Efficient side-coupling to photonic crystal nanobeam cavities via state-space overlap

TL;DR

This paper provides design guidelines for efficiently coupling photonic crystal nanobeam cavities to bus waveguides by optimizing mode overlap in physical and k-space, enabling practical on-chip photonic devices.

Contribution

It introduces a novel approach to optimize side-coupling in PCN cavities through mode overlap adjustments in both physical and k-space.

Findings

Optimal configurations operate at a non-zero k-vector offset.

Design guidelines improve coupling efficiency for low order resonances.

Facilitates practical implementation of multiplexed photonic devices.

Abstract

We present design guidelines for realizing side-coupled photonic crystal nanobeam (PCN) cavities with efficient coupling to low order resonances through adjusting the overlap of the PCN cavity mode and a feeding bus waveguide in both physical and k-space. We show that optimal side-coupled configurations function at a non-zero k-vector offset between the bus waveguide and PCN cavity modes. The straightforward design of side-coupled PCNs with high contrast resonances opens the door to their practical implementation in multiplexed, on-chip photonic devices.