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Optical frequency combs, which emit pulses of light at discrete, equally spaced frequencies, are cornerstones of modern-day frequency metrology, precision spectroscopy, astronomical observations, ultrafast optics and quantum information.sup.1-7. Chip-scale frequency combs, based on the Kerr and Raman nonlinearities in monolithic microresonators with ultrahigh quality factors.sup.8-10, have recently led to progress in optical clockwork and observations of temporal cavity solitons.sup.11-14. But the chromatic dispersion within a laser cavity, which determines the comb formation.sup.15,16, is usually difficult to tune with an electric field, whether in microcavities or fibre cavities. Such electrically dynamic control could bridge optical frequency combs and optoelectronics, enabling diverse comb outputs in one resonator with fast and convenient tunability. Arising from its exceptional Fermi-Dirac tunability and ultrafast carrier mobility.sup.17-19, graphene has a complex optical dispersion determined by its optical conductivity, which can be tuned through a gate voltage.sup.20,21. This has brought about optoelectronic advances such as modulators.sup.22,23, photodetectors.sup.24 and controllable plasmonics.sup.25,26. Here we demonstrate the gated intracavity tunability of graphene-based optical frequency combs, by coupling the gate-tunable optical conductivity to a silicon nitride photonic microresonator, thus modulating its second- and higher-order chromatic dispersions by altering the Fermi level. Preserving cavity quality factors up to 10.sup.6 in the graphene-based comb, we implement a dual-layer ion-gel-gated transistor to tune the Fermi level of graphene across the range 0.45-0.65 electronvolts, under single-volt-level control. We use this to produce charge-tunable primary comb lines from 2.3 terahertz to 7.2 terahertz, coherent Kerr frequency combs, controllable Cherenkov radiation and controllable soliton states, all in a single microcavity. We further demonstrate voltage-tunable transitions from periodic soliton crystals to crystals with defects, mapped by our ultrafast second-harmonic optical autocorrelation. This heterogeneous graphene microcavity, which combines single-atomic-layer nanoscience and ultrafast optoelectronics, will help to improve our understanding of dynamical frequency combs and ultrafast optics.Coupling graphene sheets with a silicon nitride ring microresonator allows the nonlinear cavity dynamics to be altered by a gate voltage, resulting in tunable, chip-scale, optical frequency combs., Author(s): Baicheng Yao [sup.1] [sup.2] [sup.7] , Shu-Wei Huang [sup.1] [sup.8] , Yuan Liu [sup.3] [sup.9] , Abhinav Kumar Vinod [sup.1] , Chanyeol Choi [sup.1] , Michael Hoff [sup.1] , [...]

In optics, the ability to measure individual quanta of light (photons) enables a great many applications, ranging from dynamic imaging within living organisms (1) to secure quantum communication (2). Pioneering photon counting experiments, such as the intensity interferometry performed by Hanbury Brown and Twiss (3) to measure the angular width of visible stars, have played a critical role in our understanding of the full quantum nature of light (4). As with matter at the atomic scale, the laws of quantum mechanics also govern the properties of macroscopic mechanical objects, providing fundamental quantum limits to the sensitivity of mechanical sensors and transducers. Current research in cavity optomechanics seeks to use light to explore the quantum properties of mechanical systems ranging in size from kilogram-mass mirrors to nanoscale membranes (5), as well as to develop technologies for precision sensing (6) and quantum information processing (7,8). Here we use an optical probe and single-photon detection to study the acoustic emission and absorption processes in a silicon nano-mechanical resonator, and perform a measurement similar to that used by Hanbury Brown and Twiss to measure correlations in the emitted phonons as the resonator undergoes a parametric instability formally equivalent to that of a laser (9). Owing to the cavity-enhanced coupling of light with mechanical motion, this effective phonon counting technique has a noise equivalent phonon sensitivity of 0.89 ± 0.05. With straightforward improvements to this method, a variety of quantum state engineering tasks using mesoscopic mechanical resonators would be enabled (10), including the generation and heralding of single-phonon Fock states (11) and the quantum entanglement of remote mechanical elements (12,13)., Measurement of the properties of mechanical systems in the quantum regime typically involves heterodyne detection of a coupled optical or electrical field, yielding a continuous signal proportional to the displacement [...]

Thermoelastic damping is a critical loss mechanism in micromachined resonators used for sensing and communication applications. In this paper, thermoelastic damping of the axisymmetric vibration of laminated circular plate resonators will be discussed. Based on the classical laminated plate theory assumptions, the governing equations of coupled thermoelastic problems are established for axisymmetric out-of-plane vibration of trilayered circular plate with fully clamped boundary conditions. The analytical expression for thermoelastic damping is obtained and the accuracy is verified through comparison with FEM results. Then the effect of material selection and the volume fraction of the covering layers are numerically evaluated. Finally, the thermoelastic damping for different vibration modes is also evaluated. PACS Nos.: 07.20.Dt, 46.25.Hf, 62.20.D-, 81.40.Jj, 65.40.De. L'amortissement thermo-elastique est un mecanisme critique de perte dans les resonateurs micro-usines utilises dans les applications de senseur et de communication. Nous etudions ici l'amortissement thermo-elastique des vibrations de symetrie axiale dans des resonateurs lamines circulaires. Sur la base de la theorie classique des plaques laminees, nous obtenons les equations directrices des problemes thermo-elastiques couples pour des vibrations a symetrie axiale hors plan de plaques circulaires tri-couches avec des conditions limites encastrees. Nous obtenons une expression analytique pour l'amortissement thermo-elastique et en verifions la precision en comparant les resultats avec ceux de FEM. Nous evaluons alors numeriquement l'effet du materiau selectionne et la fraction en volume des couches de recouvrement. Nous evaluons finalement l'amortissement thermo-elastique pour differents modes de vibration. [Traduit par la Redaction], 1. Introduction Miniaturized resonators are widely used as sensors and modulators in micro- and nanoelectromechanical systems [1-4]. For resonators, it is desired to design and construct systems with as little [...]

Quantum states of mechanical motion can be important resources for quantum information, metrology and studies of fundamental physics. Recent demonstrations of superconducting qubits coupled to acoustic resonators have opened up the possibility of performing quantum operations on macroscale motional modes.sup.1-3, which can act as long-lived quantum memories or transducers. In addition, they can potentially be used to test decoherence mechanisms in macroscale objects and other modifications to standard quantum theory.sup.4,5. Many of these applications call for the ability to create and characterize complex quantum states, such as states with a well defined phonon number, also known as phonon Fock states. Such capabilities require fast quantum operations and long coherence times of the mechanical mode. Here we demonstrate the controlled generation of multi-phonon Fock states in a macroscale bulk acoustic-wave resonator. We also perform Wigner tomography and state reconstruction to highlight the quantum nature of the prepared states.sup.6. These demonstrations are made possible by the long coherence times of our acoustic resonator and our ability to selectively couple a superconducting qubit to individual phonon modes. Our work shows that circuit quantum acoustodynamics.sup.7 enables sophisticated quantum control of macroscale mechanical objects and opens up the possibility of using acoustic modes as quantum resources.Circuit quantum acoustodynamics is used to achieve controlled generation of multi-phonon Fock states in a bulk acoustic-wave resonator, which are demonstrated to have a quantum nature., Author(s): Yiwen Chu [sup.1] [sup.2] , Prashanta Kharel [sup.1] [sup.2] , Taekwan Yoon [sup.1] [sup.2] , Luigi Frunzio [sup.1] [sup.2] , Peter T. Rakich [sup.1] [sup.2] , Robert J. Schoelkopf [...]

The de Broglie's hypothesis that every particle is associated with a fictitious phase wave has a real, classical analog that we call 'phase pseudowaves'. Such pseudowaves are inherent to beams of ordinary particles whose parameters vary as periodic functions. Through impacting the behavior of common resonators, phase pseudowaves create interference patterns reproducing unordinary features of light and quantum interference in the double-slit experiment. Sensors containing a resonant tank circuit and measuring the wave amplitude respond in the same way to ordinary waves and phase pseudowaves. It may prove to be the case that light interference transpires to be the superposition of waves, wave packages or phase pseudowaves, which do not interact in a 'normal' manner on a resonator. Keywords: phase pseudowave, interference on a resonator, de Broglie's waves, double-slit experiment, light interference, quantum interference, 1. Introduction In 1923 the French physicist Louis de Broglie introduced the term << fictitious phase wave) as a means of describing wave fields of an unknown nature (<< a [...]

Acoustic heating in resonators is studied. The governing equation of acoustic heating is derived by means of the special linear combination of conservation equations in differential form, allowing the reduction of all acoustic terms in the linear part of the final equation, but preserving terms belonging to the thermal mode responsible for heating. This equation is instantaneous and includes nonlinear acoustic terms that form a source of acoustic heating, it is valid for weakly nonlinear flows with weak attenuation. In general, dynamics of sound in a resonator is described by coupling nonlinear equations. Though the equation for heating relates to any sound field that may exist in a resonator, establishing a sound field is a problem itself. It is well known that employment of the different scales method and averaging over the sound period makes it possible to consider sound waves of opposite directions separately, without accounting for their interaction in the volume of the resonator, if they are periodic with zero mean perturbations. It also allows the adding together of contributions of oppositely propagating waves in the production of heat. Some examples of acoustic heating in resonators, relating to periodic sound branches with zero mean perturbations, are discussed. PACS Nos: 43.35.Fj, 43.25.Gf Nous etudions l'effet thermoacoustique (chauffage acoustique) dans des resonateurs. L'equation directrice du chauffage acoustique est obtenue via des combinaisons lineaires speciales des equations de conservation sous forme differentielle, permettant de reduire tous les termes acoustiques dans la partie lineaire de l'equation finale, mais preservant les termes qui appartiennent au mode thermique responsable du chauffage. Cette equation est instantanee et inclut des termes acoustiques non lineaires qui forment la source du chauffage acoustique et elle reste valide pour des ecoulement legerement non lineaires avec attenuation. En general, la dynamique du son dans un resonateur est decrite en couplant des equations non lineaires. Meme si l'equation pour le chauffage est appropriee pour tout champ sonore qui peut exister dans un resonateur, l'etablissement du champ sonore est un probleme a lui seul. Il est bien connu que l'utilisation d'echelles differentes et la prise de moyennes sur la periode sonore rendent possible de considerer separement les ondes sonores de directions opposees, sans avoir a s'occuper de leur interaction dans le resonateur, a condition qu'elles soient periodiques avec des perturbations moyennes nulles. Cela rend egalement possible d'additionner ensemble les contributions au chauffage des ondes se propageant en directions opposees. Nous discutons quelques exemples de chauffage acoustique dans des resonateurs sous ces conditions. [Traduit par la Redaction], 1. Introduction Research on standing waves with finite amplitudes in acoustic resonators is one of the most promising directions in nonlinear acoustics in view of the many technical and physical [...]

We propose a system that can be used to generate a dark soliton pulse array by using multidark soliton sources in the microring resonators and an optical multiplexer, where the different dark soliton center wavelengths can be generated. To verify the simulation results, the experimental setup was employed by using the Brillouin enhanced fiber laser in the fiber ring resonator (loop) system, where two different systems, called forward and backward schemes, were used to generate the dark soliton arrays. Three different center wavelengths of dark solitons were generated and seen to be in good agreement with the theoretical results. OCIS codes: 140.0140, 190.0190, 060.0060.

This review provides a summary of work on the resonant nonlinear dynamics of micro- and nanoelectromechanical systems. This research area, which has been active for approximately a decade, involves the study of nonlinear behaviors arising in small scale, vibratory, mechanical devices that are typically integrated with electronics for use in signal processing, actuation, and sensing applications. The inherent nature of these devices, which includes low damping, desired resonant operation, and the presence of nonlinear potential fields, sets an ideal stage for the appearance of nonlinear behavior. While nonlinearities are typically avoided in device design, they have the potential to allow designers to beneficially leverage nonlinear behavior in certain applications. This paper provides an overview of the fundamental research on nonlinear behaviors arising in micro-/nanoresonators, including direct and parametric resonances in individual resonators and coupled resonator arrays, and also describes the active exploitation of nonlinear dynamics in the development of resonant mass sensors, inertial sensors, and electromechanical signal processing systems. This paper closes with some brief remarks about important ongoing developments in the field. [DOI: 10.1115/1.4001333]

We propose and simulate a new kind of compact polarizing beam splitter (PBS) based on a photonic crystal ring resonator (PCRR) with complete photonic bandgaps. The two polarized states are separated far enough by resonant and nonresonant coupling between the waveguide modes and the microring modes. Some defect holes are utilized to control the beam propagation. The simulated results obtained by the finite-difference time-domain method show that high transmission (over 95%) is obtained and the polarization separation is realized with a length as short as 3.1 [micro]m. The design of the proposed PBS can be flexible, thanks to the advantages of PCRRs. [c] 2010 Optical Society of America OCIS codes: 230.4555, 130.3120, 230.5440, 230.1360.

This paper studies two linear resonator sources, which use a continuous 2.45-GHz microwave excitation to produce stable microplasmas, in air and in argon, at atmospheric pressure. The discharges are produced and sustained within the 50-200-[micro]m gap created between two metal electrodes with either 6 or 14 mm in length. Particular attention is given to the design and optimization of the sources (in terms of frequency tuning and power coupling), following a complementary approach based on simulations and experiments. Optical-emission-spectroscopy diagnostics allow one to deduce the rotational, vibrational, and excitation gas temperatures and the electron density (using Stark broadening measurements of the [H.sub.[beta]] line-emission profile). Index Terms--Atmospheric-pressure discharges, linear resonator, microplasma, microwave, optical diagnostics, power coupling.

There has been a recent trend to reduce the size of photonic waveguide devices to enable high-density integration in silicon photonic integrated circuits. However, this miniaturization tends to result in increased polarization dependency. Particularly challenging is designing devices based on ring waveguides with small radii, which exacerbates the polarization sensitivity. For these microring resonators, a legitimate question is then: Is it possible to simultaneously maintain the conditions of single-mode and structural polarization independence while shrinking the size of both the bend radius and the waveguide cross section, and, if so, how small can the ring resonator be? We demonstrate theoretically the feasibility of achieving this via deeply etched submicrometer silicon-on-insulator rib waveguides, and we show that, for a given cladding and core thickness, the radius of a polarization independent microring resonator can be as small as 3 [micro]m, being limited chiefly by the residual birefringence of the resonator cavity and the bend losses. OCIS codes: 130.0130, 230.5750, 250.5300.

We have demonstrated resonant frequency tuning of nanowire resonator operated in both atmospheric circumstance and high vacuum environment using electrostatic spring-softening effect. The nanowire is synthesized at any desired position by focused ion beam-chemical vapor deposition (FIB-CVD) on the sidewall of batch-processed micro electrode. The resonant frequency in a vacuum chamber of 2.5 x [10.sup.-4] Pa is 1.564 MHz under the driving voltage of 5 [V.sub.DC] [+ or -] 5 [V.sub.AC]. When 30 [V.sub.DC] tuning bias is applied on tuning electrode, the resonant frequency is reduced to 1.529 MHz due to the electrostatic spring-softening effect while the driving bias is maintained. For the tuning bias of 60 V, the resonant frequency at atmospheric pressure has been tuned from 1.49 MHz to 1.41 MHz under the c riving voltage of 30 [V.sub.DC] [+ or -] 10 [V.sub.AC]. The method demonstrated both in high vacuum and at atmospheric pressure is a simple and effective way to tune the deviated resonant frequency of nanowire resonator to the desired value without the alteration of the structure or post fabrication process. Index Terms--Electrostatic force, electrostatic spring effect, focused ion beam-chemical vapor deposition (FIB-CVD), frequency tuning, nanowire resonator, resonant frequency.

In this study, we have introduced a new attempt to reduce the noise level of a slim-type optical disk drive (ODD) using the concept of a Helmholtz resonator, which is a container with a neck through which the air can flow in and out. The Helmholtz resonator is known to generate a resonant sound when we apply disturbances across the opening of the neck but it is also known to absorb the acoustic noise to some extent, especially the noise of resonant frequency. The resonator is realized in the ODD using a tray, which carries a disk. A tray is prepared with various sizes of holes and hole configurations. The experimental results show that the total sound pressure level (SPL) can be reduced by more than 1.5 dB when a compound resonator type is employed. Index Terms--Helmholtz resonator, noise level reduction, slim-type ODD.

We present in-depth discussion of the design and optimization of a nanomechanical sensor using a silicon cantilever comprising a two-dimensional photonic crystal (PC) nanocavity resonator arranged in a U-shaped silicon PC waveguide. For example, the minimum detectable strain, vertical deflection at the cantilever end, and force load are observed as 0.0133%, 0.37 [micro]m, and 0.0625 [micro]N, respectively, for a 30 [micro]m long and 15 [micro]m wide cantilever. In the graph of strain versus resonant wavelength shift, a rather linear relationship is observed for various data derived from different cantilevers. Both the resonant wavelength and the resonant wavelength shift of cantilevers under deformation or force loads are mainly a function of defect length change. Results point out that all these mechanical parameters are mainly dependent on the defect length of the PC nanocavity resonator. This new PC cantilever sensor shows promising linear characteristics as an optical nanomechanical sensor. OCIS codes: 230.4685, 350.4238, 280.4788, 140.3945, 230.3990, 130.5296.

Arrays of small nanomechanical resonators with dual geometry have been fabricated for sensitive biological detection. The arrays consist of silicon nitride resonating 100 nm thick cantilevers with sensing gold areas alternately placed on the free and fixed cantilever ends. The Au areas act as sensing regions as can be functionalized by means of thiol chemistry. The nanomechanical arrays provide a double flavor of the adsorbed molecules: the added mass reported by the cantilevers with the Au area at the tip and the nanoscale elasticity reported by the cantilevers with the Au area at the clamp. The devices were applied for DNA detection based on Watson-Crick pairing rules. The proposed design for nanomechanical resonators provides higher specificity for DNA sensing in comparison with conventional single cantilevers. The nanoscale elasticity induced by the DNA hybridization arises from the intermolecular interactions between the adsorbates bound to the cantilever and the surface stress.

A thin film bulk acoustic wave resonator (FBAR) used in the RF frequency region of a few gigahertz is considered and its impedance is evaluated by using a harmonic analysis with the three-dimensional finite element method. In particular, the spurious characteristics caused by variations in the electrode area, as well as all the resonant modes and the mode shapes are analyzed. A design procedure is presented by using a prediction software tool. An experimental prototype is built and the measured results are compared to the numerical ones. Index Terms--Film bulk acoustic wave resonator (FBAR), finite element analysis, multiphysics, piezoelectric material.

We present a photonic-crystal (PC) channel-drop filter (CDF) design based on 3 x 3 PC ring resonators. The normalized transmission spectra for single-ring and dual-ring configurations have been investigated using two-dimensional finite-difference time-domain (FDTD) technique in a square-lattice dielectric-rod PC structure. First, we investigate a single ring and we show that backward and forward dropping is possible in the third communication window. Then we add another ring and waveguide to develop a new CDF. This filter consists of an input and three outputs. Our FDTD simulation yields more than 85% efficiency over each output port. OCIS codes: 230.5298, 230.3120.

A mechanical quartz microresonator (tuning fork) is used to detect electromagnetic radiation. The detection scheme is based on forces created due to the incident electromagnetic radiation on the piezoelectric tuning fork. A force can be created due to the transfer of the photon momentum of the incident electromagnetic radiation. If the surfaces of the tuning fork are nonuniformly heated, a second force acts on it, the so-called photophoretic force. These processes occur for all wavelengths of the incident radiation, making the detector suitable for sensing of ultraviolet, visible, and mid-infrared light, even THz-radiation. Here the detector is characterized in the visible range; noise analysis is performed for 650 nm and 5.26 [micro]m. A linear power characteristic and the dependence on pulse lengths of the incoming light ate shown. Examples for applications for the visible and mid-infrared spectral region are given by 2f and absorption spectroscopy of oxygen and nitric oxide, respectively. OCIS codes: 120.1880, 040.6808, 230.4910.

The use of a whispering gallery mode (WGM) resonator with an ultrahigh quality factor Q is promising in highly sensitive, label-free, lab-on-a-chip sensor applications. We investigated a novel method of using the differential frequency of TE and TM modes to reduce the thermal noise baseline, which commonly limits the sensitivity of WGM sensors. We studied the temperature dependence of WGM based sensors and experimentally demonstrated the reduction of temperature fluctuation and thus a significant improvement in the practical sensor detection limit. OCIS codes: 120.6810, 140.4780, 170.4520, 230.5750.

A double-pass negative-branch hybrid resonator is applied to a 10 kW chemical oxygen iodine laser. The resonator is folded in such a way that the dimension of the stable direction is reduced. The intensity distributions of the near and far fields of the laser beam and the sensitivity against tilts of the output mirror are investigated. A comparison between theory and experiment is performed. It is shown that the folded hybrid resonator provides a better beam quality and therefore a higher power density in the far field than a single-pass hybrid resonator. The sensitivity against tilts of the resonator mirrors in the stable direction is reduced. OCIS codes: 140.1550, 140.3410, 140.4780, 230.5750.

The design, fabrication and demonstration of the operation of a 195 [micro]m * 195 [micro]m on-chip resonator on Si, working at 15 GHz with a Q-factor of 93.81 is described. The proof-of-concept demonstration has shown that high-Q on-chip resonators can be used in transmissive telemetric sensors.

We investigate the capability of open source freeware ray tracing rendering software to demonstrate the imaging properties of canonical optical resonators. This software can directly visualize the imaging properties of canonical resonators. We can also demonstrate effects such as the trapping of light rays in geometrically stable resonators and the formation of fractal intensity patterns in the eigenmodes of geometrically unstable resonators.

Using an array of m x n nonlinear ring resonators (m = 1, 3, 5, and n = 1, 2, 3) coupled to the upper arm of a Mach-Zehnder interferometer (MZI), we have proposed an all-optical switch structure. Using a 5 x 3 array, we have shown the possibility of designing an all-optical switching device with a threshold intensity as low as 15 mW/[m.sup.2] and switching window of ~35 ps. While using m x 1 arrays, we have achieved switching windows smaller than 10 ps, at the expense of higher switching thresholds, ranging from 37 to 55mW/[m.sup.2]. The whole structure is based on a square lattice photonic crystal of lattice constant a = 600 nm, formed by rods of radius r = 90 nm in an air background. The linear rods' refractive index is taken to be the same as that of [Si.sub.0.75][Ge.sub.0.25]; i.e., nr = 3.6, whereas the nonlinear rod's refractive index and Kerr index parameter are taken to be [n.sub.0] = 1.4 and [n.sub.2] = [10.sup.-14] [m.sup.2]/W. The center wavelength at which the nonlinear rings are designed to make the resonance is taken to be [[lambda].sub.0] = 1550 nm in free space. OCIS codes: 230.1150, 230.4555, 230.5298.

Universal detectors that maintain high sensitivity as the detection volume is reduced to the subnanoliter scale can enhance the utility of miniaturized total analysis systems ([mu]-TAS). Here the unique scaling properties of the suspended microchannel resonator (SMR) are exploited to show universal detection in a 10 pL analysis volume with a density detection limit of ~1 [micro]g/[cm.sup.3] (10 Hz bandwidth) and a dynamic range of 6 decades. Analytes with low IN extinction coefficients such as polyethylene glycol (PEG) 8 kDa, glucose, and glycine are measured with molar detection limits of 0.66, 13.5, and 31.6 [micro]M, respectively. To demonstrate the potential for real-time monitoring, gel titration chromatography was used to separate different molecular weights of PEG as the SMR acquired a chromatogram by measuring the eluate density. This work suggests that the SMR could offer a simple and sensitive universal detector for various separation systems from liquid chromatography to capillary electrophoresis. Moreover, since the SMR is itself a microfluidic channel, it can be directly integrated into [mu]-TAS without compromising overall performance.

A micro-optical force sensor concept based on the morphology-dependent shifts of optical modes of dielectric microspheres is investigated. The optical resonances, commonly referred to as the whispering gallery modes (WGM), were excited by evanescently coupling light from a tunable diode laser using a tapered single-mode fiber. A compressive force applied to the sphere induces a change in both the shape and the index of refraction of the sphere leading to a shift in WGM. By tracking the shifts, the force magnitude is determined using solid silica as well as solid and hollow Polymethyl-methacrylate (PMMA) microsphere resonators. A measurement sensitivity as high as d[lambda]/dF = 7.664 nm/N was demonstrated with a 960 [micro]m hollow PMMA sphere. OCIS codes: 280.4788, 350.3950, 230.3990, 230.4555, 140.3948.

Semiconductor laser devices based on triangular resonators can provide cheap, compact, and high performance optical sources for optical communications, computing, defense, and biological applications. I modify the original structure by introducing three trenches and analyze their effects on the electromagnetic modes propagating in the triangular cavity. I also analyze the coupling of light into single-mode waveguides. These analyses are conducted by using two-dimensional finite difference time-domain methods. Results show that the introduction of such trenches can considerably reduce the quality factors of most of the modes, but one mode is not significantly degraded, providing nearly single-mode operation. The effects of radiation losses are further investigated by introducing a photonic crystal shielding around the triangular structure. Finally I solve the rate equations to obtain the steady-state response for these structures. OCIS codes: 140.2020, 130.3120.

We demonstrate a method of controlling the alignment of a laser beam to a Fabry-Perot resonator through synchronous detection of the misalignment arising from modulating the orientation of a single beam-steering mirror. The horizontal and vertical tilt of the mirror are modulated in quadrature to drive a circular motion of the beam orientation. A corresponding modulation of the intensity of the optical field circulating in the cavity is measured at either the reflected or transmitted port and demodulated synchronously to derive two error signals to indicate the vertical and horizontal misalignment. These signals are fed back to the beam-steering mirror to suppress fluctuations below 30 Hz. This method avoids the complexity of monitoring off-axis cavity modes and is particularly effective in the case where unwanted pointing fluctuations are introduced by one or two elements in the optical setup. We have applied the technique to two Fabry-Perot resonators in use as precision frequency references, delivering a result of 10 dB suppression of alignment fluctuations at 1 Hz and an improvement in frequency stability by up to a factor of 4. OCIS codes: 120.2230, 120.3940, 220.1140.

A compact two-dimensional (2-D) finite-difference time-domain (FDTD) method is proposed to analyze the propagation characteristics of arbitrary guiding structures. By transforming electromagnetic field variables into new forms of periodic variables, which also can be resolved from the Maxwell's equations, one can convert the 2-D transmission line problem into an equivalent resonator problem based on the idea of translating the transmission distance-related attenuation part of complex propagation constant into a time-dependent damping factor. As a result, the FDTD method for resonator can be made use of to simulate the lossy guiding structures. Attenuation constants can be obtained by means of the quality factors of equivalent resonators. It means that some leaky wave antennas can also be analyzed by using this method. Numerical simulations show that the proposed method can quickly and accurately extract the phase constants and attenuation constants of lossy guiding structures. Index Terms--Complex propagation constant, equivalent resonator, finite-difference time-domain (FDTD) method, leaky wave antenna, quality factor.

A systematic study of the high frequency electrical properties of electro-textiles is presented in this paper. First, conductive thread characterization is completed with a waveguide cavity method. The effect of conductive thread density and comparison of several different types of conductive threads are included. Second, comparisons of knitted patterns and weave patterns are made in terms of effective electrical conductivity through a microstrip resonator method. The effect of various weave patterns on conductive and dielectric loss is detailed. Finally, the relevance of the high frequency characterization of the electro-textile materials is shown through electro-textile patch antenna fabrication and measurements. The efficiency of the fully fabric patch antenna is as high as 78% due to the use of low loss electrotextiles characterized in this paper. Index Terms--Conducting materials, electro-textile, materials testing, microwave resonators.

Miniaturized hexagonal stepped-impedance resonators and their applications to bandpass filters are presented. Based on the odd- and even-mode equivalent circuits, the resonance characteristics of these resonators are investigated. A series of circuit configurations, including the third-order Chebyshev, tri-section, and fifth-order cascaded trisection filters, are constructed by the proposed resonators. These filters are very compact and have good stopband responses. Measured results validate the analysis and theoretical prediction with good agreement. Index Terms--Bandpass filter, hexagonal stepped-impedance resonator, miniaturization.

In this paper, inkjet-printed UHF and microwave circuits fabricated on paper substrates are investigated for the first time as an approach that aims for a system-level solution for fast and ultra-low-cost mass production. First, the RF characteristics of the paper substrate are studied by using the microstrip ring resonator in order to characterize the relative permittivity ([[epsilon].sub.T]) and loss tangent (tan [delta]) of the substrate at the UHF band for the first time reported. A UHF RFID tag module is then developed with the inkjet-printing technology, proving this approach could function as an enabling technology for much simpler and faster fabrication on/in paper. Simulation and well-agreed measurement results, which show very good agreement, verify a good performance of the tag module. In addition, the possibility of multilayer RF structures on a paper substrate is explored, and a multilayer patch resonator bandpass filter demonstrates the feasibility of ultra-iow-cust 3-D paper-on-paper RF/wireless structures. Index Terms--Cavity resonator, dielectric characterization, inkjet printing, loss tangent, low-cost RF modules, multilayer, paper, printable electronics, relative permittivity, resonator bandpass filter (BPF), RF identification (RFID), ring resonator, UHF, wireless local area network (WLAN).

40-GHz monolithic microwave integrated circuit (MMIC) single-pole--double-throw and multiple-port bandpass filter-integrated switches based on electronically switchable resonators are proposed. The proposed multifunction chip integrates a multiple-port switch with bandpass filter functions in a single chip. The switchable resonators are formed by quarter-wavelength stepped-impedance resonators with passive HEMT loading at one end. By properly allocating the resonant frequencies of the resonators in their on and off modes, a filter-integrated switch can perform a bandpass response with spurious suppression in the on state and achieve wideband isolation in the off state. The technique of using shared resonators is also introduced in the circuit design to reduce the overall circuit size. The results show the proposed circuits successfully integrate a MMIC switch with bandpass filter functions into a single circuit component. Index Terms--Bandpass filter, monolithic microwave integrated circuit (MMIC), multiple port, single-pole double-throw (SPDT), stepped-impedance resonator (SIR), switch.

In this paper, synthesis and design techniques of dualand triple-passband filters with Chebyshev and quasi-elliptic symmetric frequency responses are proposed and demonstrated for the first time on the basis of substrate integrated waveguide technology. The inverter coupled resonator section is first investigated, and then a dual-passband Chebyshev filter, a triple-passband Chebyshev filter, and a dual-passband quasi-elliptic filter, which consist of the inverter coupled resonator sections, are synthesized from the generalized low-pass prototypes having Chebyshev or quasi-elliptic responses, respectively. Subsequently, theses filters with a symmetric response are designed and implemented using the substrate integrated waveguide scheme over the K-band frequency range. The inverter coupled resonator sections composed of side-by-side horizontally oriented substrate integrated waveguide cavities are coupled, in turn, by post-wall irises. 50-[OMEGA] microstrip lines are used to directly excite the filters. Measured results are presented and compared to those simulated by Ansoft's High Frequency Structure Simulator (HFSS) software package. A good agreement between the simulated and measured results is observed, which has also validated the proposed concept of design and synthesis with the substrate integration technology. Index Terms--Dual-passband filter, inverter coupled resonator section, quasi-elliptic, substrate integrated waveguide, triple-passband filter.

This paper reports a novel capacitive detection method, called the sideband-ratio (SBR) detection, which is robust to variations of such critical parameters as the nominal capacitance, frequency, and amplitude of the probing voltage and gain of the transimpedance amplifier. The approach constructively utilizes the inherent nonlinearity of paralleilplate sense capacitors in order to measure the amplitude of sinusoidal motion. In the case of parallel-plate detection signal, multiple harmonics exist and each carry information about the amplitude of mechanical motion. The SBR method robustly extracts the amplitude of motion from the ratio of multiple sidebands. This paper presents theoretical background and analysis of this nonlinear measurement method. A real-time measurement algorithm is implemented in software and simulated. Feasibility of the developed approach is demonstrated experimentally. [2006-0292] Index Terms--Automatic calibration, capacitive detection, electromechanical amplitude modulation (EAM), gyroscopes, modulation, parallel plates, resonators, self-calibration, sidebands.

The resonant properties of a closed and symmetric cyclic array of N coupled microring resonators (coupled-microring resonator regular N-gon) are for the first time determined analytically by applying the transfer matrix approach and Floquet theorem for periodic propagation in cylindrically symmetric structures. By solving the corresponding eigenvalue problem with the field amplitudes in the rings as eigenvectors, it is shown that, for even or odd N, this photonic molecule possesses 1 + N/2 or 1 + N resonant frequencies, respectively. The condition for resonances is found to be identical to the familiar dispersion equation of the infinite coupled-microring resonator waveguide with a discrete wave vector. This result reveals the so far latent connection between the two optical structures and is based on the fact that, for a regular polygon, the field transfer matrix over two successive rings is independent of the polygon vertex angle. The properties of the resonant modes are discussed in detail using the illustration of Brillouin band diagrams. Finally, the practical application of a channel-dropping filter based on polygons with an even number of rings is also analyzed. OCIS codes: 130.3120, 230.5750.

A nonparaxial scalar diffraction integral is used to determine numerically the resonance modes of a two-dimensional nearly concentric Fabry-Perot resonator. Numerical examples are provided, and results are compared to those published by Laabs and Friberg [IEEE J. Quantum Electron. 35, 198 (1999)]. Discrepancies are reported and further discussed on the basis of the difference between the solution space supported by the numerical method used here and the one used by Laabs and Friberg. OCIS codes: 050.2230, 120.2230, 350.5500.

We have tested a new kind of Fabry-Perot long-baseline optical resonator proposed to reduce the thermal noise sensitivity of gravitational wave interferometric detectors--the 'mesa beam' cavity--whose flat top beam shape is achieved by means of an aspherical end mirror. We present the fundamental mode intensity pattern for this cavity and its distortion due to surface imperfections and tilt misalignments, and contrast the higher order mode patterns to the Gauss-Laguerre modes of a spherical mirror cavity. We discuss the effects of mirror tilts on cavity alignment and locking and present measurements of the mesa beam tilt sensitivity. OCIS codes: 140.4780, 120.2230, 230.0040.

A finite element formulation is developed for solving the problem related to thermoelastic damping in beam resonator systems. The perturbation analysis on the governing equations of heat conduction, thermoelasticity; and dynamic motion leads to a linear eigenvalue equation for the exponential growth rate of temperature, displacement, and velocity. The numerical solutions for a simply supported beam have been obtained and shown in agreement with the analytical solutions found in the literature. Parametric studies on a variety of geometrical and material properties demonstrate their effects on the frequency and the quality factor of resonance. The finite element formulation presented in this work has advantages over the existing analytical approaches in that the method can be easily extended to general geometries without extensive computations associated with the numerical iterations and the analytical expressions of the solution under various boundary conditions. [DOI: 10.1115/1.2748472] Keywords: thermoelastic damping, beam resonator, eigenvalue, finite element method

A new type of microstrip bandpass filter is presented with a center frequency operation at 2.5GHz which lies in the S-band frequency range. The filter is designed to be much smaller compared to the same type of parallel-coupled bandpass filter. The simulation results are excellent and the filter is suitable for integration within various microwave subsystems. Keywords: Band pass filter, microwave, S-band frequency Mohd Fadzil Ain, Mandeep Singh Jit Singh, Prabhu, Syed Idris Syed Hassan School of Electrical and Electronic Engineering, University Sains Malaysia, 14300, Nibong Tebal, Seberang Perai Selatan, Pulau Pinang, Malaysia, INTRODUCTION Bandpass filters are filters containing one or more combination of capacitance and inductance which are designed mathematically to respond to design frequencies while rejecting all other out of band [...]

1. Introduction Spherical acoustic resonators (1) have been successfully applied to measurement of the universal gas constant (2) and to gas thermometry (3-7). The radial (0, n) acoustic modes are […]

The impedance of a passive noise control device is strictly positive real, if the device is installed in noise fields with weak mean flows. Passive noise control devices are, therefore, more reliable than active ones. Active control may be applied to a Helmholtz resonator to introduce electronic resonance. It will affect the impedance [Z.sub.act] of the resonator A controller may be designed such that (a) [Z.sub.act] is small and resistive at some tunable frequencies; and (b) Re{[Z.sub.act]} [greater than or equal to] 0 in the entire frequency range of interest. If criterion (a) is satisfied, the active resonator can suppress duct noise at tunable frequencies. It is difficult to design a controller to satisfy criterion (b) because parameters of the controller depend on acoustic parameters of the noise field. A new method is proposed here to design an active controller to meet both criteria simultaneously. The satisfaction of criterion (b) implies a positive real [Z.sub.act] and a robust active resonator with respect to parameter variation in the noise field. Experimental results are presented to verify the performance of the active resonator. [DOI: 10.1115/1.2345678]

Transient characteristics of switched resonators have been studied. The resonators exhibit controllable impedance and energy storage behaviors during an alternating charging and discharging process. It is discovered that these unique characteristics of switched resonators can lead to novel RF envelope signal processing functions. The paper discusses the basic theory of switched resonators and the designing methodology of relevant RF signal processing applications. Two applications are presented as examples. The first example is a variable, reflective attenuator which uses the controllable impedance of the switched resonators to achieve different attenuation/reflection levels. In the second example, a simple, compact and efficient RF pulse compression technique based on the switched resonator concept is introduced. It utilizes the charging/discharging characteristics of the circuit resonator by varying the resonator's Q-factor. The approach compresses the duration of the modulated pulse without changing the phase characteristics of the RF carrier. The pulse compression technique can also be implemented with other type of resonators including distributed resonators, as demonstrated through the experiments. Index Terms--Envelope-based RF signal processing, pulse compression, pulse generator, switched resonators, variable RF attenuators.

The mode frequencies and quality factors (Q-factors) in two-dimensional (2-D) deformed square resonators are analyzed by finite-difference time-domain (FDTD) technique. The results show that the deformed square cavities with circular and cut corners have larger Q-factors than the perfect ones at certain condition.

A study that focuses upon the conventional quartz crystal nanobalance (QCN) gas sensor is presented by adopting Taguchi's signal-to-noise ratio analysis. A time- and cost-efficient finite element analysis method is utilized to investigate the effects of the deposited mass upon the resonant frequency output of the QCN biosensor.

The variation of the electromechanical coupling and the quality factor of the resonators, for both the longitudinal and the shear modes as a function of the degree of film texture is studied. The film growth is in the competitive growth mode, thus enhancing column growth along the mean deposition flux.

The performance of quartz crystal resonator (QXR) force sensors, which utilize symmetrical incomplete circular QXR's as indicative factors are affected by transverse force. However, the main focus of the effect of transverse force is mainly on the two types of QXR force sensors that are sensitivity and linearity.

Byline: Asim Iqbal, Ahmet Selamet Impact of mean flow on the acoustic attenuation performance of a Helmholtz resonator is investigated computationally. To determine the time-dependent flow field, two-dimensional unsteady, turbulent, and compressible Navier-Stokes equations are solved. Pressure obtained from the flow field is used to calculate the Helmholtz resonator's transmission loss at different velocities. Increasing the mean flow velocity in the main duct is shown computationally to reduce the peak transmission loss in general and force a shift in the fundamental resonance frequency to a higher value. These predictions are consistent with the trends observed in the experimental studies available in the literature. Also, at discrete Strouhal numbers, the simulations capture the flow-acoustic coupling which transforms the Helmholtz resonator essentially to a noise generator. The approach presented here demonstrates the ability of a numerical tool to study the complex interactions of the flow field with the acoustics of Helmholtz resonators effectively.