Process for making multifunction integrated optics chips having high

Abstract

Methods for making proton-exchanged, multi-function integrated optics chips, preferably chips based on the stable, rhombohedral lithium niobate structure, and having substantially diffused protons, while being substantially free of microcracking and of internal stresses that can result in microcracking, and yet having optimally high electro-optic coefficients, include the steps of: forming a multi-function integrated optics chip substrate from a substrate such as lithium niobate; affixing a removable mask or mask pattern to at least one surface of the chip to form one or more proton-exchanged patterns of desired size and shape at the surface of the chip; treating the masked chip with a proton-exchanging acid such as benzoic acid at a temperature and for a time sufficient to cause substantial proton exchange at and below the unmasked surface of the chip, but for a time insufficient to create any microcracking or internal stresses that lead to microcracking in the chip; removing the mask or mask pattern from the chip; and thermally annealing the chip, in an oxygen-containing environment, at a temperature and for a time sufficient to diffuse the hydrogen ions at and near the surface of the chip substantially below its surface, at a temperature and for a time sufficient to optimize the polarization extinction ratio of the chip, and for a time and at a temperature sufficient to restore and to optimize the electro-optic coefficient and to reduce light and propagation losses in the chip.