| 摘要 |
PROBLEM TO BE SOLVED: To make an element size smaller than heretofore and then to improve productivity and yield. SOLUTION: The sectional plane of a first waveguide 21 is set to about 8×8μm for transmitting light in a single mode. A taper part 22 succeeding to the first waveguide 21 shifts the light propagated through the first waveguide 21 to a multi-mode. A straight line part 23 succeeding to the wide width end part of the taper part 22 brings the wave front of the light shifted to the multi- mode from a spherical shape close to a planar shape. On the outgoing end side of the straight line part 13, a second waveguide 24 and a third waveguide 25 in a single mode are arranged so that the incident end surface is opposed to the outgoing end surface of the straight line part 23 through a minute gap. These waveguides 24, 25 are formed so as to be away from each other along a radius R of curvature of <=50mm, e.g. 20mm accordingly to be away from the incident end. The width and the length of the straight line part 23 are set in the optimum value that a connection loss between the straight line part 23 and the second and the third waveguides 24, 25 becomes minimum, e.g. 15μm and 100μm. |
