MSc/BSc thesis projects and student research assistant: AEI 10m Prototype

Job Offer from July 04, 2022

The 10 m Prototype research group is currently offering thesis projects for Bachelors and Masters students.

The AEI 10 m Prototype is a facility undertaking research which focusses on the development and testing of new technologies and techniques for ground based gravitational-wave detectors. We are currently constructing the Sub-SQL Interferometer, which is a 10 m Michelson interferometer similar to current gravitational-wave detectors. This interferometer is designed to be limited by the standard quantum limit (SQL) of interferometry and will allow test and development of techniques to suppress quantum noise. More information about the facility and research can be found on the 10 m prototype homepage.

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We are currently offering thesis projects for the following topics. These topics can be tailored for either a MSc or BSc project.

Scattered light characterisation

All optics, such as mirrors and lenses, scatter some light into all directions when illuminated with a laser beam. Scattered laser light in gravitational-wave interferometers can severely limit the sensitivity as the scattered light can recombine with the interferometer light resulting in unwanted interference and noise.

An experiment, known as the scatterometer, has been built to quantitatively characterise the level of scattered light produced by different optical components by measuring the bidirectional reflectivity distribution function (BRDF). This is used to ensure that optics installed in the 10 m Prototype produce a sufficiently low amount of scattered light.

This project will focus on improving the “scatterometer” and will include:

  • Installation of an improved light source and imaging system
  • Mechanical improvements to the assembly
  • Characterisation of the BRDF of various optics such as lenses and mirrors

Scattered light mitigation

It is not possible to completely avoid scattered light from optics and even very low levels are expected to contribute enough noise to prevent the sub-SQL Interferometer from being limited by quantum noise. Apparatus needs to be installed in the vacuum system to remove scattered light from the system before it is able to recombine with the interferometer light. Baffles are an example such a device which can be installed to shield core optics from scattered light.

This project will involve:

  • Characterising potential materials for use as baffles in terms of reflectivity, scattering, and vacuum compatibility
  • Designing, installing and testing systems to determine where baffling is most urgently needed in the vacuum system (cameras and point source illumination)
  • Designing, building and installing baffles for different components and testing their performance

Interferometric inertial motion sensor using a suspended mirror

All optics installed in the vacuum system of the AEI 10 m Prototype are mounted on our seismic isolation platforms. Electronic feedback loops are implemented to minimise the motion of these platforms, which in turn suppresses seismic motion in the sub-SQL interferometer. These loops utilize a range of different motions sensors, including seismometers, to sense the platform motion.

These platforms are only able to support a limited mass and hence it is critical to optimise the weight of the apparatus installed on the platform. This project will investigate the use of existing suspended mirrors as seismometer-like inertial sensors by using an interferometer to measure the mirror motion. A homodyne quadrature interferometer (HoQI) will be used to measure the position of the suspended mirror.

This project will involve:

  • Incorporation and adaptation of existing mirror suspensions into seismometers
  • Construction of the homodyne quadrature interferometers
  • Sensitivity characterisation of the sensor/s

Optical levers

The angular motion of an object can be measured using laser beams by measuring the lateral displacement of the beam at a fixed distance away. These are currently utilised in the AEI 10 m Prototype to measure the angular motion of our seismically isolated platforms by sending a laser beam from one platform to the other platform 10 m away, and measuring the position on a quadrant photodiode.

Currently, the laser beam for each optical lever is prepared outside of the vacuum system and individual optical fibres are used to deliver the beam into the vacuum system. This project will investigate reducing this to a single optical fibre to couple the light into the vacuum system and splitting the light into multiple beams for different optical levers inside the vacuum system.

This project will also investigate the use of modulated laser beams for the optical levers to decouple the optical lever signals from other laser light used in the vacuum system.

This project will involve:

  • Designing and setting up the laser distribution system for the various optical levers using free-space optics and optical fibres
  • Developing and testing the use of modulated laser light for the optical levers
  • Characterising the quadrant photodiodes used to sense the optical levers

Student research assistant

In addition to MSc/BSc thesis students, we are also looking for highly motivated students to work as research assistant (wissenschaftliche Hilfskraft) in our laboratory. This is an excellent opportunity to gain some laboratory experience.

The actual tasks will depend on the needs at the time, but could include:

  • Assist setting up experiments
  • Performing measurements with existing apparatus
  • Electronics work, e.g. soldering, cable making, device testing
  • Preparing and cleaning components for use in high vacuum environments
  • Mechanical design of components


Interested students for any of the above topics should contact David Wu for more details.

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