Cavity Enhanced Faraday Rotation of Semiconductor Quantum Dots

TL;DR

This paper demonstrates a cavity-enhanced method to significantly amplify Faraday rotation in semiconductor quantum dots, enabling sensitive spin dynamics measurements at low power levels.

Contribution

It introduces a planar cavity approach that boosts Faraday rotation signals in quantum dots, allowing for improved detection sensitivity in spin studies.

Findings

Achieved nearly 30-fold enhancement of Faraday rotation.

Enhanced rotation scales with cavity quality factor.

Low power measurements reveal spin precession dependencies.

Abstract

A dielectric vertical cavity is used to study the spin dynamics of molecularly self-assembled colloidal CdSe quantum dots (QDs). Using this structure, a nearly 30-fold enhancement of Faraday rotation is observed, which scales with the quality factor of the cavity. In this classical nonperturbative regime, the amplified rotation is attributed to optically excited spins interacting with multiple passes of the probe photons in the cavity. By applying this general planar cavity motif to Faraday rotation, dynamical measurements are accessible at extremely low powers on relatively small numbers of quantum confined spins. In CdSe QDs, low power measurements reveal that contributions from exciton and electron spin precession are largely dependent upon the power of excitation. We demonstrate that this scheme is amenable to both soft and hard systems as a means to increase detection sensitivity.