Combined effects due to phase, intensity, and contrast in electrooptic modulation: application to ferroelectric materials

Abstract

The combination of phase, intensity, and contrast effects during electrooptic modulation is theoretically and experimentally 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 modulators 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.

Frequency and wavelength dependences of electro-optic coefficients in inorganic crystals

“…The λ/4-plate axis was also set at 45 degrees to the crystal axis, while the analyzer was oriented at an azimuthal angle β. The transfer function of the light intensity transmitted through the setup can be written as [4]:…”

Frequency dispersion of electro-optical properties over a wide range by means of time-response analysis

“…transfer function of the light intensity transmitted through the setup ͓Fig. 1͑b͔͒ can be written as 7 :…”

“…The so-called linear working point M 1 is associated with the modulation-depth method ͑MDM͒ and can be used to determine the EO coefficient as a function of frequency. Measuring the peak-to-peak amplitude i pp of the modulated signal at the point M 1 , one can obtain the EO coefficient directly from the following equation 7 :…”

Frequency and wavelength dependencies of the electro-optic coefficients in SBN:60 single crystal

“…1), the so-called linear working point corresponding to 50% transmission (I max − I min )/2 can be used to determine the unclamped EO coefficient as a function of frequency. Measuring the peak-to-peak amplitude i pp of the modulated signal at the point M 1 , the EO coefficient can be derived from the following equation [17]:…”