Single-photon distributed free-space spectroscopy

TL;DR

This paper introduces a novel distributed free-space spectroscopy technique using a comb-referenced single-photon lidar for remote sensing of atmospheric molecules over large distances with high resolution.

Contribution

It develops a new multidimensional remote sensing method that combines single-photon lidar with frequency scanning for atmospheric spectroscopy in free-space environments.

Findings

Successfully measured CO2 and HDO spectra over 6 km

Achieved 60 m range resolution and 10 min time resolution

Demonstrated potential for atmospheric and chemical research

Abstract

Spectroscopy is a well-established nonintrusive tool that has played an important role in identifying substances and quantifying their compositions, from quantum descriptions to chemical and biomedical diagnostics. Challenges exist in accurate measurements in dynamic environments, especially for understanding chemical reactions in arbitrary free-space. We develop a distributed free-space spectroscopy realized by a comb-referenced frequency-scanning single-photon lidar, providing multidimensional (time-range-spectrum) remote sensing. A continuous field experiment over 72 hours is deployed to obtain the spectra of multiple molecules (CO2 and HDO) in free-space over 6 km, with a range resolution of 60 m and a time resolution of 10 min over a spectrum span of 30 GHz. The CO2 and HDO concentrations are retrieved from the spectra acquired. This distributed free-space spectroscopy holds much promise for increasing knowledge of atmospheric environments and chemistry research, especially for complex molecular spectra evolution in any location over large areas.