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Register a new userSpin-optomechanical coupling between light and a nanofiber torsional mode
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Light that carries linear or angular momentum can interact with a mechanical object giving rise to optomechanical effects. In particular, a photon transfers its intrinsic angular momentum to an object when the object either absorbs the photon or changes the photon polarization, as in an action/reaction force pair. Here, we present the implementation of light-induced selective resonant driving of the torsional mechanical modes of a single-mode tapered optical nanofiber. The nanofiber torsional mode spectrum is characterized by polarimetry, showing narrow natural resonances (Q$approx$2,000). By sending amplitude modulated light through the nanofiber, we resonantly drive individual torsional modes as a function of the light polarization. By varying the input polarization to the fiber, we find the largest amplification of a mechanical oscillation (>35 dB) is observed when driving the system with light containing longitudinal spin on the nanofiber waist. These results present optical nanofibers as a platform suitable for quantum spin-optomechanics experiments.
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Linearly polarized light can exert a torque on a birefringent object when passing through it. This phenomena, present in Maxwells equations, was revealed by Poynting and beautifully demonstrated in the pioneer experiments of Beth and Holbourn. Modern uses of this effect lie at the heart of optomechanics with angular momentum exchange between light and matter. A milestone of controlling movable massive objects with light is the reduction of their mechanical fluctuations, namely cooling. Optomechanical cooling has been implemented through linear momentum transfer of the electromagnetic field in a variety of systems, but remains unseen for angular momentum transfer to rotating objects. We present the first observation of cooling in a rotational optomechanical system. Particularly, we reduce the thermal noise of the torsional modes of a birefringent optical nanofiber, with resonant frequencies near 200 kHz and a Q-factor above $mathbf{2times10^4}$. Nanofibers are centimeter long, sub-micrometer diameter optical fibers that confine propagating light, reaching extremely large intensities, hence enhancing optomechanical effects. The nanofiber is driven by a propagating linearly polarized laser beam. We use polarimetry of a weak optical probe propagating through the nanofiber as a proxy to measure the torsional response of the system. Depending on the polarization of the drive, we can observe both reduction and enhancement of the thermal noise of many torsional modes, with noise reductions beyond a factor of two. The observed effect opens a door to manipulate the torsional motion of suspended optical waveguides in general, expanding the field of rotational optomechanics, and possibly exploiting its quantum nature for precision measurements in mesoscopic systems.
Achieving cavity-optomechanical strong coupling with high-frequency phonons provides a rich avenue for quantum technology development including quantum state-transfer, memory, and transduction, as well as enabling several fundamental studies of macroscopic phononic degrees-of-freedom. Reaching such coupling with GHz mechanical modes however has proved challenging, with a prominent hindrance being material- and surface-induced-optical absorption in many materials. Here, we circumvent these challenges and report the observation of optomechanical strong coupling to a high frequency (11 GHz) mechanical mode of a fused-silica whispering-gallery microresonator via the electrostrictive Brillouin interaction. Using an optical heterodyne detection scheme, the anti-Stokes light backscattered from the resonator is measured and normal-mode splitting and an avoided crossing are observed in the recorded spectra, providing unambiguous signatures of strong coupling. The optomechanical coupling rate reaches values as high as $G/2pi = 39 text{MHz}$ through the use of an auxiliary pump resonance, where the coupling dominates both the optical ($kappa/2pi = 3 text{MHz}$) and the mechanical ($gamma_text{m}/2pi = 21 text{MHz}$) amplitude decay rates. Our findings provide a promising new approach for optical quantum control using light and sound.
We report on the modification of the optical and mechanical properties of a silicon 1D optomechanical crystal cavity due to thermo-optic effects in a high phonon/photon population regime. The cavity heats up due to light absorption in a way that shifts the optical modes towards longer wavelengths and the mechanical modes to lower frequencies. By combining the experimental optical results with finite-difference time-domain simulations we establish a direct relation between the observed wavelength drift and the actual effective temperature increase of the cavity. By assuming that the Youngs modulus decreases accordingly to the temperature increase, we find a good agreement between the mechanical mode drift predicted using a finite element method and the experimental one.
We experimentally demonstrate simultaneous spatial and temporal compression in the propagation of light pulses in multimode nonlinear optical fibers. We reveal that the spatial beam self-cleaning recently discovered in graded-index multimode fibers is accompanied by significant temporal reshaping and up to four-fold shortening of the injected sub-nanosecond laser pulses. Since the nonlinear coupling among the modes strongly depends on the instantaneous power, we explore the entire range of the nonlinear dynamics with a single optical pulse, where the optical power is continuously varied across the pulse profile.
We present a design methodology and analysis of a cavity optomechanical system in which a localized GHz frequency mechanical mode of a nanobeam resonator is evanescently coupled to a high quality factor (Q>10^6) optical mode of a separate nanobeam optical cavity. Using separate nanobeams provides flexibility, enabling the independent design and optimization of the optics and mechanics of the system. In addition, the small gap (approx. 25 nm) between the two resonators gives rise to a slot mode effect that enables a large zero-point optomechanical coupling strength to be achieved, with g/2pi > 300 kHz in a Si3N4 system at 980 nm and g/2pi approx. 900 kHz in a Si system at 1550 nm. The fact that large coupling strengths to GHz mechanical oscillators can be achieved in SiN is important, as this material has a broad optical transparency window, which allows operation throughout the visible and near-infrared. As an application of this platform, we consider wide-band optical frequency conversion between 1300 nm and 980 nm, using two optical nanobeam cavities coupled on either side to the breathing mode of a mechanical nanobeam resonator.
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