Resonance Frequency Of Cavity Research Articles

(Invited) Plasmonic Patch Nanoantennas for Reproducible and High-Sensitivity Chemical Detection with Surface-Enhanced Raman Spectroscopy

Excitations of surface plasmon polaritons at metal/dielectric interfaces can lead to a number of interesting optical effects in nonlinear harmonics generation, nanofocusing, enhanced optical scattering and emission. In particular, Raman signals from molecules in contact with or close proximity of metallic nanostructures can be enhanced by many orders of magnitudes, a phenomenon called surface-enhanced Raman scattering (SERS). Studies have shown that with certain plasmonic nanostructures, the SERS signals are detectable even in single molecular level, making SERS a potential label-free and high-sensitivity bio/chemical sensing modality. However, it is challenging to reach single molecule SERS in a reproducible way, as nanogaps between plasmonic nanostructures are commonly required. While nanopatterning techniques such as electron beam lithography are versatile in creating various nanostructures, creating nanogaps below 20nm reducibly remains a challenge. Here we present plasmonic patch antennas as a platform for SERS applications. The patch antennas are made of metallic patches on the top of a metal film separated by a dielectric layer. This vertical metal-dielectric-metal design makes it possible to reproducibly control the gap size in nanometers by using thin film deposition techniques such as atomic layer deposition. In this talk, we will present numerical and experimental studies on resonant cavity modes of these plasmonic patch antennas, a simple expression relating the cavity resonant frequencies with the geometric parameters of the antennas. We will also present experimental tests on SERS enhancement factors by the plasmonic patch antennas, and a comparison of their performances with commercial SERS substrates.

Sub-kilohertz excitation lasers for quantum information processing with Rydberg atoms

Quantum information processing using atomic qubits requires narrow linewidth lasers with long-term stability for high fidelity coherent manipulation of Rydberg states. In this paper, we report on the construction and characterization of three continuous-wave (CW) narrow linewidth lasers stabilized simultaneously to an ultra-high finesse Fabry-Perot cavity made of ultra-low expansion (ULE) glass, with a tunable offset-lock frequency. One laser operates at 852~nm while the two locked lasers at 1018~nm are frequency doubled to 509~nm for excitation of $^{133}$Cs atoms to Rydberg states. The optical beatnote at 509~nm is measured to be 260(5)~Hz. We present measurements of the offset between the atomic and cavity resonant frequencies using electromagnetically induced transparency (EIT) for high-resolution spectroscopy on a cold atom cloud. The long-term stability is determined from repeated spectra over a period of 20 days yielding a linear frequency drift of $\sim1$~Hz/s.

Modeling the interaction of a heavily beam loaded SRF cavity with its low-level RF feedback loops

A superconducting radio frequency (SRF) cavity provides superior stability to power high intensity light sources and can suppress coupled-bunch instabilities due to its smaller impedance for higher order modes. Because of these features, SRF cavities are commonly used for modern light sources, such as the TLS, CLS, DLS, SSRF, PLS-II, TPS, and NSLS-II, with an aggressive approach to operate the light sources at high beam currents. However, operating a SRF cavity at high beam currents may result with unacceptable stability problems of the low level RF (LLRF) system, due to drifts of the cavity resonant frequency caused by unexpected perturbations from the environment. As the feedback loop gets out of control, the cavity voltage may start to oscillate with a current-dependent characteristic frequency. Such situations can cause beam abort due to the activation of the interlock protection system, i.e. false alarm of quench detection. This malfunction of the light source reduces the reliability of SRF operation. Understanding this unstable mechanism to prevent its appearance becomes a primary task in the pursuit of highly reliable SRF operation. In this paper, a Pedersen model, including the response of the LLRF system, was used to simulate the beam-cavity interaction of a SRF cavity under heavy beam loading. Causes for the onset of instability at high beam current will be discussed as well as remedies to assure the design of a stable LLRF system.

Liquids electrical characterization sensor using a hybrid SIW resonant cavity

AbstractA new sensor based on substrate integrated waveguide (SIW) technology is proposed as an option for liquids electrical characterization. The sensor employs a rectangular waveguide resonant cavity filled with air, with two opposite side walls implemented by closely spaced metallic vias. The resulting structure is a hybrid SIW resonant cavity. The two noncontinuous walls of the hybrid SIW cavity allow the liquid insertion, filling its entire internal volume. The resonance frequency of the hybrid SIW cavity is used to determine the dielectric constant of the liquid to be characterized. A sensor using a hybrid SIW cavity operating in TE101 mode was designed to resonate at 5.9 GHz when filled with air. The sensor was employed to measure the dielectric constant of binary mixtures of distilled water and ethanol. Dielectric constants ranging from 21 to 79 were obtained, corresponding to measured resonance frequencies from 1,247 to 647 MHz, respectively. Good agreement was observed between computational electromagnetic simulation and experimental results. The dependence of the volumetric fraction of ethanol in the binary mixture on the sensor resonance frequency was expressed using a third‐order polynomial approximation.

Widely tunable optical parametric oscillation in a Kerr microresonator.

We report on the first experimental demonstration of widely tunable parametric sideband generation in a Kerr microresonator. Specifically, by pumping a silica microsphere in the normal dispersion regime, we achieve the generation of phase-matched four-wave mixing sidebands at large frequency detunings from the pump. Thanks to the role of higher-order dispersion in enabling phase matching, small variations of the pump wavelength translate into very large and controllable changes in the wavelengths of the generated sidebands: we experimentally demonstrate over 720nm of tunability using a low-power continuous-wave pump laser in the C-band. We also derive simple theoretical predictions for the phase-matched sideband frequencies and discuss the predictions in light of the discrete cavity resonance frequencies. Our experimentally measured sideband wavelengths are in very good agreement with theoretical predictions obtained from our simple phase-matching analysis.

Determination of Moisture Content in Synthetic Moulding Sand on the Grounds of Relative Permittivity Measurement

AbstractThe presented research was aimed at searching for an exact and effective method of determining moisture content in traditional moulding sands. By measuring resonance frequency and quality factor of a waveguide resonance cavity, relative permittivity was determined for different synthetic moulding sands. Analysis of the presented results confirms a linear relation between relative permittivity values and moisture content values in the selected traditional moulding sands. The obtained linear relationship can be used as a reference characteristic for evaluation of humidity of moulding sand.

Effects of functional endoscopic sinus surgery on the acoustics of the sinonasal tract

Nasal and paranasal cavities are supposed to contribute substantially to the vocal tract resonator properties. However, their acoustical effects as well as the effects of sinus surgery on the voice remain unclear. In this work we investigate resonance phenomena of paranasal sinuses prior to and after various rhinosurgical procedures in cadaveric human sinonasal tracts and corresponding 3D casts. Nasal and paranasal cavities of formalin-preserved cadavers and corresponding 3D replicas were excited by sine-tone sweeps from an earphone placed in the epipharynx. The response was picked up by a microphone at the nostrils. Different FESS procedures were performed and the acoustical responses following excitation were recorded. The measured acoustical changes in the obtained transfer functions were then evaluated. Marked low frequency dips were detected in the transfer functions when sinus cavities were included in the nasal resonator system. These dips showed a significant correlation with sinus volumes. Following FESS procedures they moved upwards in frequency depending on the extent of the surgical intervention. The transfer functions obtained in cadaveric situs and 3D replicas showed dips at the resonance frequencies of the paranasal cavities. Marked acoustic effects in terms of increase in dip frequency following FESS procedures were reproducibly documented.

Interference Switch of a Superconducting Resonance Microwave Compressor

We propose a superconducting interference switch of a resonance microwave compressor on the basis of a waveguide H-plane tee, whose lateral arm contains a switching cavity having controllable parameters and based on another H-plane tee. The transmission coefficient of the switch is evaluated for the case of controlling the Q-factor and/or resonance frequency of the switching cavity externally. It is shown that the proposed switch can ensure high-efficiency transmission of the stored energy to the load at a minimal value of the controlling parameter (compared with the known solutions).

A proposed method to measure weak magnetic field based on a hybrid optomechanical system

Optomechanical systems have long been considered in the field of precision measurement. In this work, measurement of weak magnetic field in a hybrid optomechanical system is discussed. In contrast to conventional measurements based on detecting the change of magnetic flux, our scheme presents an alternative way to measure the magnetic field with a precision of 0.1 nT. We show that the effective cavity resonance frequency will be revised due to the electromagnetic interactions. Therefore, a resonance valley in the transmission spectrum of the probe field will shift in the presence of the magnetic field, and the width of an asymmetric transparency in the optomechanically induced transparency (OMIT) shows a strong dependence on the magnetic field strength. Our results may have potential application for achieving high precision measurement of the magnetic field.

Observation of the Bloch-Siegert shift in a driven quantum-to-classical transition

We show that the counter-rotating terms of the dispersive qubit-cavity Rabi model can produce relatively large and nonmonotonic Bloch-Siegert shifts in the cavity frequency as the system is driven through a quantum-to-classical transition. Using a weak microwave probe tone, we demonstrate experimentally this effect by monitoring the resonance frequency of a microwave cavity coupled to a transmon and driven by a microwave field with varying power. In the weakly driven regime (quantum phase), the Bloch-Siegert shift appears as a small constant frequency shift, while for strong drive (classical phase) it presents an oscillatory behaviour as a function of the number of photons in the cavity. The experimental results are in agreement with numerical simulations based on the quasienergy spectrum.

Resonance frequency control of RF normal conducting cavity using gradient estimator of reflected power

Control of the natural resonance frequency of an RF cavity is essential for accelerator structures due to their high cavity sensitivity to internal and external vibrations and the dependency of resonant frequency on temperature changes. Due to the relatively high radio frequencies involved (MHz to GHz), direct measurement of the resonant frequency for real-time control is not possible by using conventional microcontroller hardware. So far, all operational cavities are tuned using phase comparison techniques. The temperature dependent phase measurements render this technique labor and time intensive. To eliminate the phase measurement, reduce man hours and speed up cavity start up time, this paper presents a control theme that relies solely on the reflected power measurement. The control algorithm for the nonlinear system is developed through Lyapunov’s method. The controller stabilizes the resonance frequency of the cavity using a nonlinear control algorithm in combination with a gradient estimation method. Experimental results of the proposed system on a test cavity show that the resonance frequency can be tuned to its optimum operating point while the start up time of a single cavity and the accompanied man hours are significantly decreased. A test result of the fully commissioned control system on one of TRIUMF’s DTL tanks verifies its performance under real environmental conditions.

Electrical Properties of Multilayer Systems Composed of Foundry Tooling and Moulding Sand

Abstract Within the research, selected multilayer technological systems created as combinations of water-glass containing moulding sand with foundry tooling, were characterised on the grounds of their electrical properties. By measuring resonance frequency and quality factor of a waveguide resonance cavity, real component of permittivity εr’ and loss tangent tgδ were determined for multilayer foundry systems with various qualitative and quantitative compositions. It was demonstrated that combination of a sandmix and foundry tooling with known dielectric properties results in a system with different physico-chemical properties, whose relation to the parameters of individual components of the system is undefined at this research stage. On the grounds of measurement results, theoretical value of microwave heating power, dissipated in unit volume of the selected multilayer foundry system, was determined. Knowledge of theoretical heating power and evaluation of physical, chemical and structural changes occurring in moulding sands exposed to microwaves in such a technological system makes a ground for empirical modelling of the process of microwave heating of foundry moulds and cores.

Collective strong coupling of cold atoms to an all-fiber ring cavity

Large-scale quantum networks could allow a wide variety of applications in quantum computing and simulation. Here we demonstrate the operation of a single node for use in such a network. We employ a ring geometry all-fiber cavity system for cavity quantum electrodynamics with an ensemble of cold atoms. The fiber cavity contains a nanofiber section, which mediates atom–light interactions through an evanescent field. We observe well-resolved vacuum Rabi splitting of the cavity transmission spectrum in the weak driving limit due to collective enhancement of the coupling rate by the ensemble of atoms, and present a simple theoretical model to describe this. In addition, we stabilize the cavity resonant frequency by utilizing the thermal properties of the nanofiber. This work represents an important step toward implementing a large-scale all-fiber quantum network.

High-Q photonic resonators and electro-optic coupling using silicon-on-lithium-niobate

Future quantum networks, in which superconducting quantum processors are connected via optical links, will require microwave-to-optical photon converters that preserve entanglement. A doubly-resonant electro-optic modulator (EOM) is a promising platform to realize this conversion. Here, we present our progress towards building such a modulator by demonstrating the optically-resonant half of the device. We demonstrate high quality (Q) factor ring, disk and photonic crystal resonators using a hybrid silicon-on-lithium-niobate material system. Optical Q factors up to 730,000 are achieved, corresponding to propagation loss of 0.8 dB/cm. We also use the electro-optic effect to modulate the resonance frequency of a photonic crystal cavity, achieving a electro-optic modulation coefficient between 1 and 2 pm/V. In addition to quantum technology, we expect that our results will be useful both in traditional silicon photonics applications and in high-sensitivity acousto-optic devices.

Modulation dynamic response of optical‐injection‐locked wavelength‐tunable semiconductor laser diodes

The effect of optical injection locking (OIL) on modulation dynamics of tunable laser diodes (TLDs) is investigated. The stable locking boundary map of OIL TLD which depends on the lasing wavelength was calculated and the TLD response in different injection states was investigated. Dramatic change in the emission spectra and the relaxation oscillation frequency (ROF) and huge improvement of these characteristics under OIL is demonstrated. Effect of the OIL parameters (frequency detuning and power ratio) on the TLD dynamics was studied for different tuning wavelengths. We show that forward optical injection and positive frequency detuning and blue-wavelength tuning are preferable regimes for enhanced modulation performance of OIL TLDs. Large increase of the ROF (>20GHz) and the modulation bandwidth (>25GHz) of the OIL TLD are demonstrated. The novel feature of the modulation response of the OIL TLD compared with usual single-mode lasers emitting at a fixed wavelength is the frequency dispersion of the differential gain in TLDs which increases with wavelength tuning. It is shown that the differential gain increase with wavelength tuning and the optical injection effect on the cavity resonance frequency shift contribute to a substantial enhancement of the modulation response of the OIL TLD.

Output field-quadrature measurements and squeezing in ultrastrong cavity-QED

We study the squeezing of output quadratures of an electro-magnetic field escaping from a resonator coupled to a general quantum system with arbitrary interaction strengths. The generalized theoretical analysis of output squeezing proposed here is valid for all the interaction regimes of cavity-quantum electrodynamics: from the weak to the strong, ultrastrong, and deep coupling regimes. For coupling rates comparable or larger then the cavity resonance frequency, the standard input–output theory for optical cavities fails to calculate the variance of output field-quadratures and predicts a non-negligible amount of output squeezing, even if the system is in its ground state. Here we show that, for arbitrary interaction strength and for general cavity-embedded quantum systems, no squeezing can be found in the output-field quadratures if the system is in its ground state. We also apply the proposed theoretical approach to study the output squeezing produced by: (i) an artificial two-level atom embedded in a coherently-excited cavity; and (ii) a cascade-type three-level system interacting with a cavity field mode. In the latter case the output squeezing arises from the virtual photons of the atom-cavity dressed states. This work extends the possibility of predicting and analyzing the results of continuous-variable optical quantum-state tomography when optical resonators interact very strongly with other quantum systems.

Gain and Efficiency of a Superconducting Microwave Compressor with a Switching Cavity in an Interference Switch

We study the processes of radiation output from a microwave storage cavity through a superconducting interference switch, which is based on a H-junction with a superconducting switching cavity connected to the side branch of the junction for various ways of controlling the parameters of the switching cavity. It is shown that efficient control over radiation output in such a switch can be achieved by varying the resonance frequency or Q-factor of the switching cavity, as well as by varying these parameters simultaneously. It is found that in the case of controlling the resonance frequency of the switching cavity, there exists an optimal interval of the frequency variation, within which the total efficiency and extraction efficiency are maximum. When the Q-factor of the switching cavity changes, the dependence of the total efficiency and extraction efficiency on the Q-factor has the monotonic character. The mixed regime of radiation output control is also studied. The envelopes of the output compressor pulses are plotted on the basis of recurrent relationships between the amplitudes of the waves in the system for three regimes of switch operation. It is shown that pulses with an almost rectangular shape of the envelope can be formed in the regime of controlling the switching cavity by varying the Q-factor. An example of possible realization of the switching cavity is considered.

Assessment of sound insulation of naturally ventilated double skin facades

The sound insulation spectrum is analysed of 18 double glazing arrangements facades, of which 9 double skin facades were measured in situ and 9 in a laboratory setting. The influence of the cavity thickness, the parallelism of the two glass panels, the absorptivity of the cavity and the effect of the size of ventilation slots are investigated. The results are compared with double layer wall insulation prediction models. Also a new, simple model is proposed that predicts the sound insulation of naturally ventilated double skin facades, based on the coincidence frequency, the structural resonance frequencies, the cavity resonance frequencies, the façade construction, the dimensions the and material properties. The model predictions are validated by measurement data.

External Control of Dissipative Coupling in a Heterogeneously Integrated Photonic Crystal—SOI Waveguide Optomechanical System

Cavity optomechanical systems with an enhanced coupling between mechanical motion and electromagnetic radiation have permitted the investigation of many novel physical effects. The optomechanical coupling in the majority of these systems is of dispersive nature: the cavity resonance frequency is modulated by the vibrations of the mechanical oscillator. Dissipative optomechanical interaction, where the photon lifetime in the cavity is modulated by the mechanical motion, has recently attracted considerable interest and opens new avenues in optomechanical control and sensing. In this work we demonstrate an external optical control over the dissipative optomechanical coupling strength mediated by the modulation of the absorption of a quantum dot layer in a hybrid optomechanical system. Such control enhances the capability of tailoring the optomechanical coupling of our platform, which can be used in complement to the previously demonstrated control of the relative (dispersive to dissipative) coupling strength via the geometry of the integrated access waveguide.

Universal switching of plasmonic signals using optical resonator modes

We propose and investigate, both experimentally and theoretically, a novel mechanism for switching and modulating plasmonic signals based on a Fano interference process, which arises from the coupling between a narrow-band optical Fabry–Pérot cavity and a surface plasmon polariton (SPP) source. The SPP wave emitted from the cavity is actively modulated in the vicinity of the cavity resonances by altering the cavity Q-factor and/or resonant frequencies. We experimentally demonstrate dynamic SPP modulation both by mechanical control of the cavity length and all-optically by harnessing the ultrafast nonlinearity of the Au mirrors that form the cavity. An electro-optical modulation scheme is also proposed and numerically illustrated. Dynamic operation of the switch via mechanical means yields a modulation in the SPP coupling efficiency of ~80%, while the all-optical control provides an ultrafast modulation with an efficiency of 30% at a rate of ~0.6 THz. The experimental observations are supported by both analytical and numerical calculations of the mechanical, all-optical and electro-optical modulation methods.