The Electro-Optic Effect in Uniaxial Crystals of the Dihydrogen Phosphate Type*,† III Measurement of Coefficients

The electro-optic coefficients of two crystals have been measured by both static and dynamic methods. For NH4H2PO4, r63=2.54, r41=6.25; for KH2PO4, r63=3.15, r41=2.58 (units 10−7 c.g.s., 20°C λ5560). The variation of the electro-optic response with the frequency of the applied field is given and related to the piezoelectric vibrations of the crystal. A theoretical relation for the difference in the electro-optic constants measured at constant stress and at constant strain is derived, which provides a check on the consistency of the presently available electro-optic, photo-elastic, piezoelectric, and elastic coefficients for these crystals. The use of a.c. methods to obtain high precision in polarization measurements is discussed.