Directional free-space coupling from photonic crystal waveguides

TL;DR

This paper introduces a perturbative approach for efficiently coupling specific modes in photonic crystal waveguides to free-space modes, enabling improved mode conversion with minimal design changes.

Contribution

It presents a novel perturbative design method for coupling photonic crystal waveguide modes to free-space modes, enhancing efficiency and selectivity.

Findings

Achieved selective coupling of a specific waveguide mode to a Gaussian free-space mode.

Demonstrated minimal perturbation design for efficient mode interconversion.

Applicable to various photonic crystal waveguide configurations.

Abstract

We present a general approach for coupling a specific mode in a planar photonic crystal (PC) waveguide to a desired free-space mode. We apply this approach to a W1 PC waveguide by introducing small index perturbations to selectively couple a particular transverse mode to an approximately Gaussian, slowly diverging free space mode. This "perturbative photonic crystal waveguide coupler" (PPCWC) enables efficient interconversion between selectable propagating photonic crystal and free space modes with minimal design perturbations.