To suppress higher order mode propagation, to suppress waveguide loss and to increase optical output when the light from a light emitting element of an end face light transmission type is subjected to end face coupling at the incident end face of an optical waveguide.

The core end face portion at the incident end face of the optical waveguide WG1 is formed as a planoconvex surface part 4. While a laser beam emitted from the active layer 11 of the light emitting element 10 has spreading components to a certain extent in a horizontal direction and a vertical direction. The horizontal components among these components are converged by the lens effect of the planoconvex surface part 4 and are eventually propagated in the state of a small incident angle to parallel light beams or at the boundary between a core 3 and a clad 2, i.e., lower order mode propagation is eventually made possible. The planoconvex surface part 4 may be formed by anisotropic etching via an etching mask having a similar edge profile. When the core end face is nearly a spherical surface, the vertical components in addition to the horizontal components are converged as well.