Optical trapping of transversal motion for an optically levitated mirror

Optomechanical systems are suitable systems to elucidate quantum phenomena at the macroscopic 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. In order to realize optical levitation, all degrees of freedom need to be trapped. So far, longitudinal trapping and rotational trapping with optical radiation pressure have been well studied and validated with various experiments. On the other hand, less attention has been paid to transversal trapping. Here, we experimentally confirmed transversal trapping of a mirror of a Fabry-Perot cavity for the first time by using a torsional pendulum. By this demonstration, we proved experimentally that optical levitation is realizable with only two Fabry-Perot cavities that are aligned vertically. This work paves the way toward optical levitation and realizing a macroscopic quantum system.