Cavity Optomechanics Research Articles

Semiconductor-on-diamond cavities for spin optomechanics.

Optomechanical cavities are powerful tools for classical and quantum information processing that can be realized using nanophotonic structures that co-localize optical and mechanical resonances. Typically, phononic localization requires suspended devices that forbid vertical leakage of mechanical energy. Achieving this in some promising quantum photonic materials such as diamond requires non-standard nanofabrication techniques, while hindering integration with other components and exacerbating heating related challenges. As an alternative, we have developed a semiconductor-on-diamond platform that co-localizes phononic and photonic modes without requiring undercutting. We have designed an optomechanical crystal cavity that combines high optomechanical coupling with low dissipation, and we show that this platform will enable optomechanical coupling to spin qubits in the diamond substrate. These properties demonstrate the promise of this platform for realizing quantum information processing devices based on spin, phonon, and photon interactions.

Polaromechanics: polaritonics meets optomechanics

Cavity exciton polariton physics and cavity optomechanics have evolved into mature and active domains with, so far, very little connections between them. We argue here that there are strong reasons to bridge the two fields, opening interesting opportunities. Polaritons are entities sharing the properties of photons and excitons in a controllable way. They can lead to tunable and strongly enhanced optomechanical couplings and, through them, to single-particle cooperativies C0 > 1 as well as ultra-strong optomechanical coupling in the many-particle regime. Besides, exciton-exciton Coulomb interactions define a new regime of non-linear many-body optomechanics with notable and largely unexplored consequences. Conversely, coherent vibrations can add a qualitatively distinct ingredient to the field of polaritonics by introducing the variable of time. Indeed, the mechanics built-in in polariton resonators allows for controllable time-modulation up to frequencies of tens of GHz with important consequences for the control of quantum emitters and bidirectional optical-to-microwave conversion. Most interestingly, it also enables polaritons to access Floquet physics, Landau-Zenner-Stückelberg state preparation, spinor pseudo-magnetic resonance, as well as optomechanically induced non-reciprocal phenomena. This guest-editorial addresses the opportunities and challenges in these emerging field.

Frequency conversion in a hybrid cavity-optomechanical system

We propose a scheme to realize frequency conversion of photons, using a hybrid system with a qubit coupled to both a resonator cavity and an optomechanical cavity. In this system, a high-energy photon can be converted into a low-energy photon plus a phonon and vice versa; the qubit works as an intermediate medium with its states unchanged. Moreover, the process can be exquisitely tuned by changing the frequency of the qubit or the resonator mode, providing additional control for the conversion. We further analyze the system dynamics and demonstrate two Rabi oscillation behaviors with dissipations. With the state-of-the-art techniques in cavity quantum electrodynamics and optomechanical systems, our proposal would be implemented and an efficient and controllable quantum light source can be achieved.

Parametrically Driven Inertial Sensing in Chip‐Scale Optomechanical Cavities at the Thermodynamical Limits with Extended Dynamic Range

AbstractRecent scientific and technological advances have enabled the detection of gravitational waves, autonomous driving, and the proposal of a communications network on the Moon (Lunar Internet or LunaNet). These efforts are based on the measurement of minute displacements and their corresponding force transduction, which enables acceleration, velocity, and position determination for navigation. State‐of‐the‐art accelerometers use capacitive or piezoresistive techniques and micro‐electromechanical systems (MEMS) via integrated circuit (IC) technologies to drive transducers and convert their output for electric readout. In recent years, laser optomechanical transduction and readout have enabled highly sensitive detection of motional displacement. Here the theoretical framework is further examined for the novel mechanical frequency readout technique of optomechanical transduction when the sensor is driven into oscillation mode. Theoretical and physical agreements are demonstrated, and the most relevant performance parameters are characterized by a device with a 1.5 mg Hz−1 acceleration sensitivity, a 2.5 fm Hz−1/2 displacement resolution corresponding to a 17.02 µg Hz−1/2 force‐equivalent acceleration, and a 5.91 Hz nW−1 power sensitivity, at the thermodynamical limits. In addition, a novel technique is presented for dynamic range extension while maintaining the precision sensing sensitivity. This inertial accelerometer is integrated on‐chip and enabled for packaging, with a laser‐detuning‐enabled approach.

Quantum criticality induced strong coupling between resonant modes

We propose a scheme to achieve a strong interaction between an optical cavity and a single polariton mode of an optomechanical cavity, despite a weak initial coupling between the two. This interaction is made possible by quantum criticality, and the coupled system comprising two optical cavities and an optomechanical cavity displays a phenomenon similar to the concepts of electromagnetically induced transparency (EIT) and Autler–Townes splitting in atomic physics.

Proton radiation effects on optically transduced silicon carbide microdisk resonators

Circular microdisk mechanical resonators vibrating in their various resonance modes have emerged as important platforms for a wide spectrum of technologies including photonics, cavity optomechanics, optical metrology, and quantum optics. Optically transduced microdisk resonators made of advanced materials such as silicon carbide (SiC), diamond, and other wide- or ultrawide-bandgap materials are especially attractive. They are also of strong interest in the exploration of transducers or detectors for harsh environments and mission-oriented applications. Here we report on the first experimental investigation and analysis of energetic proton radiation effects on microdisk resonators made of 3C-SiC thin film grown on silicon substrate. We fabricate and study microdisks with diameters of ∼48 µm and ∼36 µm, and with multimode resonances in the ∼1 to 20 MHz range. We observe consistent downshifts of multimode resonance frequencies, and measure fractional frequency downshifts from the first three flexural resonance modes, up to ∼-3420 and -1660 ppm for two devices, respectively, in response to 1.8 MeV proton radiation at a dosage of 1014/cm2. Such frequency changes are attributed to the radiation-induced Young’s modulus change of ∼0.38% and ∼0.09%, respectively. These devices also exhibit proton detection responsivity of ℜ ≈ -5 to -6 × 10−6 Hz/proton. The results provide new knowledge of proton radiation effects in SiC materials, and may lead to better understanding and exploitation of micro/nanoscale devices for harsh-environment sensing, optomechanics, and integrated photonics applications.

Discriminating quantum gravity models by gravitational decoherence

Several phenomenological approaches to quantum gravity predict the existence of a minimal measurable length and/or a maximum measurable momentum near the Planck scale. When embedded into the framework of quantum mechanics, such constraints induce a modification of the canonical commutation relations and thus a generalization of the Heisenberg uncertainty relations, commonly referred to as generalized uncertainty principle (GUP). Different models of quantum gravity imply different forms of the GUP. For instance, in the framework of string theory the GUP is quadratic in the momentum operator, while in the context of doubly special relativity it includes an additional linear dependence. Among the possible physical consequences, it was recently shown that the quadratic GUP induces a universal decoherence mechanism, provided one assumes a foamy structure of quantum spacetime close to the Planck length. Along this line, in the present work we investigate the gravitational decoherence associated to the linear-quadratic GUP and we compare it with the one associated to the quadratic GUP. We find that, despite their similarities, the two generalizations of the Heisenberg uncertainty principle yield decoherence times that are completely uncorrelated and significantly distinct. Motivated by this result, we introduce a theoretical and experimental scheme based on cavity optomechanics to measure the different time evolution of nonlocal quantum correlations corresponding to the two aforementioned decoherence mechanisms. We find that the deviation between the two predictions occurs on time scales that are macroscopic and thus potentially amenable to experimental verification. This scenario provides a possible setting to discriminate between different forms of the GUP and therefore different models of quantum gravity.

Nonlinear Sideband Cooling to a Cat State of Motion.

The ability to prepare a macroscopic mechanical resonator into a quantum superposition state is an outstanding goal of cavity optomechanics. Here, we propose a technique to generate cat states of motion using the intrinsic nonlinearity of a dispersive optomechanical interaction. By applying a bichromatic drive to an optomechanical cavity, our protocol enhances the inherent second-order processes of the system, inducing the requisite two-phonon dissipation. We show that this nonlinear sideband cooling technique can dissipatively engineer a mechanical resonator into a cat state, which we verify using the full Hamiltonian and an adiabatically reduced model. While the fidelity of the cat state is maximized in the single-photon, strong-coupling regime, we demonstrate that Wigner negativity persists even for weak coupling. Finally, we show that our cat state generation protocol is robust to significant thermal decoherence of the mechanical mode, indicating that such a procedure may be feasible for near-term experimental systems.

Auxiliary-Cavity-Induced Ultrasensitive and Ultrahigh-Resolution Biomolecule Mass Sensing in a Hybrid Spinning Resonator System

We theoretically demonstrate an ultrasensitive and ultrahigh-resolution biomolecule mass sensing based on a spinning resonator system, which includes a spinning whispering-gallery-mode (WGM) optomechanical cavity and an auxiliary optical cavity. When the WGM cavity is spinning along the clockwise or counterclockwise direction, the cavity field will undergo different Sagnac effect. If the Sagnac effect and the auxiliary optical cavity are simultaneously taken into consideration, not only the line width of the transmission spectrum is significantly squeezed, but also the transmission intensity will be extremely enhanced, which indicates an ultrasensitive and ultrahigh-resolution mass sensor. When the mass of external biomolecules (such as baculovirus or coronavirus) is deposited on the resonator, their mass can be determined by tracking the resonance frequency shifts in the transmission spectrum. Thus, our research can provide a method to classify kinds of viruses, especially can be used to identify 2019-nCoV.

Strong squeezing and robust entanglement in a second-order coupled optomechanical cavity assisted by a Kerr nonlinear medium

We investigate theoretically an optomechanical system composed of an optical mode and a mechanical mode interacting through first-order coupling and second-order coupling in the presence of a Kerr nonlinear medium. We study how the nonlinearities (second-order optomechanical coupling and Kerr nonlinearity) alter the optical output spectrum, optical quadrature squeezing and optomechanical entanglement. It is shown that the intensity of the output optical spectrum decreases drastically with an increase in second-order optomechanical coupling while it increases significantly with an increase in Kerr nonlinear parameter. More interestingly, by choosing suitable second-order optomechanical coupling and detuning of the optical cavity field, one can achieve strong squeezing of the cavity light field. Further, these nonlinearities play an important role in creating robust optomechanical entanglement between optical and mechanical modes. Hence, the presence of various nonlinearities in the system can be a good platform for achieving the squeezing of light and robust optomechanical entanglement which can be used in realizing better quantum optomechanical devices.

Enhanced Entanglement and Controlling Quantum Steering in a Laguerre–Gaussian Cavity Optomechanical System with Two Rotating Mirrors

AbstractGaussian quantum steering is a type of quantum correlation in which two entangled states exhibit asymmetry. An efficient theoretical proposal is presented for the control of quantum steering and enhancement of entanglement in a Laguerre–Gaussian (LG) cavity optomechanical system. The system contains two rotating mirrors and a coherently driven optical parametric amplifier (OPA). The numerical results show significantly improved mirror‐mirror and mirror‐cavity entanglements by controlling the system parameters such as parametric gain, parametric phase, and the frequency of the two rotating mirrors. In addition to bipartite entanglement, our system also exhibits mirror‐cavity‐mirror tripartite entanglement as well. Another intriguing finding is the control of quantum steering, for which several results were obtained by investigating it for various system parameters. It is shown that the steering directivity is primarily determined by the frequency of two rotating mirrors. Furthermore, for two rotating mirrors, quantum steering is found to be asymmetric both one‐way and two‐way. Therefore, it can be asserted that the current proposal may help in the understanding of non‐local correlations and entanglement verification tasks.

Improving Mechanical Oscillator Cooling in a Double-Coupled Cavity Optomechanical System with an Optical Parametric Amplifier

We investigate the cooling phenomenon of a mechanical oscillator in a double-coupled cavity optomechanical system. Our model includes two single-mode optical cavities. The left cavity is an optomechanical system with an optical parametric amplifier, and the right cavity is a standard optical cavity. The two optical cavities couple with each other by exchanging photons. The optomechanical system is effectively driven by an input laser field. By solving the linear quantum Langevin equation of the system under a steady-state condition, we can obtain the position fluctuation spectrum and momentum fluctuation spectrum of the mechanical oscillator, and then, the expression of its effective temperature is obtained. Through numerical analysis, we find the change in the effective temperature of the mechanical oscillator under different physical parameters. The results show that the cooling of the mechanical oscillator can be significantly improved in the presence of optical parameter amplification and adjustment of optical cavity parameters. Our cooling solutions have potential applications for the preparation of nonclassical states of mechanical oscillators, high-precision measurements, and quantum information processing.

Parameter investigations on lithium-niobate-based photonic crystal optomechanical cavity

In this paper, to fully understand the influence of nanofabrication error issues on the lithium-niobate-based device, the systematic simulations and optimizations of lithium-niobate-based photonic crystal (PhC) optomechanical cavity considering the material dispersion and inclination angle of PhC air hole are investigated in details. The structural parameter influences on the PhC band gap, the line defected waveguide transmission characteristics, the optical resonant wavelength of the PhC microcavity, and the mechanical resonant frequency are all discussed. The effects of the simulation methods on the PhC band gap are investigated as well. And finally, the opto-mechanical coupling rate of the lithium-niobate-based PhC optomechanical cavity structure is calculated. Such obtained results can help researchers to precisely design the required optomechanical cavity for specific applications.

Enhancement of the group delay in quadratic coupling optomechanical systems subjected to an external force

We theoretically study the effect of the quadratic coupling strength on optomechanical systems subjected to a continuous external force. Quadratic coupling strength originates from strong coupling between the optical and the mechanical degrees of freedom. We show that the quadratic coupling strength reduces the amplitude of the dispersion spectra at the resonance in both blue- and red-sideband regimes. However, it increases (decreases) the amplitude of the absorption spectrum in the blue- (red-)sideband regime. Furthermore, in both sideband regimes, the effective detuning between the pump and the cavity deviates with the quadratic coupling strength. Thereby, appropriate selection of the quadratic coupling strength results in an important magnification (in absolute value) of the group delay for both slow and fast light exiting from the optomechanical cavity.

Phononically shielded photonic-crystal mirror membranes for cavity quantum optomechanics.

We present a highly reflective, sub-wavelength-thick membrane resonator featuring high mechanical quality factor and discuss its applicability for cavity optomechanics. The 88.5 nm thin stoichiometric silicon-nitride membrane, designed and fabricated to combine 2D-photonic and phononic crystal patterns, reaches reflectivities up to 99.89 % and a mechanical quality factor of 2.9 × 107 at room temperature. We construct a Fabry-Perot-type optical cavity, with the membrane forming one terminating mirror. The optical beam shape in cavity transmission shows a stark deviation from a simple Gaussian mode-shape, consistent with theoretical predictions. We demonstrate optomechanical sideband cooling to mK-mode temperatures, starting from room temperature. At higher intracavity powers we observe an optomechanically induced optical bistability. The demonstrated device has potential to reach high cooperativities at low light levels desirable, for example, for optomechanical sensing and squeezing applications or fundamental studies in cavity quantum optomechanics; and meets the requirements for cooling to the quantum ground state of mechanical motion from room temperature.

High-precision angular rate detection based on an optomechanical micro hemispherical shell resonator gyroscope.

Cavity optomechanics with picometer displacement measurement resolution has shown vital applications in high-precision sensing areas. In this paper, an optomechanical micro hemispherical shell resonator gyroscope (MHSRG) is proposed, for the first time. The MHSRG is driven by the strong opto-mechanical coupling effect based on the established whispering gallery mode (WGM). And the angular rate is characterized by measuring the transmission amplitude changing of laser coupled in and out from the optomechanical MHSRG based on the dispersive resonance wavelength shift and/or dissipative losses varying. The detailed operating principle of high-precision angular rate detection is theoretically explored and the fully characteristic parameters are numerically investigated. Simulation results show that the optomechanical MHSRG can achieve scale factor of 414.8 mV/ (°/ s) and angular random walk of 0.0555 °/ h1/2 when the input laser power is 3 mW and resonator mass is just 98 ng. Such proposed optomechanical MHSRG can be widely used for chip-scale inertial navigation, attitude measurement, and stabilization.

Macroscopic Entangled Cat State in Cavity Optomechanics

Macroscopic Entangled Cat State in Cavity Optomechanics

Synthetic magnetism for solitons in optomechanical array

Discrete optical and mechanical solitonic waves are widely used for photonic/phononic information processing. Here we propose a synthetic magnetism to generate and to control solitonic waves in 1D−optomechanical array. Each optomechanical cavity in the array couples to its neighbors through photon and phonon coupling. We create the synthetic magnetism by modulating the phonon hopping rate through both the modulation of frequency and phase between resonators at different sites. When the synthetic magnetism effect is not taken into account, the mechanical coupling play a crucial role of controlling and switching the waves from bright to dark solitons, and it even induces rogue wave-like a shape in the array. For enough mechanical coupling strength, the system enters into a strong coupling regime through splitting/crossing of solitonic waves, leading to multiple waves propagation in the array. Under the synthetic magnetism effect, the phase of the modulation enables a good control of the wave propagation, and it also switches soliton shape from bright to dark, and even induces rogue waves as well. Similarly to the mechanical coupling, the synthetic magnetism offers another flexible way to generate plethora of solitonic waves for specific purposes. This work opens new avenues for optomechanical platforms and sheets light on their potentiality of controlling and switching solitonic waves based on synthetic magnetism.

Auxiliary-Cavity-Assisted Slow and Fast Light in a Photonic Molecule Spinning Optomechanical System

We investigate the coherent optical propagation in a photonic molecule spinning optomechanical system consisting of two whispering gallery microcavities in which one of the optical cavities is a spinning optomechanical cavity and the other one is an ordinary auxiliary optical cavity. As the optomechanical cavity is spinning along the clockwise or counterclockwise direction, the cavity field can undergo different Sagnac effects, which accompanies the auxiliary optical cavity, together influencing the process of the evolution of optomechanically induced transparency and its related propagation properties, such as fast and slow light effects. The numerical results indicate that the enhanced slow and fast light and the conversion from fast to slow light (or slow to fast light) are determined by the spinning direction of the optomechanical cavity and the coupling of the two optical cavities. The study affords further insight into the photonic molecule spinning optomechanical systems and also indicates promising applications in quantum information processing.

Tunable Transparency and Group Delay in Cavity Optomechanical Systems with Degenerate Fermi Gas

We theoretically investigate the optical response and the propagation of an external probe field in a Fabry–Perot cavity, which consists of a mechanical mode of trapped, ultracold, fermionic atoms inside and simultaneously driven by an optical laser field. We investigate the electromagnetically-induced transparency due to coupling of the optical cavity field with the collective density excitations of the ultracold fermionic atoms via radiation pressure force. Moreover, we discuss the variations in the phase and group delay of the transmitted probe field with respect to effective cavity detuning as well as pumping power. It is observed that the transmitted field is lagging in this fermionic cavity optomechanical system. Our study shall provide a method to control the propagation as well as the speed of the transmitted probe field in this kind of fermionic, ultracold, atom-based, optomechanical cavity system, which might have potential applications in optical communications, signal processing and quantum information processing.