HETERODYNE INTERFEROMETRIC MEASUREMENT OF THE THERMOOPTICAL COEFFICIENTS OF POTASSIUM NIOBATE

A heterodyne interferometric technique is applied to determine the the rmo-optic coefficients of a potassium niobate crystal with a GaAlAs di ode laser. The heterodyne beats signal, resulting from the beating of the carrier and two side-band frequencies, is related to the phase shi ft difference between the carrier and the side-bands. This phase shift difference is determined with a phase sensitive detection technique a nd is found to be temperature dependent. From the temperature dependen ce, the thermo-optic coefficients of the potassium niobate crystal alo ng the b and c crystallographic axes are determined to be -4.5x10(-5) and 6.7x10(-5 degrees)C(-1), respectively. (C) 1998 American Institute of Physics. [S0021-8979(98)07616-6]