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We report the dependence of the magnetization dynamics in a square artificial spin-ice lattice on the in-plane magnetic field angle. Using two complementary measurement techniques—broadband ferromagnetic resonance and micro-focused Brillouin light scattering spectroscopy—we systematically study the evolution of the lattice dynamics, for both a coherent radio frequency excitation and an incoherent thermal excitation of spin dynamics. We observe a splitting of modes facilitated by inter-element interactions that can be controlled by the external field angle and magnitude. Detailed time-dependent micromagnetic simulations reveal that the split modes are localized in different regions of the square network. This observation suggests that it is possible to disentangle modes with different spatial profiles by tuning the external field configuration. [ABSTRACT FROM AUTHOR]

Quenching has been established as a viable method to increase the depolarization temperature in (100-x) Na1/2Bi1/2TiO3–xBaTiO3 (NBT–xBT). The proposed hypothesis of a stabilized ferroelectric order would entail changes in the polarized volume. To this end, air-quenched and furnace cooled samples of four compositions of NBT–xBT with x = 3, 6, 9, and 12 mol. % BT were studied. Upon quenching, all the compositions demonstrate an increase in the ferroelectric to relaxor transition temperature, TF-R, by 23–44 °C and enhanced lattice distortion. Resonance frequency damping analysis was utilized to measure Young's modulus in the temperature range of 25 °C to 800 °C and to estimate the volume fraction of polar nanoregions using a composite model. Quenching leads to an 8% decrease in Young's modulus, but to an increase in the volume fraction of polar nanoregions by 12% at 300 °C for NBT-6BT. Transmission electron microscopy investigations of quenched NBT-6BT reveal a combination of lamellar domains and more homogenous areas with nanometer-sized domains. The existence of lamellar domains in quenched morphotropic phase boundary compositions together with enhanced lattice distortion and a decrease in dielectric frequency dispersion substantiate the premise of a stabilized ferroelectric order. [ABSTRACT FROM AUTHOR]

The mechanical analog of optical frequency combs, phononic frequency combs, has recently been demonstrated in mechanical resonators and has been attributed to coupling between multiple phonon modes. This paper investigates the influence of the mode structure on comb generation using a model of two nonlinearly coupled phonon modes. The model predicts that there is only one region within the amplitude-frequency space where combs exist, and this region is a subset of the Arnold tongue that describes a 2:1 autoparametric resonance between the two modes. In addition, the location and shape of the comb region are analytically defined by the resonance frequencies, quality factors, mode coupling strength, and detuning of the driving force frequency from the mechanical resonances, providing clear conditions for comb generation. These results enable comb structure engineering for applications in areas as broad as sensing, communications, quantum information science, materials science, and molecular science. [ABSTRACT FROM AUTHOR]

The magnetic field dependence of the resonance frequencies of Co1−xFex thin film microfabricated resonators was examined for fields applied in the plane of the film. Remarkably, the observed resonance frequency shift with an applied magnetic field did not saturate even up to fields of nearly 2 T. A minimized mechanical and magnetic free energy model of clamped–clamped resonators revealed that for a two-dimensional structure, both bending and torsional modes are allowed, but would have have very different resonance shift behavior with the applied field. A post-anneal of the structure confirms this case by increasing the stress-induced anisotropy of CoFe, which selectively enhances the contribution of the torsional mode and creates the non-saturating field-induced frequency shift. By using the resonance shift in this device in a potential magnetic field sensing paradigm, such a non-saturating torsional mode may be useful for applications such as nuclear magnetic resonance or MRI, which specifically requires sensitive detection of small fluctuations in high magnetic fields. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate an uncooled, sensitivity-enhanced infrared (IR) detector based on a Lamb wave sensor coated with polydopamine (PDA). The real-time resonant frequency responses of the sensors with and without PDA coating were measured as functions of IR intensity. Compared to the traditional Lamb wave sensor, the PDA-coated Lamb sensor exhibits a highly linear relationship between resonance frequency and IR intensity, and the slope representing the sensitivity of IR detection is nearly one order of magnitude higher. The enhanced sensitivity is mainly attributed to the optical-thermal transition of PDA nanoparticles rather than the modulation of the thermal-acoustic effect. This mechanism for achieving highly sensitive uncooled IR detectors holds great promise for application in photo-thermal therapy along with other military and civilian fields. [ABSTRACT FROM AUTHOR]

Enhancing the output power at small input acceleration is a major concern for enabling practical application of vibration energy harvesters. In this study, a two-degree of freedom system (2-DOF) was employed to solve this issue. The numerical calculations using the lumped parameter model of the piezoelectric vibration energy harvesters (pVEHs) with 2-DOF indicate that the harvesters show two resonance peak and an increase in the output power of several ten times compared with the harvester with a single degree of freedom. Based on calculations, the prototype of pVEH with 2-DOF was fabricated using a micro-machined pVEH and a metal cantilever. The output power of the harvester is 3.4 μW at 0.1 Grms, which is 17 times higher than that of the micro-electro-mechanical system-pVEH. Moreover, the resonance frequency on the pVEH with 2-DOF is easily adjusted because of the coupled vibration of the two masses. [ABSTRACT FROM AUTHOR]

A common use of atomic force microscopy is quantifying local forces through tip-sample interactions between the probe tip and a sample surface. The accuracy of these measurements depends on the accuracy to which the cantilever spring constant is known. Recent work has demonstrated that the measured spring constant of a cantilever can vary up to a factor of five, even for the exact same cantilever measured by different users on different microscopes. Here, we demonstrate that a standard method for calibrating the spring constant (using oscillations due to thermal energy) is susceptible to ambient acoustic noise, which can alter the result significantly. We demonstrate a step-by-step method to measure the spring constant by actively driving the cantilever to measure the resonance frequency and the quality factor, giving results that are unaffected by acoustic noise. Our method can be performed rapidly on any atomic force microscope without any expensive additional hardware. [ABSTRACT FROM AUTHOR]

There exist numerous vibration modes in a resonant structure, and these modes can interact with each other. Here, the internal resonance between the fundamental mode and higher order modes is observed in a polyvinylidene fluoride piezoelectric membrane as a resonant mass sensor. Higher order modes draw energy from the fundamental one and vibrate at integer times of the fundamental mode's frequency. The resonance frequency shift of the fundamental mode can thus be magnified integer times through internal resonance. The sensitivity of the resonant mass sensor, defined by the resonance frequency shift caused by mass change, is enhanced based on this mechanism. The sensing characteristics are experimentally studied with a concentrated mass load attached to the sensor. The sensitivity improvement of directly using higher order modes and detecting the internal resonance response is tested and compared in our experiment. An 11 times sensitivity magnification is achieved with the internal resonance method, which has an obvious advantage over the higher order method. [ABSTRACT FROM AUTHOR]

This paper presents the experimental realization of an ultrafast electron microscope operating at a repetition rate of 75 MHz based on a single compact resonant microwave cavity operating in a dual mode. This elliptical cavity supports two orthogonal TM110 modes with different resonance frequencies that are driven independently. The microwave signals used to drive the two cavity modes are generated from higher harmonics of the same Ti:Sapphire laser oscillator. Therefore, the modes are accurately phase-locked, resulting in periodic transverse deflection of electrons described by a Lissajous pattern. By sending the periodically deflected beam through an aperture, ultrashort electron pulses are created at a repetition rate of 75 MHz. Electron pulses with τ = (750 ± 10) fs pulse duration are created with only (2.4 ± 0.1) W of microwave input power; with normalized rms emittances of ϵn,x = (2.1 ± 0.2) pm rad and ϵn,y = (1.3 ± 0.2) pm rad for a peak current of Ip = (0.4 ± 0.1) nA. This corresponds to an rms normalized peak brightness of B n p , rms = (7 ± 1) × 10 6 A/m2 sr V, equal to previous measurements for the continuous beam. In addition, the FWHM energy spread of ΔU = (0.90 ± 0.05) eV is also unaffected by the dual mode cavity. This allows for ultrafast pump-probe experiments at the same spatial resolution of the original TEM in which a 75 MHz Ti:Sapphire oscillator can be used for exciting the sample. Moreover, the dual mode cavity can be used as a streak camera or time-of-flight electron energy loss spectroscopy detector with a dynamic range >104. [ABSTRACT FROM AUTHOR]

Magnetic sensors based on the interaction between the delta-E effect and surface acoustic waves (SAWs) are promising devices due to their simple driving circuits. In this study, a magnetic sensor composed of a (Fe90Co10)78Si12B10 magnetic layer and Love-type SAW resonator was investigated. The resonance frequency sensitivities (RFS) of the sensor resulting from the delta-E effect are 76.06 Hz/μT and 364.28 Hz/μT in the L-direction (along the easy axis) and W-direction (along the hard axis), respectively. The maximum RFS achieved by this magnetic sensor is 663.98 Hz/μT along the hard axis, with a resonance frequency of 221.76 MHz. The shift of resonance frequency shows a good linearity along with the external magnetic field in the L-direction. The curves of frequency response demonstrate point symmetry rather than the expected axial symmetry in both directions, due to the existence of residual magnetization. Non-zero RFS at zero magnetic field also appears in this device, because of the non-zero change of the Young's modulus at zero magnetic field. The good linearity and high sensitivity mean that the investigated magnetic sensor can be applied for weak DC magnetic field detection. [ABSTRACT FROM AUTHOR]

We report on an electrical detection method of ultrasensitive carbon nanotube mechanical resonators. The noise floor of the detection method is reduced using a RLC resonator and an amplifier based on a high electron mobility transistor cooled at 4.2 K. This allows us to resolve the resonance frequency of nanotube resonators with an unprecedented quality. We show that the noise of the resonance frequency measured at 4.2 K is limited by the resonator itself, and not by the imprecision of the measurement. The Allan deviation reaches ∼10−5 at 125 ms integration time. When comparing the integration time dependence of the Allan deviation to a power law, the exponent approaches ∼1/4. The Allan deviation might be limited by the diffusion of particles over the surface of the nanotube. Our work holds promise for mass spectrometry and surface science experiments based on mechanical nano-resonators. [ABSTRACT FROM AUTHOR]

This letter reports a phononic crystal (PnC) cavity resonance device to realize an enhanced directional acoustic sensing. The acoustic cavity in the PnC device is designed with a line defect produced by replacing a line array from a perfect PnC. The line-defect PnC will make a defect band related to the cavity resonance within the perfect PnC band gap range. The design enhances the input sound wave at the resonance frequency of the acoustic cavity under the normal incidence, which produces an enhanced direction-sensitive response. The proposed device shows desirable directional acoustic sensing property, and the sensing frequency can be decreased by enlarging the effective refractive index of the acoustic cavity. The PnC cavity resonance devices present broad application prospects in weak signal detection and sound source localization. [ABSTRACT FROM AUTHOR]

The origin of amplitude reduction in Tapping Mode Atomic Force Microscopy (TM-AFM) is typically attributed to the shift in resonance frequency of the cantilever due to the nonlinear tip-sample interactions. In this paper, we present a different insight into the same problem which, besides explaining the amplitude reduction mechanism, provides a simple reasoning for the relationship between tip-sample interactions and operation parameters (amplitude and frequency). The proposed formulation, which attributes the amplitude reduction to an interference between the tip-sample and dither force, only deals with the linear part of the system; however, it fully agrees with experimental results and numerical solutions of the full nonlinear model of TM-AFM. [ABSTRACT FROM AUTHOR]

Most electromechanical devices are in two-dimensional metallic drums under high tensile stress, which causes increased mechanical frequency and quality factor. However, high mechanical frequencies lead to small zero-point displacements xzp, which limits the single-photon interaction rate g0. For applications which demand large g0, any design with increased xzp is desirable. It is shown that a patterned drum by a spiral shape can resolve this difficulty, which is obtained by a reduction of mechanical frequency while the motion mass is kept almost constant. An order of magnitude increase in g0 and agreement between simulations and interferometric measurements is observed. [ABSTRACT FROM AUTHOR]

A droplet-based flexible wireless force sensor has been developed for remote tactile-sensing applications. By integration of a droplet-based capacitive sensing unit and two circular planar coils, this inductor-capacitor (LC) passive sensor offers a platform for the mechanical force detection in a wireless transmitting mode. Under external loads, the membrane surface of the sensor deforms the underlying elastic droplet uniformly, introducing a capacitance response in tens of picofarads. The LC circuit transduces the applied force into corresponding variations of its resonance frequency, which is detected by an external electromagnetic coupling coil. Specifically, the liquid droplet features a mechanosensitive plasticity, which results in an increased device sensitivity as high as 2.72MHz N-1. The high dielectric property of the droplet endows our sensor with high tolerance for noise and large capacitance values (20–40 pF), the highest value in the literature for the LC passive devices in comparable dimensions. It achieves excellent reproducibility under periodical loads ranging from 0 to 1.56N and temperature fluctuations ranging from 10 °C to 55 °C. As an interesting conceptual demonstration, the flexible device has been configured into a fingertip-amounted setting in a highly compact package (of 11 mm x 11 mm x 0.25 mm) for remote contact force sensing in the table tennis game. [ABSTRACT FROM AUTHOR]

We report on measurements of the shift in resonance frequency of "spoof" surface plasmon polariton propagation along a 2-D metamaterial slow-wave structure induced by a gaseous plasma near the metamaterial/air interface. A transmission line circuit model for the metamaterial structure interprets the introduction of a plasma as a decrease in unit cell capacitance, causing a shift in the plasmon dispersion to higher frequency. We show through simulations and experiments that the effects of this shift at the resonance frequency and attenuation below and above resonance depend on the plasma density. The shifts recorded experimentally are small owing to the low plasma densities generated near the structure, ~1011 cm-3, but simulations show that a shift of ~3% of the resonance frequency can be generated at plasma densities of ~1012 cm-3. [ABSTRACT FROM AUTHOR]

We experimentally report the bidirectional reconfiguration of an out-of-plane deformable microcantilever based metamaterial for advanced and dynamic manipulation of terahertz waves. The microcantilever is made of a bimaterial stack with a large difference in the coefficient of thermal expansion of the constituent materials. This allows for the continuous deformation of microcantilevers in upward or downward direction in response to positive or negative temperature gradient, respectively. The fundamental resonance frequency of the fabricated microcantilever metamaterial is measured at 0.4 THz at room temperature of 293 K. With decreasing temperature, the resonance frequency continuously blue shifts by 30 GHz at 77 K. On the other hand, with increasing temperature, the resonance frequency gradually red shifts by 80 GHz and saturates at 0.32 THz for 400 K. Furthermore, as the temperature is increased above room temperature, which results in the downward actuation of the microcantilever, a significant resonance line-narrowing with an enhanced quality factor is observed due to tight field confinement in the metamaterial structure. The thermal control of the microcantilever possesses numerous inherent advantages such as enhanced tunable range (~37.5% in this work compared to previously reported microcantilever metamaterials), continuous tunability, and repeatable operations. The microcantilever metamaterial also shows high robustness to operate at cryogenic conditions and hence opens up the possibility of using meta-devices in harsh environments such as space, polar, and deep sea applications. [ABSTRACT FROM AUTHOR]

Surface acoustic wave (SAW) devices using embedded interdigital transducers (IDTs) on an AlN/diamond/Si layered substrate are fabricated, and their performances are investigated. The Sezawa mode is the dominant resonance with the highest resonant frequency up to 17.7GHz, a signal amplitude of 20 dB, and an electromechanical coupling coefficient of 0.92%. Comparing these SAW devices with those having the conventional IDTs on the same layered structure, the output SAW power and resonant frequency of devices are improved by 10.7% and 1.1%, respectively, for the embedded IDT devices. This is because the different field distribution leads to the different Bragg reflection and phase velocity for the two types of IDTs. The radiation frequency characteristics indicate that the advantages of the embedded IDTs would be useful for high frequency, high power applications such as monolithic integrated millimeter-wave integrated circuit and high speed communications. [ABSTRACT FROM AUTHOR]

We present a wafer trimming technique for producing superconducting micro-resonator arrays with highly uniform frequency spacing. With the light-emitting diode mapper technique demonstrated previously, we first map the measured resonance frequencies to the physical resonators. Then, we fine-tune each resonator's frequency by lithographically trimming a small length, calculated from the deviation of the measured frequency from its design value, from the interdigitated capacitor. We demonstrate this technique on a 127-resonator array made from titanium-nitride and show that the uniformity of frequency spacing is greatly improved. The array yield in terms of frequency collisions improves from 84% to 97%, while the quality factors and noise properties are unaffected. The wafer trimming technique provides an easy-to-implement tool to improve the yield and multiplexing density of large resonator arrays, which is important for various applications in photon detection and quantum computing. [ABSTRACT FROM AUTHOR]

We design a 3D acoustic metamaterial having a coiling resonant structure with high symmetry. Eigenstate analysis reveals that such a 3D metamaterial has two significant Mie-type eigenmodes, monopole and dipolar resonances. Large blocking of sound waves in the low-frequency range between monopole and dipolar resonances is observed numerically and experimentally. The effective properties extracted from the reflection and transmission coefficients show negative bulk modulus around the monopole resonant frequency and negative mass density around the dipolar resonant frequency. By employing the proposed two-scale model, the metamaterial system demonstrates the functionalities of sound cloaking and super-tunneling within a finite space. [ABSTRACT FROM AUTHOR]

Dynamic acousto-elastic testing, a pump-probe scheme, is employed to investigate the recovery of consolidated granular media systems from the non-equilibrium steady state established by a pump strain field. This measurement scheme makes it possible to follow the recovery from the nonequilibrium steady state over many orders of magnitude in time. The recovery is described with a relaxation time spectrum that is found to be independent of the amplitude of the non-equilibrium steady state (pump amplitude) and of the environment in which samples reside. The nonequilibrium steady state and its slow recovery are the laboratory realization of phenomena that are found in many physical systems of practical importance. [ABSTRACT FROM AUTHOR]

Methods for controlling the periodic molecular orientation of liquid crystals using ultrasound vibrations and estimating the orientational direction are proposed. An ultrasonic liquid crystal cell was used, consisting of a liquid crystal layer sandwiched by two glass plates fitted with piezoelectric ultrasound transducers. The transmitted light intensity distribution through the cell was measured by changing the polarization direction to investigate the orientation direction of the liquid crystal molecules. The transmitted light distributions changed periodically owing to the flexural vibration of the cell at resonance frequencies of 43.9 and 70.7 kHz. The orientational direction of the liquid crystal molecules correlated with the vibrational distribution of the glass substrates, and the molecular orientation was changed periodically by the acoustic radiation force. The interval and intensity of the transmitted light could be controlled by the driving frequency and voltage amplitude, respectively. [ABSTRACT FROM AUTHOR]

This letter presents a high performance bimorph piezoelectric MEMS harvester with bulk PZT thick films on both sides of a flexible thin beryllium-bronze substrate via bonding and thinning technologies. The upper and lower PZT layers are thinned down to about 53 μm and 76 μm, respectively, and a commercial beryllium bronze with the thickness of about 50 μm is used as the substrate. The effective volume of this device is 30.6mm3. The harvester with a tungsten proof mass generated the close-circuit peak-to-peak voltage of 53.1 V, the output power of 0.979 mW, and the power density of 31.99 mW/cm3 with the matching load resistance of 360 kΩ at the applied acceleration amplitude of 3.5 g and the applied frequency of 77.2 Hz. Meanwhile, in order to evaluate the stability, the device was measured continuously under applied acceleration amplitudes of 1.0 g and 3.5 g for one hour and demonstrated a good stability. Then, the harvester was utilized to light up LEDs and about twenty-one serial LEDs were lighted up at resonance under an applied acceleration amplitude of 3.0 g. [ABSTRACT FROM AUTHOR]

We developed a wireless and passive piezoelectric resonant sensor for contimuous volatile organic compound detection. An equivalent circuit is proposed to model the sensing system, and Lamb wave resonators are adopted to demonstrate the wireless interrogation achieved by near-field inductive coupling. The wireless sensing system is employed to monitor the ethanol vapor concentration, and the sensitivity of the wireless sensor barely degrades compared to that of the wired one. Further, we simultaneously and wirelessly tracked several resonance frequencies of a monolithic sensor array, which demonstrates its potential for high-throughput and real-time point-of-care test. [ABSTRACT FROM AUTHOR]

The effect of coupling between the extensional bulk mode and the flexural mode of a cantilever beam resonator has been experimentally studied by exciting the two modes simultaneously. The modal frequency shift of linear extensional bulk mode shows a quadratic relationship with the square of flexural mode's amplitude displacement, and a frequency shift up to 1492 Hz is observed when the flexural mode is driven by a AC signal Vac of 3 V and a DC bias of 30 V. The flexural mode shows a Duffing-like behavior with a softening nonlinearity and its frequency shift is influenced not only by its own nonlinear amplitude-frequency effect but also the extensional mode's amplitude as predicted. The nonlinear coupling coefficient is found to be about two orders of magnitude larger than the softening nonlinearity. [ABSTRACT FROM AUTHOR]

Miniaturization calls for micro-actuators that can be powered wirelessly and addressed individually. Here, we develop functional surfaces consisting of arrays of acoustically resonant microcavities, and we demonstrate their application as two-dimensional wireless actuators. When remotely powered by an acoustic field, the surfaces provide highly directional propulsive forces in fluids through acoustic streaming. A maximal force of ~0.45mN is measured on a 4×4mm2 functional surface. The response of the surfaces with bubbles of different sizes is characterized experimentally. This shows a marked peak around the micro-bubbles' resonance frequency, as estimated by both an analytical model and numerical simulations. The strong frequency dependence can be exploited to address different surfaces with different acoustic frequencies, thus achieving wireless actuation with multiple degrees of freedom. The use of the functional surfaces as wireless ready-toattach actuators is demonstrated by implementing a wireless and bidirectional miniaturized rotary motor, which is 2.6×2.6×5mm3 in size and generates a stall torque of ~0.5mN.mm. The adoption of micro-structured surfaces as wireless actuators opens new possibilities in the development of miniaturized devices and tools for fluidic environments that are accessible by low intensity ultrasound fields. [ABSTRACT FROM AUTHOR]

We present a microelectromechanical system, in which a silicon beam is attached to a comb-drive actuator, which is used to tune the tension in the silicon beam and thus its resonance frequency. By measuring the resonance frequencies of the system, we show that the comb-drive actuator and the silicon beam behave as two strongly coupled resonators. Interestingly, the effective coupling rate (~1.5 MHz) is tunable with the comb-drive actuator (+10%) as well as with a side-gate (-10%) placed close to the silicon beam. In contrast, the effective spring constant of the system is insensitive to either of them and changes only by ±0.5%. Finally, we show that the comb-drive actuator can be used to switch between different coupling rates with a frequency of at least 10 kHz. [ABSTRACT FROM AUTHOR]

Bimaterial cantilevers have recently been used in, for example, the calorimetric analysis with picowatt resolution in microscopic space based on state-of-the-art atomic force microscopes. However, thermally induced effects usually change physical properties of the cantilevers, such as the resonance frequency, which reduce the accuracy of the measurements. Here, we propose an approach to circumvent this problem that uses an optical microcavity formed between a metallicμayer coated on the back of the cantilever and one coated at the end of an optical fiber irradiating the cantilever. In addition to increasing the sensitivity, the optical rigidity of this system diminishes the thermally induced frequency shift. For a coating thickness of several tens of nanometers, the input power is 5-10 μW. These values can be evaluated from parameters derived by directly irradiating the cantilever in the absence of the microcavity. The system has the potential of using the cantilever both as a thermometer without frequency shifting and as a sensor with nanometercontrolled accuracy. [ABSTRACT FROM AUTHOR]

Compact electret energy harvesters, based on a design recently introduced, are presented. Using electret surface potentials in the 400V regime and a seismic mass of 10 g, it was possible to generate output power up to 0.6 mW at 36 Hz for an input acceleration of 1 g. Following the presentation of an analytical model allowing for the calculation of the power generated in a load resistance at the resonance frequency of the harvesters, experimental results are shown and compared to theoretical predictions. Finally, the performance of the electret harvesters is assessed using a figure of merit. [ABSTRACT FROM AUTHOR]

We demonstrate a high-efficiency tunable acoustic absorber for low frequencies (<500Hz) with subwavelength thickness. The acoustic absorber is based on split tube resonators and could reach highefficiency absorption at tunable resonance frequency with wavelength in air at least 30 times larger than its total thickness in simulations and experiments. The resonance frequency and high-efficiency absorption of the absorber are robust under oblique incidence even at large angles. The absorber could have potential applications for acoustic engineering due to its high structural stability, ease of fabrication, subwavelength thickness, and robust high-efficiency. [ABSTRACT FROM AUTHOR]

We have experimentally investigated the microwave transmission of the cavity-magnon-polariton (CMP) generated by integrating a low damping magnetic insulator onto a 2D microwave cavity. The high tunability of our planar cavity allows the cavity resonance frequency to be precisely controlled using a DC voltage. By appropriately tuning the voltage and magnetic bias, we can observe the cavity photon magnon coupling and the magnetic coupling between a magnetostatic mode and the generated CMP. The dispersion of the generated CMP was measured by either tuning the magnetic field or the applied voltage. This electrical control of CMP may open up avenues for designing advanced on-chip microwave devices that utilize light-matter interaction. [ABSTRACT FROM AUTHOR]

In this research, we developed wireless, inductive, pressure sensors with high sensitivity and investigated the effects of the inner materials (copper or ferrite) on the performance of the sensors. The proposed sensor is comprised of two parts, i.e., the top and the bottom parts. The top part includes a micro coil and a capacitor for the wireless transfer of data, and the bottom part includes the inner materials and a thick or thin flexible membrane to induce changes in the inductance. An anchor is used to assemble the top and bottom parts. The behavior of the sensor with copper was based on the eddy current effect, and, as the pressure increased, its resonance frequency increased, while its phase depth decreased exponentially. The principle of the sensor with ferrite was related to the effective permeability between a ferrite and a coil, and its response was the opposite of that with copper, i.e., as the pressure increased, the resonance frequency decreased linearly, and the phase depth increased linearly. These different operational mechanisms can be explained by the changes in the equations of inductance presented in this paper. After characterizing four different types of inductive pressure sensors in ambient air, one type of inductive pressure sensor was used to monitor the intraocular pressure (IOP) of a rabbit's eye as a biomedical application. The results showed that, in the animal tests, the measured responsivity and sensitivity were 16.7 kHz/mmHg and 1340 ppm/mmHg, respectively. These data indicate that the proposed sensor is a good candidate for monitoring IOP. [ABSTRACT FROM AUTHOR]

Planar anisotropy Nd2Co17 flakes fractured along c crystal plane were fabricated by surfactantassisted high-energy ball milling technique. The magnetic flakes have a diameter range of 5-20 µm and a typical thickness of approximately 120 nm. The frequency dependence of complex permeability of Nd2Co17 epoxy resin composite has been investigated in the frequency range of 0.1-18 GHz. The measurement results show that the natural resonance frequency reaches 12.5 GHz while the initial permeability survives up to 2.26. The superior high frequency properties come from the large out-of-plane anisotropy field and the flake structure fractured along the c crystal plane of Nd2Co17. The planar anisotropic Nd2Co17 flakes have significant potential applications in the high-frequency devices working in the frequency beyond 10 GHz. [ABSTRACT FROM AUTHOR]

We present experiments on acoustic carpet cloaking by using a metasurface made of graded Helmholtz resonators. The thin metasurface, placed over the object to hide, is designed such that the reflection phase shifts of the resonators at the resonance frequency are tuned to compensate the shape of the object to cloak. Experimental as well as numerical results show the efficiency of the cloak at the resonance frequency. The reflection of a short pulse is also reported to inspect the broadband character of the cloak. [ABSTRACT FROM AUTHOR]

We report on experimental investigation and analysis of γ-ray radiation effects on two-dimensional molybdenum disulfide (MoS2) drumhead nanomechanical resonators vibrating at megahertz frequencies. Given calibrated dosages of γ-ray radiation of ~5000 photons with energy at 662 keV, upon exposure over 24 or 12 h, all the MoS2 resonators exhibit ~0.5-2.1% resonance frequency upshifts due to the ionizing γ-ray induced charges and their interactions. The devices show γ-ray photon responsivity of ~30-82 Hz/photon, with an intrinsic γ-ray sensitivity (limit of detection) estimated to approach ~0.02-0.05 photon. After exposure expires, resonance frequencies return to an ordinary tendency where the frequency variations are dominated by long-term drift. These γ-ray radiation induced frequency shifts are distinctive from those due to pressure variation or surface adsorption mechanisms. The measurements and analyses show that MoS2 resonators are robust yet sensitive to very low dosage γ-ray, demonstrating a potential for ultrasensitive detection and early alarm of radiation in the very low dosage regime. [ABSTRACT FROM AUTHOR]

We present a resonant micromechanical magnetic field sensor, which utilizes the magnetically induced change in elastic modulus, i.e., the delta-E effect. The sensor is based on magnetoelectric thin film composites, resulting in high sensitivity at room temperature and at low frequencies. The cantilever is electrically excited and read out by a 2 μm AlN piezoelectric layer. Depending on its magnetization, the 2 μm thin film of amorphous (Fe90Co10)78Si12B10 changes its elasticity, which results in a shift of the cantilever's resonance frequency. The sensor is operated in the first or second transversal bending mode at 7.6 kHz or 47.4 kHz. With a limit of detection of 140 pTHz-0.5 at 20 Hz under a magnetic bias field and 1 nTHz-0.5 without external bias field, this sensor exceeds all comparable designs by one order of magnitude. [ABSTRACT FROM AUTHOR]

A single-passage, bimodal magnetic force microscopy technique optimized for scanning samples with arbitrary topography is discussed. A double phase-locked loop system is used to mechanically excite a high quality factor cantilever under vacuum conditions on its first mode and via an oscillatory tip-sample potential on its second mode. The obtained second mode oscillation amplitude is then used as a proxy for the tip-sample distance, and for the control thereof. With appropriate z-feedback parameters, two data sets reflecting the magnetic tip-sample interaction and the sample topography are simultaneously obtained. [ABSTRACT FROM AUTHOR]

Strong parametric mode coupling in mechanical resonators is demonstrated at room temperature by using the photothermal effect in thin membrane structures. Thanks to the large stress modulation by laser irradiation, the coupling rate of the mechanical modes, defined as half of the mode splitting, reaches 2.94 kHz, which is an order of magnitude larger than electrically induced mode coupling. This large coupling rate exceeds the damping rates of the mechanical resonators and results in the strong coupling regime, which is a signature of coherent mode interaction. Roomtemperature coherent mode coupling will enable us to manipulate mechanical motion at practical operation temperatures and provides a wide variety of applications of integrated mechanical systems. [ABSTRACT FROM AUTHOR]

The electromagnetic properties including ac conductivity, permittivity, and permeability of percolative Fe/Al2O3 composites, which were prepared by in-situ synthesis process, are investigated in the radio frequency range. There is an obvious percolation transition with the increase of iron contents. When iron content is beyond but near the percolation threshold, the negative permittivity and permeability are simultaneously obtained from 631MHz to 1GHz in sample FA30. Further increasing iron content, the Fano-like resonances are observed, and the resonance frequency where the permittivity changes from negative to positive shifts to lower frequency. In addition, the frequency region of negative permittivity and negative permeability are not overlapped any more. Hopefully, the percolative Fe/Al2O3 composites with tunable negative permittivity and negative permeability can be used as electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

An operating semiconductor laser has been studied using a scanning probe microscope. A shift of the resonance frequency of probe that is due to its heating by laser radiation has been analyzed. The observed shift is proportional to the absorbed radiation and can be used to measure the laser near field or its output power. A periodical dependence of the measured signal has been observed as a function of distance between the probe and the surface of the laser due to the interference of the outgoing and cantilever-reflected waves. Due to the multiple reflections resulting in the interference, the light absorption by the probe cantilever is greatly enhanced compared with a single pass case. Interaction of infrared emission of a diode laser with different probes has been studied. [ABSTRACT FROM AUTHOR]

To obtain higher power P and frequency f emissions from the intrinsic Josephson junctions in a high-Tc superconducting Bi2Sr2CaCu2O8+δ single crystal, we embedded a rectangular stand-alone mesa of that material in a sandwich structure to allow for efficient heat exhaust. By varying the current-voltage (I-V) bias conditions and the bath temperature Tb, f is tunable from 0.3 to 1.6 THz. The maximum P of a few tens of iW, an order of magnitude greater than from previous devices, was found at Tb ~ 55 K on an inner I-V branch at the TM(1,0) cavity resonance mode frequency. The highest f of 1.6 THz was found at Tb = 10 K on an inner I-V branch, but away from cavity resonance frequencies. A possible explanation is presented. [ABSTRACT FROM AUTHOR]

A single-tube on-beam quartz enhanced photoacoustic spectroscopy (SO-QEPAS) spectrophone, which employs a custom-made quartz tuning fork (QTF) having a prong spacing of 700 lm and operating at the 1st overtone flexural mode, is reported. The design of QTF prong geometry allows the bare QTF to possess twice higher Q-factor values for the 1st overtone resonance mode falling at ∼17.7 kHz than in the fundamental resonance mode at ∼2.8 kHz, resulting in an 8 times higher QEPAS signal amplitude when operating in the 1st overtone resonance mode. Both the vertical position and length of the single-tube acoustic micro-resonator (AmR) were optimized to attain optimal spectrophone performance. Benefiting from the high overtone resonance frequency and the quasi 1st harmonic acoustic standing waves generated in the SO-QEPAS configuration, the AmR length is reduced to 14.5 mm. This allows the realization of compact spectrophone and facilitates the laser beam alignment through the QTF þ AmR system. The signal enhancement in the overtone resonance mode and the high acoustic coupling efficiency between the AmR and QTF in the SOQEPAS configuration yields an overall sensitivity enhancement factor of ∼with respect to the bare custom QTF operating in the fundamental resonance mode. [ABSTRACT FROM AUTHOR]

High-index dielectrics are widely used in microwave antennas to control the radiation characteristics. Liquid water, with a high dielectric index at microwave frequency, is an interesting material to achieving tunable functionalities. Here, we demonstrate a water-loaded microwave antenna system that has high loss-tolerance and wideband tunability enabled by fluidity. Our simulation and experimental results show that the resonance frequency can be effectively tuned by the size of loading water. Furthermore, the antenna systems with water loading can achieve high radiation efficiency (>90%) in the ultra-high-frequency (0.3–3 GHz) band. This work brings about opportunities in realistic tunable microwave antenna designs enabled by liquid. [ABSTRACT FROM AUTHOR]