Secondary-ion mass spectroscopy characterization of proton-exchanged LiNbO_3 waveguides

Abstract

Channel waveguides fabricated in LiNbO(3) substrates by proton exchange in melts of benzoic acid have been analyzed by secondary-ion mass spectroscopy. The depletion of lithium from the waveguide regions, owing to proton exchange, was found to depend to a strong degree on guide width as well as diffusion time for common (249 degrees C) ion-exchange temperatures. In addition to a reduced depth, a guide formed by diffusing through a 6-microm-wide metallic aperture for 10 min suffered 60% less lithium depletion near its surface than one formed by diffusing through a 12-microm aperture for the same time. Optical measurements were performed at 1060 and 1320 nm in guides of width ranging from 5 to 10 microm.