Patent ID: 7343056

Claim:
An acoustooptic filter comprising: an acoustooptic substrate; an optical waveguide disposed along a surface of the acoustooptic substrate; an interdigital electrode disposed on the acoustooptic substrate, the interdigital electrode exciting a surface acoustic wave; and a surface wave waveguide for the surface wave excited by the interdigital electrode extending in substantially a same direction as the optical waveguide and coupled to the surface acoustic wave excited by the interdigital electrode such that the mode of the light guided to the optical waveguide is converted by the surface acoustic wave, the surface wave waveguide including a phase match condition changer that changes a phase match condition of the surface acoustic wave and the light guided to the optical waveguide at a mutual action area by about 0.235% or more from a state in which phases are matched, the mutual action area being an area where the surface acoustic wave and the light guided to the optical waveguide act upon each other.