Isleif, Katharina-Sophie

The Any Light Particle Search II (ALPSII) is an experiment currently being built at DESY in Hamburg, Germany, that will use a light-shining-through-a-wall (LSW) approach to search for axion-like particles. ALPSII represents a significant step forward for these types of experiments as it will use 24 superconducting dipole magnets, along with dual, high-finesse, 122m long optical cavities. This paper gives the first comprehensive recipe for the realization of the idea, proposed over 30 years ago, to use optical cavities before and after the wall to increase the power of the regenerated photon signal. The experiment is designed to achieve a sensitivity to the coupling between axion-like particles and photons down to gαγγ=2×10−11GeV−1 for masses below 0.1meV, more than three orders of magnitude beyond the sensitivity of previous laboratory experiments. The layout and main components that define ALPSII are discussed along with plans for reaching design sensitivity. An accompanying paper (Hallal et al., (2021)) offers a more in-depth description of the heterodyne detection scheme, the first of two independent detection systems that will be implemented in ALPSII.

LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring distances between free-floating test masses housed in three satellites in a triangular constellation with laser links in-between. Each satellite contains two optical benches that are articulated by moving optical subassemblies for compensating the breathing angle in the constellation. The phase reference distribution system, also known as backlink, forms an optical bi-directional path between the intra-satellite benches. In this work we discuss phase reference implementations with a target non-reciprocity of at most 2π μrad Hz-1, equivalent to 1 pm √Hz-1 for a wavelength of 1064 nm in the frequency band from 0.1 mHz to 1 Hz. One phase reference uses a steered free beam connection, the other one a fiber together with additional laser frequencies. The noise characteristics of these implementations will be compared in a single interferometric set-up with a previously successfully tested direct fiber connection. We show the design of this interferometer created by optical simulations including ghost beam analysis, component alignment and noise estimation. First experimental results of a free beam laser link between two optical set-ups that are co-rotating by ±1° are presented. This experiment demonstrates sufficient thermal stability during rotation of less than 10-4 K √Hz-1 at 1 mHz and operation of the free beam steering mirror control over more than 1 week.