Internal Thermal Effects in Axial Paratellurite-Based Acoustooptic Deflector

The thermal angular deviation of the zero and working orders in an axial paratellurite-based acoustooptic deflector is experimentally investigated at a control power up to 6.5 W in the continuous mode. Regional measurements (near the transducer, in the middle, and at the sound absorber) are performed for variants of +1 and –1 working order diffraction and show a linear dependence of the angular deviation on the control power. A qualitative description of deviation of the working order as a combined action of two factors is proposed: (1) zeroth-order deviation at passage of two thermal optically denser prisms attached to the transducer and sound absorber and (2) reduction in the diffraction angle due to the growth in the sound speed at crystal heating. The inhomogeneity of the temperature field cannot be used to uniquely separate the contributions of these factors to the averaged working-order deviation. It is shown that the technology of the liquid contact between the endface surface of a piezoelectric transducer and the body increases the stability of the deflector parameters as light passes in the zone adjacent to the transducer. It is revealed that for +1 order diffraction there is a zone with a minimum thermal deviation between the piezoelectric transducer and the absorber. This is explained by the mutual compensation between the zeroth-order deviation (in the field of the thermal optical wedge from the absorber) and the factor of increased in sound speed.