Propagation properties of light in optomechanical waveguides arrays (OMWAs) are studied for the first time, to the best of our knowledge. Due to the strong mechanical Kerr effect, the optical self-focusing and self-defocusing phenomena can be realized in the arrays of subwavelength dielectric optomechanical waveguides with the milliwatt-level incident powers and micrometer-level lengths. Compared with the conventional nonlinear waveguide arrays, the required incident powers and lengths of the waveguides are decreased by five orders of magnitude and one order of magnitude, respectively. Furthermore, by adjusting the deformation of the nanowaveguides through a control light, the propagation path of the signal light in the OMWA can be engineered, which could be used as a splitting-ratio-tunable beam splitter. This work provides a new platform for discrete optics and broadens the application of integrated optomechanics.
We report enhanced optomechanical coupling by embedding a nano-mechanical beam resonator within an optical race-track resonator. Precise control of the mechanical resonator is achieved by clamping the beam between two low-loss photonic crystal waveguide couplers. The low insertion loss and the rigid mechanical support provided by the couplers yield both high mechanical and optical Q-factors for improved signal quality.
The ultra-short range force, van der Waals force (VWF), will rise rapidly when one nanoscale waveguide is close to another one, and be stronger than the external transverse gradient force (TGF). We theoretically investigate the giant influence of the VWF on the device performance in a typical optomechanical system consisting of a suspended silicon waveguide and a silica substrate including waveguide deformation stiction and failure mechanism. The device shows unique optically-activated plastic/elastic behaviors and stiction due to the VWF. When the input optical power is above the critical pow…
Photonic devices exhibiting all-optically reconfigurable polarization dependence with a large dynamic range would be highly attractive for active polarization control. Here, we report that strongly polarization-selective nonlinear optomechanical interactions emerge in subwavelength waveguides. By using full-vectorial finite element analysis, we find that at certain core ellipticities (aspect ratios) the forward simulated light scattering mediated by a specific acoustic mode is eliminated for one polarization mode, whereas that for the other polarization mode is rather enhanced. This intriguing…
In this paper we study and design quasi-2D optomechanical crystals, waveguides, and resonant cavities formed from patterned slabs. Two-dimensional periodicity allows for in-plane pseudo-bandgaps in frequency where resonant optical and mechanical excitations localized to the slab are forbidden. By tailoring the unit cell geometry, we show that it is possible to have a slab crystal with simultaneous optical and mechanical pseudo-bandgaps, and for which optical waveguiding is not compromised. We then use these crystals to design optomechanical cavities in which strongly interacting, co-localized …
It is shown that optomechanical forces can cause nonlinear self-channelling of light in a planar dual-slab waveguide. A system of two parallel silica nanowebs, spaced ~100 nm and supported inside a fibre capillary, is studied theoretically and an iterative scheme developed to analyse its nonlinear optomechanical properties. Steady-state field distributions and mechanical deformation profiles are obtained, demonstrating that self-channelling is possible in realistic structures at launched powers as low as a few mW. The differential optical nonlinearity of the self-channelled mode can be as much…
Laser cooling of mechanical degrees of freedom is one of the most significant achievements in the field of opto-mechanics. Here, we report, for the first time to the best of our knowledge, efficient passive optomechanical cooling of the motion of a freestanding waveguide coupled to a whispering-gallery-mode (WGM) resonator. The waveguide is an 8 mm long glass-fiber nanospike, which has a fundamental flexural resonance at Ω/2π = 2.5 kHz and a Q-factor of 1.2 10**5. Upon launching 250 μW laser power at an optical frequency close to the WGM resonant frequency, we observed cooling of the nanospike…
We report quantitative experimental measurements of the Abraham force associated with a propagating optical wave. We isolate this force using a guided light wave undergoing an adiabatic mode transformation (AMT) along a liquid-filled hollow optical fiber (HOF). Utilizing this light intensity distribution within the liquid, we were able to generate a time-averaged non-vanishing Abraham force density, while simultaneously suppressing the Abraham-Minkowski force density. The incident laser field induced a linear axial displacement of the air-liquid interface inside the HOF, which provided a direc…
Stimulated Brillouin scattering was recently observed in nanoscale silicon waveguides. Surprisingly, thermally-driven photon-phonon conversion in these structures had not yet been reported. Here, we inject an optical probe in a suspended silicon waveguide and measure its phase fluctuations at the output. We observe mechanical resonances around 8 GHz with a scattering efficiency of $10^{-5} \, \text{m}^{-1}$ and a signal-to-noise ratio of 2. The observations are in agreement with a theory of noise in these waveguides as well as with stimulated measurements. Our scheme may simplify measurements …
The mechanical properties of light have found widespread use in the manipulation of gas-phase atoms and ions, helping create new states of matter and realize complex quantum interactions. The field of cavity-optomechanics strives to scale this interaction to much larger, even human-sized mechanical objects. Going beyond the canonical Fabry-Perot cavity with a movable mirror, here we explore a new paradigm in which multiple cavity-optomechanical elements are wired together to form optomechanical circuits. Using a pair of optomechanical cavities coupled together via a phonon waveguide we demonst…
Radiation-pressure-induced optomechanical coupling permits exquisite control of micro- and mesoscopic mechanical oscillators. This ability to manipulate and even damp mechanical motion with light---a process known as dynamical backaction cooling---has become the basis for a range of novel phenomena within the burgeoning field of cavity optomechanics, spanning from dissipation engineering to quantum state preparation. As this field moves toward more complex systems and dynamics, there has been growing interest in the prospect of cooling traveling-wave phonons in continuous optomechanical wavegu…
We develop a systematic method for deriving a quantum optical multi-mode Hamiltonian for the interaction of photons and phonons in nanophotonic dielectric materials by applying perturbation theory to the electromagnetic Hamiltonian. The Hamiltonian covers radiation pressure and electrostrictive interactions on equal footing. As a paradigmatic example, we apply our method to a cylindrical nanoscale waveguide, and derive a Hamiltonian description of Brillouin quantum optomechanics. We show analytically that in nanoscale waveguides radiation pressure dominates over electrostriction, in agreement …
Flexible control of photons and phonons in silicon nanophotonic waveguides is a key feature for emerging applications in communications, sensing and quantum technologies. Strong phonon leakage towards the silica under-cladding hampers optomechanical interactions in silicon-on-insulator. This limitation has been circumvented by totally or partially removing the silica under-cladding to form pedestal or silicon membrane waveguides. Remarkable optomechanical interactions have been demonstrated in silicon using pedestal strips, membrane ribs, and photonic/phononic crystal membrane waveguides. Stil…
Optomechanical gradient forces arise from evanescent fields of guided waves in parallel photonic waveguides. When designed to be of attractive nature, they increase exponentially as the gap between the waveguides decreases. Moreover, the amplitude of the gradient force can be well controlled due to its linear dependence on the input laser power. Here, we propose to exploit the intrinsic nonlinear nature of the optomechanical gradient force to induce a tunable 3-wave coupling between the fundamental modes of two doubly clamped nanophotonic beams. For one of the beams having half the width of th…
In the well-known stimulated Brillouin scattering (SBS) process, spontaneous acoustic phonons in materials are stimulated by laser light and scatter the latter into a Stokes sideband. SBS becomes more pronounced in optical fibers and has been harnessed to amplify optical signals and even achieve lasing. Exploitation of SBS has recently surged on integrated photonics platforms as simultaneous confinement of photons and phonons in waveguides leads to drastically enhanced interaction. Instead of being optically stimulated, coherent phonons can also be electromechanically excited with very high ef…
We explore the possibility of achieving a significant nonlinear phase shift among photons propagating in nanoscale waveguides exploiting interactions among photons that are mediated by vibrational modes and induced through Stimulated Brillouin Scattering (SBS). We introduce a configuration that allows slowing down the photons by several orders of magnitude via SBS involving sound waves and two pump fields. We extract the conditions for maintaining vanishing amplitude gain or loss for slowly propagating photons while keeping the influence of thermal phonons to the minimum. The nonlinear phase a…
Optomechanical devices sensitively transduce and actuate motion of nanomechanical structures using light. Single--crystal diamond promises to improve the performance of optomechanical devices, while also providing opportunities to interface nanomechanics with diamond color center spins and related quantum technologies. Here we demonstrate dissipative waveguide--optomechanical coupling exceeding 35 GHz/nm to diamond nanobeams supporting both optical waveguide modes and mechanical resonances, and use this optomechanical coupling to measure nanobeam displacement with a sensitivity of $9.5$ fm/$\s…
Nanophononics has the potential for information transfer, in an analogous manner to its photonic and electronic counterparts. The adoption of phononic systems has been limited, due to difficulties associated with the generation, manipulation, and detection of phonons, especially at GHz frequencies. Existing techniques often require piezoelectric materials with an external radiofrequency excitation that are not readily integrated into existing CMOS infrastructures, while non-piezoelectric demonstrations have been inefficient. In this work, we explore the optomechanical generation of coherent ph…
We demonstrate a new type of optomechanical system employing a movable, micron-scale waveguide evanescently-coupled to a high-Q optical microresonator. Micron-scale displacements of the waveguide are observed for milliwatt(mW)-level optical input powers. Measurement of the spatial variation of the force on the waveguide indicates that it arises from a cavity-enhanced optical dipole force due to the stored optical field of the resonator. This force is used to realize an all-optical tunable filter operating with sub-mW control power. A theoretical model of the system shows the maximum achievable…
Fully reconfigurable add-drop filters (ADFs) have important applications in optical communication and information processing. Here we demonstrate a broadly tunable add-drop filter based on a double-disk cavity optomechanical system, side-coupled with a pair of tapered fiber waveguides. By varying the coupling rates between the cavity and the two waveguides, we investigate the dependence of the through (drop) efficiency on the coupling rates, which agrees well with the theoretical results. By optimizing the cavity-waveguide coupling rates, a drop efficiency of 89% and a transmission of 1.9% hav…
Collective phenomena emerging from non-linear interactions between multiple oscillators, such as synchronization and frequency locking, find applications in a wide variety of fields. Optomechanical resonators, which are intrinsically non-linear, combine the scientific assets of mechanical devices with the possibility of long distance controlled interactions enabled by travelling light. Here we demonstrate light-mediated frequency locking of three distant nano-optomechanical oscillators positioned in a cascaded configuration. The oscillators, integrated on a chip along a coupling waveguide, are…
We develop a rigorous theoretical framework for interaction-induced phenomena in the waveguide quantum electrodynamics (QED) driven by mechanical oscillations of the qubits. Specifically, we predict that the simplest set-up of two qubits, harmonically trapped over an optical waveguide, enables the ultrastrong coupling regime of the quantum optomechanical interaction. Moreover, the combination of the inherent open nature of the system and the strong optomechanical coupling leads to emerging parity-time (\PT) symmetry, quite unexpected for a purely quantum system without artificially engineered …
We theoretically demonstrate complete all-optical control of light group velocity via a cavity optomechanical system composed of an optical cavity and a mechanical resonator. The realization depends on no specific materials inside the cavity, and the control of light group velocity stems from the interaction between the signal light and the moving optical diffraction grating within the cavity in analogy to the stimulated Brillouin scattering(SBS). Furthermore, we show that a tunable switch from slow light to fast light can be achieved only by simply adjusting the pump-cavity detuning. The sche…
One of the major advances needed to realize all-optical information processing of light is the ability to delay or coherently store and retrieve optical information in a rapidly tunable manner. In the classical domain, this optical buffering is expected to be a key ingredient to managing the flow of information over complex optical networks. Such a system also has profound implications for quantum information processing, serving as a long-term memory that can store the full quantum information contained in an optical pulse. Here we suggest a novel approach to light storage involving an optical…
We demonstrate an optomechanical platform where optical mode conversion mediated by mechanical motion enables arbitrary tailoring of polarization states of propagating light fields. Optomechanical interactions are realized in a Fabry-Perót resonator, which naturally supports two polarization-degenerate states while an optical control field induces rotational symmetry breaking. Applying such principles, the entire Poincaré sphere is spanned by just optical control of the driving field, realizing reciprocal and non-reciprocal optomechanically-induced birefringence for linearly polarized and circ…
Lithium Niobate (LN or just niobate) thin-film micro-photonic resonators have promising prospects in many applications including high efficiency electro-optic modulators, optomechanics and nonlinear optics. This paper presents free-standing thin-film lithium niobate photonic resonators on a silicon platform using MEMS fabrication technology. We fabricated a 35um radius niobate disk resonator that exhibits high intrinsic optical quality factor (Q) of 484,000. Exploiting the optomechanical interaction from the released free-standing structure and high optical Q, we were able to demonstrate acous…
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 Young's mod…
We present the basic ingredients of continuum optomechanics, i.e. the suitable extension of cavity-optomechanical concepts to the interaction of photons and phonons in an extended waveguide. We introduce a real-space picture and argue which coupling terms may arise in leading order in the spatial derivatives. This picture allows us to discuss quantum noise, dissipation, and the correct boundary conditions at the waveguide entrance. The connections both to optomechanical arrays as well as to the theory of Brillouin scattering in waveguides are highlighted. We identify the 'strong coupling regim…
Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic mod…
We propose an optomechanical structure consisting of a photonic-crystal (holey) membrane suspended above a layered silicon-on-insulator substrate in which resonant bonding/antibonding optical forces created by externally incident light from above enable all-optical control and actuation of stiction effects induced by the Casimir force. In this way, one can control how the Casimir force is expressed in the mechanical dynamics of the membrane, not by changing the Casimir force directly but by optically modifying the geometry and counteracting the mechanical spring constant to bring the system in…
We study the propagation of light in a resonator optical waveguide consisting of evanescently coupled optomechanical crystal array. In the strong driving limit, the Hamiltonian of system can be linearized and diagonalized. In this case we obtain the polaritons, which is formed by the interaction of photons and the collective excitation of mechanical resonators. By analyzing the dispersion relations of polaritons, we find that the band structure can be controlled by changing the related parameters. It has been suggested an engineerable band structure can be used to slow and stop light pulses.
In this article, we rigorously analyze the effects of the dispersion forces (Casimir and van der Waals forces) on a nano-optomechanical device based on a silicon waveguide and a silicon dioxide substrate, surrounded by air and driven by optical forces. The dispersion forces are calculated using a modified Lifshitz theory, in order to take into account the device thickness and material s dielectric permittivities, which are obtained from experimental optical data and validated by means of a rigorous 3D FDTD simulation. We also take into account the mechanical nonlinearity of the waveguide, whic…
Photon carries linear momentum and angular momentum simultaneously. Within the light-matter interaction process, exchange of linear momentum results in optical forces, whereas exchange of angular momentum leads to optical torques. Use of optical forces (light pressure or damping) have been long and wide in quantum optomechanics, however, those of optical torque and optical angular momentum are not. Here we propose a theoretical framework based on optical angular momentum and optical torques to derive the Hamiltonians of cavity orbital and spin angular momentum optomechanical systems, respectiv…
Vibrational resonance amplifies a weak low-frequency signal by use of an additional non-resonant high-frequency modulation. The realization of weak signal enhancement in integrated nonlinear optical nanocavities is of great interest for nanophotonic applications where optical signals may be of low power. Here, we report experimental observation of vibrational resonance in a thermo-optically bistable photonic crystal optomechanical resonator with an amplification up to +16 dB. The characterization of the bistability can interestingly be done using a mechanical resonance of the membrane, which i…
An interleaved, chirped electro-optic dual comb system is demonstrated for rapid, high dynamic range measurements of cavity optomechanical sensors. This approach allows for the cavity displacements to be interrogated at measurement times as fast as 10 μs over ranges far larger than can be achieved with alternative methods. While the performance of this novel readout approach is evaluated with an optomechanical accelerometer, this method is applicable to a wide range of applications including temperature, pressure, and humidity sensing as well as acoustics and molecular spectroscopy.
Optical isolation, non-reciprocal phase transmission and topological phases for light based on synthetic gauge fields have been raising significant interest in the recent literature. Cavity-optomechanical systems that involve two optical modes coupled to a common mechanical mode form an ideal platform to realize these effects, providing the basis for various recent demonstrations of optomechanically induced non-reciprocal light transmission. Here, we establish a unifying theoretical framework to analyze optical non-reciprocity and breaking of time-reversal symmetry in multimode optomechanical …
A widely-known paradigm in optomechanical systems involves coupling the square of the position of a mechanical oscillator to an electromagnetic field. We discuss how, in the so-called resolved sideband regime, this system allows to simulate dynamics similar to ordinary optomechanics, where the position of the oscillator is coupled to the field, but with the roles of the oscillator and the field interchanged. We show that realisation of this system is within reach, and that it opens the door to an otherwise inaccessible parameter regime.
We demonstrate highly efficient coupling of light from an optical fiber to a silicon photonic crystal optomechanical cavity. The fiber-to-cavity coupling utilizes a compact (L ~ 25 um) intermediate adiabatic coupler. The optical coupling is lithographically controlled, broadband, relatively insensitive to fiber misalignment, and allows for light to be transferred from an optical fiber to, in principle, any photonic chip with refractive index greater than that of the optical fiber. Here we demonstrate single-sided cavity coupling with a total fiber-to-cavity optical power coupling efficiency of…
Synthetic magnetism has been used to control charge neutral excitations for applications ranging from classical beam steering to quantum simulation. In optomechanics, radiation-pressure-induced parametric coupling between optical (photon) and mechanical (phonon) excitations may be used to break time-reversal symmetry, providing the prerequisite for synthetic magnetism. Here we design and fabricate a silicon optomechanical circuit with both optical and mechanical connectivity between two optomechanical cavities. Driving the two cavities with phase-correlated laser light results in a synthetic m…
Coherent inter-conversion between an optical and a mechanical excitation in an optomechanical resonator can be used for the storage of an optical pulse as an excitation in a mechanical oscillator. This optomechanical light storage is enabled by external writing and readout pulses at one mechanical frequency below the optical resonance. In this paper, we expand an earlier experimental study [Phys. Rev. Lett. 107, 133601 (2011)] on storing an optical pulse as a radial breathing mode in a silica microsphere. We show that the heterodyne beating between a readout pulse and the corresponding retriev…
Using light to measure an object's motion is central to operating mechanical sensors that probe forces and fields. Cavity optomechanical systems embed mechanical resonators inside optical resonators. This enhances the sensitivity of optomechanical measurements, but only if the mechanical resonator does not spoil the properties of the optical cavity. For example, cavity optomechanical detection of resonators made from optically absorbing materials, or whose geometry does not possess suitable spatial symmetry, is challenging. Here we demonstrate a system that overcomes challenges in measuring hi…
