Cavity Coupling Research Articles

Efficient operation near the quantum limit in external cavity diamond Raman laser

We realize efficient operation of the first Stokes (1240.3 nm) and the second Stokes (1485.8 nm) in external cavity diamond Raman lasers (DRLs) through efficient cavity coupling management and study their output performance. Firstly, an output pulse energy of 0.26 mJ at the first Stokes is generated and the slope efficiency is 84.3%, which closely approaches the quantum limit of 85.8%. Secondly, an output pulse energy of 0.26 mJ at the first Stokes and 0.18 mJ at the second are generated simultaneously. The total Raman output pulse energy is 0.44 mJ with a slope efficiency of 73.0%. To our knowledge, this is the highest slope efficiency in dual-wavelength external cavity DRLs. At the maximum pump level, by managing the cavity coupling, the energy ratio of the second Stokes to the first can be changed from 0.69 to 1.92. Highly efficient operation in external cavity DRLs is very important in practical applications, such as remote sensing, scanning lidar and laser range finding.

Nonlinear dynamics and flutter of plate and cavity in response to supersonic wind tunnel start

The transient response of a plate and a cavity is investigated in a supersonic wind tunnel start experiment where the freestream flow inside the test section reaches turbulent flow at Mach 2. Experimentally measured plate displacement time history shows flutter onset, transition to limit cycle oscillation, and stabilization at a static deformed state during the 30 s run. To analyze and interpret the measured plate response, a fully coupled aero-thermal-acousto-elastic analysis is carried out. A theoretical–computational model is formulated with a nonlinear structural plate model, acoustic pressure equation for the stationary fluid in a cavity, and the first-order Piston Theory aerodynamics. A linear stability analysis is performed that includes the nonlinear added stiffness due to an initial deformation to investigate the combined effects of freestream coupling and temperature differential on system stability. Also, direct time integration of the nonlinear fluid structural equations of motion is performed using experimentally measured flow parameters as inputs. All stability transitions are captured using the theoretical model with good agreement with experiment for transitions from no flutter to flutter/limit cycle oscillations (LCO) although the theoretical LCO amplitude is approximately $$50\%$$ larger than measured. The system’s sensitivity to cavity coupling, temperature differential, thickness calibration, static pressure differential, and turbulent pressure fluctuations are investigated. Lastly, snap-through buckling analyses in response to periodic and quasi-static excitations are conducted.

Nonclassical Effects Based on Husimi Distributions in Two Open Cavities Linked by an Optical Waveguide.

Nonclassical effects are investigated in a system formed by two quantum wells, each of which is inside an open cavity. The cavities are spatially separated, linked by a fiber, and filled with a linear optical medium. Based on Husimi distributions (HDs) and Wehrl entropy, we explore the effects of the physical parameters on the generation and the robustness of the mixedness and HD information in the phase space. The generated quantum coherence and the HD information depend crucially on the cavity-exciton and fiber cavity couplings as well as on the optical medium density. The HD information and purity are lost due to the dissipation. This loss may be inhibited by increasing the optical susceptibility as well as the couplings of the exciton-cavity and the fiber-cavity. These parameters control the regularity, amplitudes, and frequencies of the generated mixedness.

Coupled Cavity Mid-IR Quantum Cascade Lasers Fabricated by Dry Etching

In this work, two-section, coupled cavity, mid-IR quantum cascade lasers (QCLs) were characterized in terms of their tuning range and emission stability under operation towards potential application in detection systems. Devices were processed by inductively coupled plasma reactive ion etching (ICP-RIE) from InP-based heterostructure, designed for emission in the 9.x micrometer range. Single mode devices were demonstrated with a better than 20 dB side mode suppression ratio (SMRS). The fabrication method resulted in improved yield, as well as high repeatability of individual devices. Continuous, mode-hop-free tuning of emission wavelength was observed across ~4.5 cm−1 for the range of temperatures of the heat sink from 15 °C to 70 °C. Using the thermal perturbation in the lasing cavity, in conjunction with controlled hopping between coupled-cavity (CC) modes, we were able to accomplish tuning over the range of up to ~20 cm−1.

Controllable bistable optical switch and normal mode splitting in hybrid optomechanical semiconductor microcavity containing single quantum dot driven by amplitude modulated field

We theoretically explore optical bistability for the possible signature of all-optical switching and their performance in a hybrid quantum optomechanical system comprising of two semiconductor microcavities coupled optically. One of the cavity is driven by an external amplitude-modulated pump laser while the second cavity, which contains a quantum dot (QD), is indirectly driven by light transmitted from the first cavity and a transverse optical field. The generated bistable behavior due to optomechanical nonlinearity shows a typical optical switching behavior and it can be controlled by changing the laser power, QD cavity coupling, modulating amplitude/frequency and the optomechanical coupling. A clear signature of energy exchange between the mechanical and optical modes is visible from the mechanical displacement spectrum. These results suggest that the present system can be used in sensitive optical switches and optical sensors.

Enhanced modulation characteristics in broken symmetric coupled microring lasers.

The dynamical behavior of broken symmetric coupled cavity lasers is theoretically investigated. The frequency response of this class of lasers is obtained using small signal analysis under direct modulation. Our model predicts a modulation bandwidth enhancement as a broken symmetric laser, operating in the parity-time (PT) symmetry and non-PT symmetry domains. This theoretical prediction is numerically examined in a laser system based on an InGaAs quantum dot platform. Our results clearly show that in these structures, in addition to the injection current, the gain-loss contrast can be used as a new degree of freedom in order to control the characteristic poles of the frequency response function.

Split-gate cavity coupler for silicon circuit quantum electrodynamics

Coherent charge-photon and spin-photon coupling has recently been achieved in silicon double quantum dots (DQDs). Here, we demonstrate a versatile split-gate cavity-coupler that allows more than one DQD to be coupled to the same microwave cavity. Measurements of the cavity transmission as a function of level detuning yield a charge cavity coupling rate of gc/2π= 58 MHz, a charge decoherence rate of γc/2π= 36 MHz, and a cavity decay rate of κ/2π= 1.2 MHz. The charge cavity coupling rate is in good agreement with device simulations. Our coupling technique can be extended to enable simultaneous coupling of multiple DQDs to the same cavity mode, opening the door to long-range coupling of semiconductor qubits using microwave frequency photons.

Quantum speed-up process of atom in dissipative cavity

In this work, we obtain an analytical representation of the density operator of an atom in a dissipative cavity when the reservoir is at zero temperature and the total number of excitations is N = 1. We also investigated the quantum speed limit time (QSLT) of the atom and the non-Markovianity in the dynamics process. The results show that the QSLT and the non-Markovianity can be effectively manipulated by the atom–cavity coupling and the reservoir parameters. Both of the atom–cavity coupling and the detuning can induce a sudden transition from Markovian to non-Markovian dynamics, and this transition is the main physical reason of the quantum speed-up process. The critical value of the sudden transition from no speed-up to speed-up the atom–cavity coupling and the reservoir parameters. The corresponding physical explanation is also provided for our results.

Effects of cavity coupling on 1D defect modes: a theoretical model

We develop an analytical solution based on the cavity coupling that can be used to predict the output performance of the 1D defect modes. This solution gives a concise analytical expression of every emission wavelength of the defect modes with arbitrary defect numbers. The splitting and the resonance modes are explained qualitatively by the proposed theoretical model. The output performance obtained by the analytical solution are in good consistency with that obtained by the numerical simulations using the finite-difference time-domain method. These results may provide a useful alternative to customize the 1D coupled defect mode laser.

Coupled Polymer-Membrane Equilibration and Cavity Ring-down Spectrometry for the Highly Sensitive Determination of Dissolved Methane in Environmental Waters

High sensitivity field-based analysis of dissolved methane in surface water and groundwater is needed to monitor the environmental impacts of natural gas-field development and understand microbial carbon cycling in water bodies. A new analytical technique using a polymer membrane contactor coupled to a laser-based cavity ring-down spectrometer was developed and tested. By recirculating a water sample for approximately 10 mins, equilibrium was established between dissolved methane in the sample and methane in the measured gas phase according to Henry’s Law. The performance of the system was investigated by replicate analyses of several different water samples, spike recovery tests, comparison to analysis by head-space gas chromatography, and consideration of memory effects. The technique provided an adequate detection limit for the determination of natural background concentrations of methane in environmental waters and was approximately 28 times more sensitive than analysis by gas chromatography. The system is field-capable, simple to operate and calibrate, and takes advantage of the low-drift characteristics of the cavity ring-down spectrometer.

Broadband enhancement of light-matter interaction in photonic crystal cavities integrating site-controlled quantum dots

The fabrication of integrated quantum dot (QD)-optical microcavity systems is a requisite step for the realization of a wide range of nanophotonic experiments (and applications) that exploit the ability of QDs to emit nonclassical light, e.g., single photons. Thanks to their \ensuremath{\sim}20-nm positioning accuracy and to their proven potential for single-photon operation, the QDs obtained by spatially selective hydrogen irradiation of dilute-nitride semiconductors ---such as Ga(AsN) and Ga(PN)---are uniquely suited for integration with photonic nanodevices. In the present work, we demonstrate the ability to deterministically integrate single, site-controlled Ga(AsN)/Ga(AsN):H QDs within a photonic crystal (PhC) cavity. The properties of the fabricated QD-PhC cavity systems are then probed by photon correlation---providing clear evidence of single-photon emission---and time-resolved microphotoluminescence spectroscopy. Detailed information on the dynamics of our integrated nanodevices can be inferred by comparing these experiments to the solutions of a rate-equations system, developed by taking into account all the main processes leading to the capture, relaxation, and recombination of carriers in and out of the QD. This allows us to follow the evolution of the relevant recombination rates in our system for varying energy detuning, \ensuremath{\Delta}$E$, between the QD and the PhC cavity. When the QD exciton transition is nearly resonant with the cavity mode, a large (gtenfold) enhancement of the spontaneous emission rate is observed, in substantial agreement with Jaynes-Cummings (JC) theory. For intermediate detunings (\ensuremath{\Delta}$E$ \ensuremath{\sim} 1.5--3.5 meV), on the other hand, the observed enhancement is significantly larger than that predicted by JC theory, due to the important role played by acoustic phonons in mediating the QD-PhC cavity coupling in a solid-state environment. Apart from its fundamental interest, the observation of such phonon-mediated, broadband enhancement of light-matter interaction significantly relaxes the requirements for the realization of a large variety of cavity QED-based experiments and applications. These include many photonic devices for which the use of site-controlled Ga(AsN)/Ga(AsN):H QDs would be inherently advantageous, such as those based on the coupling between more than one QD and a single cavity mode (e.g., few-QD nanolasers and QD solids).

Higher-order exceptional points: A route for flat-top optical filters

We study theoretically the formation and properties of higher-order exceptional points (EPs) in optical parity-time symmetric systems (PTSSs) consisting of a finite number of coupled resonators. The analysis shows that only specific configurations of such PTSSs exhibit high-order EPs. We derive the conditions for the formation of higher-order EP in these PTSSs and discuss the properties of the eigenmodes. By taking advantage of the fundamental link between EPs and the formation of a white-light cavity, we utilize the conditions at which high-order EPs are formed for designing broadband, maximally flat, optical filters. By selecting the coupling coefficients between the resonators accordingly we show the bandwidth of such coupled cavity filters cannot only be enhanced substantially compared to other common design approaches, but also provide flat spectral response where these design approaches fail completely.

Atomic microwave-to-optical signal transduction via magnetic-field coupling in a resonant microwave cavity

Atomic vapors offer many opportunities for manipulating electromagnetic signals across a broad range of electromagnetic spectra. Here, a microwave signal with an audio frequency modulation encodes information in an optical signal by exploiting an atomic microwave-to-optical double resonance and magnetic-field coupling that is amplified by a resonant high-Q microwave cavity. Using this approach, audio signals are encoded as amplitude or frequency modulations in a GHz carrier, transmitted through a cable or over free space, demodulated through cavity-enhanced atom-microwave interactions, and, finally, optically detected to extract the original information. This atom-cavity signal transduction technique provides a powerful means by which to transfer information between microwave and optical fields, all using a relatively simple experimental setup without active electronics.

Controlled-Phase Gate Using Dynamically Coupled Cavities and Optical Nonlinearities.

We show that relatively simple integrated photonic circuits have the potential to realize a high fidelity deterministic controlled-phase gate between photonic qubits using bulk optical nonlinearities. The gate is enabled by converting travelling continuous-mode photons into stationary cavity modes using strong classical control fields that dynamically change the effective cavity-waveguide coupling rate. This architecture succeeds because it reduces the wave packet distortions that otherwise accompany the action of optical nonlinearities [J. Shapiro, Phys. Rev. A 73, 062305 (2006)PLRAAN1050-294710.1103/PhysRevA.73.062305; J. Gea-Banacloche, Phys. Rev. A 81, 043823 (2010)PLRAAN1050-294710.1103/PhysRevA.81.043823]. We show that high-fidelity gates can be achieved with self-phase modulation in χ^{(3)} materials as well as second-harmonic generation in χ^{(2)} materials. The gate fidelity asymptotically approaches unity with increasing storage time for an incident photon wave packet with fixed duration. We also show that dynamically coupled cavities enable a trade-off between errors due to loss and wave packet distortion. Our proposed architecture represents a new approach to practical implementation of quantum gates that is room-temperature compatible and only relies on components that have been individually demonstrated.

Modeling of plasma combustion ignition on an electromagnetic wave driven metasurface

We present a multi-physics model of combustion ignition phenomena in an atmospheric pressure hydrogen-air mixture ignited by a microwave surface plasma discharge. The surface plasma is generated over a resonant metasurface structure that provides sufficient field intensification to break down and sustain a discharge. Specifically, a surface electromagnetic (EM) wave mode known as the spoof surface plasmon polariton (SSPP) is excited to yield a hybrid resonance that results from coupling of cavity and surface EM wave modes. Motivated by the need for a large, volumetric ignition kernel for applications in combustion ignition, we numerically demonstrate the volumetric surface plasma discharge enabled by the use of this particular EM wave mode in a high pressure operating regime. We discuss the transient evolution of a centimeter scale plasma kernel and subsequent ignition kernel formation. High density combustion enhancing radical species (O, H, OH) are produced throughout the bulk plasma, which leads to successful ignition. A parametric study shows that the large size of a plasma kernel is attributed to the shortening of ignition delay.

Novel Coupling Cavities for Improving the Performance of G-Band Ladder-Type Multigap Extended Interaction Klystrons

A pair of ladder-type multigap cavities, namely, wide-coupling cavity and narrow-coupling cavity, were comparatively studied to improve the performance of $G$ -band extended interaction klystrons (EIKs). It is found that the narrow-coupling cavity has higher effective characteristic impedance and stronger electric field distribution which lead to relatively stronger beam–wave interaction strength and obviously better output characteristics. Particle-in-cell (PIC) simulation confirmed this conclusion. Under an working voltage of 16.5 kV, current of 0.3 A, and operating mode of $\pi $ mode, the narrow-coupling cavity structure has greater output power and wider bandwidth. Specifically, when the ratio of long and short slots is 1.13, 1.21, and 1.26, compared with the wide coupling cavity structure, the output power of the narrow coupling cavity structure is increased by 40, 90, and 50 W, and the bandwidth is significantly increased by 50, 100, and 200 MHz, respectively. Then a maximum output power of 400 W, a gain of 39 dB, a bandwidth of 500 MHz can be achieved with our narrow-coupling cavity structure EIK in $G$ -band. Thus, such structures show potential performance improvement of millimeter-wave and terahertz EIK.

Controlling one-way quantum steering in a modulated optomechanical system

We investigate in detail the properties of the stationary quantum steering of two mechanical modes, where the two mechanical modes interact with two coupling cavity modes, and two four-tone driving lasers are used to pump the two cavity modes. By controlling the pumping lasers, the two cavity modes can act as two engineered reservoirs to cool the two mechanical modes to a squeezed state. When the damping rates of the two mechanical modes are different, numerical simulation results show that there are parameter regions where the state of the two mechanical modes only has one-way quantum steering, which is the most prominent feature of quantum steering from quantum entanglement.

Non-Lorentzian Local Density of States in Coupled Photonic Crystal Cavities Probed by Near- and Far-Field Emission.

Recent theories proposed a deep revision of the well-known expression for the Purcell factor, with counterintuitive effects, such as complex modal volumes and non-Lorentzian local density of states. We experimentally demonstrate these predictions in tailored coupled cavities on photonic crystal slabs with relatively low optical losses. Near-field hyperspectral imaging of quantum dot photoluminescence is proved to be a direct tool for measuring the line shape of the local density of states. The experimental results clearly evidence non-Lorentzian character, in perfect agreement with numerical and theoretical predictions. Spatial maps with deep subwavelength resolution of the real and imaginary parts of the complex mode volumes are presented. The generality of these results is confirmed by an additional set of far-field and time-resolved experiments in cavities with larger modal volume and higher quality factors.

Guest Editorial for the special issue on devices and circuits for millimeter‐wave and THz applications

Guest Editorial for the special issue on devices and circuits for millimeter‐wave and THz applications

Coupling of SiV-containing nanodiamonds to a Fabry-Perot microcavity

The possibility of increasing the spontaneous emission rate for silicon-vacancy (SiV) centers in nanodiamonds placed in a Fabry-Perot microcavity was studied. For this purpose, a plano-concave open access microcavity was designed. The cavity was tested using diamond nanocrystallites, placed on a flat mirror. Nanodiamonds were synthesized from adamantane and Si-containing adamantane derivative by high pressure, high temperature (HPHT) technique. The controlled room temperature cavity coupling gives rise to a resonant Purcell enhancement of the SiV zero-phonon line by a factor 1.4.