The refractive index profiles of titanium-diffused LiNbO3 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 Δn/n = 10−4 with a local resolution of the index profile of <0.1 μm in depth and ~1 μm in width.
© 1990 Optical Society of America.
Jochen Steffen, Andreas Neyer, Edgar Voges, and Norbert Hecking, "Refractive index profile measurement techniques by reflectivity profiling: vidicon imaging, beam scanning, and sample scanning," Appl. Opt. 29, 4468-4472 (1990)