Refractive index profile measurement techniques by reflectivity profiling: vidicon imaging, beam scanning, and sample scanning

Abstract

The refractive index profiles of titanium-diffused LiNbO(3) planar and channel waveguides are determined directly by measuring the reflectivity of angular polished surfaces. Three measurement techniques are described and compared: (1) large area illumination of the angular polished waveguide and imaging of the reflected light to a vidicon, (2) scanning of a focused beam across the sample, and (3) scanning of the sample under a focused beam. Preference is given to the last method which provides an accuracy of Deltan/n = 10(-4) with a local resolution of the index profile of <0.1 microm in depth and ~1 microm in width.