Precision Flat Polishing Of Lithium Niobate

Abstract

Lithium niobate (LiNbO3) is a man-made, birefringent, electro-optically active crystal. We have used LiNbO3 in the fabrication of 75mm diameter, thin, solid Fabry-Perot etalons [1], and 50mm diameter birefringent plates for a Lyot filter. The tight tolerances on the transmitted wavefront for these components require that the material be of extremely high quality and that the surfaces be polished flat to λ/30, or better. Cutting and grinding of LiNbO3 presents no problems, since diamond cutting tools and conventional, loose, abrasive grinding can be used, but precision polishing requires special techniques.