All optically biaxial crystals exhibit orientations in which they behave as thermally insensitive (TI) wave plates. Given sufficient electro-optic coupling at these orientations, biaxial, ferroelectric crystals may be advantageously employed as single-crystal, temperature-insensitive electro-optic modulators. I have experimentally confirmed the TI orientation in the principal dielectric plane of the biaxial crystal KTiOPO<sub>4</sub> (KTP). KTP behaves as a TI wave plate at 33.7 deg from the <i>Z</i> axis in the <i>X–Z</i> principal plane. The effective electro-optic coupling, R<sub>eff</sub>, at this orientation is 19 pm/V. The electro-optic coupling and utility of these TI orientations in KTiOAsO<sub>4</sub> and KNbO<sub>3</sub> are also examined. The calculated <i>R</i><sub>eff</sub> of KNbO<sub>3</sub> at the TI orientation is expected to be >2000 pm/V.
© 1995 Optical Society of America
Christopher A. Ebbers, "Thermally insensitive, single-crystal, biaxial electro-optic modulators," J. Opt. Soc. Am. B 12, 1012-1020 (1995)