Mark J. Gunning

Interferometric investigation of the quadratic electro-optic effect in KDP

Abstract A Michelson interferometer was used to study the quadratic electro-optic effect in KDP. The values for three individual coefficients, determined for the first time by interferometric means, are g 1111 =−4.0, g 3311 =−0.6, and g 2211 =0.2 (in units of 10 −20 m 2 V −2 ). The lattice contribution, which forms the dominant part of g 1111 and g 3311 , is discussed in terms of the bond polarizability model. The results provide further evidence that the third-order bond polarizability is of comparable magnitude for crystals of different structure and composition.

The quadratic electrooptic effect and estimation of antipolarization in ADP

Abstract The quadratic electrooptic coefficients g 1111 and g 2211 have been measured interferometrically in ADP at room temperature. In addition, ‖g 1111-g 2211‖ was determined by a dynamic polarimetric technique at the same temperature. Both experiments yield values for g 1111-g 2211 at 21 C and λ = 0.633 μm with an average of (−5.9±0.5)×10−20 m2/V2. An estimate is made, using this value, of the spontaneous antipolarization appearing in the antiferroelectric phase of ADP. This antipolarization is found to be comparable in magnitude with the spontaneous polarizations observed in ferroelectrics belonging to the KDP family of crystals.

Algebraic determination of the principal refractive indices and axes in the electro-optic effect

A systematic algebraic approach is presented as a preferred alternative to an iterative numerical method for deriving expressions for the principal refractive indices and dielectric axes of a nonmagnetic crystal in a uniform electric field. This approach is applicable for an arbitrary field and for any symmetry point group. The results, to the chosen order in the field, are expressed algebraically in terms of measurable crystal tensors. Illustrations are given of the linear electro-optic effect for the point groups 4?3m, 3m, 4?2m, and 1 and of the quadratic effect in 4?2m. The latter serves to highlight a shortcoming in the numerical approach. Comparisons are drawn with numerical results published previously.

Physical implications of the use of primitive and traceless electric quadrupole moments

Theories of certain electromagnetic effects, such as chiral phenomena in fluids and crystals and gyrotropic birefringence in antiferromagnetic crystals, require the inclusion of electric quadrupole contributions for a full description of the effect. In a number of these theories the electric quadrupole moment is defined to be traceless, as indeed is the general practice for such moments in nuclear physics. It is shown that, when the traceless quadrupole moment is used in the derivation of the wave equation that describes light propagation through an optically active uniaxial medium, this equation and properties derived from it, in particular refractive index, depend in general on the arbitrary origin used to specify the quadrupole moment. This is physically unacceptable for an observable property of a substance. By contrast, this defect does not occur if the definition of the primitive quadrupole moment is adopted, namely Σqr α r β.

Interferometric measurements of electrostrictive coefficients of KDP and ADP in transmission

Abstract Results of an investigation of the electrostrictive effect in KDP and ADP crystals are presented. The measurements at RT of the sign and magnitude of some electrostrictive coefficients were made in transmission with a stabilized Michelson interferometer by placing the crystals in two media of different refractive index. The results obtained are of the order of 10−20 m2V−2. These values are much smaller than those measured previously at RT by employing a static electric field. However, our results are comparable in magnitude with others obtained at low temperatures and with those found by using dynamic fields.

The Quadratic Electrooptic Coefficient g1111 — g2211 of DKDP Crystals

Results of measurements of the quadratic electrooptic coefficient g1111-g2211 in DKDP crystals are presented. Its absolute value is found to be 3.40 × 10 -20 m 2 /V 2 , i.e. two orders of magnitude smaller than the values reported earlier. The applicability of the assumption of a rough constancy of intrinsic electrooptic coefficients in KDP-type crystals is discussed.