Optomechanical Effects Research Articles

Negative Optical Torque

Light carries angular momentum, and as such it can exert torques on material objects. Applications of these opto-mechanical effects were limited initially due to their smallness in magnitude, but later becomes powerful and versatile after the invention of laser. Novel and practical approaches for harvesting light for particle rotation have since been demonstrated, where the structure is always subjected to a positive optical torque along a certain axis if the incident angular momentum has a positive projection on the same axis. We report here an interesting phenomenon of “negative optical torque”, meaning that incoming photons carrying angular momentum rotate an object in the opposite sense. Surprisingly this can be realized quite straightforwardly in simple planar structures. Field retardation is a necessary condition and discrete rotational symmetry of material object plays an important role. The optimal conditions are explored and explained.

On two optomechanical effects of laser-induced electrostriction in dielectric liquids

This paper presents electrostriction from the phenomenological perspective, and gives details on two mechanical effects arising from laser-matter interaction. Electrostriction is the tendency of materials to compress in the presence of a varying electric field. In this paper, the investigated materials are polar and nonpolar dielectric liquids. It is stressed that the dominant factor is the time evolution of the laser pulse, which causes tensile stresses and acoustic waves. The study is supported by experimental realization of electrostriction, which can be detected only at favorable conditions (observed in water, but not in castor oil). This study will shed light in developing measurement techniques (e.g., laser-induced grating spectroscopy) and in explaining the onset of cavities and laser-induced liquid breakdown.

Detection of Coriolis force and rotational Doppler effect by using slow light

We consider optomechanical effects that are related to the appearance of an additional optical phase due to the motion of an ultradispersive medium and the rotational Doppler effect for light. We have theoretically shown that the enhanced Fizeau effect on atoms in a cavity can be observed and the change of phase is sensitive to the mechanical motion. These two effects can be applied to the measurement of rotations as small as 10−17 s−1 Hz1/2. It is worth noting here that the measurement of rotation is not related to Sagnac interferometry.

Photoexcitaion effect on transport properties of CeZnSbO

We have investigated a tunability of transport properties of CeZnSbO by optical light with the photon energy larger than the optical band gap. While CeZnSbO is reported to be a nearly degenerate semiconductor, in the present work, a sample of a non-degenerate type can be prepared. The electrical resistivity has been found to be highly sensitive to sample quality. The examinations of photoexcitation effect have revealed that the results depend on the type of semiconductor: degenerate and non-degenerate types. For a degenerate semiconductor, freezing of carriers at low temperatures can be resolved by increasing the fluence rate. On the other hand, in a non-degenerate type, the activation energy at high temperatures is almost independent of fluence rate. We have additionally found a possible opto-mechanical effect in a composite of CeZnSbO and a small amount of Zn4Sb3.

Amplification effects in optomechanics via weak measurements

We revisit the scheme of single-photon weak-coupling optomechanics using postselection, proposed by Pepper, Ghobadi, Jeffrey, Simon, and Bouwmeester [Phys. Rev. Lett. 109, 023601 (2012)], by analyzing the exact solution of the dynamical evolution. Positive and negative amplification effects of the displacement of the mirror's position can be generated when the Kerr phase is considered. This effect occurs when the postselected state of the photon is orthogonal to the initial state, which cannot be explained by the usual weak measurement results. The amplification effect can be further modulated by a phase shifter, and the maximal displacement state can appear within a short evolution time.

Prospect of detecting single-photon-force effects in cavity optomechanics

Cavity optomechanical systems are approaching a strong-coupling regime where the coherent dynamics of nanomechanical resonators can be manipulated and controlled by optical fields at the single photon level. Here we propose an interferometric scheme able to detect optomechanical coherent interaction at the single-photon level which is experimentally feasible with state-of-the-art devices.

Polarization-dependent optomechanics mediated by chiral microresonators

Chirality is one of the most prominent and intriguing aspects of nature, from spiral galaxies down to aminoacids. Despite the wide range of living and non-living, natural and artificial chiral systems at different scales, the origin of chirality-induced phenomena is often puzzling. Here we assess the onset of chiral optomechanics, exploiting the control of the interaction between chiral entities. We perform an experimental and theoretical investigation of the simultaneous optical trapping and rotation of spherulite-like chiral microparticles. Due to their shell structure (Bragg dielectric resonator), the microparticles function as omnidirectional chiral mirrors yielding highly polarization-dependent optomechanical effects. The coupling of linear and angular momentum, mediated by the optical polarization and the microparticles chiral reflectance, allows for fine tuning of chirality-induced optical forces and torques. This offers tools for optomechanics, optical sorting and sensing and optofluidics.

Full modal simulation of opto-mechanical effects in optical systems

The interaction of light with optical elements via radiation pressure plays a predominant role in determining the dynamics of many optical configurations, in particular when the mirrors composing the system have small masses or the light power is large. Gravitational wave interferometric detectors fall in the second category: opto-mechanical effects have been measured in first generation instruments and will be very relevant in second and third generations. So far, radiation pressure effects were studied using analytical models or simulation tools which were limited to specific optical systems or low order Hermite–Gauss modes. In this paper we present the first tool, to our knowledge, capable of a complete Hermite–Gauss modal simulation of radiation pressure induced effects, based on the modal interferometer simulation toolbox (MIST), described in details in a previous paper. This tool opens the possibility of the simulation of radiation pressure effects in realistic interferometric systems that include beam and optical element aberrations. The application of this tool to gravitational wave detectors will allow to better understand the incidence of realistic optical defects on the instrument operation and sensitivity. We also expect that this tool will be useful outside the gravitational wave community, for application on interferometric systems where radiation pressure dynamics is dominant, such as opto-mechanically-induced transparency, light mirror cavities and membrane-in-a-cavity systems. In this paper we describe the formalism used to implement radiation pressure in the MIST simulation tool and we give some example applications, including the first results on parametric instabilities in Fabry–Perot cavities based on a complete modal optical simulation.

Design of single-mode waveguides for enhanced light-sound interaction in honeycomb-lattice silicon slabs

We present the design of two waveguides (ladder and slot-ladder waveguides) implemented in a silicon honeycomb photonic-phononic crystal slab, which can support slow electromagnetic and elastic guided modes simultaneously. Interestingly, the photonic bandgap extends along the first Brillouin zone; so with an appropriate design, we can suppress propagation losses that arise coupling to radiative modes. From the phononic point of view, we explain the slow elastic wave effect by considering the waveguide as a chain of coupled acoustic resonators (coupled resonant acoustic waveguide), which provides the mechanism for slow elastic wave propagation. The ladder waveguide moreover supports guided phononic modes outside the phononic bandgap, similar to photonic slab modes, resulting in highly confined phononic modes propagating with low losses. Such waveguides could find important applications to the observation of optomechanical and electrostriction effects, as well as to enhanced stimulated Brillouin scattering and other opto-acoustical effects in nanoscale silicon structures. We also suggest that they can be the basis for a “perfect” photonic-phononic cavity in which damping by coupling to the surroundings is completely forbidden.

Laser Theory for Optomechanics: Limit Cycles in the Quantum Regime

Optomechanical systems can exhibit self-sustained limit cycles where the quantum state of the mechanical resonator possesses nonclassical characteristics such as a strongly negative Wigner density, as was shown recently in a numerical study by Qian et al. [Physical Review Letters, 109, 253601 (2012)]. Here we derive a Fokker-Planck equation describing mechanical limit cycles in the quantum regime which correctly reproduces the numerically observed nonclassical features. The derivation starts from the standard optomechanical master equation, and is based on techniques borrowed from the laser theory due to Haake's and Lewenstein. We compare our analytical model with numerical solutions of the master equation based on Monte-Carlo simulations, and find very good agreement over a wide and so far unexplored regime of system parameters. As one main conclusion, we predict negative Wigner functions to be observable even for surprisingly classical parameters, i.e. outside the single-photon strong coupling regime, for strong cavity drive, and rather large limit cycle amplitudes. The general approach taken here provides a natural starting point for further studies of quantum effects in optomechanics.

Quantum opto-mechanics: from rotation to Coriolis force detection

We consider an opto-mechanical effect that is related to the appearance of additional optical phase due to motion of an ultra-dispersive medium, the enhanced Fizeau effect. We have theoretically shown that the enhanced Fizeau effect on a single atom in a cavity can be observed. It has been shown that the change of phase is sensitive to the mechanical motion and can be applied to measurement of possible displacements as small as cm Hz. One of application can be the detection of weak forces exerted on a single atom.

All-optical tunable filters based on optomechanical effects in two-dimensional photonic crystal cavities

All-optical tunable filters are basic elements for various micro-optical circuits. Obtaining all-optical tunability remains a challenge for micro-optical circuits. Optical forces with significant effects in nanophotonic systems provide new ways for wavelength tuning. In this Letter, the optomechanical effects in two-dimensional photonic crystal cavities are investigated. Simulations based on the finite element method demonstrate that forces arise in single and coupled cavities with movable rods inside. The optical force controls the positions of the movable rods and, thus, the resonance wavelength of the cavity, based on which tunable filter is designed. The operating wavelength of the cavity or the filter for the signal can be tuned by a control light with a different frequency. The results have potential applications for various integrated circuits.

Optomechanical effect on the Dicke quantum phase transition and quasi-particle damping in a Bose–Einstein condensate: a new tool to measure weak force

We make a semi-classical steady state analysis of the influence of mirror motion on the quantum phase transition for an optomechanical Dicke model in the thermodynamic limit. An additional external mechanical pump is shown to modify the critical value of atom–photon coupling needed to observe the quantum phase transition. We further show how to choose the mechanical pump frequency and cavity–laser detuning to produce extremely cold condensates. The present system can be used as a quantum device to measure weak forces.

Optomechanical effects of two-level systems in a back-action evading measurement of micro-mechanical motion

We show that the two-level systems (TLS) in lithographic superconducting circuits act as a power-dependent dielectric leading to non-linear responses in a parametrically coupled electromechanical system. Driven TLS shift the microwave resonance frequency and modulate the mechanical resonance through the optical spring effect. By pumping with two tones in a back-action evading measurement, these effects produce a mechanical parametric instability which limits single quadrature imprecision to 1.4 xzp. The microwave resonator noise is also consistent to a TLS-noise model. These observations suggest design strategies for minimizing TLS effects to improve ground-state cooling and quantum non-demolition measurements of motion.

Energy-efficient utilization of bipolar optical forces in nano-optomechanical cavities

Nanoscale all-optical circuits driven by optical forces have broad applications in future communication, computation, and sensing systems. Because human society faces huge challenges of energy saving and emission reduction, it is very important to develop energy-efficient nano-optomechanical devices. Due to their high quality (Q) factors, resonance modes of cavities are capable of generating much larger forces than waveguide modes. Here we experimentally demonstrate the use of resonance modes of double-coupled one-dimensional photonic crystal cavities to generate bipolar optical forces. Attractive and repulsive forces of -6.2 nN and 1.9 nN were obtained with respective launching powers of 0.81 mW and 0.87 mW in the waveguide just before cavities. Supported by flexible nanosprings (spring constant 0.166 N/m), one cavity is pulled to (pushed away from) the other cavity by 37.1 nm (11.4 nm). The shifts of the selected resonance modes of the device are mechanically and thermally calibrated with an integrated nanoelectromechanical system actuator and a temperature-controlled testing platform respectively. Based on these experimentally-obtained relations, probe mode shifts due to the optomechanical effect are decoupled from those due to the thermo-optic effect. Actuated by the third-order even pump mode, the optomechanical shift of the second-order even probe mode is found to be about 2.5 times its thermal shift, indicating a highly efficient conversion of light energy to mechanical energy.

Tuning group-velocity dispersion by optical force

We propose an optomechanical approach for dispersion dynamic tuning and microengineering by taking advantage of the optical force in nano-optomechanical structures. Simulations of a suspended coupled silicon waveguide show that the zero-dispersion wavelength can be tuned by 40 nm by an optical pump power of 3 mW. Our approach exhibits great potential for broad applications in dispersion-sensitive processes, which not only offers a new root toward versatile tunable nonlinear photonics but may also open up a great avenue toward a new regime of nonlinear dynamics coupling between nonlinear optical and optomechanical effects.

Quantum optical mouse to detect Coriolis force

We describe an opto-mechanical effect that introduces an additional phase into a coherent light field. This effect is accomplished via the motion of a cavity which contains an ultradispersive medium. We have theoretically shown that this change of the phase, due to the enhanced Fizeau effect, can be used to measure displacements as small as . This technique can be used to detect the Coriolis Force.

Coupling a small torsional oscillator to large optical angular momentum

We propose a new configuration for realizing torsional optomechanics: an optically trapped windmill-shaped dielectric interacting with Laguerre–Gaussian cavity modes containing both angular and radial nodes. In contrast to existing schemes, our method can couple mechanical oscillators smaller than the optical beam waist to the in-principle unlimited orbital angular momentum that can be carried by a single photon, and thus generate substantial optomechanical interactions. Combining the advantages of small mass, large coupling, and low clamping losses, our work conceptually opens the way for the observation of quantum effects in torsional optomechanics. 10.1080/09500340.2013.778341-SUP0001 Supplementary data

Measurement of coupled cavities' optomechanical coupling coefficient using a nanoelectromechanical actuator

In this Letter, we report an approach to experimentally determine the optomechanical coupling coefficient of coupled cavities, taking advantage of the ultra-fine cavity positioning capability of a nanoelectromechanical system (NEMS) actuator design. The approach is simple and flexible and can measure the optomechanical coupling coefficient as a function of the coupled cavities' slot gap. In addition, the ratio of mechanical detunings of the odd and even resonance modes can make the existing approach to the decoupling of thermo-optic and optomechanical effects more precise and applicable to more types of cavities.

Optical forces through guided light deflections

Optical trapping and manipulation typically relies on shaping focused light to control the optical force, usually on spherical objects. However, one can also shape the object to control the light deflection arising from the light-matter interaction and, hence, achieve desired optomechanical effects. In this work we look into the object shaping aspect and its potential for controlled optical manipulation. Using a simple bent waveguide as example, our numerical simulations show that the guided deflection of light efficiently converts incident light momentum into optical force with one order-of-magnitude improvement in the efficiency factor relative to a microbead, which is comparable to the improvement expected from orthogonal deflection with a perfect mirror. This improvement is illustrated in proof-of-principle experiments demonstrating the optical manipulation of two-photon polymerized waveguides. Results show that the force on the waveguide exceeds the combined forces on spherical trapping handles. Furthermore, it shows that static illumination can exert a constant force on a moving structure, unlike the position-dependent forces from harmonic potentials in conventional trapping.