Optical trapping of the transversal motion for an optically levitated mirror

Abstract: Optomechanical systems are suitable for elucidating quantum phenomena at the macroscopic scale in the sense of the mass scale. The systems should be well-isolated from the environment to avoid classical noises, which conceal quantum signals. Optical levitation is a promising way to isolate optomechanical systems from the environment. To realize optical levitation, all degrees of freedom need to be trapped. Until now, longitudinal trapping and rotational trapping of a mirror with optical radiation pressure have been studied in detail and validated with various experiments. However, less attention has been paid to the transversal trapping of a mirror. Herein, we report a pioneering result where we experimentally confirmed transversal trapping of a mirror of a Fabry-P\'erot cavity using a torsional pendulum. Through this demonstration, we experimentally proved that optical levitation is realizable with only two Fabry-P\'erot cavities that are aligned vertically. This work paves the way toward optical levitation and realizing a macroscopic quantum system.