Doctoral Student (M/F) - High-sensitivity interferometry for the development of crystalline coatings dedicated to gravitational wave detectors

Job Description

Thesis Subject

The first detection of gravitational waves from the merger of black holes, announced by the LIGO-Virgo collaboration in 2016, opened the field of gravitational astronomy. The first detection of a gravitational wave from the merger of two neutron stars, coinciding with a gamma-ray burst, paved the way for multi-messenger astronomy. Since then, nearly 400 events have been detected by the LIGO and Virgo detectors. These results have been recognized with several awards, including the 2017 Nobel Prize in Physics. The Virgo detector is based on a Michelson-type laser interferometer with arms three kilometers long. The passage of a gravitational wave produces a differential change in the length of the arms, which translates into a light signal at the interferometer's output. To increase the distance at which these events can be observed, the detectors' sensitivity must be improved. In the frequency range where the detector is most sensitive, around 100 Hz, the main limitation stems from the thermal noise of the mirrors that make up the interferometer. In particular, mechanical dissipation in the reflective coatings is the source of thermal noise. For this reason, the research community working on gravitational wave detection is seeking coatings with lower thermal noise. One area of research involves replacing coatings made of amorphous dielectric materials with single-crystal coatings based on III-V materials similar to those used in electronics. To be viable, these materials must also possess excellent optical properties.
In this context, the Virgo group at LAPP is coordinating a project aimed at developing coatings based on GaAs/AlGaAs multilayers. The project, funded by the ANR, is being carried out in collaboration with the CEA in Grenoble, the LMA in Lyon, and two companies in the Paris region. LAPP's role is to develop an optical bench capable of measuring the thermal noise of these coatings to guide their development. The measurement is based on a very high-finesse optical cavity, one of whose mirrors is coated with the reflective treatment whose thermal noise is to be measured. The cavity must be illuminated with a laser beam whose frequency is modulated to excite several modes of the cavity simultaneously. Measuring the variation in the resonance frequencies of these modes allows the thermal noise to be determined. The interferometry technology used is similar to that employed in the Virgo project. The challenge lies in the low amplitude of the thermal noise, which requires a bench with very high sensitivity, capable of measuring the thermal noise without being limited by environmental and laser noise. The bench will be installed at LAPP, and its development draws on the expertise accumulated in Annecy over more than three decades in the field of gravitational wave detection. It should be noted that such a high-sensitivity optical bench can also be used to measure the thermal noise of mirrors or coatings based on other technologies. The student will therefore work on a versatile optical bench, which will also be useful for the development of mirrors for the future European gravitational wave project, the Einstein Telescope. In addition to the thesis work on the development of the optical bench, the student will participate in the coating development project, which will expose them to various fields of expertise. This context will provide excellent training for the student. Finally, the student will have the opportunity to discuss and present their work at various meetings of the international LIGO-Virgo-KAGRA collaboration.

Your Work Environment

The LAPP (Laboratoire d'Annecy de Physique des Particules) is a laboratory under the Institute of Nuclear and Particle Physics (IN2P3), an institute of the French National Centre for Scientific Research (CNRS) that coordinates programs in these fields. LAPP is a joint research unit (UMR 5814) of the CNRS and the Université Savoie Mont-Blanc (USMB).
Over 150 researchers, faculty researchers, engineers, technicians, administrative staff, students, and foreign visitors work at LAPP. The research conducted at LAPP aims to study the physics of elementary particles and their fundamental interactions, as well as to explore their connections with the large-scale structures of the Universe. The work of LAPP teams seeks, among other things, to understand the origin of particle mass, to unravel the mystery of dark matter, and to determine what happened to the antimatter present in our Universe at the time of the Big Bang.
Virgo is an international experiment for the detection of gravitational waves based in Pisa, Italy. Its detection principle is a Michelson interferometer with arms measuring over 3 km. The Virgo group at LAPP consists of 10 physicists, 12 engineers and technicians, as well as 4 PhD students and postdoctoral researchers. The group participates in the construction and operation of the Virgo detector and in the preparation of improvements planned by 2030, including: the laser detection system at the interferometer output, electronics and software for detector control and data acquisition, optical benches integrated into the "squeezing" system to reduce quantum noise in the detector, and detector calibration. The group is also involved in data characterization and in the search for gravitational waves from compact object coalescences, stochastic backgrounds, or rotating neutron stars. Additionally, the group is beginning to contribute to the design of the future gravitational wave detector, the Einstein Telescope (2030+).

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions