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

• Published in: arXiv.org 2011-04
• Main Authors: Friedrich, Daniel, Barr, Bryan W, Brückner, Frank, Hild, Stefan, Nelson, John, Mcarthur, John, Plissi, Michael V, Edgar, Matthew P, Huttner, Sabina H, Sorazu, Borja, Kroker, Stefanie, Britzger, Michael, Ernst-Bernhard Kley, Danzmann, Karsten, Tünnermann, Andreas, Strain, Ken A, Schnabel, Roman
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Fabry-Perot interferometers; Fused silica; Gravitational waves; Observatories; Reflectance; Silicon dioxide; Variation
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1104.2780

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.