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Ground-based gravitational-wave (GW) detectors use kilometre-long Michelson interferometers to detect relative GW strain signals at the level of 10^-23. Given the size of the infrastructures, optical signals occasionally have to be carried over several tens of metres – or more – through optical fibres, for applications such as optical-cavity length control or laser phase-locking. Due to the extreme sensitivity reached by modern ground-based GW detectors, exquisite control of the phase noise introduced by these optical fibres is required.

IJCLab is part of the international Virgo collaboration. In particular, the laboratory hosts then CALVA platform, which is designed to develop and characterise optical-cavity stabilisation techniques, notably thanks to a 50m-long suspended Fabry-Perot cavity. Such an experimental setup, along with the local metrology expertise, makes the CALVA platform a unique testbed for cavity-stabilisation techniques in France.

In this context, the proposed internship aims at characterising experimentally a system for fibre-phase-noise cancellation which will be used to improve the Advanced Virgo detector. The goal is to obtain a reduction in phase noise by a factor of 10. The intern will be required to study and get acquainted with the optical setup, as well as the underlying feedback system and signal processing to characterise and improve the system. Testing the feedback system will notably be carried out by injecting artificial noise into the system and characterising the obtained level of noise reduction.
This internship may be followed by a PhD thesis. Please check this page.