Scattering-Free Optical Levitation of a Cavity Mirror

Abstract

We demonstrate the feasibility of levitating a small mirror using only radiation pressure. In our scheme, the mirror is supported by a tripod where each leg of the tripod is a Fabry-Perot cavity. The macroscopic state of the mirror is coherently coupled to the supporting cavity modes allowing coherent interrogation and manipulation of the mirror motion. The proposed scheme is an extreme example of the optical spring, where a mechanical oscillator is isolated from the environment and its mechanical frequency and macroscopic state can be manipulated solely through optical fields. We model the stability of the system and find a three-dimensional lattice of trapping points where cavity resonances allow for build up of optical field sufficient to support the weight of the mirror. Our scheme offers a unique platform for studying quantum and classical optomechanics and can potentially be used for precision gravitational field sensing and quantum state generation.Recently much effort has been directed toward the development of new fabrication methods and experimental techniques for controlling optomechanical interactions at the quantum level [1,2]. Optomechanical effects have been observed in mechanical objects with masses ranging from femtograms, as in nano-optomechanical systems [3], to kilograms in the case of gravitational wave antennae [4]. Reaching the quantum regime in optomechanical systems is fundamentally interesting as one is then in a position to prepare macroscopic quantum states, which can, for example, be employed in tests of large-scale quantum decoherence [5] and models of gravity [6,7]. The main barrier to reaching the quantum regime is thermalization resulting from intrinsic coupling to environmental reservoirs. This is generally hard to avoid since most mechanical oscillators are supported by some mechanical structure that acts as a bridge for thermal fluctuations. One method to limit thermalization is to operate in cryogenic environments. Nevertheless, the dissipation of energy through the mechanical support still contributes significantly to the decoherence of the mechanical state [8]. Fabrication of a phononic-band gap structure into the substrate [9] has been proposed as one way to reduce the dissipation. Optical trapping [10] and levitation [11][12][13][14] have also been suggested as possible routes to low-dissipation quantum optomechanics. In the recent proposals, despite the mechanical support being completely removed, scattering from the levitated object leads to interaction with the environment and lowering of optomechanical coupling.Radiation pressure within an optical resonator can be used to couple the mechanical oscillations of a suspended cavity mirror with the optical mode [15,16]. Such coupling between optical and mechanical systems can be used for a variety of applications, including precision measurement [17], the creation of a mechanical quantum harmonic oscillator [15,[18][19][20], control of quantum macroscopic coherence [21], the generation of squeezed light for quantum informa...

A classical channel model for gravitational decoherence

“…This is largely due to the ability to use laser cooling techniques to prepare harmonically trapped particles of large mass in the ground state [24,30]. It is possible that carefully controlled optical levitation [25][26][27][28], or magnetic levitation [29,30] experiments on two gravitationally coupled masses might reach the regime discussed in this paper but it will not be easy. It should be noted in connection with equation (33) that laser cooling also changes both the temperature and the quality factor.…”

Photothermally induced transparency

“…* Ping.Lam@anu.edu.au Here, we theoretically propose and experimentally demonstrate a transparency phenomenon induced by the photothermal effects in an optical cavity. In a similar manner to radiation pressure [13,25,26], the photothermal effects couples cavity optical path length to the intracavity power. This is due to the absorption of photons by the cavity mirrors leading to thermal expansion and refractive index change of the mirror coating and substrate.…”

Towards thermal noise free optomechanics

“…The use of optical forces as restoring forces of mechanical resonators has been investigated in various configurations from 1g mirror pendulums stiffened with a linear optical spring [8], picogram mirror resonators suspended from fibres [9], to optically levitated sub-micron particles [10,11] and mirrors [12]. However, systems using linear optical spring effects will ultimately be limited by quantum radiation pressure noise induced heating.…”