Multiband polaritonic filter made of piezoelectric superlattices

The polaritonic band structures and transmission spectra of piezoelectric-modulated superlattices are investigated for a variety of supercell configurations. In the absence of a defect layer a polaritonic-like band gap exists and relative band gap can reach as large as 19% for superlattices made of LiNbO₃. In the presence of a defect layer, the positions and number of defect modes can be controlled directly by the number of domains in a supercell, the widths of defect modes are determined by layer thickness difference between defect domain and the periodic domain. Such uniformly distributed in-gap modes make them ideal candidates for the potential multiband filters.