The integration of the heterodyne readout system in ALPS-II *

The Any Light Particle Search (ALPS) experiment searches for weakly interaction sub-eV particles, like the axion-like particles. ALPS is a Light Shining through a Wall (LSW) experiment which is independent from any solar or galactic models. It uses a strong laser field inside a 100 m long string of HERA magnets to produce axions on one side of the wall and detects regenerated photons in a second 100 m long string on the other side. It directly probes the Lagrangian of the axion to two photon coupling without the need for any external or background axions. Furthermore, ALPS-II adds optical resonators on both sides of the wall in order to increase the conversion probability of photons to axions and axions to photons, improving the sensitivity of the experiment by many orders of magnitude.

The coherence of the axion production and photon regeneration process allows ALPS to use a heterodyne detection method which detects the regenerated photons at the fundamental limit. I will report on the optical layout, the control strategy and the status of the heterodyne readout scheme for ALPS II.