Optomechanical Model Research Articles

Coherent Electron-Vibron Interactions in Surface-Enhanced Raman Scattering (SERS).

In this Letter we identify coherent electron-vibron interactions between near-resonant and nonresonant electronic levels that contribute beyond standard optomechanical models for off-resonant or resonance surface-enhanced Raman scattering (SERS). By developing an open-system quantum model using first molecular interaction principles, we show how the Raman interference of both resonant and nonresonant contributions can provide several orders of magnitude modifications of the SERS peaks with respect to former optomechanical models and over the fluorescence backgrounds. This cooperative optomechanical mechanism allows for generating an enhancement of nonclassical photon pair correlations between Stokes and anti-Stokes photons, which can be detected by photon-counting measurements. Our results demonstrate Raman enhancements and suppressions of coherent nature that significantly impact the standard estimations of the optomechanical contribution from SERS spectra and their quantum mechanical observable effects.

Degeneracy and Photon Trapping in a Dissipationless Two-Mode Optomechanical Model.

In this work, we theoretically study a finite and undamped two-mode optomechanical model consisting of a high quality optical cavity containing a thin, elastic, and dielectric membrane. The main objective is to investigate the precursors of quantum phase transition in such a model by studying the behavior of some observables in the ground state. By controlling the coupling between membrane and modes, we find that the two lowest energy eigenstates become degenerate, as is indicated by the behavior of the mean value of some operators and by other quantifiers as a function of the coupling. Such degenerate states are characterized by a coherent superposition of eigenstates describing one of the two modes preferentially populated and the membrane dislocated from its equilibrium position due the radiation pressure (Schrödinger's cat states). The delocalization of the compound system photons+membrane results in an increase in fluctuations as measured by Robertson-Schrödinger uncertainty relations.

Poster Session: Dynamic optomechanical eye model for the validation of peripheral aberration measurement.

Many myopia control products based on the peripheral defocus theory have emerged on the market in the past five years. However, efficient measurement of peripheral aberrations is still not a well-addressed problem. To validate the aberrometer for peripheral aberration measurement, a dynamic wide field optomechanical eye model is designed and fabricated. This model consists of a plano-convex lens representing cornea (f'=30mm), a double-convex lens representing crystalline lens (f'=100mm), and a spherical retinal screen with a 12mm radius. To optimize the quality of spot-field images get from the Hartman-Shack sensor, the materials and surface treatment for the retina are studied. The model has a movable retina to achieve Zernike 4th item (Z4 focus) ranging from -6.28-＋6.84 μm. As for M (Mean sphere equivalent), it can achieve -11.85D-+10.88D at 0° visual field and -6.97D-+5.88D at 30° visual field with a 4mm pupil size. To allow a changing pupil size, a slot at the back of the cornea mount and a series of thin metal sheets with 2, 3, 4, and 6 mm holes are manufactured. Both on-axis aberrations and peripheral aberrations of the eye model are verified by commercial aberrometer VX130 (Luneau Technology, France) and the feasibility of the eye model to mimic a human eye in a peripheral aberration measuring system is illustrated.

Entanglement boosts quantum synchronization between two oscillators in an optomechanical setup

We present an optomechanical model to explore how the entanglement can be associated with quantum synchronization of two mechanical oscillators. As both these entities can be characterized in terms of variances of a set of EPR-like conjugate quadratures, we investigate whether this leads to a specific condition for simultaneous existence of the both. In our model, one of the oscillators makes the cavity, while the other is kept suspended inside the cavity, and the always-on coupling between the two is mediated via the same cavity mode. We show that in presence of amplitude modulation with the same frequency as that of the oscillators, these oscillators get nearly complete quantum synchronized and entangled simultaneously in the steady state. We also show that entanglement always becomes accompanied by quantum synchronization, though the reverse is not necessarily true. Moreover, when entangled, the oscillators exhibits near-complete synchronization. Thus, entanglement delivers a catalytic effect on the quantum synchronization in the specific system we considered. This behaviour can be observed for a large range of relevant parameters.

How bending deformation affects the performance of polarization converters based on slot waveguides

Polarization is an important characteristic of light and plays a critical role in many natural and industrial processes. In this paper, we present an optical gradient force actuated polarization converter based on a slot waveguide, which can convert linearly polarized light into circularly polarized light. The working principle of the presented polarization converter is that optical gradient forces deform the slot waveguide to adjust its birefringence, thus yielding a desired phase shift between two orthogonal components of light. An optomechanical model with all possible mechanical boundaries is developed to solve the bending deformation of polarization converters. The effective index method and dispersion relation method are used for the calculation of birefringence and optical gradient forces, respectively. The influences of the width of waveguides and the initial width of the slot on the working performance of polarization converters are discussed. It is found that these influences are independent of the mechanical boundaries. An empirical formula for describing the relation between the working power and length of polarization converters is given. This empirical formula may be helpful when designing such polarization converters.

Opto-mechanical self-adjustment model of the human eye.

The eye has specific optical and biomechanical properties that jointly regulate the eye's quality of vision, shape, and elasticity. These two characteristics are interdependent and correlated. Contrary to most currently available computational models of the human eye that only focus on biomechanical or optical aspects, the current study explores the inter-relationships between biomechanics, structure, and optical properties. Possible combinations of mechanical properties, boundary conditions, and biometrics were specified to ensure the opto-mechanical (OM) integrity to compensate for physiological changes in intraocular pressure (IOP) without compromising image acuity. This study evaluated the quality of the vision by analyzing the minimum spot diameters formed on the retina and drew how the self-adjustment mechanism affects the eye globe shape by adopting a finite element (FE) model of the eyeball. The model was verified by a water drinking test with biometric measurement (OCT Revo NX, Optopol) and tonometry (Corvis ST, Oculus).

Dynamic opto-mechanical eye model with peripheral refractions.

Many myopia control methods based on the peripheral defocus theory have emerged towards applications in recent years. However, peripheral aberration is a critical issue, which is still not well-addressed. To validate the aberrometer for peripheral aberration measurement, a dynamic opto-mechanical eye model with a wide visual field is developed in this study. This model consists of a plano-convex lens representing cornea (f' = 30 mm), a double-convex lens representing crystalline lens (f' = 100 mm), and a spherical retinal screen with a radius of 12 mm. To optimize the quality of spot-field images from the Hartman-Shack sensor, the materials and surface topography for the retina are studied. The model has an adjustable retina to achieve Zernike 4th item (Z4 focus) ranging from -6.28 µm to +6.84 µm. As for mean sphere equivalent, it can achieve -10.52 D to +9.16 D at 0° visual field and -6.97 D to +5.88 D at 30° visual field with a pupil size of 3 mm. To realize a changing pupil size, a slot at the back of the cornea mount and a series of thin metal sheets with 2, 3, 4, and 6 mm holes are generated. Both on-axis aberrations and peripheral aberrations of the eye model are verified by a well-used aberrometer and the eye model to mimic a human eye in a peripheral aberration measurement system is illustrated.

Nonlinear effects in a Floquet-driven optomechanical system

We investigate theoretically the nonlinear effects in a Floquet-driven optomechanical system with quadratic coupling. When the periodically modulated driving field is strong, we establish an effective time-dependent model to describe this system. Using the Keldysh approach, we calculate the retarded Green's function to study the response behavior of the system to external probing. We find that when the $n\mathrm{th}$ sideband of a probe field satisfies the condition of two-phonon resonance, the transparency window occurs. In addition, we find some abnormal behaviors of the output field, which have no counterpart in the standard optomechanical models. These results provide a promising platform for controlling light propagation and light manipulation operations which have potential applications in quantum precision measurement techniques.

Low Power Coherent Ising Machine Based on Mechanical Kerr Nonlinearity.

Finding a reliable Ising machine for solving nondeterministic polynomial-class problems has attracted great attention in recent years, where an authentic system can be expanded with polynomial-scaled resources to find the ground state Ising Hamiltonian. In this Letter, we propose an extremely low power optomechanical coherent Ising machine based on a new enhanced symmetry breaking mechanism and highly nonlinear mechanical Kerr effect. The mechanical movement of an optomechanical actuator induced by the optical gradient force greatly increases the nonlinearity by a few orders and significantly reduces the power threshold using conventional structures capable of fabrication via photonic integrated circuit platforms. With the simple but strong bifurcation mechanism and remarkably low power requirement, our optomechanical spin model opens a path for chip-scale integration of large-size Ising machine implementations with great stability.

Quantum signatures in a quadratic optomechanical heat engine with an atom in a tapered trap

We investigate how quantum signatures can emerge in a single atom heat engine consisting of an atom confined in a tapered trap and subjected to hot and cold thermal reservoirs. A similar system was realized experimentally in Science 352, 325 (2016)SCIEAS0036-807510.1126/science.aad6320. We model such a system using a quadratic optomechanical model and identify an effective Otto cycle in the system’s dynamics. We compare the engine’s performance in quantum and classical regimes by evaluating the power dissipated. We find that lowering the temperature is insufficient to make the single atom engine in Science 352, 325 (2016)SCIEAS0036-807510.1126/science.aad6320 a genuine quantum-enhanced heat engine. We show that it is necessary to make the trap more asymmetric and confined to ensure that quantum correlations cause an enhancement in the power output.

Opto-Mechanical Eye Models, a Review on Human Vision Applications and Perspectives for Use in Industry

The purpose of this review is to aggregate technical information on existent optomechanical eye models (OME) described in the literature, for image quality assessment in different applications. Several physical eye models have been reviewed from peer-reviewed papers and patent applications. A typical eye model includes an artificial cornea, an intraocular lens or other lens to simulate the crystalline lens, an aperture as the pupil, and a posterior retinal surface, which may be connected to a light sensor. The interior of the eye model may be filled with a fluid to better emulate physiological conditions. The main focus of this review is the materials and physical characteristics used and the dimensional aspects of the main components including lenses, apertures, chambers, imaging sensors and filling medium. Various devices are described with their applications and technical details, which are systematically tabulated highlighting their main characteristics and applications. The models presented are detailed and discussed individually, and the features of different models are compared when applicable, highlighting strengths and limitations. In the end there is a brief discussion about the potential use of artificial eye models for industrial applications.

Chiral Thermodynamics in Tailored Chiral Optical Environments

We present an optomechanical model that describes the stochastic motion of an overdamped chiral nanoparticle diffusing in the optical bistable potential formed in the standing-wave of two counter-propagating Gaussian beams. We show how chiral optical environments can be induced in the standing-wave with no modification of the initial bistability by controlling the polarizations of each beam. Under this control, optical chiral densities and/or an optical chiral fluxes are generated, associated respectively with reactive vs. dissipative chiral optical forces exerted on the diffusing chiral nanoparticle. This optomechanical chiral coupling bias the thermodynamics of the thermal activation of the barrier crossing, in ways that depend on the nanoparticle enantiomer and on the optical field enantiomorph. We show that reactive chiral forces, being conservative, contribute to a global, enantiospecific, change of the Helmholtz free energy bistable landscape. In contrast, when the chiral nanoparticle is immersed in a dissipative chiral environment, the symmetry of the bistable potential is broken by non-conservative chiral optical forces. In this case, the chiral electromagnetic fields continuously transfer, through dissipation, mechanical energy to the chiral nanoparticle. For this chiral nonequilibrium steady-state, the thermodynamic changes of the barrier crossing take the form of heat transferred to the thermal bath and yield chiral deracemization schemes that can be explicitly calculated within the framework of our model. Three-dimensional stochastic simulations confirm and further illustrate the thermodynamic impact of chirality. Our results reveal how chiral degrees of freedom both of the nanoparticle and of the optical fields can be transformed into true thermodynamics control parameters, thereby demonstrating the significance of optomechanical chiral coupling in stochastic thermodynamics.

Quantum simulation of tunable and ultrastrong mixed-optomechanics.

We propose a reliable scheme to simulate tunable and ultrastrong mixed (first-order and quadratic optomechanical couplings coexisting) optomechanical interactions in a coupled two-mode bosonic system, in which the two modes are coupled by a cross-Kerr interaction and one of the two modes is driven through both the single- and two-excitation processes. We show that the mixed-optomechanical interactions can enter the single-photon strong-coupling and even ultrastrong-coupling regimes. The strengths of both the first-order and quadratic optomechanical couplings can be controlled on demand, and hence first-order, quadratic, and mixed optomechanical models can be realized. In particular, the thermal noise of the driven mode can be suppressed totally by introducing a proper squeezed vacuum bath. We also study how to generate the superposition of coherent squeezed state and vacuum state based on the simulated interactions. The quantum coherence effect in the generated states is characterized by calculating the Wigner function in both the closed- and open-system cases. This work will pave the way to the observation and application of ultrastrong optomechanical effects in quantum simulators.

Opto-mechanical modeling and experimental implementation of an FBG-based piezoelectric bimorph actuator for high voltage sensing applications

This paper proposes a highly simplified optical voltage sensor by using a piezoelectric bimorph and a Fiber Bragg Grating (FBG) that can be used for high voltage applications with a relatively good accuracy and stability. In this work the theoretical framework for the whole opto-mechanical operation of the optical sensor is detailed and compared to experimental results. In the analysis, a correction term to the electric field is derived to account for the linear strain distribution across the piezoelectric layer improving the designing equations and giving more criteria for future developments. Finally, some experimental results from a laboratory scale optical-based high voltage sensing setup are discussed, and shown to be in excellent agreement with theoretical expected behavior for different voltage magnitudes.

Performance analysis and optimization of inertial confinement fusion cascaded frequency converters based on the integrated optomechanical method

Due to the unique mechanical and optical characteristics, it is difficult to carry out experimental research and online measurement for large-aperture ICF frequency converters. To analyze and optimize the performance of the frequency converters under complex process loads, we present an integrated optomechanical method that correlates actual process loads with laser critical characteristics. Based on the established optomechanical model, the key factor that induces the loss of harmonic generation efficiency is identified. In addition, the proposed method is conductive to rapid evaluation, prediction, and optimization of comprehensive performance of frequency converters. Thereby, we propose an adaptive frequency conversion system (AFCS). The results indicate that AFCS can not only minimize the phase mismatching of second harmonic generation doubler but also significantly improve the quality of far-field focal spot.

Optomechanical Modeling and Validation of a Distributed Bragg Reflector Force Sensor With Drift and Temperature Compensation

Distributed Bragg reflector fiber laser with the dual-polarization mode is commonly used as a sensing element in optical sensors. Lateral force on such a fiber induces birefringence and results in beating frequency generation in it. Also, the change in the magnitude of the lateral force is correlated to the shift in the beating frequency. This article presents a multi-physics optomechanical model for a fiber laser force sensor based on the birefringence phenomenon. To this end, a theoretical model for the sensing principle was developed through employing the elastic beam theory, Hertzian contact mechanics, and optical birefringence principle. Based on the linearity of the developed optomechanical model to the lateral force and ambient temperature variation, a multi-linear regression calibration for the force sensor was proposed and experimentally validated. Also, the temperature-induced drift in the beating frequency was compensated through exponential adjustment. Moreover, the calibration results showed a relatively small sensitivity for temperature sensing with respect to the external force (cross-talk). This phenomenon was predicted with the theoretical model. Verification of the calibration revealed a root-mean-square error of 0.12°C and 0.04 N for temperature and force sensing, respectively. Furthermore, the validation study showed a root-mean-square error of 0.04± 0.03 N and zero hysteresis for the developed sensor. Moreover, the theoretical sensitivity to external force was similar to the experimental results. For future applications, the compliance of the sensor specifications with the requirements of three surgical procedures was confirmed through comparison with the available literature.

Spatial localization and pattern formation in discrete optomechanical cavities and arrays

We investigate theoretically the generation of nonlinear dissipative structures in optomechanical (OM) systems containing discrete arrays of mechanical resonators. We consider both hybrid models in which the optical system is a continuous multimode field, as it would happen in an OM cavity containing an array of micro-mirrors, and also fully discrete models in which each mechanical resonator interacts with a single optical mode, making contact with Ludwig and Marquardt (2013 Phys. Rev. Lett. 101, 073603). Also, we study the connections between both types of models and continuous OM models. While all three types of models merge naturally in the limit of a large number of densely distributed mechanical resonators, we show that the spatial localization and the pattern formation found in continuous OM models can still be observed for a small number of mechanical elements, even in the presence of finite-size effects, which we discuss. This opens new venues for experimental approaches to the subject.

Changes in temperature inside an optomechanical model of the human eye during emulated transscleral cyclophotocoagulation.

Currently, many diseases of the eye are treated by laser surgery. An understanding of light propagation and the heating of eye tissue during laser exposure is crucial to improving the outcome of these procedures. Here, we present the development of physical and computational models of the human eye by combining optical light propagation and thermal characteristics. For the physical model, all parts of the eye, including cornea, lens, ciliary body, sclera, aqueous and vitreous humors, and iris, were fabricated using a 3D printed holder and modified polydimethylsiloxane. We also present a computational model based on finite element analysis that allows for a direct comparison between the simulation and experimental measurements. These models provide an opportunity to directly assess the rise in temperature in all eye tissues. The simulated and physical models showed good agreement for the transmission of light at varying incident angles. The heating of optical components was investigated in the retina and the ciliary body during simulated laser surgery. Temperature increases of 45.3°C and 30.6°C in the retina and ciliary bodies, respectively, were found in the physical model after 1 minute of exposure to 186 mW of 850 nm laser radiation. This compared to 29.8°C and 33.9°C increases seen under the same conditions in the simulation model with human eye parameters and 48.1°C and 28.7°C for physical model parameters. These results and these models are very promising for further investigation of the impact of laser surgery.

Fisher-information-based estimation of optomechanical coupling strengths

The formalism of quantum estimation theory, focusing on the quantum and classical Fisher information, is applied to the estimation of the coupling strength in an optomechanical system. In order to estimate the optomechanical coupling, we have considered a cavity optomechanical model with non-Markovian Brownian motion of the mirror and employed input-output formalism to obtain the cavity output field. Our estimation scenario is based on balanced homodyne photodetection of the cavity output field. We have explored the difference between the associated measurement-dependent classical Fisher information and the quantum Fisher information, thus addressing the question of whether it is possible to reach the lower bound of the mean squared error of an unbiased estimator by means of balanced homodyne detection. We have found that the phase of the local oscillator in the homodyne detection is crucial; certain quadrature measurements allow very accurate estimation.

Design and optimization of the micro-vibration isolation system for large space telescope

With increasing demands for better image quality, the aperture and size of a space telescope are becoming larger, and stability requirements are becoming more stringent. To reduce the influence of micro-vibrations on image quality from telescope platform, isolating vibrations of the whole telescope optical payload must be taken into account. To this end, a method to design and optimize a vibration isolation system (VIS) was developed. A dynamic model coupling the telescope optical payload and the platform in orbit was established to assist in the design and optimization of a configuration for the VIS, the objective being to minimize the frequency bandwidth of the integral modes of the telescope optical payload. Isolators with multidirectional elasticity were designed, and the frequency bandwidth of the integral modes was further narrowed by optimizing the structural parameters of the isolators. A viscous fluid damper was designed to suppress the VIS's resonance modes and its damping coefficients tested. Moreover, a micro-vibration integrated optomechanical analysis model was established. The influence of micro-vibration on line-of-sight of a space telescope with VIS was analyzed. The simulation results in the time and frequency domain show that the designed VIS can effectively attenuate the micro-vibrations transmitted to the telescope optical payload.