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Hybrid plasmonica??phononic cavity design for enhanced optomechanical coupling in lithium niobate
摘要： A hybrid plasmonic–phononic cavity design which enables high vacuum coupling rate has been proposed in lithium niobate (LN) phononic crystals (Phncs) that have been perforated by air holes and coated with thin silver film. By tailoring the geometry, optomechanical interaction between the plasmonic modes (produced by the metal/insulator) and the phononic modes (confined by the phononic bandgap effect) is greatly enhanced. Numerical results based on finite-element method (FEM) reveal that in this hybrid plasmonic–phononic design, high vacuum coupling rate that predominantly contributed by moving boundary effect is on the order of 106?Hz, which is about one to two orders higher than that contributed by photoelastic effect shown in conventional phoxonic crystal designs. Results evidence how the vacuum coupling rate depends on geometrical parameters like the radius of the defect air hole, the thickness of silver layer, and LN layer. The simultaneous confinement and strong coupling, combined with other advantages as lack of constraint to the refractive index, and integration of piezoelectric material and metal in a chip, this hybrid design may be suitable for non-invasive biological sensing, optomechanically tunable plasmonic heater for drug release and lab-on-chip devices.
关键词： Optomechanics,Plasmonic-phononic cavity,Vacuum coupling rate,Photoelastic effect,Lithium niobate,Moving boundary effect
更新于2025-09-23 15:21:01
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Thermodynamic consistency of the optomechanical master equation
摘要： We investigate the thermodynamic consistency of the master equation description of heat transport through an optomechanical system attached to two heat baths, one optical and one mechanical. We employ three different master equations to describe this scenario: (i) The standard master equation used in optomechanics, where each bath acts only on the resonator that it is physically connected to; (ii) the so-called dressed-state master equation, where the mechanical bath acts on the global system; and (iii) what we call the global master equation, where both baths are treated nonlocally and affect both the optical and mechanical subsystems. Our main contribution is to demonstrate that, under certain conditions including when the optomechanical coupling strength is weak, the second law of thermodynamics is violated by the first two of these pictures. In order to have a thermodynamically consistent description of an optomechanical system, therefore, one has to employ a global description of the effect of the baths on the system.
关键词： heat transport,thermodynamics,second law of thermodynamics,optomechanics,master equation
更新于2025-09-23 15:21:01
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Optomechanical Bell Test
摘要： Over the past few decades, experimental tests of Bell-type inequalities have been at the forefront of understanding quantum mechanics and its implications. These strong bounds on specific measurements on a physical system originate from some of the most fundamental concepts of classical physics—in particular that properties of an object are well-defined independent of measurements (realism) and only affected by local interactions (locality). The violation of these bounds unambiguously shows that the measured system does not behave classically, void of any assumption on the validity of quantum theory. It has also found applications in quantum technologies for certifying the suitability of devices for generating quantum randomness, distributing secret keys and for quantum computing. Here we report on the violation of a Bell inequality involving a massive, macroscopic mechanical system. We create light-matter entanglement between the vibrational motion of two silicon optomechanical oscillators, each comprising approx. 1010 atoms, and two optical modes. This state allows us to violate a Bell inequality by more than 4 standard deviations, directly confirming the nonclassical behavior of our optomechanical system under the fair sampling assumption.
关键词： Bell test,quantum mechanics,entanglement,nonclassical behavior,optomechanics
更新于2025-09-23 15:21:01
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Modelling of Cavity Optomechanical Magnetometers
摘要： Cavity optomechanical magnetic ?eld sensors, constructed by coupling a magnetostrictive material to a micro-toroidal optical cavity, act as ultra-sensitive room temperature magnetometers with tens of micrometre size and broad bandwidth, combined with a simple operating scheme. Here, we develop a general recipe for predicting the ?eld sensitivity of these devices. Several geometries are analysed, with a highest predicted sensitivity of 180 pT/√Hz at 28 μm resolution limited by thermal noise in good agreement with previous experimental observations. Furthermore, by adjusting the composition of the magnetostrictive material and its annealing process, a sensitivity as good as 20 pT/√Hz may be possible at the same resolution. This method paves a way for future design of magnetostrictive material based optomechanical magnetometers, possibly allowing both scalar and vectorial magnetometers.
关键词： magnetometer,quantum sensing,cavity-optomechanics
更新于2025-09-23 15:21:01
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An optomechanical heat engine with feedback-controlled in-loop light
摘要： The dissipative properties of an optical cavity can be effectively controlled by placing it in a feedback loop where the light at the cavity output is detected and the corresponding signal is used to modulate the amplitude of a laser ?eld which drives the cavity itself. Here we show that this effect can be exploited to improve the performance of an optomechanical heat engine which makes use of polariton excitations as working ?uid. In particular we demonstrate that, by employing a positive feedback close to the instability threshold, it is possible to operate this engine also under parameters regimes which are not usable without feedback, and which may signi?cantly ease the practical implementation of this device.
关键词： optomechanics,feedback,quantum heat engine
更新于2025-09-23 15:19:57
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Exceptional points enhance second-order sideband generation in a whispering-gallery-mode microresonator optomechanical system coupled with nanoparticles
摘要： We theoretically investigate the second-order sideband generation (SSG) in a whispering-gallery-mode (WGM) microresonator optomechanical system, in which the WGM microresonator couples with two nanoparticles. The nanoparticles can induce the optical coupling of the clockwise- (CW) and the counterclockwise- (CCW) WGM fields. And by continuously adjusting the relative phase angle between two nanoparticles, two eigenmodes of the optomechanical system coalesce and the so-called exceptional points (EPs) emerge periodically. It is shown that in the WGM microresonator optomechanical system coupled with nanoparticles the second-order sideband can be generated due to the nonlinear optomechanical interactions, modulated periodically by the relative phase angle between two nanoparticles, and enhanced significantly at the EPs. Particularly, considering the frequency shift caused by the nanoparticles at the EPs, the generation and absorption of the second-order sideband can be flexibly realized. These results may have potential applications for high precision measurements and manipulation of light propagation in optical cavities.
关键词： second-order sideband,exceptional points,cavity optomechanics
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - On Chip Sub-Wavelength Grating Fabry-Perot Cavity, toward Integrated Cavity Optomechanics Applications
摘要： Sub-Wavelength Grating (SWG) periodic media are comprised of alternative dielectric layers with a pitch Λ small enough in comparison to the wavelength to supress any diffraction or interference effect. As a good first approximation, SWG media can be considered as uniform and lossless ones, with an averaging effect over the dielectric permittivity [1]. The use of SWG media as core and/or cladding materials of optical waveguides was first proposed and demonstrated in 2010 [2] as a way to realize easy engineering of the refractive guided index of light with simple lithographic patterning. Since then, SWG waveguides have found various applications such as waveguide crossing, multimode interferometers, optical filters, mid-infrared waveguides, or even optical biosensing [3]. We propose to include SWG waveguides within a suspended Fabry-Perot (FP) cavity (see Fig. 1a). The core of the cavity is formed by alternative Silicon and Air SWG layers, while the input and output mirrors are two Direct Bragg Reflectors (DBR). The whole structure is fully suspended through the use of two support arms. We present the theoretical modelization, technological realization and optical characterisations of such a cavity. The design was conducted through both an analytical model that treats SWG media with equivalent refractive indexes, and two dimensional effective index Finite-Difference Time-Domain (FDTD) simulations. Actual devices were realized on 200 mm silicon on insulator (SOI) wafers in our clean room facilities with e-beam patterning of the waveguide level, and characterized via full-scale wafer optical spectrum measurement between 1520 nm and 1580 nm. At time of writing, we measured optical quality factors of 10 000 over 2 μm long cavities. We believe this kind of suspended structure can be used in the field of Cavity Optomechanics, where an optical cavity is coupled to a mechanical resonator [4]. Indeed, because it is fully suspended, we await mechanical resonance to occur, the cavity behaving similarly to a doubly clamped holey cantilever (see Fig. 1c). Apart from the traditional optical phase shift occurring with propagation length variations of the cavity, there should also be a phase shift arising from the SWG nature of the waveguide, whose equivalent refractive index depends on the pitch Λ (and thus length) of the cavity. Due to this additional effect, we expect a strong optomechanical coupling rate.
关键词： Sub-Wavelength Grating,silicon on insulator,optical waveguides,Fabry-Perot cavity,cavity optomechanics
更新于2025-09-12 10:27:22
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[Advances In Atomic, Molecular, and Optical Physics] Volume 68 || Collective motion of an atom array under laser illumination
摘要： We develop a theoretical formalism for the study of light-induced motion of atoms trapped in a two-dimensional (2D) array, considering the effect of multiple scattering of light between the atoms. We find that the atomic motion can be described by a collective diffusion equation, wherein laser-induced dipole–dipole forces couple the motion of different atoms. This coupling leads to the formation of collective mechanical modes of the array atoms, whose spatial structure and stability depend on the parameters of the illuminating laser and the geometry of the 2D array. We demonstrate the application of our formalism for the analysis of light-induced heating of the 2D array. The presented approach should be useful for treating the optomechanical properties of recently proposed quantum optical platforms made of atomic arrays.
关键词： laser illumination,dipole–dipole interactions,optomechanics,atom array,collective motion
更新于2025-09-11 14:15:04
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Quantum Dot Optomechanics in Suspended Nanophononic Strings
摘要： The optomechanical coupling of quantum dots and flexural mechanical modes is studied in suspended nanophononic strings. The investigated devices are designed and monolithically fabricated on an (Al)GaAs heterostructure. Radio frequency elastic waves with frequencies ranging between f = 250 and 400 MHz are generated as Rayleigh surface acoustic waves on the unpatterned substrate and injected as Lamb waves in the nanophononic string. Quantum dots inside the nanophononic string exhibit a 15-fold enhanced optomechanical modulation compared to those dynamically strained by the Rayleigh surface acoustic wave. Detailed finite element simulations of the phononic mode spectrum of the nanophononic string confirm that the observed modulation arises from valence band deformation potential coupling via shear strain. The corresponding optomechanical coupling parameter is quantified to 0.15 meV nm?1. This value exceeds that reported for vibrating nanorods by approximately one order of magnitude at 100 times higher frequencies. Using this value, a derived vertical displacement in the range of 10 nm is deduced from the experimentally observed modulation. The results represent an important step toward the creation of large scale optomechanical circuits interfacing single optically active quantum dots with optical and mechanical waves.
关键词： nanomechanics,optomechanics,quantum dots,Lamb waves,hybrid quantum systems
更新于2025-09-11 14:15:04
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Mechanotunable Plasmonic Properties of Colloidal Assemblies
摘要： Noble metal nanoparticles can absorb incident light very efficiently due to their ability to support localized surface plasmon resonances (LSPRs), collective oscillations of the free electron cloud. LSPRs lead to strong, nanoscale confinement of electromagnetic energy which facilitates applications in many fields including sensing, photonics, or catalysis. In these applications, damping of the LSPR caused by inter- and intraband transitions is a limiting factor due to the associated energy losses and line broadening. The losses and broad linewidth can be mitigated by arranging the particles into periodic lattices. Recent advances in particle synthesis, (self-)assembly, and fabrication techniques allow for the realization of collective coupling effects building on various particle sizes, geometries, and compositions. Beyond assemblies on static substrates, by assembling or printing on mechanically deformable surfaces a modulation of the lattice periodicity is possible. This enables significant alteration and tuning of the optical properties. This progress report focuses on this novel approach for tunable spectroscopic properties with a particular focus on low-cost and large-area fabrication techniques for functional plasmonic lattices. The report concludes with a discussion of the perspectives for expanding the mechanotunable colloidal concept to responsive structures and flexible devices.
关键词： colloidal self-assembly,deformation,plasmonic lattice,plasmon resonance coupling,optomechanics
更新于2025-09-11 14:15:04