Simultaneous cooling of coupled mechanical oscillators using whispering gallery mode resonances

Abstract

Abstract:We demonstrate simultaneous center-of-mass cooling of two coupled oscillators, consisting of a microsphere-cantilever and a tapered optical fiber. Excitation of a whispering gallery mode (WGM) of the microsphere, via the evanescent field of the taper, provides a transduction signal that continuously monitors the relative motion between these two microgram objects with a sensitivity of 3 pm. The cavity enhanced optical dipole force is used to provide feedback damping on the motion of the micron-diameter taper, whereas a piezo stack is used to damp the motion of the much larger (up to 180 µm in diameter), heavier (up to 1.5 × 10 −7 kg) and stiffer microsphere-cantilever. In each feedback scheme multiple mechanical modes of each oscillator can be cooled, and mode temperatures below 10 K are reached for the dominant mode, consistent with limits determined by the measurement noise of our system. This represents stabilization on the picometer level and is the first demonstration of using WGM resonances to cool the mechanical modes of both the WGM resonator and its coupling waveguide.

Cramér-Rao bound for time-continuous measurements in linear Gaussian quantum systems

“…[30] (it is possible to include also the continuous measurement on the oscillator environment, which can be performed experimentally in certain optomechanical setups, for example, by monitoring the light scattered from a levitating nanosphere [14,46]). …”

Characterization and Testing of a Micro-g Whispering Gallery Mode Optomechanical Accelerometer

“…where Ω m is the fundamental mechanical resonance frequency of the microsphere-cantilever identified in the power spectral density (PSD=S(f )) of T as previously outlined in [3]. Tailoring the geometry of the microsphere-cantilever can tune Ω m by considering Euler-Bernoulli beam theory for a cantilever with an optical cavity end-mass m s :…”

“…Obtaining a high signal-to-noise measurement of dT requires the laser to sit on the detuned slope of the WGM resonance for dispersively coupled systems. Previously, this was achieved using a Pound-Drever Hall lock [3]. However, this becomes unstable in the presence of driven vibrations and a passive lock is employed instead on WGM resonances with > 50 MHz linewidths [22].…”

“…S IGNIFICANT progress in the field of optomechanics has stimulated a new generation of photonic motion detectors that surpass the sensitivity of current standards, with aims to approach fundamental limits set by quantum mechanics [1]. These systems rely on the coupling between mechanical motion and light, which is enhanced when using an optical resonator such as a Fabry-Perot cavity [2], spherical cavities that support whispering gallery modes (WGMs) [1], [3]- [10], and nanocavities in the form of photonic crystals [11], [12]. Through optimization of the optical field geometry and the mechanical test-mass, sensitivities on the order of 10 −18 m·Hz − 1 2 [1], [13], [14] can be reached, allowing laser cooling of macroscopic motion [1], [15], force sensing [8], and recently the discovery of gravitational waves [13].…”

Chalcogenide microresonators tailored to distinct morphologies by the shaping of glasses on silica tapers

“…Single discrete optical microresonators have been increasingly demanded for their exploitation in a plethora of applications such as biological sensing [6], optomechanics [7], cavity quantum electrodynamics [8], lasers [9], and all-optical signal processing [10]. Consequently, developing practical and low-cost techniques to produce high-quality-factor glass microresonators in application-specific shapes with a robust way of integration and the capability of sensitive tuning is crucial for photonic applications.…”