A method for measuring the mode-index ratio n of two regions of a planar waveguide with an accuracy of better than 2 in 105 is presented. Simple and reliable techniques were utilized to produce two contiguous waveguides, with different refractive indices, on a common substrate. The two waveguiding regions were fabricated both in LiNbO3 and in BK-7 glass by using titanium indiffusion followed by a proton-exchange (TIPE) process and a two-step Ag+/Na+ ion-exchange technique, respectively. The measured mode-index ratios obtained by our method agreed well with values obtained with the conventional prism-coupling technique.
© 1992 Optical Society of America
George S. Agapiou and Carl M. Verber, "Method for measuring the mode-index ratio of two regions in a planar waveguide," Appl. Opt. 31, 1257-1260 (1992)