K. Ehret- ALPS Collaboration

In the last years it has been realized, that extensions of the Standard Model may manifest itself also at meV energy scales. The low energy frontier is a rich complement to the conventional high-energy particle physics landscape. The search for these new particles initiated experi-mental activities around the world. ”Light shining through a wall ” (LSW) experiments search for Weakly Interacting Sub-eV Particles (WISP). Potential WISP candidates are axion-like particles or hidden sector photons. The ALPS (Any Light Particle Search) experiment located at DESY in Hamburg exploits resonant laser power build-up in a large-scale optical cavity to boost the available power for the WISP production. After some upgrades the experiment provides now the most stringent laboratory constraints on WISP production. The concept, challenges and status of LSW experiments as well as their future potential are presented.