| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an optical waveguide element and its manufacturing method capable of coupling to an optical fiber with high coupling efficiency. SOLUTION: A buffer layer 2 formed on a single crystal substrate 1 and an optical waveguide layer 3 formed on the buffer layer 2 are provided, a recessed part is formed in the buffer layer 2, the optical waveguide layer 3 is provided so as to fit into the recessed part and whereby a channel optical waveguide 4 is formed. Clad layers 6, which have refractive index smaller than that of the optical waveguide layer 3 and whose thicknesses are increased in a taper toward the end surface, are provided on the upper surfaces of the light incident side and the light exiting side of the optical waveguide layer 3 with the same width as that of the single crystal substrate 1. A mode field diameter is enlarged and a coupling loss between the optical fiber and the optical waveguide element is largely reduced by providing the clad layers 6 in such a manner. Also, the mode field diameter is gradually decreased and an optical propagation loss is reduced by increasing the thickness of the clad layers 6 in a taper toward the end surface.</p> |
