Microcavities with suspended subwavelength structured mirrors

TL;DR

This paper explores microcavities with suspended subwavelength structured mirrors, revealing a regime where the transmission spectrum is dominated by a single, narrow linewidth mode, useful for high-Q applications.

Contribution

It identifies a novel regime in microcavities with structured mirrors where a single, narrow mode dominates, enabling advanced optomechanics and sensing.

Findings

Single mode transmission in the regime where free-spectral range exceeds Fano resonance width

Linewidth of the mode can be narrower than the Fano resonance and cavity linewidths

Potential applications in high-Q microcavities, optomechanics, and sensing

Abstract

We investigate the optical properties of microcavities with suspended subwavelength structured mirrors, such as high-contrast gratings or two-dimensional photonic crystals slabs, and focus in particular on the regime in which the microcavity free-spectral range is larger than the width of a Fano resonance of the highly reflecting structured mirror. In this unusual regime, the transmission spectrum of the microcavity essentially consists in a single mode, whose linewidth can be significantly narrower than both the Fano resonance linewidth and the linewidth of an equally short cavity without structured mirror. This generic interference effect---occuring in any Fabry-Perot resonator with a strongly wavelength-dependent mirror---can be exploited for realizing small modevolume and high quality factor microcavities and, if high mechanical quality suspended structured thin films are used, for optomechanics and optical sensing applications.