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