Patent ID: 7539378

Claim:
An optical waveguide divice, comprising: a first optical waveguide; a second optical waveguide formed from a material or in a structure different from that of said first optical waveguide and connected to said first optical waveguide; and a 1×1 multimode interference waveguide formed by increasing the widths of said first and second optical waveguides in proximity of a connection interface between said first and second optical waveguides; wherein said first optical waveguide is an active waveguide wherein absorption is high when current is not injected but gain can be generated when current is injected; and said second optical waveguide is a passive waveguide wherein absorption is low when no voltage is applied or no current is injected; said optical waveguide device further comprising: an active waveguide electrode for injecting current to said active waveguide; and a passive waveguide electrode for performing current injection or voltage application to said passive waveguide; said active waveguide electrode being formed also above said 1×1 multimode interference waveguide while said passive waveguide electrode is not formed above said 1×1 multimode interference waveguide.