Erlangen 2022 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 16: Precision Measurements and Metrology IV (joint session Q/A)

A 16.3: Vortrag

Mittwoch, 16. März 2022, 11:15–11:30, Q-H11

Precision Optical Techniques in the ALPS II Experiment — •Todd Kozlowski — University of Florida, Gainesville, USA

On behalf of the ALPS Collaboration. The Any Light Particle Search II (ALPS II) is a "light-shining-through-the-wall" experiment currently in commissioning at DESY. ALPS II will search for axion-like particles (ALPs), a family of hypothetical particles outside of the Standard Model which have a feeble coupling to the electromagnetic field, motivated by exciting astrophysical hints. The experiment aims to detect light which has undergone photon-ALP and subsequent ALP-photon conversion in the presence of a magnetic field. ALPS II utilizes a pair of 122-meter long high finesse Fabry-Perot optical resonators to improve detection sensitivity. One of the resonators will store 150 kW of circulating light to improve the amplitude of the generated axion field. The second resonator, located on the other side of a light-tight (but ALP transparent) barrier, will build up the regenerated laser field to gain a factor >10,000 in signal enhancement. The resulting signal, on the order of 1 photon/day, can then either be counted by a cryogenic photon counter or detected as modulation of a reference field. The experiment requires a control scheme to allow for the two cavities to both be held simultaneously on resonance with the same frequency of light, without any light from the first resonator entering the second. I will discuss the optical technologies utilized in this experiment, including nested optical offset phase locking, heterodyne interferometric readout of ultra-low optical fields, and alignment sensing and control. I will also present updates from the in-progress experimental commissioning.