International Summer Research Program in Gravitational-Wave Physics:
Research Experiences for Undergraduates around the world

  • Searching for long-lived binary inspirals in future gravitational-wave detectors:
    Current gravitational-wave interferometers have detected binary neutron star and binary black hole systems that last less than O(100 s) and O(1 s), respectively. However, future detectors, such as Einstein Explorer and LISA, will be sensitive to binary systems that spend a lot more time in the detector frequency band. Thus, current techniques based on matched filtering, the ideal signal processing technique that correlates a template signal with the data, will need to be revised to account for a continuously changing noise distribution, gaps in the data, and noise disturbances. We have developed a method that is robust towards these three problems, but we have not yet applied it to long-lived sources in future detectors. This project will involve adapting this method to insprialing binary systems: e.g. neutron star inspirals in Einstein Telescope, and extreme mass ratio inspirals/binary black hole inspirals in LISA, quantifying its sensitivity towards these sources, and determining the degree to which we can localize these sources in the sky.

    Mentor: Andrew Miller

  • Gravitational wave detector instrumentation studies:
    Detecting gravitational waves (GWs) was possible by a step-by-step advancement of different techniques to keep optical cavities on-resonance (locking) while containing high optical powers. One of the essential techniques is the Pound-Drever-Hall (PDH) technique [1] which acts on mirror positions or laser frequency to keep a cavity locked. In addition to these useful techniques, a powerful diagnostic tool was developed for studying complex interferometers like GW detectors, called the phase camera (PC) [2]. This device can observe the amplitude and phase of laser wavefronts in 2D. More recently, PCs have been developed at Nikhef [3] and were installed in Advanced Virgo [4], a GW detector near Pisa, Italy. To increase sensitivity, GW detectors are increasing their optical power. Higher powers will create stronger thermal effects in the large mirrors, which are ~40 kg fused silica substrates. One of these thermal effects is a change of the radius of curvature (RoC) of the cavity mirrors. This can have an effect on the shape of the beam inside the cavities as the mirrors act as a lens for the incoming beam. When an input beam waist position and/or size are not matched to the cavity eigenmode (the preferred beam shape of the cavity as shown in Fig. 1), we speak of mode mismatch (MM).

    Figure 1: Position and size mismatch of the waist of input beam 1 to the waist of cavity eigenmode beam 2. A mismatch in waist position b and waist size Δw gives rise to 90 degree out-of-phase cylindrical spatial beam modes. Adapted from [5].

    MM is a source of optical loss as power is reflected in cylindrical modes that can't be used for GW detection. At the moment, no gravitational wave detector has an automated way to control MM. To combine above, a MM experimental set-up is being built at UCLouvain, shown in Fig. 2. The three different beams split off the beam coming from the polarizing beam splitter (PBS) are used to provide error signals for the waist position (QPDpos) and size (QPDsize) mode mismatch using a mode converter [6], do the same using the PC and lock the cavity (PDlock,) using the PDH method. The IREU student will work with our PhD student Ricardo and Research Scientist Joris to further build, characterize and optimize this optical setup. Other than some data-analysis skills (e.g. python or matlab) and general lab experience, there are not much prerequisites a student should have for this project.
    Figure 2: Optical set-up to generate mismatch error signals interrogating a (coupled) cavity. Sidebands of 20 MHz are added to the carrier beam by an Electro-Optic Modulator (EOM) and a pick-off beam is transformed into a frequency shifted reference beam by an Acousto-Optic Modulator (AOM). Two lenses separated by dmm can be moved to generate a mode mismatch. The reflected beam is split towards a PDH locking photodiode and two mode matching sensors: the mode converter and the phase camera. Not shown are Guoy phase telescopes and the demodulation electronics for the mode matching sensors.

    With an interest for optics and a healthy appetite for troubleshooting experiments, the student will learn:
    • general understanding of gravitational wave detector( component)s;
    • aligning optical cavities and set-ups;
    • simulating optical beams and signals using optical simulation tools;
    • using experiment and simulation to characterize and optimize;
    • signal processing and control of opto-mechanical systems;
    • reporting and presenting their results.

    Our GW research group is part of the Centre for Cosmology, Particle Physics and Phenomenology (CP3). It is a rich environment, with interaction with many different kinds of people from all over the world focusing on various kinds of experimental and theoretical physics. For more information on our people and the projects we work on, please visit our website.

    [1] R. W. P. Drever et al., B Photophys. Laser Chem. 31(2), 97–105 (1983)
    [2] K. Goda et al., Opt. Lett. 29 (13), 1452–4 (2004)
    [3] K. Agatsuma et al., Opt. Express 27, 18533-18548 (2019)
    [4] F. Acernese et al., Class. Quantum Grav. 32 024001 (2015)
    [5] J. Miller and M. Evans, Optics Lett., Vol. 39, pp. 2495-2498 (2014)
    [6] Fabian Magaña-Sandoval et al., Phys. Rev. D 100, 102001 (2019)

    Mentor: Joris van Heijningen

  • Past IREU Projects
    Other Prior Projects