| 摘要 |
PURPOSE:To obtain the small-sized and low-loss directional coupler by forming the lower clad layer of the noncoupling part of an S-shaped optical waveguide in a ridge shape. CONSTITUTION:An upper clad layer 31, a core layer 21, and the lower clad layer 11 are etched individually by using two kinds of masks, i.e. 1st mask having a specific Y-branch part shape and 2nd mask which is larger than the 1st one. Then the 1st mask is used for the upper clad layer 31, and the core layer 21 is etched with an anisotropic etchant enabling selective etching. Two optical waveguides have upper clad layers 31, core layers 21, and lower clad layers 11 formed in a ridge shape at the noncoupling part, namely, a mutual branching part and the upper clad layers 31 are formed in the ridge shape having the specific branch shape at the Y branch part. Consequently, the zero- gap optical directional optical coupler which has small mode conversion loss is obtained. |
