Programmable Polarization-Independent Electrooptic Matched Bandpass Filter Utilizing Symmetric Branch Beam Splitters in Ti : LiNbO3

A polarization-independent two-port guided-wave electrooptically tunable bandpass filter with programmable spectral output in Ti: LiNbO₃ at the 1530-nm wavelength regime is presented. The design utilizes an asymmetric interferometer with interdigital electrode sets on its arms that allow the control of the polarization coupling coefficient on individual sets electronically for the simultaneous tuning and apodization of the spectral output. The operation of a device with 16 electrode sets is demonstrated, and good agreement with theoretical predictions is obtained. The number of selectable channels depends on the number of electrode sets. A 3-dB bandwidth of ~1 nm and a tuning range of 10 nm are measured. Nearest sidelobes ~20 dB below the main peak are realized. Fiber-to-fiber insertion loss is < 4.6 dB. The maximum voltage that is used for selecting channels at plusmn4.8 nm away from the center channel wavelength with apodization is 17.3 V.