| 摘要 |
PURPOSE:To detect beams in divided form by utilizing the difference of the positions of cut-off according to wavelength in the waveguide of a single mode, a section thereof shrinks in the direction of propagation of beams, by disposing a layer with narrow forbidden band width to the upper section or outside of the waveguide. CONSTITUTION:N-InGaAsP 2, the ratio of composition of Ga and As therein is reduced and loss thereof is sufficiently low to waveguide beams on an N-InP substrate 1, is formed onto the substrate, N-InP 3 is buried, and the photo-detecting layer 4 of N-InGaAs is stacked. Even the thickest section of the layer 2 satisfies the condition of the single mode. When beams containing wavelength lambda1, lambda2 are propagated from the thicker side of the layer 2, lambda1 and lambda2 are cut off at different positions with the reduction of thickness. The lowermost-dimensional mode also has practical effective cut-off frequency in an asymmetric slab waveguide or a three-dimensional waveguide. When P layers 6, 6' and positive electrode 7, 7' are formed to the layer 4 on layer thickness corresponding to cut- off through the windows of an insulating film 5 and a negative electrode 8 in common with the layer 4 is shaped, beams can be divided and detected, a diffraction grating is unnecessitated and manufacture is easy. |
