PRODUCTION OF OPTICAL BRANCHING AND OPTICAL COUPLING CIRCUIT

摘要

PURPOSE:To make possible the adjustment of a optical branching ratio and optical coupling ratio with high accuracy and to obviate the exertion of an influence to the operating characteristic of the other optical circuits on the same substrate by executing an ion exchange in part of the optical branching circuit or optical coupling circuit after thermal diffusion of a metal and adjusting the refractive index distribution by ion exchange conditions. CONSTITUTION:The directional coupler type optical branching circuit 22 is first formed on the LiNbO3 substrate 1 by thermal diffusion of Ti. Guided light is thereafter excited by prism or end face coupling to a piece of the incident waveguides 21 of the Ti- diffused LiNbO3 directional coupler type optical branching circuit 22. The exit light to two exit waveguides 23 is prism-coupled and the branching ratio of the light is measured. The ion exchange is executed only in the part of the inter-waveguide space of the directional coupler to change the refractive index distribution of the directional coupler part in the case of the optical branching ratio is different from a prescribed value. The coupling length is adjusted and the optical branching ratio is adjusted by changing the coupling stage of the light wave between the two optical waveguides of the directional coupler in the above-mentioned manner.