Photonic crystal superlattices in electro-optic slab waveguides

摘要

A tunable two-dimensional photonic crystal (2D-PC) design is proposed in which the background medium is composed of an electro-optic material such as lead lanthanum zirconate titanate. The lattice structure is based upon the 2D triangular lattice of holes in a dielectric background; however, holes of two different radii are used and arranged in such a way to create a superlattice structure. The optical properties of this structure are modified by applying an electrical bias so that the dielectric constant is changed from 6.2 to 6.75. Numerical calculations show the band structure of the superlattice is highly modified in comparison to the triangular lattice. In particular, the first full photonic band gap decreases in width and band splitting occurs at high symmetry points of the lattice. From the analysis of the equifrequency contours resulting from the dispersion surface, the angle of refraction of an incident beam was calculated. By changing the biasing conditions on the structure, the refracted beam can be tuned > 55° at an incident angle of 14°. This represents an increase of functionality over the regular triangular lattice which is tunable over 5 — 10° for a 1.36 change in dielectric constant.