Method of optical axis determination in crystals by use of light depolarization measurements

The paper presents a new method of optical axis determination in uniaxial crystals by use of light depolarization measurements. Partially temporary coherent light may be depolarized during propagation through birefringent media. Degree of polarization fading depends on coherency of light, birefringence of the medium as well as direction of the optical axis of the medium. Hence a light beam passing through the crystal for three perpendicular directions may change degree of polarization in different way and it allows to calculate azimuth of the optical axis. In the test experiments we applied a laser diode lasing at 670 nm and a cube made with lithium niobate (&Dgr;n= 0.086, 1=5mm) as a tested crystal. Degree of polarization of light outgoing from the crystal was measured by use of high quality Glann-Thomson polarizer and a quarter wave plate. The optical axis orientation determined in the crystal was in good agreement with axis azimuth found by use a standard microscopic method.