Electro-optic tunable band-stop filters using piezoelectric superlattices

A novel band-stop filter, which uses the piezoelectric superlattices with the external direct-current (DC) electric fields, is presented. The forbidden band of the band-stop filter can be generated by the coupling between lattice vibration and electromagnetic waves and can be tuned continuously and reversibly by the DC electric field via the electro-optic effect. The band structures and transmission spectra of the band-stop filter show that the relative bandwidth of forbidden bands will be increased from 0.43% to 26.2% and their sizes can be broadened from 0.043 GHz to 2.98 GHz when the DC electric field is increased from 0 to 1.343×106 V/m. The bandwidth tunability by the electro-optic effect provides a good guidance for the filter design that works in broadband frequencies.