Gain enhanced Fano resonance in a coupled photonic crystal cavity-waveguide structure

TL;DR

This paper proposes a coupled photonic crystal cavity-waveguide system with gain to enhance Fano resonance, resulting in steeper spectral lines and higher transmissivity, useful for optical switching and sensing.

Contribution

It introduces a novel gain-assisted design to significantly improve Fano resonance in photonic crystal structures.

Findings

Transmission can be increased sixfold with gain.

Fano resonance line shape becomes steeper with gain.

Enhanced Fano resonance improves optical device performance.

Abstract

Systems with coupled cavities and waveguides have been demonstrated as optical switches and optical sensors. To optimize the functionalities of these optical devices, Fano resonance with asymmetric and steep spectral line shape has been used. We theoretically propose a coupled photonic crystal cavity-waveguide structure to achieve Fano resonance by placing partially reflecting elements in waveguide. To enhance Fano resonance, optical gain material is introduced into the cavity. As the gain increases, the transmission line shape becomes steepened and the transmissivity can be six times enhanced, giving a large contrast by a small frequency shift. It is prospected that the gain enhanced Fano resonance is very useful for optical switches and optical sensors.