Andreas Freise :: Year 4 Projects

Year 4 Projects

Within the scope of my research activities I am currently offering the following 4th-year projects. For further information on individual projects, please contact me. Short descriptions of projects completed in previous years can be found here.

How to upgrade gravitational wave detectors

Supervisors: Andreas Freise

The LIGO project has recently announced the first detection of a gravitational wave. This achievement is the result of several decades of work, in particular in experimental physics. We are involved in the design, construction and operation of large scale detectors, such as LIGO and the Einstein Telescope. We want to improve these detectors further, to a sensitivity which allows regular detections of GW events, establishing the new era of gravitational wave astronomy. The laser interferometers in the detectors consist of many optical and electro-optical components and can only be analysed or understood as a whole. We have developed our own numerical modelling tools to analyse the performance of laser interferometers at the quantum limit. One of the current challenges is to understand and improve the opto-mechanical sensing and control systems.

The aim of this student project is to investigate the control systems for the postion and orientation of the mirrors and laser beams in the LIGO interferometers. The students will first be studying the theory of laser interferometry and their description in numerical models. Expertise in programming is required as the students will develop Python scripts to perform modelling tasks. Examples for our use of Python for laser interferometer can be found at

Enhancing the bandwidth of advanced gravitational-wave detectors for astronomy

Supervisors: Haixing Miao

Advanced gravitational-wave (GW) detectors such as LIGO are Michelson interferometers. To measure the tiny GW signal---a strain of spacetime, not only do they have kilometre long arm length, but also introduce additional mirrors in the two arms to form optical cavities. The light bounces back and forth multiple times inside the arm cavities, which effectively increases the arm length. However, this makes the detector less responsive to the high-frequency GW signal, of which the wavelength is comparable or even smaller than the effective arm length. In another word, introducing arm cavities reduces our detector bandwidth in frequency.

One interesting idea studied in PhysRevLett.115.211104 allows us to enhance the bandwidth by using active optomechanical filters. In this project, we will study the feasibility of implementing this idea to the proposed third-generation GW detector: the Einstein Telescope (ET). The original ET design consists of a pair of detectors: one optimised for low-frequency GW signal and the other for high frequency, like a xylophone. It is interesting to see whether we can push the bandwidth of the low-frequency detector to achieve a sensitivity comparable to the xylophone design with just one detector. The outcome of this project can provide guidelines to the design of ET-like third generation GW detectors for astronomy.

This project is theoretical, and students who enjoy mathematical derivations are welcome.

Interferometric sensors in Gravitational-Wave detectors

Supervisors: Conor Mow-Lowry

Gravitational-wave observatories are the most sensitive instruments ever made. Our work helps to improve the sensitivity and robustness of these delicate instruments, increasing their astrophysical reach and operating time. Seismic motion (and other sources of vibration) shake the mirrors of the observatories, and despite having the most sophisticated vibration isolation systems in the world, they still limit performance. We are developing a new class of interferometric sensors to improve the vibration isolation systems of gravitational-wave observatories.

The aim of this year 4 project is to determine how to implement improved sensors into the Advanced LIGO gravitational-wave detectors to best improve their performance. Students will adapt the existing control scheme, with the potential to apply novel control ideas and optimisation techniques, to optimally suppress the motion of the gravitational test masses. This project will involve modelling of physical systems using experimental data.