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Register a new userOptical and mechanical mode tuning in an optomechanical crystal with light-induced thermal effects
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Added by
Daniel Navarro Urrios
Publication date
2016
fields
Physics
and research's language is
English
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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.
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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 theoretically study a strongly-driven optomechanical system which consists of a passive optical cavity and an active mechanical resonator. When the optomechanical coupling strength is varied, phase transitions, which are similar those observed in $mathcal{PT}$-symmetric systems, are observed. We show that the optical transmission can be controlled by changing the gain of the mechanical resonator and loss of the optical cavity mode. Especially, we find that: (i) for balanced gain and loss, optical amplification and absorption can be tuned by changing the optomechanical coupling strength through a control field; (ii) for unbalanced gain and loss, even with a tiny mechanical gain, both optomechanically-induced transparency and anomalous dispersion can be observed around a critical point, which exhibits an ultra-long group delay. The time delay $tau$ can be optimized by regulating the optomechanical coupling strength through the control field and improved up to several orders of magnitude ($tausim2$ $mathrm{ms}$) compared to that of conventional optomechanical systems ($tausim1$ $mumathrm{s}$). The presence of mechanical gain makes the group delay more robust to environmental perturbations. Our proposal provides a powerful platform to control light transport using a $mathcal{PT}$-symmetric-like optomechanical system.
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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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