| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical branching element and an optical semiconductor integrated circuit device having a multimode interference waveguide, in which distribution of distortion caused by an insulating film is suppressed to decrease deviation.SOLUTION: A layered structure of a semiconductor clad layer, a semiconductor waveguide core layer and a semiconductor clad layer is prepared, and at least the underside semiconductor clad layer is partially etched to form a mesa type multimode interference waveguide. An upper surface of the obtained waveguide is covered with a first insulating film while a side surface is covered with a second insulating film having a coefficient of thermal expansion in an opposite magnitude relation with the coefficients of thermal expansion of the semiconductor clad layer and of the semiconductor waveguide core layer, to the magnitude relation between the first insulating film and the above layers. |
