Optical inhomogeneity testing in large boules of uniaxial crystals by imaging conoscope

A computer-controlled imaging conoscope has been used for investigation of optical homogeneity in large boules of doped and undoped uniaxial crystals. Two birefringence inhomogeneity maps acquired for two perpendicular directions in the crystal [z-optical axis, and perpendicular to it (x or y direction), respectively] are satisfactory to conclude whether the boule is (or not) suitable for optical applications. Such investigations are indispensable in factory check of crystalline boules grown by different techniques, and are also potential in scientific researches. An example for an undoped LiNbO3 is presented for illustrating the method.