Higher-order Laguerre-Gauss interferometry for gravitational-wave detectors with in situ mirror defects compensation
The use of higher-order Laguerre-Gauss modes has been proposed to decrease the influence of thermal noise in future generation gravitational-wave interferometric detectors. The main obstacle for their implementation is the degeneracy of modes with same order, which highly increases the requirements on the mirror defects, beyond the state-of-the-art polishing and coating techniques. In order to increase the mirror surface quality, it is also possible to act in situ, using a thermal source, sent on the mirrors after a proper shaping. In this paper we present the results obtained on a tabletop Fabry-Pérot Michelson interferometer illuminated with a LG_(3,3) mode. We show how an incoherent light source can reduce the astigmatism of one of the mirrors, increasing the quality of the beam in one of the Fabry-Pérot cavities and then the contrast of the interferometer. The system has the potential to reduce more complex defects and also to be used in future gravitational-wave detectors using conventional Gaussian beams.
© 2015 American Physical Society. Received 5 October 2015; published 18 November 2015. The authors would like to thank the Laboratoire d'Annecy-le-Vieux de Physique des Particules for the support with the digital control system and photodiode readout; H. Halloin and P. Prat for discussions and support with the analog electronics. M. Granata and R. Ward have contributed to the realization of the LG3,3 generator described in , and F. Kéfélian has contributed at the realization of the LG3,3 interferometer described in . G. V. would like to acknowledge the support of the National Science Foundation and the LIGO Laboratory. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation, and operates under Cooperative Agreement No. PHY-0757058. Advanced LIGO was built under Award No. PHY-0823459. Finally, we would like to thank Adam Kutynia and Nicolas Smith-Lefebvre for their help in setting up the DMD board, Gary Hamming for the reading of the manuscript, and Eric Genin, Antonino Chiummo and Paul Fulda for useful discussions. This work is supported by the Agence Nationale de la Recherche under Grant No. 2010-BLANC-0416-01. M. T. is supported by the European Gravitational Observatory.
Published - PhysRevD.92.102002.pdf