Confocal shift interferometry of coherent emission from trapped dipolar excitons

TL;DR

This paper presents a confocal shift-interferometer for high-resolution coherence mapping of luminescent samples at cryogenic temperatures, applied to trapped dipolar excitons in semiconductors.

Contribution

It introduces a fiber-based confocal interferometer capable of measuring spatial and temporal coherence of excitonic emission at very low temperatures.

Findings

Spatial coherence length matches the confocal setup's point spread function.

Temporal coherence persists down to 250 mK.

The technique enables high-resolution coherence mapping at cryogenic temperatures.

Abstract

We introduce a confocal shift-interferometer based on optical fibers. The presented spectroscopy allows measuring coherence maps of luminescent samples with a high spatial resolution even at cryogenic temperatures. We apply the spectroscopy onto electrostatically trapped, dipolar excitons in a semiconductor double quantum well. We find that the measured spatial coherence length of the excitonic emission coincides with the point spread function of the confocal setup. The results are consistent with a temporal coherence of the excitonic emission down to temperatures of 250 mK.