Electronically tunable optical filter using acoustic waves

Claim 1

An electronically tunable optical filter comprising: a substrate having a planar surface; a thin film optical waveguide mounted upon said planar surface of said substrate; an input light source optically coupled to said waveguide film at a first position for launching a light beam of a first waveguide mode into said waveguide in a preferred direction; a tunable electronic signal source capable of producing a variable frequency signal at its output; an acoustic transducer electronically connected to the output of said signal source and mounted on said waveguide film at a second position proximate said first position; said acoustic transducer propagating an acoustical wave at a selected frequency, determined by said signal source, on the surface of said waveguide film along said preferred direction to convert the mode of said light beam to a second waveguide mode having a different number of points where the electric field is zero than does said first waveguide mode of said light beam, when the selected frequency and phase of said acoustical wave matches the frequency and phase of said light beam; a metallic plate mounted on said waveguide film at a third position along said preferred direction proximate said acoustic transducer for selectively blocking said first waveguide mode component of said light beam and passing said second waveguide mode component.