We report the development of a phonon laser based on the center-of-mass oscillation of an optically levitated silica nanosphere in a free-space optical dipole trap. A parametric feedback scheme based on the detection of the oscillator’s center-of-mass is used to provide a cooling signal that intrinsically depends on the oscillator’s mean phonon occupation. When an amplification signal is added to the feedback at the mechanical resonance, these two signals produce center-of-mass dynamics that are analogous to those of a single-mode optical laser. Observed phenomena include a threshold in oscillation amplification, a transition from Brownian motion below threshold to coherent oscillation above threshold, reduction in the linewidth of the oscillation spectrum, and gain saturation. We also analyze the statistical phonon number distributions above and below threshold. The observed dynamics are described by a model that includes both stimulated and spontaneous emission of center-of-mass phonons. Importantly, the operation of this phonon laser relies on externally controllable, feedback-based parameters and therefore allows tuning of the threshold via these parameters. We also explore the use of the levitated nanoparticle phonon laser as a detector of weak external forces via injection locking.
We theoretically consider light storage in a single nanoparticle levitated in an optical dipole trap and subjected to nonlinear feedback cooling. The storage protocol is realized by controlling the coupling between mechanical displacement and signal pulse by maneuvering the intensity of writing and readout pulses. The process involves writing and readout pulses at one mechanical frequency below the signal pulse. We demonstrate that during the writing pulse, a signal pulse is stored as a mechanical excitation of the nanoparticle oscillation. It is then shown that a readout pulse at later time can retrieve the stored optical information from the mechanical oscillator. A long storage lifetime of 2 ms is obtained in our system due to the absence of clamping losses. Further, we describe that our protocol can be used for wavelength conversion and shows a saturation in the conversion efficiency as a function of cooperativities of the writing and readout pulses. We also illustrate that the presence of linear feedback heating can lead to the amplification of the retrieved photon energy. Our prototype for light storage with levitated optomechanics can be used to explore the possibility of quantum memories for photonic states.
Conference Committee Involvement (3)
Quantum Information Science, Sensing, and Computation XII
29 April 2020 | Anaheim, California, United States
Quantum Information Science, Sensing, and Computation XI
18 April 2019 | Baltimore, Maryland, United States
Quantum Information Science, Sensing, and Computation X