Transmission spectrum reconfiguration in long-period gratings electrically induced in Pockels-type media with the help of a periodical electrode structure

The perturbation to the refractive index induced by a periodic electric field from structured electrodes is analyzed for a transverse-electric-transverse-electric and transverse-magnetic-transverse-magnetic copropagating mode coupling in a planar waveguide with electrooptic (EO) core/claddings. The analysis accounts for material birefringence and propagation mode losses due to light absorption by the electrodes. The results of the mode coupling are used to calculate the EO-induced transmission spectra with account for the mode attenuation. Two types of electrode materials, gold and indium-tin oxide, are analyzed in terms of their polarization-dependent-loss contributions. It is shown that the proposed design provides possibility of fully controlling the transmission spectrum through independent electric adjustment of the bandwidth, the attenuation level, and the resonance wavelength position. However, the filter performance is highly polarization sensitive. The proposed design can provide fully reconfigurable long-period grating filter only on the basis of a polarization-maintained platform.