Speaker
Description
The proposed Einstein Telescope (ET), a third generational European gravitational-wave (GW) detector, plans to extend the frequency band below 10 Hz and achieve a broadband sensitivity improvement by at least an order of magnitude over current ground-based detectors such LIGO, Virgo and KAGRA. ET will have 10 km underground interferometers in a triangular configuration with each arm consisting cryogenic low-frequency (ET-LF) and high-frequency (ET-HF).
To achieve such prominent sensitivity, ET-HF is expected to operate at 3 MW intra-cavity power, to raise GW sidebands signal above vacuum fluctuations and reduce quantum shot noise impact. Such high-power is more susceptible to optical loss mechanisms, in particular, thermo-elastic and thermo-optics deformations, resulting due to distortion in eigenmode of the interferometer cavities from fundamental Gaussian mode to higher-order modes (HOM). Such mode mismatch reduces the coherent power and increases losses.
Current detectors use open-loop thermal compensation systems (TCS) to ease such distortions using CO2 projections, ring heaters and Hartmann sensors. But these systems lack the robustness and adaptability as HOM sensing and control will be critical in managing optical losses in the megawatt regime.
I will talk about how I plan to address this research issue by demonstrating first-ever closed loop transverse mode sensing and control. I will also talk about ET-OPT laboratory of UCLouvain, which will consist of 10 m long Fabry-Perot suspended optical cavity operating at same ET-HF power densities. I will also discuss implementation of thermally actuated suspended active mode-matching stages (TSAMS) for mode actuation and phase camera as mode diagnostics. Upon successful demonstration of this technique, it will be deployed in close collaboration with ULiege at Virgo for O5 full-scale detector operations and ETpathfinder to integrate with cryogenic operations and squeezed light injections.