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The University of Texas System

Ohannes Eknoyan

Henry F Taylor

In filters fabricated on a birefringent electrooptic substrate ( ), a tunable electrooptic add-drop filter apparatus ( ) includes two input single mode waveguides ( ) and a first beam splitter ( ) connected to the waveguides ( ). A polarization converter ( ) is connected to the waveguides ( ) after the first beam splitter ( ) wherein each polarization converter ( ) includes more than one set of spaced apart, spatially periodic, strain-inducing pads ( ). Electrode(s) ( ) are provided in proximity to the polarization converter ( ). A second beam splitter ( ) is provided connected to the waveguides ( ) after the polarization converter ( ). Finally, two output single mode waveguides ( ) are connected to the second beam splitter ( ).

Tunable electrooptic add-drop filter apparatus and method

A two-port guided wave tunable filter in a birefringent electrooptic and/or acoustooptic substrate material includes two 3-port, symmetric Y-branch beam splitters connected by two waveguide sections in which phase-matched polarization coupling occurs, with an input port and an output port. The optical path difference between the beam splitters is half an optical wavelength, and the polarization coupling regions between the beam splitters are relatively displaced by an odd integral multiple of half the spatial period of the perturbation responsible for the coupling. In one embodiment, an electrooptic tunable filter, the polarization coupling in the waveguides is caused by a spatially periodic strain-inducing film and tuning results from an applied electric field. In another embodiment, an acoustooptic tunable filter, polarization coupling results from a surface acoustic wave and tuning is accomplished by changing the acoustic frequency. Alternatively, four port electrooptic and acoustooptic tunable filters are formed by replacing the 3-port beam splitters with 4-port directional couplers, where in each of the directional couplers the splitting ratio for TE input polarization plus the splitting ratio for TM input polarization is substantially equal to one.

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College Station, TX, United States of America

Ohannes Eknoyan