Experimental determination and the theoretical model of an equivalent temperature of nonlinear optical crystals interacting with high-power laser radiation

Abstract

We present the results of the use of resonant ultrasound spectroscopy to study changes in temperature of crystals during their interaction with high-power laser radiation. To measure the nonuniform temperature of a crystal, use is made of the frequency (calibrated at uniform temperature θ) of the nth mode of the piezoelectric resonance Rfn(θ) and its change ΔRfn(Pin) upon crystal irradiation by laser light with an average power Pin. A spatially inhomogeneous distribution of thermodynamic temperature in the crystal at a fixed laser power Pin is set in correspondence with equivalent temperature θeq(Pin), defined in this paper. A mathematical model is proposed, justifying the correctness of its introduction. This parameter can be used to study any piezoelectric crystals interacting with laser radiation.