Production and Detection of Axion-like Particles by Interferometry

TL;DR

This paper proposes a novel interferometry method for detecting axion-like particles, enhancing sensitivity over traditional photon-regeneration experiments by using phase shifts, squeezed light, and optical cavities.

Contribution

It introduces an interferometry-based detection scheme for ALPs that improves sensitivity through phase measurement, noise reduction, and optical enhancement techniques.

Findings

Sensitivity to ALP-photon coupling improved by a factor of about 3.

Use of squeezed light reduces shot noise, enhancing detection capabilities.

Optical delay lines and cavities significantly boost the signal strength.

Abstract

We propose an interferometry experiment for the detection of axion-like particles (ALPs). As in ordinary photon-regeneration (light shining through a wall) experiments, a laser beam traverses a region permeated by a magnetic field, where photons are converted to ALPs via the Primakoff process, resulting in a slight power loss and phase shift. The beam is then combined with a reference beam that originates from the same source. The detection of a change in the output intensity would signal the presence of ALPs (or possibly other particles that couple to the photon in a similar way). Because only one stage of conversion is needed, the signal is of ${\cal O}(g^2_{a\gamma \gamma})$, as opposed to ${\cal O}(g^4_{a\gamma \gamma})$ for photon-regeneration experiments, where $g_{a\gamma \gamma}$ is the coupling between ALPs and photons. This improvement over photon-regeneration is nullified by the presence of shot noise, which however can be reduced by the use of squeezed light, resulting in an improvement in the sensitivity to $g_{a\gamma\gamma}$ over ordinary photon-regeneration experiments by an order of $10^{1/2}$ assuming $10{\rm dB}$ noise suppression. Additionally, our setup can incorporate straightforwardly optical delay lines or Fabry-Perot cavities, boosting the signal by a factor of $n\sim10^3$, where $n$ is the number of times the laser beam is folded. This way, we can constrain $g_{a\gamma\gamma}$ better by yet another factor of $n^{1/2}\sim 10^{1.5}$, as compared to the $n^{1/4}$ boost that would be achieved in photon-regeneration experiments.