Ferroelectric material, two-color holographic recording medium, and wavelength selection filter

摘要

A ferroelectric material in which the refractive index change can be induced by irradiation with light at two different wavelengths without performing a reduction treatment or doping impurities. The ferroelectric material of the invention in which the refractive index change is induced by irradiation with light at two different wavelengths is a lithium tantalate single crystal with the composition of Li₂O/(Li₂OTa₂O₅)0.4966 to 0.4995. Preferably, the ferroelectric material is a lithium tantalate single crystal with the composition of Li₂O/(Li₂OTa₂O₅)0.4974 to 0.4989. Preferably, the infrared absorption coefficient in the OH stretching mode falls within a range of 0 cm¹ to 0.15 cm¹ (0 cm¹ and 0.15 cm¹ are included in the range).