Modified annular photonic crystals with enhanced dispersion relations: Polarization insensitive self-collimation and nanophotonic wire waveguide designs

摘要

A novel (to our best knowledge) type of photonic crystal (PC) structure called modified annular PC (MAPC) that is composed of dielectric rods with off-centered air holes is thoroughly studied. The plane wave expansion method is applied for spectral analysis. A complete photonic bandgap region with a considerable value of gap width Δω/ω = 7.06% is achieved by optimizing the structural parameters of the proposed periodic medium. By introducing geometrical asymmetry to the primitive cell of PC, we engineer the dispersion properties of the proposed photonic structure such that conventional equifrequency contours for the second band can be transformed into tilted rectangular shapes. This feature enables us to demonstrate the polarization insensitive tilted self-collimation effect. A hybrid structure composed of dielectric nanowire and MAPCs is offered to obtain a high degree of polarization independent guiding of light. The two-dimensional finite-difference time-domain method is carried out to verify the light guiding efficiencies. Polarization insensitive optical functionalities achieved by MAPC structure can be deployed in integrated optical circuits.