Extreme polishing and measuring performance fostered by the extreme accuracy needed for future upgrades of visible gravitational waves detector

The extreme and out of the ordinary sensitivity shared by the main gravitational waves detector like LIGO, Virgo and KAGRA has recently enabled to access to a new source of information for astronomy. However, future upgrades and new challenges continue to be addressed for reaching wider horizons of meas urable universe events through the gravitational waves. It leads to tighter and tighter specifications in several domains and in particular in the accuracy of the optics at the core of the detector. <br/> <br clear="all"/> For the optical surfaces of the critical optics of these detectors, the current specifications for instrumentations are not sufficient. For instance and concerning Advanced Virgo + critical mirrors (End Mirrors and Input Mirrors), the specification of their SFE (Surface Form error) is now reaching the accuracy level of one atom size, the angstrom, and for optical part up to 550 mm in diameter and 200 mm in thickness. <br/> <br clear="all"/> Besides this, the complete optical part is polished and shall have lateral reference surfaces that are at the level of usual specification of optical surfaces in astronomy. <br/> <br clear="all"/> Thales SESO is in charge of producing these uncommon optics and will present these extremely accurate optical parts, comparison of optical set-up performances as well as final performances.