Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
Reciprocity of the Backlink for LISA
A phase reference distribution system (PRDS) between the two optical benches in each LISA satellite is required. This is achieved by exchanging the local lasers of both benches via the so-called Backlink.
Photograph of the finished optical benches of the Three-Backlink Experiment constructed in the cleanroom of the AEI.
Photograph of the finished optical benches of the Three-Backlink Experiment constructed in the cleanroom of the AEI.
Experimental investigations on a fiber Backlink revealed performance-limiting challenges caused by the backscatter of the counter-propagating light inside this fiber. A potential increase of backscatter caused by radiation damage was investigated further and concluded to be uncritical.
Additional studies of coupling mechanisms and modeling of the backscatter’s influence on the measurement paved the way for the baseline LISA Backlink recommendation. It will be further tested and studied in an engineering model.
Non-Reciprocity Measurements with the Three-Backlink Experiment. The noise level is measured for pairwise combination of the three Backlinks (DFBL: Direct Fiber Backlink, FBBL: Free-Beam Backlink, FSFBL: Frequency Separated Fiber Backlink).
Credit: Lea Bischof
Non-Reciprocity Measurements with the Three-Backlink Experiment. The noise level is measured for pairwise combination of the three Backlinks (DFBL: Direct Fiber Backlink, FBBL: Free-Beam Backlink, FSFBL: Frequency Separated Fiber Backlink).
Credit: Lea Bischof
Simultaneously, the Three-Backlink Experiment compares three different implementations of a Backlink and studies different noise suppression techniques in detail. This experiment consists of two quasi-monolithic optical benches with a complex design. In the past years, they were built in a cleanroom at the AEI in Hannover. The experiment is in its commissioning phase but already shows promising disentanglement of the different Backlink performances, which enables studying their distinct noise contributions and coupling mechanism. When the experiment reaches its design sensitivity of 1 pm/sqrt(Hz), it will further enable to study of several aspects of the LISA Backlink in detail.
Literature: PhD Theses
1.
Steier, F.: Interferometry techniques for spaceborne gravitational wave detectors. Dissertation, Universität Hannover, Fakultät für Mathematik und Physik, Hannover (2008)
The gravitational-wave and experimental astrophysicist will establish a third department at the Max Planck Institute for Gravitational Physics in Hannover
The Institute for Gravitational Physics at Leibniz University Hannover will do research on and improve interferometric precision measurements and laser links between satellites
Researchers from the AEI in Potsdam and from the CEA in Saclay, Paris suggest how the planned space-based gravitational-wave observatory LISA can detect exoplanets orbiting white dwarf binaries everywhere in our Milky Way and in the nearby Magellanic Clouds.
