Fabry-Pérot-Michelson interferometer using higher-order Laguerre-Gauss modes

One of the main noise sources for future interferometric gravitational wave detectors will be the thermal fluctuations of the mirrors used as test masses. To reduce the effect of this noise without changing the mirror material, size and temperature, the use of Laguerre-Gauss (LG) modes has been proposed. In this work we report the first experimental results obtained with a Fabry-P\'erot Michelson interferometer operated with Laguerre-Gauss LG₃₃ as input mode and developed as a table-top prototype to test alignment and matching procedures, possible control issues and optical performances of the LG₃₃. Among the results obtained, we have demonstrated the degradation of the interferometer contrast of the LG₃₃ with respect to the Gaussian beam, predicted by several previous simulations works and due to the degeneracy of LG modes having the same order. In addition, the observed contrast degradation for the LG₃₃ as well as the interferometer optical properties have been explained using a numerical simulation.