| 摘要 |
PURPOSE:To improve the ON/OFF ratio of light at an exit end and to decrease transmission signal errors in optical communication by providing light absorption layers having the band gap energy smaller than the band gap energy of a light guide layer on both outsides of clad layers. CONSTITUTION:This optical modulator has the multi-layered structure consisting of the clad layer 2 composed of a lattice matching III-V compd. semiconductor crystal, the light guide layer 3 and the clad layer 4 on an InP substrate 1. The light absorption layers having the band gap energy smaller than the band gap energy of the light guide layer 3 are provided on the outside of the respective clad layers 2, 4 sandwiching the light guide layer 3 having the multi-layered structure. Leak light which is a problem with the conventional semiconductor optical modulator of an optical waveguide type is thereby absorbed in the light absorption layers 7, by which the ON/OFF ratio at the exit end face is improved and the transmission errors in optical communication are decreased. The light of the energy larger than the band gap energy of the semiconductor is absorbed in the semiconductor. |
