Acousto-Resonance Spectroscopy of Nonlinear-Optical Crystals in Process of Laser Frequency Conversion

Abstract

<p class="MsoNormal"> Dependence of the periodically poled nonlinear-optical lithium niobate (PPLN) crystal temperature on laser power in the course of laser frequency conversion was measured using piezoelectric resonance. Crystal’s temperature tuning curves are precisely measured using concept of the equivalent temperature. Both optical absorption and heat transfer coefficients of the crystal are measured employing kinetics of the crystal equivalent temperature. </p

Crystal equivalent temperature model in process of nonlinear conversion of laser radiation

“…Experiment of SHG in PPLN crystal was performed using as a pump source the continuous wave polarized single-mode ytterbium fiber laser (λ=1064 nm) [7,8]. Figure 2 a shows dependence of crystal equivalent temperature on pump power measured for two cases of pump polarization e 1 direction.…”

“…Nonlinear-optical crystal temperature measurement is of great interest directly in course of nonlinear-optical conversion of laser radiation [6][7][8]. In this case crystal is heated nonuniformly along propagation direction of laser radiation as far as optical absorption coefficients of pump and converted wavelengths can differ significantly.…”

“…In this case crystal is heated nonuniformly along propagation direction of laser radiation as far as optical absorption coefficients of pump and converted wavelengths can differ significantly. For theoretical interpretation of experimental results obtained in [6][7][8] it is necessary to elaborate model of acoustical vibration of bulk crystal sample under condition of nonuniform transverse and longitudinal crystal temperature distribution. First step to resolving of this problem is finding the solution of three dimensional heat conduction equation with spread heat source specified by the absorption of pump and generated laser radiation, which powers vary along propagation distance.…”