Waveguide grating mirror in a fully suspended 10 meter Fabry-Perot cavity

TL;DR

This paper demonstrates a fully suspended 10-meter Fabry-Perot cavity using a waveguide grating mirror with over 99.2% reflectivity, showing promise for high-precision interferometry applications like gravitational wave detection.

Contribution

It presents the first implementation of a waveguide grating mirror in a large suspended cavity, achieving high reflectivity and stable operation for potential use in advanced interferometers.

Findings

Achieved finesse of 790 indicating high mirror reflectivity

Waveguide grating reflectivity exceeds 99.2% at 1064 nm

Stable operation demonstrated in a low-noise, suspended cavity

Abstract

We report on the first demonstration of a fully suspended 10m Fabry-Perot cavity incorporating a waveguide grating as the coupling mirror. The cavity was kept on resonance by reading out the length fluctuations via the Pound-Drever-Hall method and employing feedback to the laser frequency. From the achieved finesse of 790 the grating reflectivity was determined to exceed 99.2% at the laser wavelength of 1064\,nm, which is in good agreement with rigorous simulations. Our waveguide grating design was based on tantala and fused silica and included a ~20nm thin etch stop layer made of Al2O3 that allowed us to define the grating depth accurately during the fabrication process. Demonstrating stable operation of a waveguide grating featuring high reflectivity in a suspended low-noise cavity, our work paves the way for the potential application of waveguide gratings as mirrors in high-precision interferometry, for instance in future gravitational wave observatories.