Synchronization of many coupled oscillators is widely found in nature and has the potential to revolutionize timing technologies. Here we demonstrate synchronization in arrays of silicon nitride micromechanical oscillators coupled in an all-to-all configuration purely through an optical radiation field. We show that the phase noise of the synchronized oscillators can be improved by almost 10 dB below the phase noise limit for each individual oscillator. These results open a practical route towards synchronized oscillator networks.Nano-and micromechanical oscillator arrays have the potential to enable high power and low noise integrated frequency sources that play a key role in sensing and the essential time keeping of modern technology [1][2][3][4][5]. The challenge with building scalable oscillator arrays is that micromechanical oscillators fabricated on a chip fundamentally have a spread of mechanical frequencies due to unavoidable statistical variations in the fabrication process [4,[6][7][8][9]. This dispersion in mechanical frequencies has a detrimental effect on the coherent operation in arrays of micromechanical oscillators. Here we show that arrays consisting of three, four and seven dissimilar microscale optomechanical oscillators can be synchronized to oscillate in unison coupled purely through a common optical cavity field using less than a milliwatt of optical power. We further demonstrate that the phase noise of the oscillation signal can be reduced by a factor of N below the thermomechanical phase noise limit of each individual oscillator as N oscillators are synchronized, in agreement with theoretical predictions [10,11]. The highly efficient, low loss and controllable nature of light mediated coupling could put large scale nano-and micromechanical oscillator networks in practice [12][13][14][15][16][17][18].Synchronization is a ubiquitous phenomenon found in coupled oscillator systems [10,19]. Heart beat is a result of synchronized motion of pace maker cells [20], circadian rhythm arises because of coordinated body physiology [21] and global positioning system relies on synchronized operation of clocks. On the nanoscale, synchronization has been experimentally demonstrated in nanomechanical systems coupled through mechanical connections [3], electrical capacitors [9], off-chip connections [6] and through an optical cavity [7,8]. However, these demonstrations were limited to only two oscillators. Achieving synchronization in large micromechanical oscillator networks requires scalable oscillator units and efficient and controllable coupling mechanisms [12,13,22].Here we experimentally demonstrate that arrays of free running micromechanical oscillators can be synchronized when coupled purely through a common electro- magnetic field as predicted by theories [12,13]. A conceptual view of an array of mechanical resonators coupled through light is illustrated in Figure 1a. Each optomechanical oscillator (OMO) possesses a slightly different frequency of mechanical oscillation (Ω i ) and is only connected...

We demonstrate photonic devices based on standard 3C SiC epitaxially grown on silicon. We achieve high optical confinement by taking advantage of the high stiffness of SiC and undercutting the underlying silicon substrate. We demonstrate a 20 µm radius suspended microring resonator with Q=18,000 fabricated on commercially available SiC-on-silicon substrates.

Frequency-locking and other phenomena emerging from nonlinear interactions between mechanical oscillators are of scientific and technological importance. However, existing schemes to observe such behaviour are not scalable over distance. We demonstrate a scheme to couple two independent mechanical oscillators, separated in frequency by 80kHz and situated far from each other (3.2km), via light. Using light as the coupling medium enables this scheme to have low loss and be extended over long distances. This scheme is reversible and can be generalised for arbitrary network configurations. Frequency-locking between micromechanical oscillators is critical for RF communication and signalprocessing applications [1][2][3]; however its scalability is limited by the fact that, in general, the oscillators are obliged to be in physical proximity in order to interact. Micromechanical oscillators can interact at the micronscale via electronic coupling [4] or a physical connection [5]. However, these schemes are fundamentally lossy over long distances, and therefore, are not scalable. Scaling up coupled mechanical oscillators to macro-scale networks [6][7][8] could potentially enable novel concepts in memory and computation [9][10][11], as well as provide a platform to put in practice many theories of nonlinear dynamics of coupled oscillators [12,13].Interaction of mechanical oscillators through light could, in principle, help overcome this limitation, since light can propagate over long distances with minimal loss. Recent reports [5,14,15] on frequency-locking between mechanical oscillators demonstrate interaction only over a few micrometers. In demonstrations of light-mediated coupling of two micromechanical oscillators [14,15], both mechanical oscillators are coupled to the same optical cavity, limiting the kind of network topologies that can be used and how far the oscillators can be separated.In this paper, we demonstrate a reconfigurable scheme to couple, via light, two independent micromechanical oscillators separated from each other by an effective path of 3.2km, in the master-slave configuration and show the ability to lock their oscillation frequencies. This coupling scheme is based on using light to send the information of the mechanical oscillations from the master oscillator to the slave oscillator. It is facilitated by the fact that each oscillator is an an optomechanical oscillator (OMO), consisting of co-localised optical resonances and mechanical resonances that are coupled to each other (Eqs. 1a, 1b) [16]. The mechanical resonator can be modelled as a damped simple harmonic oscillator with position 'x', effective mass m ef f , frequency Ω m and damping rate Γ m . It is driven by its interaction with an optical forceω , where |a| 2 is the energy in the optical cavity and ω is the laser frequency. g om indicates the strength of the interaction between optics and mechanics. The optical cavity can also be modelled as a damped oscillator, with a position-dependent frequency (ω 0 +g om x) and damping rate Γ opt , a...

Frequency-locking and other phenomena emerging from nonlinear interactions between mechanical oscillators are of scientific and technological importance. However, existing schemes to observe such behaviour are not scalable over distance. We demonstrate a scheme to couple two independent mechanical oscillators, separated in frequency by 80kHz and situated far from each other (3.2km), via light. Using light as the coupling medium enables this scheme to have low loss and be extended over long distances. This scheme is reversible and can be generalised for arbitrary network configurations. Frequency-locking between micromechanical oscillators is critical for RF communication and signalprocessing applications [1][2][3]; however its scalability is limited by the fact that, in general, the oscillators are obliged to be in physical proximity in order to interact. Micromechanical oscillators can interact at the micronscale via electronic coupling [4] or a physical connection [5]. However, these schemes are fundamentally lossy over long distances, and therefore, are not scalable. Scaling up coupled mechanical oscillators to macro-scale networks [6][7][8] could potentially enable novel concepts in memory and computation [9][10][11], as well as provide a platform to put in practice many theories of nonlinear dynamics of coupled oscillators [12,13].Interaction of mechanical oscillators through light could, in principle, help overcome this limitation, since light can propagate over long distances with minimal loss. Recent reports [5,14,15] on frequency-locking between mechanical oscillators demonstrate interaction only over a few micrometers. In demonstrations of light-mediated coupling of two micromechanical oscillators [14,15], both mechanical oscillators are coupled to the same optical cavity, limiting the kind of network topologies that can be used and how far the oscillators can be separated.In this paper, we demonstrate a reconfigurable scheme to couple, via light, two independent micromechanical oscillators separated from each other by an effective path of 3.2km, in the master-slave configuration and show the ability to lock their oscillation frequencies. This coupling scheme is based on using light to send the information of the mechanical oscillations from the master oscillator to the slave oscillator. It is facilitated by the fact that each oscillator is an an optomechanical oscillator (OMO), consisting of co-localised optical resonances and mechanical resonances that are coupled to each other (Eqs. 1a, 1b) [16]. The mechanical resonator can be modelled as a damped simple harmonic oscillator with position 'x', effective mass m ef f , frequency Ω m and damping rate Γ m . It is driven by its interaction with an optical forceω , where |a| 2 is the energy in the optical cavity and ω is the laser frequency. g om indicates the strength of the interaction between optics and mechanics. The optical cavity can also be modelled as a damped oscillator, with a position-dependent frequency (ω 0 +g om x) and damping rate Γ opt , a...

Optomechanical resonators suffer from the dissipation of mechanical energy through the necessary anchors enabling the suspension of the structure. Here, we show that such structural loss in an optomechanical oscillator can be almost completely eliminated through the destructive interference of elastic waves using dual-disk structures. We also present both analytical and numerical models that predict the observed interference of elastic waves. Our experimental data reveal unstressed silicon nitride (Si3N4) devices with mechanical Q-factors up to 104 at mechanical frequencies of f = 102 MHz (fQ = 1012) at room temperature.