Gap maps and intrinsic diffraction losses in one-dimensional photonic crystal slabs

TL;DR

This paper provides a theoretical analysis of photonic band structures, gap maps, and intrinsic diffraction losses in one-dimensional photonic crystal slabs, highlighting the dependence on structural parameters and polarization.

Contribution

It introduces a method combining guided mode expansion and perturbation theory to calculate photonic bands and losses in 1D photonic crystal slabs with high refractive index contrast.

Findings

Photonic band gaps depend strongly on core thickness and polarization.

Radiative losses vary nontrivially with structure parameters and mode properties.

Gaps for TE and TM modes often do not overlap.

Abstract

A theoretical study of photonic bands for one-dimensional (1D) lattices embedded in planar waveguides with strong refractive index contrast is presented. The approach relies on expanding the electromagnetic field on the basis of guided modes of an effective waveguide, and on treating the coupling to radiative modes by perturbation theory. Photonic mode dispersion, gap maps, and intrinsic diffraction losses of quasi-guided modes are calculated for the case of self-standing membranes as well as for Silicon-on-Insulator structures. Photonic band gaps in a waveguide are found to depend strongly on the core thickness and on polarization, so that the gaps for transverse electric and transverse magnetic modes most often do not overlap. Radiative losses of quasi-guided modes above the light line depend in a nontrivial way on structure parameters, mode index and wavevector. The results of this study may be useful for the design of integrated 1D photonic structures with low radiative losses.