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Sustainable exploration of the Moon could benefit from a microwave heating-based 3D Printing technology for In-Situ Resource Utilisation (ISRU) purposes such as for the fabrication of habitats and extraction of resources on the Moon. In this context, we have developed a Microwave Heating Demonstrator (MHD) payload concept, which can perform pre-defined ISRU experiments on the lunar surface. The MHD payload would also produce scientifically valuable data in its own right, which would help to establish fundamental criteria for developing a microwave heating-based 3D Printing technique, ultimately enabling lunar construction and other ISRU-derived mission activities.\ud \ud One of the major design criteria of the MHD payload was to enable sustainable heating performance at low microwave power, e.g., 250 W. This paper discusses some non-negligible phenomena during the microwave heating of lunar regolith, which need to be considered for future mission applications. We also present a design of the MHD payload development, focusing on the heating performance of the microwave cavity.

We describe the observation of a previously unreported resonance phenomenon in UWB SAR imaging and its application in a novel scheme for the retrieval of thickness and dielectric properties of scene features. The resonance was observed in a 14–50 GHz laboratory study of very high resolution SAR imagery. It presented as a periodic fluctuation in the backscatter of a scene feature in response to changes in the radar measurement frequency. The complimentary static reflectivity measurements of a range of dielectric materials showed the phenomenon could be understood as a material behaving as a resonant microwave cavity. Modeling simulations were able to accurately reproduce the observed nulling characteristics for visually homogeneous materials (acrylic, MDF, and plasterboard) and which displayed a regular frequency spacing between nulls. Those with inhomogeneous structures (chipboard and plywood) showed much more irregular nulling patterns. The spacing of the backscatter nulls is set by the product of the permittivity and thickness of the material. By exploiting diversity in viewing geometry, the two terms can be separated and measured. The scheme offers a new opportunity in the SAR surveillance and monitoring of man-made structures.

In this study, the main focus is laid on the design of an optoelectronic converter as a part of the quantum radar to enhance the entanglement between retained and returned modes at high temperatures. The electro-opto-mechanical converter has been widely studied, and the results showed that the operation at high temperature is so crucial to generate and preserve the entanglement between modes. The main problem arises because the mechanical part operating at a low frequency leads to a large number of thermally excited photons, and eventually, the entanglement between modes becomes lost. To solve the problem, we replace the mechanical part with the optoelectronic components. The optical cavity is coupled to the microwave cavity in the newly designed system through a Varactor diode excited by a photodetector. As the main goal, to improve the entanglement sustainability, the effect of the coupling factor of the microwave cavity to photodetector is investigated. The results show that the mentioned factor creates some degrees of freedom to enhance the entanglement at high temperatures compared to the electro-opto-mechanical converter. At some specific values of the coupling factor, the retained and returned fields remained completely entangled up to 5.5 K and partially entangled around 50 K.

Overcoming poor readout is an increasingly urgent challenge for devices based on solid-state spin defects, particularly given their rapid adoption in quantum sensing, quantum information, and tests of fundamental physics. However, in spite of experimental progress in specific systems, solid-state spin sensors still lack a universal, high-fidelity readout technique. Here we demonstrate high-fidelity, room-temperature readout of an ensemble of nitrogen-vacancy centers via strong coupling to a dielectric microwave cavity, building on similar techniques commonly applied in cryogenic circuit cavity quantum electrodynamics. This strong collective interaction allows the spin ensemble’s microwave transition to be probed directly, thereby overcoming the optical photon shot noise limitations of conventional fluorescence readout. Applying this technique to magnetometry, we show magnetic sensitivity approaching the Johnson–Nyquist noise limit of the system. Our results pave a clear path to achieve unity readout fidelity of solid-state spin sensors through increased ensemble size, reduced spin-resonance linewidth, or improved cavity quality factor., Conventional optical readout limits the sensitivity of solid state spin sensors due to photon shot noise and poor contrast. Here, the authors demonstrate room-temperature microwave detection of an ensemble of NV centers embedded in a microwave cavity, which offers high-fidelity readout without time overhead.

Sample preparation is one of the most time-consuming steps in diagnostic assays, particularly those involving biological samples. In this paper we report the results of finite-difference time-domain (FDTD) simulations and thermographic imaging experiments carried out with the intent of designing a microplate for rapid, high-throughput sample preparation to aid diagnostic assays. This work is based on devices known as microwave lysing triangles (MLTs) that have been proven capable of rapid sample preparation when irradiated in a standard microwave cavity. FDTD software was used to model a microplate platform as a polystyrene substrate with an array of various passive scattering elements (PSEs) of different sizes, shapes, and interelement spacings in a 2.45 GHz field identical to that of a common microwave oven. Based on the FDTD modeling, several PSE arrays were fabricated by cutting PSEs out of aluminum foil and adhering them to the bottom of regular polystyrene microplates to make prototypes. Each prototype microplate was then irradiated in a microwave cavity for a range of different times, powers, and source angles and the heating effects were observed via a forward looking infrared (FLIR) camera. Based on the results, two prototype microplate platforms have been shown to demonstrate electromagnetic and thermal enhancements similar to those seen with MLTs as well as tunable thermal responses to radio frequency (RF) irradiation.

Utilizing 3D printing to create custom microwave filters has promising aspects such as light weight and low cost, most importantly including the fact that complicated structures can be printed quickly and inexpensively. Some SLA resins have very high Coefficient of Thermal Expansion (CTE) compared to metal, so SLA 3D printed microwave filters can have frequency responses that are strongly dependent on temperature-a serious problem for narrow band filters. The presented technique overcomes this limitation, and in fact yields an SLA 3D printed filter with better temperature stability than an uncompensated metal 3D printed or a conventionally machined metal filter. Two 3D printed, temperature compensated microwave cavity notch filters have been fabricated using stereolithography (SLA) resins. Both use two different values of CTE for compensation. The 3D printed plastic parts are electroplated with copper. One filter consists of a resonant cavity with the TE011 mode coupled to a TE10 waveguide. The other is a TE101 resonant cavity coupled to TE10 waveguide. As temperature increases, the side walls of the cavities grow, lowering the resonant frequency. At the same time, for the TE011 cavity, an end-wall tuning plunger made of stereolithography resin with a higher CTE than the cavity walls expands at a faster rate. The end wall expansion increases the resonant frequency. In the case of the TE101 cavity, a metallic plunger expands much more slowly than the cavity and effectively withdraws as temperature increases, which increases the resonant frequency.

The opto-electro-mechanical system as a quantum interface between electronic information and optical information plays an important role in quantum information processing. Ground-state cooling of the macroscopic mechanical oscillator is a crucial requirement for this system in order to eliminate the effect of thermal fluctuations on transmission of information. Here, we propose a scheme of ground-state cooling for a mechanical oscillator which is coupled to an optical cavity through radiation pressure force and simultaneously coupled to a superconducting microwave cavity through an effective capacitance. Meanwhile, the periodical frequency modulations are applied to the optical mode, microwave cavity, and mechanical mode, respectively. The cooling efficiency is analyzed and cooling dynamics is simulated numerically by means of covariance matrix. The results show that the Stokes heating processes can be suppressed effectively by means of frequency modulations, and the mechanical oscillator can be cooled to near its ground-state with a higher efficiency than that of a standard optomechanical system due to the double cooling channel. Moreover, a complementary cooling effect is found between these two cooling channels, i.e., a high cooling efficiency can be achieved by cooperation between a good optical cavity and a bad microwave cavity, or vice versa. This cooperative cooling of the double channel breaks the limitation of resolved-sideband regime.

Dielectric measurements offer the possibility of highly sensitive detection of physical cell properties, and are of interest for clinical applications due to their non-destructive nature and the lack of need for cell labelling. Here we report sensitive measurements on single, living, free-flowing cells (not electrostatically or dielectrophoretically trapped, cultured or fixed directly on sensing elements) in aqueous medium at ∼9.8 GHz taken using a coupled dielectric-split ring resonator assembly. Inductive coupling between the two resonators enabled separation of microfluidic chips from RF connectors and allowed for time-resolved continuous-wave measurements on flowing single cells via the coaxial ports of a dielectric-loaded microwave cavity. Analysis via an equivalent circuit model showed that the novel resonator assembly maintained the permittivity-dependent sensitivity of a split ring resonator while operating at quality factors >1000 with lossy aqueous media (typically ∼1900). Using a microfluidic channel with a 300 × 300 μm cross section, at a water-loaded resonant amplitude of ∼−22 dB at 0 dBm input power level, shifts in amplitude due to individual cells passing through the sensing region of up to −0.0015 dB were observed. Correlations between averaged amplitude shifts and cell size as well as material properties demonstrate the diagnostic potential of this technique.

The coupled 3D and transient form of heat and Maxwell’s equations were solved to determine the temperature distribution within a carrot slice in the microwave cavity during pasteurization as a clean and energy saving process. To precisely simulate the turning of the sample, the dissipated thermal energy was applied to the carrot as a rotating heat source field. The temperature evolution pattern through time was determined for various power levels and compared to measured experimental data to validate the simulation. Additionally, an inactivation modeling for Enterococcus faecalis, Bacillus cereus, Staphylococcus aureus and Shigella flexneri based on the cumulative exposure time to the elevated temperatures was proposed. According to the results, it was shown that due to the temperature variation profiles, three inactivation phases (heating process; holding temperature; microwave turn off phase) can be introduced. The most inactivation was occurred through the first and second phases for 600 W and also the temperature level was not sufficiently high to produce a major inactivation for 200 W during the last phase. Additionally, the 400 W microwave power created the highest inactivation of bacteria through the last phase. Based on the obtained results the energy demand of the microwave thermal treatment was 52.3% lower than conventional steam surface pasteurization and also it can be used as a clean process in pasteurization of carrots instead of chemical pasteurization.

In this study, plasmonic opto-mechanical tripartite system is proposed to improve the performance of the traditional tripartite opto-mechanical system. In the new design, significantly, optical cavity and microwave cavity modes are directly coupled to each other. The originality of this work consists in embedding a microsphere in the optical cavity where the plasmon-plasmon interaction between the metal plates generates a plasmon mode inside the optical cavity and changes the electric field distribution. The plasmonic property influences the microsphere electrical properties and interacts with the photonic mode inside the optical cavity by which the microwave cavity properties are also affected through coupling to the optical cavity. Microsphere introduces a capacitor as a function of plasmonic properties that can strongly influence the microwave cavity resonance frequency. That is the feature that we want to utilize to enhance the performance of the system at high temperature. The results show that the optical cavity and microwave cavity modes remain entangled at high temperature. It is contributed to the plasmonic-based capacitor induced by the microsphere which is not affected by the thermally induced photons (noise). It is worth mentioning that the induced noise strongly restricts the traditional tripartite system operated with a wide bandwidth.

In this article, Au/As2Se3/Ag/As2Se3/Yb Schottky barriers are formed and characterized. The devices prepared by the thermal evaporation technique under vacuum pressure of 10−5 mbar are observed to exhibit metal-induced crystallization process when coated onto Au substrates. Electrically, the arsenic selenide-based Schottky devices exhibited typical metal-oxide-semiconductor (MOS) characteristics with a built-in potential of 0.17 eV. The device shows resonance–antiresonance switching, negative capacitance (NC) effect, and high to low conductance switching features in the frequency domain of 10–1800 MHz. In addition, measurement of the impedance, amplitude of reflection coefficient, return loss ( ${L}_{r}$ ), and voltage standing wave ratio (VSWR) spectra in the same domain have shown that the Au/As2Se3/Ag/As2Se3/Yb Schottky barriers display band stop features at 1180 MHz. The ${L}_{r}$ and VSWR values at this critical frequency are 29.1 dB and 1.1, respectively. The electrical characterizations of the Au/As2Se3/Ag/As2Se3/Yb MOS devices have confirmed their suitability for use as parasitic capacitance cancellers, noise reducers, and as switching clock with selective switching time scales of switching delay time less than 0.40 ns.

A versatile, modular in situ high-intensity monochromatic illumination set-up installed on a standard Q-band ESR spectrometer equipped with a cryostat and probe head for measurements at cryogenic temperatures, which can be easily assembled from commercially available optical components is presented. Using as monochromatic light sources pig-tailed laser diodes (LDs) or fiber-coupled light-emitting diodes (LEDs), a high efficiency of the light transfer (more than 95%) through an optical guide inserted in the sample holder is achieved in the sample area of the microwave cavity. With various LEDs and LDs, one can perform ESR in situ illumination experiments from UV to far-IR, in both cw and pulse mode. Its operation is illustrated with an experiment revealing the presence of certain ESR silent defects in oxygen-doped floating-zone ultrapure Si samples irradiated at room temperature with high-energy–high-fluence electron beams and pulse annealed up to 300 °C. New information is obtained by comparing the ESR spectra recorded at T = 120 K, without and with 1.06 µm across-the-gap in situ illumination.

The aim of this work was to study the spectrum of LF and HF oscillations generated by plasma bunches created and confined in the volume of a microwave cavity immersed in the magnetic field of a mirror trap. The registration of electrostatic oscillations in the plasma was carried out using two flat electrodes mounted diametrically opposite in the central part of the cavity close to its wall. This diagnostic showed the presence of low-frequency oscillations with frequencies of 130 kHz and 450 kHz. The oscillation spectrum in the microwave range was recorded at the minimum of the magnetic trap using a real-time spectrometer and a loosely coupled loop antenna. The registration of the spectra in the 40 MHz band revealed a regular change in the frequency of the fundamental oscillation mode of the cavity and the presence of two harmonics of the synchrotron radiation of the plasma bunch at frequencies of 2.25 GHz and 4.52 GHz, respectively. According to the obtained data, the parameters of the formed bunch (density, shape, volume, energy spectra of plasma components) can be restored.

In this work, we propose a shielding diaphragm based on periodic metal loops to suppress the radio-frequency interference (RFI) in the microwave cavity. The electrically small size of the developed diaphragm enables its application in the miniaturized circuit/antenna systems. Furthermore, the proposed metallic structure can be integrated into the cavity, which makes it compatible with the high-power devices. This technique can address the RFI problems in the miniaturized and high-power systems, such as tracking, telemetry, and command (TT&C) systems and millimeter-wave terminal devices.

In these proceedings we summarise a collection of recent experimental results in which high precision photonic, phononic and atomic oscillators are used to probe for new physics, such as searching for wave-like dark matter, performing Lorentz invariance tests, looking for high frequency gravitational waves and more. We focus our discussions on summarising our most recent work on a new method for constraining scalar dark matter using a photonic microwave cavity, phononic quartz mechanical resonator and atomic hydrogen transition in conjunction, while also briefly summarising various other experimental results.

As superconducting quantum processors increase in size and complexity, the scalability of standard techniques for qubit control and readout becomes a limiting factor. Replacing room temperature analog components with cryogenic digital components could allow for the realization of systems well beyond the current state-of-the-art qubit arrays with tens of qubits. The standard technique for performing a qubit measurement with heterodyne readout uses a quantum-limited cryogenic amplifier chain and requires bulky microwave components inside the refrigerator with multiple control lines and pump signals. Additionally, the result is only accessible in software at room temperature. An alternative method for measuring qubits involves mapping the qubit state onto the photon occupation in a microwave cavity, followed by subsequent photon detection using a Josephson photomultiplier (JPM). The JPM measures the qubit and stores the result in a classical circulating current. To make use of this result, we can leverage existing single flux quantum (SFQ) circuitry. An underdamped Josephson transmission line (JTL) can be coupled to the JPM and fluxons traveling along the JTL are accelerated or delayed, depending on the circulating current state of the JPM. This fluxon delay can then be converted to an SFQ logic signal resulting in a digital qubit readout with a proximal microfabricated device, paving the way for cryogenic digital feedback necessary for error-correcting codes.

Methods of atomic absorption analysis with electrothermal and (or) flame atomizers and inductively coupled argon plasma are widely used for elemental analysis of solutions. Despite the wide popularity of these analysis methods, in analytical laboratories there is a demand for spectrometers with new excitation sources as an addition or replacement to the existing set of instruments that could provide improved analytical performance, reliability, ease of operation on new equipment, and a reduction of analysis cost. The Agilent company made an attempt to develop such an instrument by launching the first production model of a microwave plasma spectrometer. However, a number of design features did not allow the use of the spectrometer to solve many analytical problems. We have summarized the principles of developing atmospheric pressure microwave nitrogen plasma of “optimal” shape for efficient heating, evaporation, atomization, and ionization of liquid samples and have developed a high-order-mode microwave cavity based on a commercial 2.45 GHz magnetron. A Grand-2 spectrometer with two hybrid assemblies of BLPP-2000 photodetector arrays is used to obtain and record spectra. The spectrometer allows simultaneous recording of spectra in the range 190-780 nm with an integration time of 2 ms. The analytical characteristics of a Grand-MP spectrometer are as follows: the linearity range of the calibration curve is 5 orders, with possible expansion to 7 orders of magnitude when using a lower intensity line, which is similar to the range of inductively coupled plasma spectrometers and far exceeds the ranges of flame atomic absorption spectrometry with 2-3 orders and Agilent MP 4210 with 4 orders; the long-term stability of the analytical signal measured for 6 hours without using the internal standard is no more than 2% relative standard deviation; The obtained detection limits are not inferior to those for Agilent MP-AES 4100, 4200, and 4210 microwave plasma spectrometers and modern flame atomic absorption spectrometers and are very close to those for radial view inductively coupled plasma spectrometers. Keywords : atomic emission analysis, microwave plasma, spectrum excitation source, magnetron, resonator, spectrometer, analytical characteristics (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.1.004 O.V. Pelipasov 1, 2 , V. А . Labusov 1 ,2 ,3 , А .N. Put'makov 1, 2 , K.N. CHernov 4 , V.M. Borovikov 1, 2 , I.D. Burumov 1, 2 , D.O. Selyunin 1, 2 , V.G. Garanin 2 , I. А . Zarubin 1, 2, 3 1 Institute of Automation and Electrometry of the Siberian Branch of the Russian Academy of Sciences, 1, Academician Koptyug ave., Novosibirsk, 630090, Russian Federation 2 LLC “VMK-Optoelektronika”, 1, Academician Koptyug ave., Novosibirsk, 630090, Russian Federation 3 Novosibirsk State Technical University, 20, Karl Marks ave., Novosibirsk, 630073, Russian Federation 4 Budker Institute of Nuclear Physics of Siberian Branch Russian Academy of Sciences (BINP SB RAS) 11, Acad. Lavrentieva Pr., Novosibirsk, 630090, Russian Federation.

The microwave cavity technique is currently the most sensitive way of looking for dark matter axions in the 0.1 GHz–10 GHz range, corresponding to masses of 0.41 µeV–41 µeV. A particular challenge for frequencies greater than 5 GHz is designing a cavity with a large volume that contains a resonant mode that shows high coupling to dark matter axions, a high quality factor, is broadly tunable, and is free from intruder modes. For the Haloscope at Yale Sensitive to Axion Cold dark matter, we have designed and constructed an optimized high frequency cavity with a tuning mechanism that preserves a high degree of rotational symmetry, critical to maximizing its figure of merit. This cavity covers an important frequency range according to recent theoretical estimates for the axion mass, 5.5 GHz–7.4 GHz, and the design appears extendable to higher frequencies as well. This paper will discuss key design and construction details of the cavity, present a summary of the design evolution, and alert practitioners of potentially unfruitful avenues for future work.

Microwave loss of a semiconducting nanowire implemented in a cavity electromechanical system enables bolometric-microwave-power measurements at millikelvin temperatures. This hybrid system consists of a superconducting microwave cavity capacitively coupled to a suspended $\mathrm{In}\mathrm{As}$ nanowire. As a constant voltage is applied across a vacuum gap between the nanowire and the bottom electrode, the nanowire resistance embedded in the microwave resonator follows its own mechanical vibration. The mechanically modulated resistance of the nanowire contributes to microwave sidebands exhibiting its mechanical resonance. The presence of this resistive component provides the device with enhanced sensitivity to microwave dissipation. This dissipation localized at the nanowire results in a temperature increase, producing a frequency shift of the mechanical resonance sensitive to the microwave power. We employ a circuit model to demonstrate that semiconducting nanowires provide optimal resistances for the nanomechanical microwave bolometry. Our technique could benefit precision microwave measurements in quantum-device research.

Quantum conversion between microwave and optical photons is an important area of quantum information science and technology. Here we propose a one-step method to realize a coherent conversion between a microwave cavity and an optical cavity utilizing a nitrogen-vacancy center ensemble (NV ensemble). An NV ensemble considered here acts as a quantum transducer, dispersively coupled to the microwave and optical cavities, enabling transfer of the quantum state and generating entangled states between microwave and optical cavities. With state-of-the-art technology, the numerical simulation is performed to demonstrate that cat states and Fock states can be high-fidelity transferred and a maximally entangled state can be efficiently synthesized between microwave and optical cavities.

An accelerating photodetector is predicted to see photons in the electromagnetic vacuum. However, the extreme accelerations required have prevented the direct experimental verification of this quantum vacuum effect. In this work, we consider many accelerating photodetectors that are contained within an electromagnetic cavity. We show that the resulting photon production from the cavity vacuum can be collectively enhanced such as to be measurable. The combined cavity-photodetectors system maps onto a parametrically driven Dicke-type model; when the detector number exceeds a certain critical value, the vacuum photon production undergoes a phase transition from a normal phase to an enhanced superradiant-like, inverted lasing phase. Such a model may be realized as a mechanical membrane with a dense concentration of optically active defects undergoing gigahertz flexural motion within a superconducting microwave cavity. We provide estimates suggesting that recent related experimental devices are close to demonstrating this inverted, vacuum photon lasing phase., Comment: Published version with supplementary material added

Microwave assisted thermal sterilization (MATS) is a novel microwave technology currently used in the commercial production of ready-to-eat meals. It combines surface heating of high-temperature circulation water with internal microwave heating in cavities. The heating pattern inside the food packages in a MATS process depends heavily on the electric field distribution formed by microwaves from the top and bottom windows of the microwave heating cavities. The purpose of this research was to study the effect of the electric field on 922 MHz microwave heating of ready-to-eat meals as they moved through the microwave chamber of a pilot-scale MATS system using the finite-difference time-domain (FDTD) method. A three-dimensional numerical simulation model was developed as a digital twin of the MATS process of food moving through the microwave chamber. The simulation showed that the electric field intensity of the MATS microwave cavity was greatest on the surface and side edge of the cavity and of the food. There was a strong similarity of the experimental heating pattern with that of the electric field distribution simulated by a computer model. The digital twin modeling approach can be used to design options for improving the heating uniformity and throughput of ready-to-eat meals in MATS industrial systems.

Herein, the effects of polycrystalline germanium dioxide substrates on the structural, morphological, optical and electrical properties of zinc selenide thin films are reported. Thin films of ZnSe coated onto GeO2 are prepared by the thermal evaporation technique under vacuum pressure of 10–5 mbar. Compared to films grown onto glass substrates, ZnSe films deposited onto GeO2 exhibited narrower band gap and improved light absorbability. When ZnSe films are recoated onto gold substrates, the insertion of GeO2 layers between Au and ZnSe shifted the resonance peaks of the capacitance spectra from 527 to 711 MHz and formed new peak at 1000 MHz making the Au/ZnSe interfaces more appropriate for use as microwave cavities and as negative capacitance sources. Analysis of the conductivity spectra in the frequency domain of 10–1800 MHz revealed the domination of quantum mechanical tunneling and correlated barriers hoping of charge carriers in the samples. The fitting of the conductivity spectra assuming combined current conduction by these two mechanisms has shown that GeO2 layers increased the density of state near the Fermi level and shortened the scattering time of charge carriers. The designed Au/GeO2/ZnSe/C devices are also found to be suitable as band pass/stop filters. The notch frequency of these filters is shifted from 1420 MHz to 1050 MHz as a result of GeO2 participation in the structure of the Au/ZnSe devices.

International audience; Silicon nitride (SiN) mechanical resonators with high quality mechanical properties are attractive for fundamental research and applications. However, it is challenging to maintain these mechanical properties while achieving strong coupling to an electrical circuit for efficient on-chip integration. Here, we present a SiN drum resonator covered with an aluminum thin film, enabling large capacitive coupling to a suspended top-gate. Implementing the full electrical measurement scheme, we demonstrate a high quality factor ~ 1E4 (comparable to that of bare drums at room temperature) and present our ability to detect ? 10 mechanical modes at low temperature. The drum resonator is also coupled to a microwave cavity, so that we can perform optomechanical sideband pumping with a fairly good coupling strength G and demonstrate mechanical parametric amplification. This SiN drum resonator design provides efficient electrical integration and exhibits promising features for exploring mode coupling and signal processing.

We demonstrate a sideband-resolved cavity electromechanical system operating at room temperature. It consists of a nanomechanical resonator, a strongly pre-stressed silicon nitride string, dielectrically coupled to a three-dimensional microwave cavity made of copper. The electromechanical coupling is characterized by two measurements, the cavity-induced eigenfrequency shift of the mechanical resonator and the optomechanically induced transparency. While the former is dominated by dielectric effects, the latter reveals a clear signature of the dynamical backaction of the cavity field on the resonator. This unlocks the field of cavity electromechanics for room temperature applications.

Herein, metal-oxide-semiconductor fields effect transistors (MOSFET) are fabricated and characterized. p − type germanium dioxide coated onto Au/ n-CdSe substrates and top contacted with carbon point contacts is used to form the MOSFET devices. The structural investigations which were carried out with the help of X-ray diffraction technique revealed large lattice mismatched polycrystalline layers of CdSe and GeO2. The design of the energy band diagram has shown the formation of two Schottky arms (Au/ n − CdSe, C/GeO2) at the interfaces of the n − CdSe/ p − GeO2 layers. The capacitance-voltage characteristics which are recorded in the frequency domain of 1.0-50.0 MHz revealed the ability of formation of NMOS and PMOS layers. The signal frequency controlled built in potential is tunable in the range of 2.34 and 5.18 eV. In addition, the conductance and capacitance spectral analyses in the frequency domain of 10-1800 MHz revealed the domination of current conduction by tunneling and correlated barriers hoping below and above 760 MHz, respectively. In addition to its features as MOSFET devices, the Au/CdSe/GeO2/C hybrid devices are found to be appropriate for use as microwave cavities.

A continuous flow dynamic nuclear polarization (DNP) employing the Overhauser effect at ambient temperatures can be used among other methods to increase sensitivity of magnetic resonance imaging (MRI). The hyperpolarized state of water protons can be achieved by flowing aqueous liquid through a microwave resonator placed directly in the bore of a 1.5 T MRI magnet. Here we describe a new open Fabry–Pérot resonator as DNP polarizer, which exhibits a larger microwave exposure volume for the flowing liquid in comparison with a cylindrical TE013 microwave cavity. The Fabry–Pérot resonator geometry was designed using quasi-optical theory and simulated by CST software. Performance of the new polarizer was tested by MRI DNP experiments on a TEMPOL aqueous solution using a blood-vessel phantom. The Fabry–Pérot resonator revealed a 2-fold larger DNP enhancement with a 4-fold increased flow rate compared to the cylindrical microwave resonator. This increased yield of hyperpolarized liquid allows MRI applications on larger target objects.

Multimode cavity quantum electrodynamics ---where a two-level system interacts simultaneously with many cavity modes---provides a versatile framework for quantum information processing and quantum optics. Due to the combination of long coherence times and large interaction strengths, one of the leading experimental platforms for cavity QED involves coupling a superconducting circuit to a 3D microwave cavity. In this work, we realize a 3D multimode circuit QED system with single photon lifetimes of $2$ ms and cooperativities of $0.5-1.5\times10^9$ across 9 modes of a novel seamless cavity. We demonstrate a variety of protocols for universal single-mode quantum control applicable across all cavity modes, using only a single drive line. We achieve this by developing a straightforward flute method for creating monolithic superconducting microwave cavities that reduces loss while simultaneously allowing control of the mode spectrum and mode-qubit interaction. We highlight the flexibility and ease of implementation of this technique by using it to fabricate a variety of 3D cavity geometries, providing a template for engineering multimode quantum systems with exceptionally low dissipation. This work is an important step towards realizing hardware efficient random access quantum memories and processors, and for exploring quantum many-body physics with photons.

The dissipative squeezing mechanism is an effective method to generate the strong squeezing, which is important in the precision metrology. Here, we propose a practical method to achieve arbitrary bosonic squeezing via introducing frequency modulation into the coupled harmonic resonator model. We analyze the effect of frequency modulation and give the analytical and numerical squeezing results, respectively. To measure the accurate dynamic squeezing in our proposal, we give a more general defination of the relative squeezing degree. Finally, the proposed method is extended to generate the strong mechanical squeezing (>3 dB) in a practical optomechanical system consisting of a graphene mechanical oscillator coupled to a superconducting microwave cavity. The result indicates that the strong mechanical squeezing can be effectively achieved even when the mechanical oscillator is not initially in its ground state. The proposed method expands the study on nonclassical state and does not need the bichromatic microwave driving technology.

Recently, a laboratory setup for microwave-based characterization of powder samples at elevated temperatures and different gas atmospheres was presented. The setup is particularly interesting for operando investigations on typical materials for exhaust gas aftertreatment. By using the microwave cavity perturbation method, where the powder is placed inside a cavity resonator, the change of the resonant properties provides information about changes in the dielectric properties of the sample. However, determining the exact complex permittivity of the powder samples is not simple. Up to now, a simplified microwave cavity perturbation theory had been applied to estimate the bulk properties of the powders. In this study, an extended approach is presented which allows to determine the dielectric properties of the powder materials more correctly. It accounts for the electric field distribution in the resonator, the depolarization of the sample and the effect of the powder filling. The individual method combines findings from simulations and recognized analytical approaches and can be used for investigations on a wide range of materials and sample geometries. This work provides a more accurate evaluation of the dielectric powder properties and has the potential to enhance the understanding of the microwave behavior of storage materials for exhaust gas aftertreatment, especially with regard to the application of microwave-based catalyst state diagnosis.

A continuous flow dynamic nuclear polarization (DNP) employing the Overhauser effect at ambient temperatures can be used among other methods to increase sensitivity of magnetic resonance imaging (MRI). The hyperpolarized state of water protons can be achieved by flowing aqueous liquid through a microwave resonator placed directly in the bore of a 1.5 T MRI magnet. Here we describe a new open Fabry-Pérot resonator as DNP polarizer, which exhibits a larger microwave exposure volume for the flowing liquid in comparison with a cylindrical TE013 microwave cavity. The Fabry-Pérot resonator geometry was designed using quasi-optical theory and simulated by CST software. Performance of the new polarizer was tested by MRI DNP experiments on a TEMPOL aqueous solution using a blood-vessel phantom. The Fabry-Pérot resonator revealed a 2-fold larger DNP enhancement with a 4-fold increased flow rate compared to the cylindrical microwave resonator. This increased yield of hyperpolarized liquid allows MRI applications on larger target objects.

The continuous cold atomic clocks have the potential to overcome the Dick effect and to develop compact devices. In this paper, we present a process towards a Raman–Ramsey clock based on a continuous beam of cold cesium using optical separated oscillatory fields instead of a microwave cavity. The Raman–Ramsey fringes for clock transition are observed with a contrast of ∼68%, and the central fringe width is ∼175 Hz for the interaction-zone separation of 30 mm.

In the tuning system based on vision sensor, the object recognition and localization is very important. In order to meet the practical tuning of the microwave cavity filter by the mechanical arm, a global recognition and localization method of multiple adjustable screws is proposed, which combines image mosaic and template matching. A high-definition global image of microwave cavity filter is composed of multiple local images according to feature point registration, and then all adjustable screws in the global image are recognized by template matching algorithm based on shape feature, which solves the problem of limited field of vision of a single industrial camera. It realizes the recognition, localization and numbering of all tuning objects in the whole tuning range, and transmits the coordinate information corresponding to the number to the mechanical arm. This method can be used to tune various types of microwave cavity filters, and it has certain versatility. The experimental results show that the recognition effect of the screws is favorable when the above method is applied to the actual tuning of 12-step microwave cavity filter with the hand-eye integrated four-axis mechanical arm. And it meets the requirements of tuning accuracy.

We investigate bipartite entanglement and quantum steering in a three-mode, hybrid electro-optomechanical system consisting of a Fabry–Perot optical cavity, a nanomechanical oscillator and a lumped-element microwave cavity. The nanomechanical resonator is directly coupled to the optical cavity on the one side via the moving mirror of the Fabry–Perot cavity, and on the other side, it is capacitively coupled to the microwave cavity. There is no direct coupling between the cavity modes. The optical cavity is blue-detuned through excitation by a laser source emitting short pulses, while the microwave cavity is red-detuned through excitation by a voltage pulse generator. The presence of bipartite entanglement between different modes is verified based on the asymmetric entanglement criteria. Specifically, the system is shown to behave effectively as a two-mode system in which a perfect bipartite EPR state can be formed by the optical cavity and the mirror. The possibility of generating genuine tripartite entanglement is also investigated by examining the necessary conditions for multiparty multimode entanglement. Simultaneous coupling of the three modes is shown to be possible in accordance with the genuine tripartite entanglement criteria. Furthermore, we establish the existence of quantum steering between the modes using the steering parameter formality and examine the monogamy relations to quantify the amount of bipartite steering shared between different modes. Notably, steering is found to be present only between the mechanical and the optical cavity modes.

Microwave cavity resonance spectroscopy is introduced and demonstrated as a new approach to investigate the generation of acoustic waves by a pulsed radio-frequency driven atmospheric-pressure plasma jet. Thanks to recent advancements in the diagnostic method, the lower detection limit for pressure changes in air is ∼0.3 Pa. Good agreement with conventional pressure transducer measurements with respect to the temporal evolution, the pressure amplitude and the spectral response is found. Fourier analysis revealed that the acoustic waves induced by the plasma can most likely be attributed to standing waves in the discharge geometry. Additionally, the plasma-induced acoustic waves of a few (tens of) Pa are proposed as an active mechanism in plasma medicine.

Atomic vapors offer many opportunities for manipulating electromagnetic signals across a broad range of the electromagnetic spectrum. 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.

We present the design of a tunable high-Q photonic bandgap (PBG) cavity, made from a periodic arrangement of dielectric rods in a woodpile like structure. We know that the axion signal rate diminishes as we move to higher axion mass searches. High quality factor achieved with this type of cavity will enable higher mass axion search with improved signal sensitivity and faster scanning rate. Quality factor in excess of the axion-Q will enable us to design interesting experiments such as the quantum non-demolition (QND) measurement of itinerant microwave photons using superconducting qubits and stimulated emission of photons.

The design of microwave cavity detectors for axion dark matter research is often accomplished using advanced full-wave electromagnetic simulation software tools. These tools provide a cost-effective approach to evaluate a wide variety of cavity configurations, frequency tuning mechanisms, and conductive or dielectric materials and coatings. One simulation software package used for this application is Ansys High Frequency Structure Simulator (HFSS), which is based upon the well-established finite element method. HFSS includes numerous features useful for microwave cavity design such as parametric geometry modeling, adaptive meshing algorithm, curvilinear mesh elements, driven modal and eigenmode matrix solvers, and optimization algorithms. This paper describes the use of the HFSS software to simulate microwave cavities for axion haloscope detectors, with an example tutorial for a cylindrical cavity. Excellent agreement between the simulated and analytical results is shown for the resonant frequency, quality factor, and form factor.

The ability to achieve strong-coupling has made cavity-magnon systems an exciting platform for the development of hybrid quantum systems and the investigation of fundamental problems in physics. Unfortunately, current experimental realizations are constrained to operate at a single frequency, defined by the geometry of the microwave cavity. In this article we realize a highly-tunable, cryogenic, microwave cavity strongly coupled to magnetic spins. The cavity can be tuned in situ by up to 1.5 GHz, approximately 15% of its original 10 GHz resonance frequency. Moreover, this system remains within the strong-coupling regime at all frequencies with a cooperativity of approximately 800., Comment: 4 pages, 4 figures

A whispering gallery microwave cavity (WGMC) is used in the classical optoelectronic oscillator (OEO). The phase noise of the WGMC-OEO running near 9.2 GHz is improved by 27 dB at 10 Hz frequency offset. © 2020 The Author(s)

CAPP-PACE is a pilot experiment of IBS/CAPP for direct detection of axions with a mass around 10 μeV based on Sikivie’s microwave cavity scheme. The detector is equipped with an 8 T superconducting magnet and employs a dilution refrigerator that lowers the physical temperature of a high Q-factor split-type cavity to less than 45 mK. The frequency tuning system utilizes piezoelectric actuators with interchangeable sapphire and copper rods. The feeble signal ( 10−24 W) from the cavity is amplified and transmitted through the RF receiver chain with a HEMT amplifier whose noise temperature is around 1 K. I will present the results of CAPP’s first physics data runs in the axion mass range from 2.45 to 2.75 GHz and discuss our future plans and R&D projects.

We propose a scheme to implement quantum controlled NOT gate and quantum phase gate in an optomechanical system based on phonon blockade. For appropriate choices of system parameters, fidelities of both the quantum gate operations are very close to unity in the absence of dissipation. Using recently achieved experimental values in a mechanical resonator coupled to a microwave cavity, we show that the quantum gate can be realized experimentally with very high fidelity., Comment: 13 pages, 5 figures

The active hydrogen maser is a core piece of equipment for the time-frequency system. Its stability and reliability directly influence system performance. The optimization of temperature coefficients for physical and circuit systems provides a direct means to further improve performance of active hydrogen masers. Based on the existing sapphire active hydrogen maser, the microwave cavity, magnetic shield, and other components of its physical package have been optimally designed, resulting in new dielectric-loaded cavity and full-size cavity, with a temperature coefficient of −10 kHz/℃ and −1 kHz/℃, respectively. Taking into account the two newly designed cavities, we have achieved active hydrogen masers with volume in completely two different directions. The hydrogen maser with a dielectric-loaded cavity achieved a stability of 2.1E-13/1s and 2.3E-15/d, and that with a full-size cavity achieved a stability of 1.5E-13/1s and 1.6E-15/d when cavity servo system was not installed. The physical package of the active hydrogen maser with a dielectric-loaded cavity can achieve a size of Φ220 mm × 500 mm, and this technical solution is the best choice for space applications.

We demonstrate the generation of coherent phonons in a quartz Bulk Acoustic Wave (BAW) resonator through the photoelastic properties of the crystal, via the coupling to a microwave cavity enhanced by a photonic lambda scheme. This is achieved by imbedding a single crystal BAW resonator between the post and the adjacent wall of a microwave reentrant cavity resonator. This 3D photonic lumped LC resonator at the same time acts as the electrodes of a BAW phonon resonator, and allows the direct readout of coherent phonons via the linear piezoelectric response of the quartz. A microwave pump, $\omega_p$ is tuned to the cavity resonance $\omega_0$, while a probe frequency, $\omega_{probe}$, is detuned and varied around the red and blue detuned values with respect to the BAW phonon frequency, $\Omega_m$. The pump and probe power dependence of the generated phonons unequivocally determines the process to be electrostrictive, with the phonons produced at the difference frequency between pump and probe, with no back action effects involved. Thus, the phonons are created without threshold and can be considered analogous to a Coherent Population Trapped (CPT) maser scheme., Comment: 7 pages, 5 figures

Many resonant structures in the microwave region need damping of parasitic or higher order modes in order to optimise their performance. In cavities or other systems operating in accelerating structures, for example, the mitigation of spurious resonance effects is indispensable to achieve high quality particle beams. We present here a parametric study on the absorption properties of a multilayered metamaterial having the shape of a truncated pyramid to be used as light, small volume damper in a microwave cavity. Full wave simulations have been performed for a single absorber varying its size and number of layers and for a linear array changing the distance between the single elements. A case study is proposed, where a single pyramid is inserted in a real pillbox cavity. Measurements of the cavity response without and with the metamaterial absorber are presented and compared with numerical results.

Microwaves provide alternative heating and allow process intensification due to their rapid, volumetric, and selective nature. Recognizing the central role of multiphase reactors in chemical industry, a recent surge in employing microwaves is observed. Here, we review the recent experimental and modeling investigations of microwave heating of multiphase reactors with emphasis on chemical engineering applications. We demonstrate that there is accumulated evidence for improved performance via microwave heating and a clear opportunity for further process intensification. In most of the cases, this improved performance stems from a temperature gradient between two phases. We discuss the ongoing debate on the mechanism by which microwaves affect chemical processes exacerbated by the inability of measuring the temperature distribution in a microwave cavity. We outline recent progress in this direction in monolith reactors and needs for future work. We underscore the lack of detailed modeling and simulation tools even for single-phase systems and emphasize the imperative for multiscale predictive modeling to bridge the experimental-modeling gap. Promising results are shown by a few recently published modeling studies that can predict the experimental measurements in complex multiphase reactors. A combination of experimental and modeling tools can provide a comprehensive picture of the microwave multiphase reactors as well as a means toward scale-up and optimization.

In order to simplify the conversion between slow light and fast light, we ameliorate the cavity-magnon coupling system and theoretically analyze the characteristics of group delay of the output field. The system under consideration consists of a microwave cavity and N yttrium iron garnets (YIGs), of which the quantity of YIG spheres is designed to be controlled by an external magnetic field. It is found, most importantly, that the conversion between fast and slow light can be realized by adjusting the number of YIG spheres that the external magnetic field acts on. Significantly, through adjusting the quantity N of magnons, the group delay can be stabilized at a required value even though the magnons are slightly detuned. Moreover, adjusting the quantity of YIG spheres can also alter the frequency corresponding to the fast-slow light effect, signifying that the conversion can be expanded to the frequency domain. Meanwhile, the cavity-magnon coupling strength required to generate the fast-slow light can be also effectively reduced by increasing the quantity of YIG spheres. Furthermore, we find that the cavity-magnon coupling strength and the cavity-field loss rate are complementary in terms of the group delay, which provides a feasible alternative for experimental design. The factors determining the slow-light limit have also been summarized based on their influence on the group delay. Our results have theoretical significance for the improvement of the generation and conversion of the fast-slow light, upgrading and innovating the information technology, especially in the field of all-optical networks.

Drying systems are widely used in food processing industries. There exist serious complications in their design and operation since the target is to minimize cost and energy while to increase efficiency and quality. Novel methods have been introduced to comply with such demand among which microwave technology is highlighted in the last decade. It is applied in this research as an applied solution for conventional hot air methods. The uniform distribution of electromagnetic field in the microwave cavity is however equivocal in the literature which may result in low quality dried products. To monitor the electromagnetic field distribution, a simulation process using Finite Element Methods was conducted. Three geometries were selected as the microwave cavity. Analysis of variance for the indicator of heat non-uniformity index showed that cavity size has significant effect (P

Transmission efficiency and quality factor are two of the most crucial characteristics in designing optical band pass filters. In this paper, we proposed a novel structure for realizing an optical filter. For the wavelength selecting part of the filter, we employed a V-shaped resonant cavity. The obtained filter has a resonant mode at 1313 nm with transmission efficiency and quality factor as much as 97 % and 3548, respectively.