Precise Method for Measuring the Quadratic Electro-Optic Effect in Noncentrosymmetric Crystals in the Presence of Natural Birefringence

Abstract

The application of the improved dynamic polarimetric method for the measurement of the quadratic electro-optic effect in NH4H2PO4 (ADP) crystal with the light beam propagating perpendicularly to its optical axis is presented. This technique can be applied in noncetrosymmetric crystals in the presence of natural birefringence even when the fast and slow rays diverge slightly, causing them to only partially interfere. The method allows for minor errors in cutting and orientation of the crystal samples, resulting in deviations from configurations in which the crystal symmetry vetoes the linear electro-optic effect. The occurring contribution of the linear effect, if it is not too large, not only does not exclude the measurement of the quadratic effect, but increases its accuracy. The method does not require any prior compensation for the natural birefringence. Its sensitivity allows for quadratic electro-optic effect measurements in ferroelectrics in temperatures significantly different from the phase transition temperature or in paraelectric crystals, for which this effect is relatively small.

Precise Measurements of the Quadratic Electro-Optic Effect in KH2PO4 Crystals Using a Sénarmont-Type System

“…In the case of a strongly birefringent sample, it is possible to use the temperature dependence of the linear birefringence to slowly move the working point along the I (Γ) characteristic [ 11 , 12 , 13 , 14 , 15 ]. In such a system, no additional retardation plate is needed (γ = 0°), and readings can be made at many points on the characteristic.…”

“…Since these changes can be achieved by rotating the analyzer, there is no need to exploit temperature changes, as in Refs. [11][12][13][14][15], which are more difficult to control. A more advanced and realistic mathematical model of the measurement system is also needed.…”