Abstract: A first terminal is connected to a second terminal by means of a first waveguide having a first radius of curvature. The first terminal (or second terminal) is connected to a third terminal by means of a second waveguide (or a third waveguide) having a second radius of curvature which is grater than the first radius of curvature. Incident light supplied from the first terminal is branched between the first waveguide and the second waveguide, and the light entering the first waveguide undergoes the greater attenuation since this waveguide has the smaller radius of curvature. Hence, the light component passing through the first waveguide has a difference in output from the component passing through the second waveguide that is sufficiently great to provide a large branching ratio.

Abstract: A laser beam generator has a pair of opposing mirrors. A reflecting surface of at least one of the opposing mirrors is constituted by a conical surface having a vertex angle of 90 degrees in order to tangentially polarize a laser beam. This conical surface is diverged toward the other opposing mirror at an angle of 45 degrees with respect to an optical axis from its vertex held alignment with the optical axis.