Combined effects due to phase, intensity and contrast in electrooptic modulation. Application to ferroelectric materials

TL;DR

This paper investigates how phase, intensity, and contrast effects interact during electrooptic modulation, affecting signal amplitude and transfer function, with experimental results on ferroelectric materials highlighting potential measurement errors.

Contribution

It provides a theoretical and experimental analysis of combined electrooptic effects, revealing their impact on modulation signals and measurement accuracy in ferroelectric materials.

Findings

Combined effects modify signal amplitude and transfer function.

Intensity modulation can shift or eliminate double-frequency points.

Experimental results in rubidium hydrogen selenate demonstrate these phenomena.

Abstract

The combination of phase, intensity, and contrast effects during electrooptic modulation is theoretically and exper- imentally investigated. One consequence of this combination is the modification of the amplitude of the single-frequency signals which are commonly used as working points for electrooptic mod- ulators and for the measurements of the electrooptic coefficients. Another consequence of direct intensity modulation is to shift the double-frequency points of the transfer function from the positions they normally occupy at the intensity extrema. They can even make them disappear if the direct intensity modulation is stronger than the phase modulation. Such phenomena are expected with any ferroelectric material in which a significant part of the incident light is deflected or scattered by domain walls or grain boundaries. They can lead to considerable mistakes in the determination of the electrooptic coefficients. Appropriate procedures to extract the different contributions are explained. Experimental results in rubidium hydrogen selenate are given, and consequences of the working of electrooptic modulators are discussed.