Cavity Coupling Research Articles

A fast vibro-acoustic modeling method of plate-open cavity coupled systems

In this paper, a fast Chebyshev-Ritz method for vibro-acoustic analytical modeling of plate-open cavity coupled systems is developed for the first time. Based on the Chebyshev spectral method and the Rayleigh-Ritz solution procedure, the vibro-acoustic model of the open cavity coupled with a rectangular plate is established. The exterior acoustic field of the open cavity is expressed by the Rayleigh integral. Additionally, the Rayleigh integral is divided into a frequency-independent singular integral and a frequency-dependent non-singular integral, accelerating the calculation process. Furthermore, the Gauss-Chebyshev-Lobato sampling method is first developed for the plate-open cavity coupling model. By converting the integrals into tensor products, the method avoids complex quadruple integrals, increasing the efficiency of the entire integral operation. The vibration and acoustic responses from the proposed method agree well with existing literature and FEM analysis results, demonstrating the convergence and correctness of the current methodology. The mechanism of cavity depth on vibro-acoustic features of plate-open cavity systems is studied, which is less focused in the published literature. Other factors governing the plate-open cavity coupled model encompassed boundary conditions, fluid mediums, and plate thickness are fully examined. The results provide a theoretical foundation for the design and future research of plate-open cavity structures.

Ultrahigh-[formula omitted] Fano resonance in a cavity-waveguide coupled system based on second-order topological photonic crystals with elliptical holes

We present a novel configuration of second-order topological photonic crystal (SOTPC) comprising interconnected dielectric material with elliptical air holes. Based on this SOTPC design, we construct a topological corner state (TCS) cavity and a topological edge state (TES) waveguide. Through the coupling of the TCS cavity with the TES waveguide, we establish a topological cavity-waveguide coupled system (TCWCS) that exhibits an ultrasharp asymmetric topological Fano resonance. Numerical simulations demonstrate that the proposed TCWCS achieves an exceptionally high quality factor exceeding 108, surpassing previously reported results by several orders of magnitude. Moreover, the refractive index sensing application implemented with TCWCS shows a sensitivity of 278 nm/RIU and a figure of merit surpassing 107 1/RIU. Notably, our simulations reveal that the lineshape and quality factor of the Fano resonance, as well as the index sensing performance in the TCWCS, are highly robust against structural defects. The demonstrated capabilities of the TCWCS open up avenues for further exploration and development in the field of topological photonics based on our proposed SOTPC.

Mode management in Bottom‐Up, Parity‐Time‐Symmetric Micro‐Cavity Lasers

AbstractThe intrinsic non‐Hermiticity of photonic devices with tunable optical gain and loss makes them excellent platforms to explore and implement applications based on parity‐time symmetry, and a notable example is mode management in micro‐cavity lasers. Thus far, parity‐time‐symmetric lasers are fabricated via conventional top‐down etching processes, which are known to cause cavity sidewall roughness that is potentially detrimental to laser performance. Bottom‐up fabrication of parity‐time‐symmetric lasers, however, has seen limited success due to strict requirements on the uniformity of cavity morphology. Here, parity‐time‐symmetric lasing is demonstrated in coupled InP micro‐ring cavities grown directly by selective area epitaxy. With a facet engineering technique, ring laser cavities with a highly deterministic morphology are realized, enabling parity‐time‐symmetric laser designs. Furthermore, benefiting from the versatility and controllability of this bottom‐up process, lasing mode selectivity can be enhanced through coupling gap tuning and cavity shape engineering, leading to single‐mode lasing with a peak side mode suppression ratio exceeding 17 dB and a threefold single‐mode brightness enhancement compared to a single, uncoupled laser cavity. This work unlocks a lasing mode management strategy that is previously unavailable to bottom‐up laser cavities, which is a major step toward the realization of on‐chip, low‐loss, and single‐mode micro‐cavity lasers.

Lifetime Reduction of Single Germanium-Vacancy Centers in Diamond via a Tunable Open Microcavity

Coupling between a single quantum emitter and an optical cavity presents a key capability for future quantum networking applications. Here, we explore interactions between individual germanium-vacancy (GeV) defects in diamond and an open microcavity at cryogenic temperatures. Exploiting the tunability of our microcavity system to characterize and select emitters, we observe a Purcell-effect-induced lifetime reduction of up to 4.5±0.3 and extract coherent-coupling rates up to 360±20 MHz. Our results indicate that the GeV defect has favorable optical properties for cavity coupling, with a quantum efficiency of at least 0.34±0.05 and likely much higher. Published by the American Physical Society 2024

Experimental study of jet and cavity coupling under vertical motion of underwater vehicle

After the underwater vehicle detaches from the launch tube and starts its engine, the interaction between the tail cavity and the high-speed jet significantly impacts its motion stability and engine efficiency. Therefore, it is crucial to study the evolution mechanism of cavities in vertical motion. However, in traditional water tunnel experiments, the evolution of the cavity differs from the actual situation of vertical launch due to the influence of buoyancy. This study investigates the dynamics and motion trajectories of tail cavities and high-speed gas jets in the vertical movement of vehicles under different Froude numbers and nozzle stagnation pressure ratios through experimentation. The experimental results show two modes of tail cavity evolution: intact cavity (IC) and foam-conical cavity (FC-CC). Increasing the Froude numbers and stagnation pressure ratios facilitates the transition of the cavity from the IC mode to the FC-CC mode, effectively suppressing the formation and intensity of re-entrant jets, thereby reducing its impact on the bottom of the vehicle and enhancing motion stability. By deriving the formula for the length of the jet core area, it was found that the jet length is linearly related to the nozzle stagnation pressure, further revealing the mechanism of cavity evolution. These findings offer a new perspective for a deeper understanding and prediction of the dynamic behavior of underwater vehicles.

High‐isolation single‐layer dual‐mode substrate‐integrated waveguide diplexers for millimetre‐wave applications

AbstractNew coupling scheme substrate‐integrated waveguide (SIW) diplexers based on dual‐mode cavities are proposed for millimetre‐wave applications. Dual‐mode SIW cavities are simultaneously employed in common input and coupling cavity to produce filtering transmission poles and transmission zero (TZ). A common input SIW cavity with two orthogonal modes is employed instead of the traditional T‐junction for circuit miniaturisation, insertion‐loss reduction, and intrinsically high isolation. A critical dual‐mode SIW cavity with diagonally distributed modes has been employed in each channel to realise a controllable stopband TZ for high selectivity of passband's skirt. To further improve channel isolation and passbands' selectivity, a SIW diplexer based on dual‐ and single‐mode cavities is proposed, and four‐pole responses for each passband channel are designed. For the verification, two millimetre‐wave diplexers have been fabricated and tested.

Double tunable Fano resonance based on a metal–insulator–metal waveguide with double coupled cavities and its application

A metal–insulator–metal (MIM) waveguide with a ring cavity (RC) and a half ring cavity (HRC) is proposed to realize the detection of two mediums simultaneously based on independently tunable double Fano resonances. Utilizing numerical simulation of the finite element method, the transmission characteristics and magnetic field distribution are investigated. The simulation findings indicate that the structure is capable of generating double Fano resonances, and the two Fano resonances are tuning independently. The maximum sensitivity and figure of merit (FOM) are 2385 nm/RIU (refractive index unit) and 31886RIU−1, respectively, and these values are achieved by changing the structural parameters and the refractive index of the insulator. Moreover, the sugar content in flavor and the concentration of ethanol solution can be detected at the same time, which indicates the high efficiency of the sensor. Therefore, these performances demonstrate that the tunable double Fano resonance based on a MIM waveguide is a hopeful method for chemical detection.

Cavity-enhanced narrowband spectral filters using rare-earth ions doped in thin-film lithium niobate

On-chip optical filters are fundamental components in optical signal processing. While rare-earth ion-doped crystals offer ultra-narrow optical filtering via spectral hole burning, their applications have primarily been limited to those using bulk crystals, restricting their utility. In this work, we demonstrate cavity-enhanced spectral filtering based on rare-earth ions in an integrated nonlinear optical platform. We incorporate rare-earth ions into high quality-factor ring resonators patterned in thin-film lithium niobate. By spectral hole burning at 4 K in a critically coupled resonance mode, we achieve bandpass filters ranging from 7 MHz linewidth, with 13.0 dB of extinction, to 24 MHz linewidth, with 20.4 dB of extinction. By reducing the temperature to 100 mK to eliminate phonon broadening, we achieve an even narrower linewidth of 681 kHz, which is comparable to the narrowest filter linewidth demonstrated in an integrated photonic device, while only requiring a small device footprint. Moreover, the cavity enables reconfigurable filtering by varying the cavity coupling rate. For instance, as opposed to the bandpass filter, we demonstrate a bandstop filter utilizing an under-coupled ring resonator. Such versatile integrated spectral filters with high extinction ratio and narrow linewidth could serve as fundamental components for optical signal processing and optical memories on-a-chip.

Discovery of dissipative microwave photonic soliton molecules in dual-bandpass optoelectronic oscillator

Optoelectronic oscillators (OEOs), which have attracted extensive studies in the past decades, are high quality-factor optoelectronic feedback loops for generating various ultra-pure microwave signals. In essence, OEOs are also dissipative nonlinear systems with multiple timescale characteristics and abundant nonlinearities, which open the possibilities for exploring localized dissipative solitary waves. In this paper, we demonstrate a new-class temporal dissipative soliton, i.e., dissipative microwave photonic soliton molecule (DMPSM), in a dual-bandpass OEO. Both the numerical simulation and experiment are conducted to reveal the physical mechanism of DMPSM generation and to evaluate the characteristics of the generated DMPSM sequences. Unlike optical soliton molecules in mode-locked lasers, the formation of DMPSMs arises from the combined action of multiple timescale coupling, nonlinear bistability, and time-delayed feedback in the OEO cavity, where the soliton interval and number in a DMPSM can be well-controlled through varying the multiple timescale variables in the OEO cavity, and the repetition frequency of the DMPSMs can be tuned through changing that of the initially injected perturbation signal. Meanwhile, the generated DMPSM sequence performs with high stability and excellent coherence, which shows enormous application potentials in pulse radar detection, dense microwave comb generation, and neuromorphology.

Enhancement of lateral shifts by Kerr nonlinearity, via atom cavity coupling

The susceptibility of a two-level atomic medium enclosed in a cavity is controlled and modified by a control driving field and cavity coupling. The susceptibility of the medium is related to the dielectric function, and reflection & transmission coefficients. The transmission and reflection coefficients are related to Goos–Hänchen Shifts in the reflection and transmission beam. Negative and positive lateral GH-shifts, and Giant shifts in the transmission and reflection beams are investigated under the effect of cavity coupling and Kerr nonlinearity. A giant shift of 2000λ in the reflection and 1000λ in the transmission beam is calculated. It is clear that both modified Giant shifts and lateral shifts are influenced by changes in the refractive index. So it will have potential applications in sensing and trapping of the optical data. The controlled and considerably enhanced GH shift show the importance of utilizing the proposed scheme for the construction of optical sensors and optical devices.

Direct Observation of Polaritonic Chemistry by Nuclear Magnetic Resonance Spectroscopy

AbstractPolaritonic chemistry is emerging as a powerful approach to modifying the properties and reactivity of molecules and materials. However, probing how the electronics and dynamics of molecular systems change under strong coupling has been challenging due to the narrow range of spectroscopic techniques that can be applied in situ. Here we develop microfluidic optical cavities for vibrational strong coupling (VSC) that are compatible with nuclear magnetic resonance (NMR) spectroscopy using standard liquid NMR tubes. VSC is shown to influence the equilibrium between two conformations of a molecular balance sensitive to London dispersion forces, revealing an apparent change in the equilibrium constant under VSC. In all compounds studied, VSC does not induce detectable changes in chemical shifts, J‐couplings, or spin‐lattice relaxation times. This unexpected finding indicates that VSC does not substantially affect molecular electron density distributions, and in turn has profound implications for the possible mechanisms at play in polaritonic chemistry under VSC and suggests that the emergence of collective behavior is critical.

Direct Observation of Polaritonic Chemistry by Nuclear Magnetic Resonance Spectroscopy.

Polaritonic chemistry is emerging as a powerful approach to modifying the properties and reactivity of molecules and materials. However, probing how the electronics and dynamics of molecular systems change under strong coupling has been challenging due to the narrow range of spectroscopic techniques that can be applied in situ. Here we develop microfluidic optical cavities for vibrational strong coupling (VSC) that are compatible with nuclear magnetic resonance (NMR) spectroscopy using standard liquid NMR tubes. VSC is shown to influence the equilibrium between two conformations of a molecular balance sensitive to London dispersion forces, revealing an apparent change in the equilibrium constant under VSC. In all compounds studied, VSC does not induce detectable changes in chemical shifts, J-couplings, or spin-lattice relaxation times. This unexpected finding indicates that VSC does not substantially affect molecular electron density distributions, and in turn has profound implications for the possible mechanisms at play in polaritonic chemistry under VSC and suggests that the emergence of collective behavior is critical.

Experimental study on the coupled flow field and thrust characteristics of tail cavity and jet

During the launch process of underwater vehicles, a tail cavity is formed at the bottom, which plays a crucial role in the engine ignition stage. The flow state within this tail cavity significantly impacts the engine's operational efficiency. Moreover, the evolution of the tail cavity and jet coupling, along with hydrodynamic characteristics, influences the motion attitude of the vehicle. This article delves into the effects of initial tail cavity length, Froude number, and pressure ratio on cavity morphology and hydrodynamic characteristics, utilizing water tunnel experiments to explore these dynamics at the vehicle's bottom. The experimental findings suggest that while the length of the initial tail cavity influences the jet's coupling mode, it does not significantly affect the cavity's ultimate morphological evolution. A larger initial cavity scale correlates with a lower initial pressure peak following nozzle activation; similarly, an increase in the Froude number leads to a decrease in the initial pressure peak. When the cavity morphology remains intact, the pressure pulsation amplitude and frequency are relatively low. In contrast, partially broken cavities and pulsating foam cavities differ in morphological structure and peak internal pressure oscillations, though their pressure pulsation frequencies are similar. During the initial phase of nozzle activation, the thrust produced by the nozzle plays a more significant role than the bottom thrust. Notably, in the initial phase of nozzle activation, the nozzle-generated thrust is more influential than the bottom thrust. The thrust pulsations from pulsating foam cavities are especially strong, with peak values surpassing the initial peak thrust. These insights offer a new insight on the dynamic behavior of underwater vehicles, crucial for refining engine startup strategies.

Unconventional photon blockade with non-Markovian effects in driven dissipative coupled cavities

Unconventional photon blockade with non-Markovian effects in driven dissipative coupled cavities

A Silicon-Based ROTE Sensor for High-Q and Label-Free Carcinoembryonic Antigen Detection.

This paper presents a biosensor based on the resonant optical tunneling effect (ROTE) for detecting a carcinoembryonic antigen (CEA). In this design, sensing is accomplished through the interaction of the evanescent wave with the CEA immobilized on the sensor's surface. When CEA binds to the anti-CEA, it alters the effective refractive index (RI) on the sensor's surface, leading to shifts in wavelength. This shift can be identified through the cascade coupling of the FP cavity and ROTE cavity in the same mode. Experimental results further show that the shift in resonance wavelength increases with the concentration of CEA. The biosensor responded linearly to CEA concentrations ranging from 1 to 5 ng/mL with a limit of detection (LOD) of 0.5 ng/mL and a total Q factor of 9500. This research introduces a new avenue for identifying biomolecules and cancer biomarkers, which are crucial for early cancer detection.

Controlling Molecular Photoisomerization in Photonic Cavities through Polariton Funneling.

Strong coupling between photonic modes and molecular electronic excitations, creating hybrid light-matter states called polaritons, is an attractive avenue for controlling chemical reactions. Nevertheless, experimental demonstrations of polariton-modified chemical reactions remain sparse. Here, we demonstrate modified photoisomerization kinetics of merocyanine and diarylethene by coupling the reactant's optical transition with photonic microcavity modes. We leverage broadband Fourier-plane optical microscopy to noninvasively and rapidly monitor photoisomerization within microcavities, enabling systematic investigation of chemical kinetics for different cavity-exciton detunings and photoexcitation conditions. We demonstrate three distinct effects of cavity coupling: first, a renormalization of the photonic density of states, akin to a Purcell effect, leads to enhanced absorption and isomerization rates at certain wavelengths, notably red-shifting the onset of photoisomerization. This effect is present under both strong and weak light-matter couplings. Second, kinetic competition between polariton localization into reactive molecular states and cavity losses leads to a suppression of the photoisomerization yield. Finally, our key result is that in reaction mixtures with multiple reactant isomers, exhibiting partially overlapping optical transitions and distinct isomerization pathways, the cavity resonance can be tuned to funnel photoexcitations into specific reactant isomers. Thus, upon decoherence, polaritons localize into a chosen isomer, selectively triggering the latter's photoisomerization despite initially being delocalized across all isomers. This result suggests that careful tuning of the cavity resonance is a promising avenue to steer chemical reactions and enhance product selectivity in reaction mixtures.

Cavity Catalysis of an Enantioselective Reaction under Vibrational Strong Coupling.

Strong light-matter interaction is emerging as an exciting tool for controlling chemical reactions. Here, we demonstrate an L-proline-catalyzed direct asymmetric Aldol reaction under vibrational strong coupling. Both the reactants (4-nitrobenzaldehyde and acetone) carbonyl bands are coupled to an infrared photon and react in the presence of L-proline. The reaction mixture is eluted from the cavity, and the conversion yields and enantiomeric excess are quantified using NMR and chiral HPLC. The conversion yields increase by up to 90 % in ON-resonance conditions. Interestingly, a large increase in the conversion yield does not affect the enantiomeric excess. Further control experiments were carried out by varying the temperature, and we propose that the rate-limiting step may not be the deciding factor in enantioselectivity. Whereas the formation of the enamine intermediate is modified by cavity coupling experiments. For this class of enantioselective reactions, strong coupling does not change the enantiomeric excess, possibly due to the large energy difference in chiral transition states. Strong coupling can boost the formation of enamine intermediate, thereby favouring the product yield. This gives more hope to test polaritonic chemistry based on enantioselective reactions in which the branching ratios can be controlled.

Gain and mode purity filtering dual polarized OAM beam generation using cavity waveguide-based 3D transmitarray

A 3D transmitarray (TA) is proposed to generate dual-polarized orbital angular momentum (OAM) beams with gain and mode purity filtering responses. The TA units are realized by square cavity filters with the same passband and different orders and inner widths, resulting in different coupling cavity numbers. The evanescent modes in the coupling cavities will greatly decrease the propagation constant, thus generating a large phase variation. The square structure of the cavity filter makes it able to support dual-polarized wave propagation with the same phase delay and insert loss. Based on these transmission characteristics, eight different TA units are designed to realize a 3-bit phase gradient within the passband of 25.4–26.7 GHz. It should be emphasized that the dispersed transmission phase and magnitude of the eight TA units in the stopbands will deteriorate the purity of the OAM beam. Therefore, the gain and mode purity filtering responses can be realized simultaneously. In order to verify the performance of the proposed OAM TA design, a TA prototype with the mode number l = −1 is fabricated by 3D printing technology. The TA can realize the maximum gain of 25.9 dB in the passband, and the rejection level is below −15.0 dB within the main beam direction. The purities of dual-polarized OAM beams are over 0.5 in the passband, and the cross-polarization is below −16.5 dB. The advantages of the OAM TA, including gain-filtering and mode purity-filtering responses, dual-polarization, and high efficiency make it a promising solution for millimeter-wave OAM sensing and communication applications.

Second-Order Sidebands and Group Delays in Coupled Optomechanical Cavity System with a Cubic Nonlinear Harmonic Oscillator

The generation of second-order sidebands and its associated group delay is an important subject in optical storage and switch. In this work, the efficiency of second-order sideband generation in a coupled optomechanical cavity system with a cubic nonlinear harmonic oscillator is theoretically investigated. It is found that the efficiency of second-order sideband generation can be effectively enhanced with the decrease in decay rate of optomechanical cavity, the increase in coupling strength between two cavities and the power of probe field. The slow light effect (i.e., positive group delay) is also observed in the proposed optomechanical cavity system, and can be controlled with the power of control field.

Cavity-modified molecular dipole switching dynamics.

Polaritonic states, which are formed by resonances between a molecular excitation and the photonic mode of a cavity, have a number of useful properties that offer new routes to control molecular photochemistry using electric fields. To provide a theoretical description of how polaritonic states affect the real-time electron dynamics in molecules, a new method is described where the effects of strong light-molecule coupling are implemented using real-time electronic structure theory. The coupling between the molecular electronic states and the cavity is described by the Pauli-Fierz Hamiltonian, and transitions between polaritonic states are induced via an external time-dependent electric field using time-dependent configuration interaction (TDCI) theory, producing quantum electrodynamics TDCI (QED-TDCI). This method is used to study laser-induced ultrafast charge transfer and dipole-switching dynamics of the LiCN molecule inside a cavity. The increase in cavity coupling strength is found to have a significant impact on the energies and transition dipole moments of the molecule-cavity system. The convergence of the polaritonic state energies as a function of the number of included electronic and photonic basis states is discussed.