Method for making low-stress large-volume not-(111)-oriented crystals with reduced stress birefringence and more uniform refractive index and crystals made thereby

摘要

A method is described for making an especially not-(111)-oriented low-stress large-volume crystal having a glide plane with reduced stress birefringence and more uniform refractive index. The method includes growing and tempering the crystal while heating and/or cooling to form a temperature gradient in order to relax stresses arising along the glide plane. During the tempering the heating and/or cooling occurs by heat transfer in a heat transfer direction and the heat transfer direction or temperature gradient is oriented at an angle of from 5° to 90° to the glide plane. Crystals with a uniform refractive index with variations of less than 0.025x10^-6 (RMS value) are produced by the method.