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

Abstract

This paper presents precise measurements of the temperature dependencies of the quadratic electro-optic coefficients g1111−g1122 and ne3g3333−no3g1133 in KH2PO4 crystals. In addition to traditional electro-optic coefficients describing changes in the function of an applied electric field, intrinsic coefficients, defined in terms of induced polarization, are also considered. Both intrinsic coefficients decrease with increases in temperature, but the relative temperature changes are of different orders of magnitude: 10−4 and 10−3 K−1. A Sénarmont-type setup was used for the electro-optic measurements. To achieve the best accuracy, a new approach was developed, in which, instead of using only one specific point on the modulator’s transmission characteristic, the operating point is changed during the measurements.

Extremely Weak Electro-Optic Kerr Effect in Methyl Silicone Oils

“…A similar value of 7.63 × 10 −16 m V −2 at room temperature was reported only for 1,4-dioxane [25], which is not suitable for being used as an immersion liquid due to its hygroscopicity, volatility, and toxicity. Our values for the Kerr constant are also at least two orders of magnitude smaller than those typical for the solid crystals used in nonlinear optics, for example, K = 8.3 × 10 −14 m V −2 for the KDP crystal at room temperature and λ = 632.8 nm (calculated according to Formula ( 14) for 𝑔 − 𝑔 given in [16]). Therefore, we expect that the electro-optical measurements of solid crystals immersed in methyl…”

“…The intrinsic electro-optic coefficients f ijkl , i.e., the coefficients defined in terms of induced electric polarization, are widely used to describe solid crystals because they show less material dependence [12,13] and less temperature dependence [14,16,29] than the g ijkl coefficients. The intrinsic coefficients have probably not been applied to liquids.…”

“…Work [11] focuses on the fact that the Kerr coefficient at room temperature has slightly smaller values for oils of lower molecular mass, and no temperature or frequency dependences are measured within the study. In the case of solid crystals, the typical temperature dependencies of various electro-optical coefficients also decrease when the measurements do not involve phase transitions [12][13][14][15][16].…”