Abstract:
An optical coupler includes a tapered portion and a grating portion. The tapered portion has a width in a second direction increasing along a first direction substantially perpendicular to the second direction. The tapered portion includes first and second ends opposed to each other in the first direction. The first end has a first width, and the second end has a second width greater than the first width. The grating portion is connected to the second end of the tapered portion, and has a curvature radius greater than a distance to the first end of the tapered portion.