Vacuum optomechanics of optically levitated objects: determination of nonlinear properties of the optical trap

Abstract

Optically levitated nanoparticles in vacuum are a promising tool aiming for the extremely sensitive force measurements in reaching up to the order of zN•Hz-1/2 and for the potential investigation in the field of quantum physics. In contrast to other mechanical oscillators, the optically trapped nanoparticle in vacuum has no clamping losses, its motion is influenced only by a laser beam and its potential profle and therefore the mechanical quality factor of such oscillator is very high. In water immersion the optical trap is almost exclusively considered as harmonic but in vacuum the optical potential anharmonicity starts to play an important role. This can be observed in power spectrum density profile where the oscillation peak is asymmetric. Here we demonstrate on the simulated trajectories of the levitated particle how the standard power spectral density method provides strongly biased values of parameters describing the optical trap and its surrounding properties.