Abstract
The laser interferometer space antenna (LISA) is a future space-based interferometric gravitational-wave detector consisting of three spacecraft in a triangular configuration. The interferometric measurements of path length changes between satellites will be performed on optical benches in the satellites. Angular misalignments of the interfering beams couple into the length measurement and represent a significant noise source. Imaging systems will be used to reduce this tilt-to-length coupling.We designed and constructed an optical test bed to experimentally investigate tilt-to-length coupling. It consists of two separate structures, a minimal optical bench and a telescope simulator. The minimal optical bench comprises the science interferometer where the local laser is interfered with light from a remote spacecraft. In our experiment, a simulated version of this received beam is generated on the telescope simulator. The telescope simulator provides a tilting beam, a reference interferometer and an additional static beam as a phase reference. The tilting beam can either be a flat-top beam or a Gaussian beam. We avoid tilt-to-length coupling in the reference interferometer by using a small photo diode placed at an image of the beam rotation point. We show that the test bed is operational with an initial measurement of tilt-to-length coupling without imaging systems.Furthermore, we show the design of two different imaging systems whose performance will be investigated in future experiments.
Highlights
The laser interferometer space antenna (LISA) is a future space-based gravitational wave detector consisting of three satellites in heliocentric orbits [1, 2].Laser-links between the spacecraft are used for measuring the tiny distance fluctuations between free-floating test masses inside the satellites caused by gravitational waves
We show that the test bed is operational with an initial measurement of tilt-to-length coupling without imaging systems
Suppression of this noise source is necessary and is achieved by imaging systems placed on the optical bench in front of the interferometer readout photodiodes
Summary
The laser interferometer space antenna (LISA) is a future space-based gravitational wave detector consisting of three satellites in heliocentric orbits [1, 2]. Laser-links between the spacecraft are used for measuring the tiny distance fluctuations between free-floating test masses inside the satellites caused by gravitational waves. Telescopes are used for sending and receiving light between spacecraft. The interferometric path length measurements are split in different parts and each satellite has optical benches with several interferometers. To detect gravitational waves these individual measurements are combined to form a Michelson-like interferometer. The freely-floating test masses and local interferometry have recently been demonstrated on the LISA Pathfinder (LPF) spacecraft [3]
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