Resonant laser power build-up in ALPS -- a "light-shining-through-walls" experiment

TL;DR

This paper reports the first successful integration of a large-scale optical cavity in a light-shining-through-walls experiment to enhance photon-to-WISP conversion, demonstrating improved power build-up and stabilization techniques.

Contribution

Introduction of a large-scale optical cavity with a feedback control system in a WISP search experiment, improving power efficiency and stability.

Findings

Successful power build-up in the optical cavity

Effective stabilization of laser power

Demonstration of data analysis procedures

Abstract

The ALPS collaboration runs a light-shining-through-walls (LSW) experiment to search for photon oscillations into "weakly interacting sub-eV particles" (WISPs) inside of a superconducting HERA dipole magnet at the site of DESY. In this paper we report on the first successful integration of a large-scale optical cavity to boost the available power for WISP production in this type of experiments. The key elements are a frequency tunable narrow line-width continuous wave laser acting as the primary light source and an electronic feed-back control loop to stabilize the power build-up. We describe and characterize our apparatus and demonstrate the data analysis procedures on the basis of a brief exemplary run.