| 摘要 |
PURPOSE:To improve the efficiency of diffraction without the increase of radiation loss by forming a recessed part for forming a grating in an optical waveguide and embedding the recessed part by a substance having a refractive index different from that of the recessed part. CONSTITUTION:An optical waveguide 2 is formed on a substrate 1 and parts 11 having a different refractive index are periodically formed in the optical waveguide 2. In the grating element, the distribution of an electric field in the optical waveguide part coincides with that of the parts 11 having the different refractive index also at respective centers and a remarkable difference is not generated between the optical waveguide 2 and the parts 11, so that radiation loss at the border between them can be almost neglected. Since the efficiency of diffraction can be increased by increasing the difference of refractive indexes between a substance constituting the optical waveguide and a substance embedded in the grating part, the efficiency of diffraction can be improved without increasing the radiation loss. |
