Research on refractive index changes of CSBN crystals under external electric field based on Michelson interferometer

Abstract

The refractive index changes in CSBN50 crystal under external electric field are experimentally investigated based on Michelson interferometer and digital image process. An expanded and collimated beam with a diameter of about 2.0 cm from a He–Ne laser with 632.8 nm wavelength is used to irradiate the crystal sample, and simultaneously, an external direct electric field is applied along the crystal c-axis with different amplitude. Because the incident light intensity is very low (about 1.5 mW), the experimental results indicate that there are almost no index changes to be observed without the presence of external electric field. When the crystal is irradiated by laser beam on the condition of applying external electric field along the c-axis, both the e-light index and o-light index are obviously changed. The changed values increase with the increasing external electric field and its signs can be controlled by the orientation of the external electric field.