Patent ID: 6879737

Claim:
An optical waveguide device, comprising: a substrate; at least one optical waveguide disposed in said substrate; a first conductive thin film layer placed in the vicinity of or on the top of said optical waveguide in said substrate and containing an oxide; and a second conductive thin film layer laminated on said first thin film layer and exhibiting acidic or neutral characteristics in its oxidized condition, wherein said substrate is a lithium niobate (LiNbO 3 ) substrate, said optical waveguide comprises two Mach-Zehnder type directional couplers and a phase shifter between these directional couplers, and said phase shifter comprises an electrode of a structure containing said first thin film layer and said second thin film layer, whereby an electric field produced in response to a voltage applied to said electrode is given to said optical waveguide to function as a variable optical attenuator.