| 摘要 |
PURPOSE:To decrease a coupling loss and waveguide loss by forming a waveguide layer large in one section (spot size) and small in the other and nearly uniformizing the specific refractive index difference over the entire length thereof. CONSTITUTION:A 1st adhesion layer 11 consisting of a fixed width part 12 of a specified width which is adhered with a material for increasing the refractive index and a varying width part 13 having a gradually increasing width is formed on a waveguide substrate 10. This 1st adhesion layer 11 is diffused into the waveguide substrate to form a tentative waveguide layer 14 and thereafter, the material to lower the refractive index is adhered thereto to form the 2nd adhesion layer 15. The non-adhesion part 16 of the 2nd adhesion layer 15 is so formed that the layer has the same axis as the axis of the 1st adhesion layer 11, has the same width as the max. width of the varying width layer 13 and has the pattern longitudinally reverse from the varying width part 13 in the varying width part 13. The waveguide layer 17 is formed large in one section (spot size) and small in the other in this way and, therefore, the coupling loss decreases if the larger section is used a the coupling part to an optical fiber. The waveguide loss in case of curving decreases in the smaller section. |
