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 KTiOPO4 (KTP). KTP behaves as a TI wave plate at 33.7 deg from the Z axis in the X–Z principal plane. The effective electro-optic coupling, Reff, at this orientation is 19 pm/V. The electro-optic coupling and utility of these TI orientations in KTiOAsO4 and KNbO3 are also examined. The calculated Reff of KNbO3 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)