Property investigation of photorefractive crystal using transport of intensity technique

Abstract

The purpose of the study was to investigate of photorefractive Bragg gratings within iron-doped lithium niobate crystals with the size of seven cubic millimeters. Polarized helium-neon laser beams with a wavelength of 633 nm have been separated into two beams and then incident on the crystal with different angles. Both beams were used for writing the grating in the crystal with the incident angle (2θ). and the angle between both beams has been founded the highest efficiency of diffraction beams. Then the transport of intensity method was used to explore the grating characteristics by using the opposite polarization of the writing helium-neon laser beam. Images in focus and defocus before and after the focal plane was recorded on a Canon digital camera. Then, these images were used to process by computer programing based on the principle of transport of intensity equation. By using this technique, the grating characteristics in lithium niobate crystals would be investigated. © 2020 SPIE.