| 摘要 |
PURPOSE:To obtain an optical branching filter which performs wavelength dispersion with a plane diffraction grating or the like by providing a refractive index distribution to a high refractive index layer of a slab waveguide to create lens effect thereby converging light. CONSTITUTION:The rays propagating in a slab wavelength 4 are reflected in a perpendicular direction by the boundary surface of a high refractive index layer 2 and a low refractive index layer 3, and advances zigzag in the layer 2. On the other hand, in a horizontal direction, they are roughly parallel rays where they advance up to a plane diffraction grating 7 according to the refractive index distribution of the layer 2. Receiving wavelength dispersion by the grating 7, they are reflected and converged at the angles varying for each wavelength, and form focuses on the end faces of output optical fibers 61-6n. As a result, the rays of respectively different wavelengths of the fibers 61-6n couple and operate as optical branching filters. With such constitution, the optical branching filter is obtained with the plane diffraction grating or the like. |
