Speaker
Description
In this talk, I present the optical design studies that we made for implementing stable power and signal recycling cavities for the gravitational wave detector Advanced Virgo+. We show that, despite the limited space available in the present infrastructure, a reshaping of the vacuum envelope allows accommodating two folded stable recycling cavities at the input and at the output of the interferometer. By means of FFT-based optical simulations, we found that astigmatism and spherical aberrations, related to the available cavity length, can be made sufficiently small by a proper optical design. We show that requirements on the mirrors radii of curvature precision can be made realistic by the ability to adjust the mirror position once they are suspended to their vibration isolation system. Moreover, this same position adjustment system can be used to compensate first order thermal effects in the input mirrors of the arm cavities. Finally, we show that nowadays mirrors surface flatness are sufficient to achieve high gain in the power recycling cavity and low optical losses in the signal recycling cavity. The latter are compatible with the present use of squeezing technology and its foreseeable future improvement.