| 摘要 |
<p>PURPOSE:To realize the optical device which has low loss, low reflection and low crosstalk characteristics, is easily connectable to an optical fiber and optically active element, and is microminiature and to reduce its cost by connecting an optical waveguide having a high refractive index difference and an optical fiber having a low refractive index difference by an optical fiber for mode matching. CONSTITUTION:The optical waveguide 3 having the specific refractive index difference DELTA1 has a structure formed by embedding a high-refractive index core 63 having an approximately rectangular shape in section into a clad layer 53 of a low refractive index formed on a substrate 7. The pigtail fiber consisting of fibers 1, 2 which are cascade connected and vary in the specific refractive index difference is connected to the input end of the optical waveguide 3. One end of the fiber 2 having the specific refractive index difference approximately equal to DELTA1 is connected to the optical waveguide and the optical fiber 1, of which the specific refractive index difference is DELTA2 (<DELTA1), is connected to the other end of the fiber 2. A dopant for controlling the refractive index in the core 62 of the fiber 2 is diffused by heating near the juncture, thereby a core diffused region 4 is formed. As a result, the mode field diameters at the connecting point 201 of the fibers 1, 2 are adjusted to the approximately equal diameters.</p> |
