LISA is an ESA-led project that aims to place a gravitational wave observatory in space in the mid-to-late 2030s. LISA will consist of three spacecraft that exchange laser beams in order to measure variations in the distance between each spacecraft on the order of tens of picometers, in the 0.1 mHz to 1 Hz frequency band, yielding a relative strain sensitivity of about 10⁻²².
In this context, the French contribution to LISA is the development of optical test benches to test and validate the performance of the interferometric core of the instrument on Earth. This effort relies on a dedicated setup composed of several optical benches, the main one being the Beams Simulator, which is responsible for simulating the laser beam emitted by the distant spacecraft. The Beams Simulator is being developed at APC with support from other laboratories and CNES. A thorough modeling of this optical bench is necessary to ensure that it can achieve its scientific objectives and reach its design sensitivity.
To this end, a new simulation tool is being developed to accurately model the behavior of the Beams Simulator, and potentially other optical systems could also benefit from this tool. The simulation combines ray tracing, using a vectorized formulation of Snell–Descartes’ law of reflection and refraction, with the propagation of generally astigmatic Gaussian beams, offering a high level of control over the physics and physical parameters of the system being modeled.
This internship will focus on contributing to the development of this tool using Python language, depending on its maturity at the start of the internship, either in the physics aspects of the modeling or in the optimization and algorithmic development. More importantly, the internship will involve using the simulation model to gain insights into the behavior of the Beams Simulator under various physical conditions.