Ultra-sensitive detection of mode splitting in active optical microcavities

TL;DR

This paper demonstrates ultra-sensitive detection of mode splitting in active microcavities by leveraging optical gain to enhance quality factors and using laser mode mixing, enabling precise measurements without wavelength scanning.

Contribution

It introduces a novel approach to detect mode splitting in active microcavities using lasing modes, eliminating the need for wavelength scanning and improving sensitivity.

Findings

Enhanced mode splitting resolution below lasing threshold.

Detection of mode splitting through heterodyne beat signals in lasing regime.

Potential applications in sub-wavelength scatterer detection and strong light-matter interaction studies.

Abstract

Scattering induced mode splitting in active microcavities is demonstrated. Below the lasing threshold, quality factor enhancement by optical gain allows resolving, in the wavelength-scanning transmission spectrum, the resonance dips of the split modes which otherwise would not be detected in a passive resonator. In the lasing regime, mode splitting manifests itself as two lasing modes with extremely narrow linewidths. Mixing of these laser modes in a detector leads to a heterodyne beat signal whose frequency corresponds to the amount of splitting. Lasing regime not only allows ultrahigh sensitivity for mode-splitting measurements but also provides an easily accessible scheme by eliminating the need for wavelength scanning around resonant modes. Mode splitting in active microcavities has immediate impact in enhancing the sensitivity of sub-wavelength scatterer detection and in studying light-matter interactions in strong coupling regime.