| 摘要 |
PURPOSE:To obtain an optical semiconductor element which can detect only a part of light in an optical waveguide layer and propagate the other light through this layer, by providing a high-order diffraction grating which can take out the light satisfying a Bragg reflection condition of two or more orders and propagated through the optical waveguide layer, and a p-n junction having a forbidden band width smaller than the optical waveguide layer. CONSTITUTION:A diffraction grating 14 corresponding to a secondary Bragg reflection condition is formed on an n-InP buffer layer, subsequently an n-InGaAsP optical waveguide layer 13. an n-InP clad layer 15 and an n<-> InGaAs optical absorption layer 16 are made to grow, a P-type region 17 is formed in a part of the optical absorption layer 16, and lastly a p electrode 18 and an n electrode 19 are formed. Since the optical absorption layer 16 has a P-n junction having a smaller forbidden band width than the optical waveguide layer 13 and is prepared of crystals having low carrier density, a depletion layer is expanded into the optical absorption layer 16 by reverse bias, and a part of light 20 propagated through the optical waveguide layer 13 is reflected in the direction not being parallel to the optical waveguide layer 13 by the diffraction grating 14, absorbed in the depletion layer of the optical absorption layer 16 and taken outside as an electric current. |
