effect.