Band gap analysis and holographic design of 3-fold hybrid triangular photonic crystals of irregular columns with large full band gaps

Abstract

A new kind of two-dimensional 3-fold photonic crystal (PhC) conforming to the hybrid triangular configuration formed by holographic lithography (HL) is proposed, and the relation between its photonic band gap properties and its specific holographic design is systematically investigated. This structure can be conveniently produced using a multiple-beam dual-exposure technique. In addition to its high complete relative band gap, namely a 22.1% gap/mid-gap ratio for the dielectric constant contrast 13.6:1 in optimized design, it has very large tolerance on the system parameters and fabrication conditions and requires a quite low dielectric constant contrast to open complete band gaps. This study reveals that the band gaps of PhCs made by HL may be widened by introducing irregularity in the columns and lowering the symmetry of the structure. Light propagation in this structure is also simulated. The results show that a transverse electric (TE) or transverse magnetic (TM) band gap can be obtained in this structure even with a very low dielectric constant contrast (e.g. 2.56:1), and this fact makes it very suitable for low-index waveguides.