Ultra-sensitive heterodyne detection at room temperature in the atmospheric windows

TL;DR

This paper demonstrates ultra-sensitive heterodyne detection at room temperature using quantum cascade lasers in atmospheric windows, achieving noise levels much lower than direct detection through phase locking and stabilization.

Contribution

It introduces a novel room temperature heterodyne detection method with unprecedented sensitivity in atmospheric windows using quantum cascade lasers.

Findings

Noise equivalent power of a few picowatts achieved

Heterodyne detection noise is six orders of magnitude lower than direct detection

Effective phase stabilization enhances detection sensitivity

Abstract

We report room temperature heterodyne detection of a quantum cascade laser beaten with a local oscillator on a unipolar quantum photodetector in two different atmospheric windows, at 4.8 $\mu$m and 9 $\mu$m. A noise equivalent power of few pW is measured by employing an active stabilization technique in which the local oscillator and the signal are locked in phase. The measured heterodyne noise equivalent power is six orders of magnitude lower than that obtained with direct detection.