Mode-field transforming planar optical waveguide device and manufacturing method

摘要

A mode-field transforming planar optical waveguide device includes an under cladding (14), a first core (16), a second core (18), and an over cladding (15). The under cladding (14) has a flat shape as a whole. The first core (16) has a quadrangular cross section and is placed on the under cladding (14). The second core (18) is placed on a tapered end portion (17) of the first core (16). The over cladding (15) is placed in a region including the tapered end portion (17) of the first core (16) and the second core (18). The under cladding (14) and the first core (16) placed thereon constitute a first optical waveguide (10). The under cladding (14), the tapered end portion (17) of the first core (16) placed on the under cladding (14), the second core (18) placed thereon, and the over cladding (15) placed on and around the second core (18) constitute a mode field size conversion portion (11). The under cladding (14), the second core (18), and the over cladding (15) constitute a second optical waveguide (12). The first core (16) is made of silicon. The first (16) and second (18) cores differ in cross-sectional shape. A manufacturing method for the optical module is also disclosed.