Electrooptic matched filter controlled by independent voltages applied to multiple sets of electrodes
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Analysis and experimental results on a polarization independent electrooptic matched filter (EMF) with a center wavelength of 1.53 μm are reported. The EMF utilizes electrooptic phase-matched TE↔TM conversion in a Ti-diffused waveguide on a LiNbO3 substrate. The operation of the EMF to select an optical frequency channel is controlled by applying independent voltages to interdigital electrode sets cascaded along a single mode waveguide. The device is inherently polarization independent and has the potential for submicrosecond tuning. The number of selectable channels N is related to the number of electrode sets P by the formula / 2 1 N P = + . A matrix analysis is used to determine the TE↔TM conversion efficiency for the case that 8 P = and 5 N = . A driving circuit for the EMF was implemented using a digital-to-analog converter (DAC) array controlled from a personal computer (PC). Transmittance spectra of a filter produced in a LiNbO3 substrate are presented. A raised cosine weighting function applied along the 3.8 cm length of an EMF provides a sidelobe suppression level better than ??17 dB with a 1.0 nm 3-dB bandwidth.