Coherent Detection of Ultra-weak Electromagnetic Fields

TL;DR

This paper demonstrates a heterodyne interferometry-based detection system capable of measuring extremely weak electromagnetic fields, crucial for experiments searching for elusive particles.

Contribution

It introduces a novel weak-field coherent detection scheme with high sensitivity suitable for particle search experiments like ALPS II.

Findings

Achieved a dark count rate of ~10^{-5} photons/sec

Successfully detected signals with field strength of 10^{-2} photons/sec

Validated the detection method's potential for ultra-weak field measurements

Abstract

We explore the application of heterodyne interferometry for a weak-field coherent detection scheme. The methods detailed here will be used in ALPS II, an experiment designed to search for weakly-interacting, sub-eV particles. For ALPS II to reach its design sensitivity this detection system must be capable of accurately measuring fields with equivalent amplitudes on the order of 10$^{-5}$ photons per second or greater. We present initial results of an equivalent dark count rate on the order of $10^{-5}$ photons per second as well as successful generation and detection of a signal with a field strength equivalent to $10^{-2}$ photons per second.