JPS6418112A - Optical branching and coupling circuit - Google Patents

Abstract

PURPOSE:To increase an angle of branching and to enable size reduction and integration by arranging a low-refractive-index layer whose thickness and refracting index are specified at the intersection part of two optical waveguides at an angle where the layer bisects the angle of the intersection and the section crosses the optical paths of light signals in optical waveguides. CONSTITUTION:Optical waveguides 5a and 5b, and 6a and 6b consisting of cores 3 and clads 4 are arranged crossing each other, and the low-refractive-index layer 8 is arranged at the intersection part 7 at the angle where the layer bisects the angle of the intersection and its section crosses at least part of the optical paths of light signals. The thickness of the layer 8 is nearly equal to or smaller than the wavelength of signal light in a medium and the refractive index is lower than those of the optical waveguides 5a and 5b, and 6a and 6b. Then 1st light input 9 inputted from the optical waveguide 5a is reflected partially by the low-refractive-index layer 8 and propagated to the optical waveguide 6b as a 2nd light output 10. The thickness (d) and refractive index of the low-refractive-index layer 8, on the other hand, are selected properly and then the 1st light input 9 is branched to the optical branch waveguides 5b and 6b. Consequently, the angle of branching is made large and the size reduction and integration are enabled.