A dark-field microscope for background-free detection of resonance fluorescence from single semiconductor quantum dots operating in a set-and-forget mode

TL;DR

This paper introduces a polarization-based dark-field microscope that enables background-free detection of resonance fluorescence from single quantum dots, achieving high suppression of scattered laser light and long-term stability for quantum optics applications.

Contribution

The authors developed a stable, wide-range, polarization-based dark-field microscope capable of background-free resonance fluorescence detection from single quantum dots.

Findings

Suppression of scattered laser light exceeds 10^7 times.

The microscope operates over 920-980 nm range and in high magnetic fields.

It maintains stability for days without realignment.

Abstract

Optically active quantum dots, for instance self-assembled InGaAs quantum dots, are potentially excellent single photon sources. The fidelity of the single photons is much improved using resonant rather than non-resonant excitation. With resonant excitation, the challenge is to distinguish between resonance fluorescence and scattered laser light. We have met this challenge by creating a polarization-based dark-field microscope to measure the resonance fluorescence from a single quantum dot at low temperature. We achieve a suppression of the scattered laser exceeding a factor of 10^7 and background-free detection of resonance fluorescence. The same optical setup operates over the entire quantum dot emission range 920-980 nm and also in high magnetic fields. The major development is the outstanding long-term stability: once the dark-field point has been established, the microscope operates for days without alignment. The mechanical and optical design of the microscope is presented, as well as exemplary resonance fluorescence spectroscopy results on individual quantum dots to underline the microscope's excellent performance.