Optical misalignment due to temperature gradients in electrooptic modulator crystals.

A possible source of misalignment of light in an optical communication system, utilizing electrooptic modulators, is the deflection of the light beam within the modulator crystal due to temperature gradients. The present paper investigates the light deflection resulting from a linear temperature gradient across various modulator crystals. The total effect is found to be the sum of two contributions, one due to the crystal expansion, the other due to the index of refraction gradient, and is found to be smaller, by the factor 10, in quartz than in KDP. The experimental method described provides also a simple way of determining dn/dT in crystals for both ordinary and extraordinary rays.