Lithium niobate crystal wafer, process for the preparation of the same, and method for the evaluation thereof

摘要

A lithium niobate crystal wafer wherein the deviations of the maximum and minimum absorption coefficients of the wafer at a wavelength of 2.87 . mu.m from the average absorption coefficient thereof at that wavelength fall within the range of .+-.0.1 cm.sup.-1 exclusive of both borders; a process for the preparation of the same; and a method for the evaluation thereof.