MSc or BSc theses: Optical simulations for space-based laser interferometers

Job Offer from May 25, 2023


This project is embedded in the working group “Interferometry in Space”, which focuses on work towards the space-based gravitational wave detector LISA and on the geodesy mission GRACE-FO and its potential successor missions. 

All of these missions rely on precision interferometers, which measure variations in the distances of two spacecraft with nanometer precision (geodesy applications in a comparably noisy Earth orbit) or picometer precision (LISA, in a very quiet heliocentric orbit). 

In the optical simulations working group, we simulate the noise performance of space-based laser interferometers, further develop simulation methods, and derive new noise mitigation strategies. Of course, we are in close contact with the experimentalists to cross-check with laboratory data and validate experimentally our methods and ideas.

We currently have two open projects, each intended for one student (BSc or MSc level).

Project #1

When simulating laboratory setups or space-based interferometers with Gaussian beams, we typically assume those beams to be perfect Gaussians. This assumption simplifies our computations significantly, but they are not realistic. One of the experimental projects is therefore focusing on experimentally characterizing the higher-order mode content of the laboratory laser beams - or in simple English: the deviations from the perfect Gaussian shape. However, what does the higher-order mode content imply? Does it change the interferometric behaviour? How? This is best analyzed with simulations and the central question of this project.

Project #2

LISA, GRACE-FO and also our laboratory experiments usually use quadrant photodiodes for reading out the interferometric phase and, thereby, the distance variations of interest. However, a quadrant photodiode consists of four segments, each delivering signals as if they were an independent photodiode. So we have four readouts and combine these to deliver one phase or displacement readout signal. This right away implies that a choice needs to be made, how four signals are combined to one, and there are different options. All of these give sensible and usable displacement readout signals, but they can differ in their noise behaviour. This project focuses, therefore, on a systematic comparison of the most commonly used options. The key aim is to find an answer to the question: which signal definition is best used in what experimental case?

Ideally, you have

  • some knowledge and interest in programming
  • some knowledge in laser interferometry (e.g. from the lecture “laser interferometry” or “Gravitationsphysik”)


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