Electric field profile effects on photorefractive grating formation In bismuth silicon oxide

Abstract

Bismuth silicon oxide (Bi12SiO20) crystals can be utilized in the transverse electrooptic configuration for several optical device applications, including spatial light modulation (such as the photorefractive incoherent-to-coherent optical converter), optical signal amplification, and holographic optical interconnections. In such applications, a uniform electric field profile within the bulk crystal is highly desirable. However, in conditions of uniform illumination, it has been shown by the technique of transverse electrooptic imaging1 that significant charge accumulation near the electrodes results in a spatially nonuniform and time varying internal electric field.2 This technique has been extended herein to examine the field profile during the process of photorefractive grating formation by simultaneously measuring both the time-dependent internal electric field and the diffraction efficiency. Numerous experimental conditions were found to affect the results, including the sequencing of the applied voltage and grating writing beams, optical shadowing of the electrodes, the grating beam intensities, the electric field probe beam intensity, and the application of dc as opposed to ac electric fields. Local field reductions of up to 75% and oscillations in the mean value of the diffraction efficiency of 50% have been observed. The implications of these results for device performance are discussed.