Notes on Evanescent Wave Bragg-Reflection Waveguides

TL;DR

This paper extends the theory of Bragg reflection waveguides by incorporating air gaps, offering a simplified and more flexible design approach, with analytical estimates of mode indices using Marcatili's method.

Contribution

It introduces an analytical extension of BRW theory with air gaps and applies Marcatili's method for faster mode index estimation.

Findings

Phase-matched designs identified but lack significant advantages

Analytical approach significantly speeds up mode index estimation

Initial results show mixed outcomes for the new design scheme

Abstract

We investigate an extended version of the Bragg reflection waveguide (BRW) with air gaps as one of the layers. This design has the potential of drastically simplifying the epitaxial structure for integrated nonlinear optical elements at the expense of more complicated structuring. This approach would afford much more flexibility for designing and varying BRW structures. Here, we discuss an extension of the established theory for BRW slabs and report our results of applying Marcatili's method for rectangular waveguides to the BRW case. With this analytic approach we can estimate the effective index of the modes orders of magnitudes faster than with full numerical techniques such as finite-difference time-domain (FDTD) or finite elements. Initial results are mixed; while phase-matched designs have been found, they currently have no significant advantage over other schemes.