Dual-comb correlation spectroscopy of thermal light

TL;DR

This paper introduces dual-comb correlation spectroscopy (DCCS) for thermal light, connecting frequency comb technology with passive optical sensing, and analyzes its sensitivity and potential for astrophysical and atmospheric applications.

Contribution

It provides the first fundamental sensitivity analysis of DCCS for thermal light and experimentally verifies its scaling at astrophysically relevant temperatures.

Findings

DCCS sensitivity scales predictably with temperature and system parameters.

Experimental verification of DCCS sensitivity at black body temperatures.

Comparison shows advantages of DCCS over traditional detection methods.

Abstract

The detection of light of thermal origin is the principal means by which humanity has learned about our world and the cosmos. In optical astronomy, in particular, direct detection of thermal photons and the resolution of their spectra have enabled discoveries of the broadest scope and impact. Such measurements, however, do not capture the phase of the thermal fields--a parameter that has proven crucial to transformative techniques in radio astronomy such as synthetic aperture imaging. Over the last 25 years, tremendous progress has occurred in laser science, notably in the phase-sensitive, broad bandwidth, high resolution, and traceable spectroscopy enabled by the optical frequency comb. In this work, we directly connect the fields of frequency comb laser spectroscopy and passive optical sensing as applied to astronomy, remote sensing, and atmospheric science. We provide fundamental sensitivity analysis of dual-comb correlation spectroscopy (DCCS), whereby broadband thermal light is measured via interferometry with two optical frequency combs. We define and experimentally verify the sensitivity scaling of DCCS at black body temperatures relevant for astrophysical observations. Moreover, we provide comparison with direct detection techniques and more conventional laser heterodyne radiometry. Our work provides the foundation for future exploration of comb-based broadband synthetic aperture hyperspectral imaging across the infrared and optical spectrum.