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A light source based on single-walled carbon nanotubes (SWNTs) is one of the promising candidates for a microsized light source on a silicon chip at telecommunication wavelengths in optical communications and optical interconnects. However, SWNT-based light emitters possess the disadvantage of having a very broad emission spectrum. Here, we present an ultranarrow-linewidth photoluminescence (PL) emitter based on a silica toroid resonator, along with SWNTs, on a silicon chip. We simultaneously managed both excitation and emission lights at telecommunication wavelengths on a silicon chip by employing a very simple in-line configuration consisting of a toroid resonator and a tapered fiber for light input and output. Owing to the extremely high Q factor of our silica toroid resonator, we obtained an ultrahigh Q factor (∼2.1 × 104) of C-band PL emission. We also demonstrated strong PL emission under laterally polarized excitation conditions owing to the strong coupling to the toroid resonator, and laterally polarized PL emission can be selectively generated independently of the excitation polarization direction. This SWNT-based PL emitter based on a simple system with a silica toroid resonator can open routes to highly integrated photonics and optoelectronics on silicon-based platforms. [ABSTRACT FROM AUTHOR]

In this paper, we report the frequency comb response experimentally and analytically in a rhombic micro-resonator with parametrical modulation. When the electrostatically actuated rhombic micro-resonator is modulated axially by a low-frequency periodic excitation, a comb-like vibration response with few equidistant positioned fingers in the frequency domain is observed. The finger spacing of frequency comb response is exactly consistent with modulation frequency and the number and amplitude of the fingers can be tuned by modulation strength. A mixed frequency comb with extra comb fingers is further generated when the resonator is modulated simultaneously by two different low-frequency excitation signals. By adjusting the relation of the two modulation frequencies, unequal spacing frequency combs are achieved for the first time, which leads to a more flexible tunability of the comb spacing for different applications. Theoretical analysis based on the dynamic model well explains the corresponding observations. [ABSTRACT FROM AUTHOR]

A semi-analytical technique for estimating the energy loss in a resonator mounted to an infinite plate substrate is proposed in this paper. In a plate, only Lamb waves have to be considered, leading to a simplified characterization of the energy carried away from a vibrating source on the plate surface. Instead of employing absorbing elements at the boundaries of the plate-resonator finite element model, it is shown how the semi-analytical approach of stitching together analytical Lamb wave expressions to the finite element model can be utilized. The approach is demonstrated for single and double cantilever configurations on a plate. The results have excellent agreement with those of conventional transient finite element simulations.

A mid-infrared (mid-IR) integrated photonic sensing module using the machine learning (ML) technique has been illustrated. The sensing wavelengths were determined via a wavelength selection model trained by a classification algorithm according to the mid-IR absorption characterization of the analytes. The spectrum of the device output ports was identified via the algorithm-enabled spectrum selection method, where two artificial neural networks (ANN) were trained to optimize the device structures. The module with the micro-resonator array can precisely monitor various gas mixtures by altering the micro-resonator geometry. Our miniaturized mid-IR sensing module enables a new technology for accurate and efficient gas detection. [ABSTRACT FROM AUTHOR]

A fully integrated regenerative CO2 MEMS sensor using a micro-resonator coated with Linear Polyethylenimine as an adsorbent layer is presented. The pyramidal cantilever micro-resonator used has a resonant frequency of 315.24 kHz with a Q factor of 1125 at atmospheric pressure. The micro-resonator was integrated with a sustaining amplifier that consumes 8 mW. The MEMS sensor sensitivity was characterized in a CO2 concentration range from 1200 to 10500 ppm, showing a frequency shift of −12 Hz at 1200 ppm with a slope of −3.50 mHz / ppm over the characterized range. The adsorption and recovery times are characterized to be as low as 170 seconds and 280 seconds, respectively. The impacts of pressure, temperature and humidity on the sensor were also characterized. The behavior of the MEMS sensor is compared to that of an optical CO2 sensor. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) have garnered significant interest owing to their unique properties and therefore, AgNPs have widespread application. However, there have been recent reports about the risks posed by AgNPs to human health and a highly sensitive tool for detecting AgNPs in aquatic environments is required to prevent their harmful effects on humans. In this article, we propose highly sensitive detection of AgNPs using a micro-resonator and the DNA assisted conjugation method. The detection method is based on the resonance frequency shift of the resonator upon adsorption of conjugated AgNPs. We have used the DNA assisted AgNPs conjugation method to amplify the mass of the detection target. By using this micro-resonator in combination with the conjugation method, we were able to achieve highly sensitive and selective detection of AgNPs, with detection limits of approximately 10 ng/mL in distilled water, which is at least 10 times more sensitive than that described in previous reports. Further, we also performed detection in real drinking water samples. [ABSTRACT FROM AUTHOR]

The goal of this paper is to show that super-gain optical parametric amplification can be achieved even in a small micro-resonator using high-intensity ultrashort pump waves, provided that the frequencies of the ultrashort pulses are tuned to maximize the intracavity magnitude of the wave to be amplified, which we call the stimulus wave. In order to accomplish this, we have performed a dispersion analysis via computational modeling of the electric polarization density in terms of the non-linear electron cloud motion and we have concurrently solved the electric polarization density and the wave equation for the electric field. Based on a series of non-linear programming-integrated finite difference time-domain simulations, we have identified the optimal pump wave frequencies that simultaneously maximize the stored electric energy density and the polarization density inside a micro-resonator by using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) optimization algorithm. When the intracavity energy and the polarization density (which acts as an energy coupling coefficient) are simultaneously high, an input wave can be strongly amplified by efficiently drawing energy from a highly energized cavity. Therefore, we propose that micrometer-scale achievement of super-gain optical parametric amplification is possible in a micro-resonator via high-intensity ultrashort "pump wave" pulses, by determining the optimal frequencies that concurrently maximize the stored electric energy density and the polarization density in a dielectric interaction medium. [ABSTRACT FROM AUTHOR]

We developed a biosensor based on radio frequency micro-resonator for sensitive detection of aqueous glucose solutions. The device incorporates a modified interdigital capacitor-based multilayer resonator realized using integrated passive device technology. In addition, reduced graphene oxide was functionalized by phenylboronic acid aided with graphene oxide for the selective binding of glucose molecules under an electromagnetic field, resulting in a reliable concentration-specific resonance characteristic of the samples. The resonance frequency and bivariate (in terms of magnitude dip and phase reversal of the reflection coefficient) characteristics were found to be linearly related to the glucose concentration, thereby demonstrating the utility of the proposed microwave passive sensor in the detection of glucose with a sensitivity of 0.32 MHz per mg · dL-1. Furthermore, the corresponding variation in the capacitance and the impedance was accessed for each concentration of the glucose solutions.

Nonlinear, mechanical microelectromechanical system (MEMS) resonating structures exhibit large displacement and a relatively broad operating bandwidth. These unique features make them particularly of interest for the development of MEMS actuators and sensors. In this work, a mechanical MEMS structure allowing the designer to determine the type of nonlinearity, that is, softening or hardening, based on its anchor scheme is presented. Effects of the excitation signal on the behavior of the proposed MEMS in the frequency domain are investigated. In this regard, a comprehensive experimental comparison among the nonlinear behaviors of softening and hardening has been conducted. To reduce the hysteresis effect to a minimum, an excitation approach, which is a pulsed sweep in frequency with a discrete resolution, is presented. The maximal velocity, quality factor, bandwidth, and resonant frequency of these two types of nonlinear MEMS resonators are compared under three different types of excitation. Finally, it is shown that the performance and characteristics extracted from nonlinear mechanical MEMS resonating structures are highly dependent on the excitation method. Hence, in the present case, the apparent performances of the MEMS resonator can increase by up to 150% or decrease by up to 21%, depending on the excitation approaches. This implies the necessity of a standardized testing methodology for nonlinear MEMS resonators for given end applications.

Amplitude amplification can improve signal-to-noise ratio, which is of great significance in engineering systems, especially in small-scale MEMS systems. Hesre, we report an approach for achieving amplification of both amplitude and frequency bandwidth using the dual-jump effect in an electric-thermal adjusted arch beam micro-resonator. Through the electrothermal adjustment of an arch beam body, dual-jump in the amplitude-frequency response is observed, where the amplitude and frequency bandwidth of the response of the nonlinear resonator are both instantly amplified. The amplified frequency bandwidth can be greatly regulated by the driving voltage, which provides a novel strategy for sensing or filter applications capitalizing on the intrinsic nonlinear phenomena of micromechanical resonators. [Display omitted] • Highly controllable dual-jump phenomenon is achieved in a micro curved beam. • Amplification of both amplitude and frequency bandwidth is achieved using the dual-jump effect. • The amplified frequency bandwidth can be greatly regulated. • Theoretical analysis effectively elucidates the mechanism of the observed phenomenon. • Provides a novel strategy for sensing or energy collection applications. [ABSTRACT FROM AUTHOR]

Harmonic generation is an attractive research field that finds a variety of application areas. However, harmonic generation within a medium of micron-scale interaction length limits the magnitude of nonlinear coupling and leads to poor harmonic generation efficiency. In this study, we present a constrained non-linear programming approach based on the Quasi-Newton Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm to obtain high-fidelity harmonic generation in optical micro-resonators. Using this approach, one can achieve high-intensity harmonic generation in a simple Fabry–Perot type optical micro-resonator. The generation of super-intense harmonics at a typical ultraviolet (UV)-ablation frequency of 820 THz and at pure yellow-light (515 THz) is investigated in particular. Moreover, we achieved more than 98% accuracy compared to well-known theoretical results. Our approach enables the design of highly efficient microscale harmonic generators to be used in integrated photonic devices.

The goal of this paper is to show that super-gain optical parametric amplification can be achieved even in a small micro-resonator using high-intensity ultrashort pump waves, provided that the frequencies of the ultrashort pulses are tuned to maximize the intracavity magnitude of the wave to be amplified, which we call the stimulus wave. In order to accomplish this, we have performed a dispersion analysis via computational modeling of the electric polarization density in terms of the non-linear electron cloud motion and we have concurrently solved the electric polarization density and the wave equation for the electric field. Based on a series of non-linear programming-integrated finite difference time-domain simulations, we have identified the optimal pump wave frequencies that simultaneously maximize the stored electric energy density and the polarization density inside a micro-resonator by using the Broyden−Fletcher−Goldfarb−Shanno (BFGS) optimization algorithm. When the intracavity energy and the polarization density (which acts as an energy coupling coefficient) are simultaneously high, an input wave can be strongly amplified by efficiently drawing energy from a highly energized cavity. Therefore, we propose that micrometer-scale achievement of super-gain optical parametric amplification is possible in a micro-resonator via high-intensity ultrashort “pump wave” pulses, by determining the optimal frequencies that concurrently maximize the stored electric energy density and the polarization density in a dielectric interaction medium.

The comparison between potential coatings for the measurement of CO2 concentration through the frequency shift in micro-resonators is presented. The polymers evaluated are linear polyethylenimine, branched polyethylenimine and reduced graphene oxide (rGO) by microwave reduction with polyethylenimine. The characterization of the coatings was made by using 6 MHz gold-plated quartz crystals, and a proof-of-concept sensor is shown with a diaphragm electrostatic microelectromechanical systems (MEMS) resonator. The methods of producing the solutions of the polymers deposited onto the quartz crystals are presented. A CO2 concentration range from 0.05 % to 1 % was dissolved in air and humidity level were controlled and evaluated. Linear polyethylenimine showed superior performance with a reaction time obtained for stabilization after the concentration increase of 345 s, while the time for recovery was of 126 s, with a maximum frequency deviation of 33.6 Hz for an in-air CO2 concentration of 0.1%.

Abstract In this paper, we demonstrate a new method to obtain a low gap between the access waveguide and the racetrack cavity of a micro-resonator based on porous silica material and using standard photolithographic process. The photolithographic process is first carried out on porous silicon layers to obtain porous silicon ridge waveguides that constitutes the racetrack micro-resonator. Then the full oxidation of the micro-resonator is performed. Because of the volume expansion of silicon that occurs during its full oxidation, the gap is reduced. Lower gaps and then lower coupling distances can be obtained using a low cost photolithographic process compared to e-beam technology. This original method proposed in this paper allows to improve the miniaturization of such porous silica micro-resonators which is of great interest for integrated optical biosensor application. Highlights • Original method to obtain a low gap between the access waveguide and the racetrack cavity of a micro-resonator based on porous silica material. • Method based on a low cost standard photolithographic process. • A gap reduction of 40% of integrated porous silica micro-resonator is obtained. • The gap reduction takes benefit of the volume expansion of silicon that occurs during the full oxidation of the porous silicon micro-resonator. [ABSTRACT FROM AUTHOR]

Group IV photonics hold great potential for nonlinear applications in the near- and mid-infrared (IR) wavelength ranges, exhibiting strong nonlinearities in bulk materials, high index contrast, CMOS compatibility, and cost-effectiveness. In this paper, we review our recent numerical work on various types of silicon and germanium waveguides for octave-spanning ultrafast nonlinear applications. We discuss the material properties of silicon, silicon nitride, silicon nano-crystals, silica, germanium, and chalcogenide glasses including arsenic sulfide and arsenic selenide to use them for waveguide core, cladding and slot layer. The waveguides are analyzed and improved for four spectrum ranges from visible, near-IR to mid-IR, with material dispersion given by Sellmeier equations and wavelength-dependent nonlinear Kerr index taken into account. Broadband dispersion engineering is emphasized as a critical approach to achieving on-chip octave-spanning nonlinear functions. These include octave-wide supercontinuum generation, ultrashort pulse compression to sub-cycle level, and mode-locked Kerr frequency comb generation based on few-cycle cavity solitons, which are potentially useful for next-generation optical communications, signal processing, imaging and sensing applications.

This work investigates different geometries for fully screen-printed self-actuated self-readout microcantilevers made using a sacrificial layer process. The microcantilevers are made of PZT sandwiched between two gold electrodes. Q-factors as high as 1300 are reported. Promising theoretical sensitivities are reported (1000 Hz/µg at 620 kHz) and applications as humidity, temperature and particles sensor are explored in this work.

This paper investigates the dynamic behavior of a micro-resonator under various levels of Alternating Current (AC) voltage, without a biased Direct Current voltage. The governing equations are developed in the framework of Euler-Bernoulli beam theory, accounting for the effects of damping, fringing field, and mid-plane stretching using von Karman nonlinear strain. The steady-state frequency response of the micro-resonator is derived from the governing equations by the method of multiple scales. The transient response is also derived by the long-time integration. The results of our work reveal that the applied AC voltage and the mid-plane stretching (quantified by a stretching parameter) determine the characteristic feature of the dynamic behavior of the micro-resonator, such as the dynamic pull-in, the frequency response of linear or hardening characteristic. A design diagram in terms of AC voltage amplitude and stretching parameter is developed to show the domains of the different dynamic behavior characteristics. Our results also reveal the significant effects of damping and boundary conditions on the dynamic behavior and the design diagram of the micro-resonator. [ABSTRACT FROM AUTHOR]

Micro/nano-electromechanical resonator based logic computation has attracted significant attention in recent years due to its dynamic mode of operation, ultra-low power consumption, and potential for reprogrammable and reversible computing. Here we demonstrate a 4-bit parity checker circuit by utilizing recently developed logic gates based on MEMS resonators. Toward this, resonance frequencies of shallow arch shaped micro-resonators are electrothermally tuned by the logic inputs to constitute the required logic gates for the proposed parity checker circuit. This study demonstrates that by utilizing MEMS resonator based logic elements, complex digital circuits can be realized. [ABSTRACT FROM AUTHOR]

This paper investigates the compound effect of shear and squeeze energy dissipation mechanisms for a silicon lateral micro-resonator with complex geometry in different environmental conditions using a 3D computational fluid dynamics (CFD) model and compares it to experimental measurements. This model shows higher accuracy compared to previous works as the analysis takes into account shear and squeezing of the fluid at the same time. The results highlight that each fluid-induced dissipation mechanism depends on thermophysical properties of the fluid (temperature, relative humidity, pressure) along with the geometry of the micro-resonator (thickness and resonant frequency). For the first time, this paper quantifies the phase lag between fluid-induced resistant moment and angle of rotation for the micro-resonator. This phase lag increases linearly with the temperature at constant relative humidity. At constant temperature, the resonant frequency of the micro-resonator is affected by variations in relative humidity of the surrounding fluid. The contribution of different segments of micro-resonator's geometry on Q-factor (Q) is studied for three specimens and the sensitivity of shear and squeeze-film damping to geometric configuration of the micro-resonator is discussed. In addition, micro-resonators with different thicknesses and resonance frequencies are analyzed to investigate the contribution of each energy loss mechanism on overall quality factor and frequency shift. The CFD simulations show that total shear-damping decreases with thickness while squeeze-film damping rapidly grows by thickening the resonator. These opposing trends result in an optimal thickness of about 30 µm that could increase sensitivity by maximizing Q factor. We also discuss the influence of ambient pressure on Q-factor, demonstrating that energy loss increases with rising ambient pressure with an exponential growth rate of 0.28 where Knudsen number is in the order of 0.001. The results of this study could provide a guideline for the design of MEMS-based environmental monitoring systems exposed to ambient air. [Display omitted] • Development of quantitative MEMS-based experimental measurement of energy loss along with three dimensional CFD simulations. • Quantification of phase lag between fluid-induced resistant moment and angle of rotation for the micro-resonator. • Unveiling the contribution of geometric features and environmental condition on phase lag, frequency shift and Q factor. • Elucidation of the fluid-induced dissipation mechanisms and their synergic effect on different segments of micro-resonator. • Thickness optimization to minimize energy dissipation and maximizing sensitivity in the micro-resonator. [ABSTRACT FROM AUTHOR]

We report on a lab-on-chip sensor system based on integrated-optical resonators. The photonic components were realized in CMOS-process compatible amorphous silicon and the microfluidic interface enabling directed analyte transport was fabricated with soft-lithography technology. The developed sensor features optical resonators with dispersion engineered resonance spectra (DERS) to match optical resonance peaks over a wavelength region of several free spectral ranges. Resonance shifts caused by changes in refractive index of the investigated analyte are tracked by red-shifting a reference spectrum through the thermo-optic effect using electrical micro-heaters. With the DERS preserving the unambiguousness of the direct proportional relation between resonance shift and necessary heating power, this sensing principle enables direct electronic readout of analyte property changes. The sensor system therefore reduces the number and the size of peripheral devices usually necessary for the analysis of integrated optical devices, resulting in a broader range of potential application scenarios. [ABSTRACT FROM PUBLISHER]

Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In micro-resonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been transformed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillating structure on the damping ratio of the system have been investigated. [ABSTRACT FROM AUTHOR]

This paper investigates the vibration behavior of micro-resonators based on the strain gradient theory, a non-classical continuum theory capable of capturing the size effect appearing in micro-scale structures. The micro-resonator is modeled as a clamped-clamped micro-beam with an attached mass subjected to an axial force. The governing equations of motion and both classical and non-classical sets of boundary conditions are developed based on the strain gradient theory. The normalized natural frequency of the micro-resonator is evaluated and the influences of various parameters are assessed. In addition, the current results are compared to those of the classical and modified couple stress continuum theories. [ABSTRACT FROM AUTHOR]

The fabrication of micro-resonators, made from porous silica ridge waveguides by using an electrochemical etching method of silicon substrate followed by thermal oxidation and then by a standard photolithography process, is reported. The design and fabrication process are described including a study of waveguide dimensions that provide single mode propagation and calculation of the coupling ratio between a straight access waveguide and the racetrack resonator. Scanning electronic microscopy observations and optical characterizations clearly show that the micro-resonator based on porous silica ridge waveguides has been well implemented. This porous micro-resonator is destined to be used as an optical sensor. The porous nature of the ridge waveguide constitutes the detection medium which will enhance the sensor sensitivity compared to usual micro-resonators based on the evanescent wave detection. A theoretical sensitivity of 1170 nm per refractive index unit has been calculated, taking into consideration experimental data obtained from the optical characterizations. [ABSTRACT FROM AUTHOR]

This paper introduces an automatic bond graph design method based on genetic programming for the evolutionary design of micro-resonator. First, the system-level behavioral model is discussed, which based on genetic programming and bond graph. Then, the geometry parameters of components are automatically optimized, by using the genetic algorithm with constraints. To illustrate this approach, a typical device micro-resonator is designed as an example in biomedicine. This paper provides a new idea for the automatic optimization design of biomedical sensors by evolutionary calculation. [ABSTRACT FROM AUTHOR]

Mode interaction in M/NEMS arouses many interests in enhancing functionality in recent years. In this paper, the dynamics of two mechanically coupled micro-resonators with frequency ratio approximately 1:3 for tuning driving strength is investigated experimentally and analytically. Mode interaction induced three stages of response, i.e., typical Duffing response, large half-flattened response and narrow full-flattened response, of the coupled resonators as driving strength increasing are observed. The amplitude relationship of two resonators for each stage is also obtained. The theoretical study based on the mathematical model successfully explains the previous observations. Almost 1-order enhancement of the amplitude stability in the response flattening range is observed finally, which makes the mechanical coupled micro-resonators brilliant candidate as an amplitude-sensing sensor. [ABSTRACT FROM AUTHOR]

This paper deals with analysis of the mechanical behavior of an electro-statically-actuated micro-beam resonator from the bifurcation view of point. The non-local constitutive relation has been used to obtain the governing deformation equations. The obtained static equation has been solved using two approaches. The dynamic equation of motion has been solved applying a Galerkin-reduced order model. Bifurcation behavior of the beam subjected to an electrostatic force has been analyzed using the both approaches. The fixed points of the beam for given voltages have been obtained and stability of them determined by studying the phase portraits for each fixed point. [ABSTRACT FROM AUTHOR]

An electronically controllable frequency trimming technique based on localized thermal oxidation of single crystalline silicon resonators is demonstrated. Thin layers of silicon dioxide can be thermally grown on silicon surfaces of resonant structures via extreme joule heating of such when biased with relatively large bias currents in an oxygen-rich environment. Changes in structural stiffness or oxidation induced internal stress causes a shift in the resonant frequency of the structures that can be used for post-fabrication frequency trimming of silicon resonators. As an added advantage, the positive temperature coefficient of Young's modulus for the added silicon dioxide layer can partially compensate the large negative temperature coefficient of frequency (TCF) for the silicon resonators. Frequency trimming as high as \sim3.7\% and TCF as low as 0.2 ppm/^\circC has been demonstrated for a 54 MHz I-shaped resonator using this technique. Furthermore, it has been demonstrated that coupling of mechanical resonance to electrical resistance and consequently joule heating of the structure can lead to a cooling effect at mechanical resonant frequency of the structure that allows the localized oxidation to stop automatically as soon as the resonator frequency reaches a targeted actuation frequency applied to the structure. The viability of this concept is demonstrated by application of both off-resonance and at-resonance actuation signals to fabricated resonators showing that as opposed to the off-resonance signals, the at-resonance signals with the same intensity do not lead to further frequency shift. [2012-0337] [ABSTRACT FROM AUTHOR]

A novel micro-laser configuration formed by integrating an InGaAs/InP pillar with a silicon photonic crystal cavity is proposed and analyzed in detail. Special attention is paid to designing the cavity such that it can accommodate large-size pillars without performance compromise. The Purcell effect is studied and predicted to be significant because of the close interaction between the cavity modes and the gain medium. An overall quality factor as high as 1\,\times 10^5 and a spontaneous emission factor close to unity are predicted. Possible limiting factors for laser performance, such as surface non-radiative recombination and the thermal dissipation properties are analyzed, and it is found that the proposed laser design is very robust. This comprehensive analysis suggests that the proposed micro-laser is a promising candidate for large-scale integration of micro-lasers on silicon for low power consumption applications, such as intra-chip optical communications. [ABSTRACT FROM PUBLISHER]

Abstract: Understanding the physics of the loss mechanism of optical microresonators is important for one to know how to use them optimally for various applications. In these three-paper series, we utilized both analytical method (Conformal Transformation Approach) and numerical method (Active-Lasing Finite-Difference Time-Domain method) to study the resonator loss and cavity quality “Q” factor and apply them to optimize the radial/tangential waveguide coupling design. Both approaches demonstrate good agreement in their common region of applicability. In Part I, we review and expand on the conformal transformation method to show how exact solution of radiation loss for the case of cylindrical micro-resonator under both TE and TM polarizations can be obtained. We show how the method can be extended to apply to microdisk case. [Copyright &y& Elsevier]

We report a systematic theoretical investigation on magnetoelastic (ME) micro-resonator sensing system. The system, composed of ME micro-resonator immersed in target liquid and excitation/test coil with network analyzer, features as a wireless sensing mode, which enables the real-time high-sensitivity pathogen detection. A detailed four-step modeling methodology and a new equivalent circuit model for the sensing system are developed, with the system design, simulation, optimization, and experimental validation. Influences of various magnetostrictive materials, resonating structures, and excitation/test coils design on system sensing performance are discussed, revealing systematic design guidelines on real ME micro-resonator system for ultrasensitive mass-sensing applications. [ABSTRACT FROM AUTHOR]

Abstract: We present a 1×4 reconfigurable demultiplexer based on cascaded silicon microring resonators. The device is fabricated on a 0.18μm complementary metal oxide semiconductor (CMOS) process. A homogeneous doped silicon slab heater is proposed and fabricated directly on the slab region of the microring resonator for thermal tuning. The flows of the heating currents in the heaters are parallel to the ring waveguide through the heavily doped slab regions located on both sides of the ring waveguide without through the waveguide core regions. The proposed doped heaters are experimentally verified with low-voltage operation and tuning efficiency of ∼77pm/mW. Without any tuning or trimming, predicted average channel spacing distribution in the whole free spectral range (FSR) is demonstrated. Full reconfigurability is also demonstrated in the demultiplexer with channel spacing of 2nm (250GHz) and 1nm (125GHz), corresponding to channel isolation of less than −21dB and −16dB, respectively. Such a low-voltage operation and reconfigurable demultiplexer is suitable for on-chip optical interconnect. [Copyright &y& Elsevier]

An efficient electrostatic resonator is designed by adding a low voltage controller to an electrostatic actuator. The closed loop actuator shows stable, and bi-sable behaviors with bounded chaotic oscillations as large as 117% of the capacitor gap. The controller voltage is decreased from a previously designed resonator to less than 9 V thereby reducing the load on the controller circuit components. Bifurcation diagrams are obtained showing the frequency and magnitude of AC voltage required for chaotic oscillations to develop. The information entropy, a measure of chaotic characteristic, is calculated for the micro-resonator and is found to be 0.732. [ABSTRACT FROM AUTHOR]

Polymer coated thermal-piezoresistive micromechanical resonant silicon nanobalances have been utilized for detection and concentration measurement of volatile organic compounds in gas phase. Polyglycolic acid, which is the main polymer ingredient of the shipley-1813 photoresist, was used as the absorbent coating layer. Experiments have shown that polymer thickness determines the achievable sensitivity towards the gas molecules. The main challenge is to coat the devices with a thick layer of polymer while still maintaining their high-Q resonance. Multiple polymer coating approaches have been demonstrated. Following polymer deposition, in order to find the sensitivity of the devices, they were tested by exposure to regular gasoline and toluene vapor. The best measurement results were obtained by utilizing the photoresist already present on the resonant structures from the fabrication process. A maximum frequency shift of 3600 ppm (55 kHz) was obtained from a 15.5 MHz resonator with a ~ 1.5 μm thick coating upon exposure to nitrogen saturated with toluene vapor at room temperature. Based on the measurement results, minimum detectable concentration of toluene in the gas phase for such devices is in the range of a few ppm. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, we propose a feed-through reduction technique for a micro-resonator with a push–pull configuration that is based on the analysis of electrical characteristics of a direct driving micro-resonator. We show that the feed-through capacitance is decreased by reducing the sizes of the driving and sensing electrodes, inserting bias electrodes between them, and by surrounding them with a bias electrode. Using the proposed methods, we succeeded in reducing the feed-through capacitance and improving the performance of the micro-resonator with a push–pull configuration. We propose designs for the push–pull configuration with small electrodes, small electrodes and the insertion of bias electrodes between the driving and sensing electrodes, and surrounding the electrodes with a bias electrode. The feed-through capacitance of the small electrode model is 41.9fF, an approximately 50% decrease from the general model (90.1fF). The feed-through capacitance of the model with inserted bias electrodes is 17.9fF. The feed-through capacitance of the model surrounded with an inserted bias electrode is 10.9fF. The electrical transmission according to the feed-through capacitance was measured for each model. The efficiency in the electrical transmission is increased from 7.83dB (the general model) to 8.94dB (the small electrodes), 9.18dB (inserting bias electrodes model) and 9.40dB (surrounded with bias electrode model). We experimentally verified that the feed-through capacitance is decreased by reducing the sizes of the driving and sensing electrodes, inserting bias electrodes, and surrounding the electrodes with bias electrodes. The feed-through capacitance reduction technique would be useful for sensors, such as a micro-resonator requiring high performance, and radio frequency (RF) devices operating at high frequencies. [Copyright &y& Elsevier]

Squeeze-film damping on microresonators is a significant damping source even when the surrounding gas is highly rarefied. This article presents a general modeling approach based on Monte Carlo (MC) simulations for the prediction of squeeze-film damping on resonators in the free-molecule regime. The generality of the approach is demonstrated in its capability of simulating resonators of any shape and with any accommodation coefficient. The approach is validated using both the analytical results of the free-space damping and the experimental data of the squeeze-film damping on a clamped–clamped plate resonator oscillating at its first flexure mode. The effect of oscillation modes on the quality factor of the resonator has also been studied and semi-analytical approximate models for the squeeze-film damping with diffuse collisions have been developed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, atomic layer deposited (ALD) alumina (Al2O3) has been demonstrated as the structural material for a micro-resonator for the first time. An electrostatically actuated micro-bridge made of chromium (Cr) coated ALD Al2O3 was used as a resonator. The resonator was formed by simple wet- and dry-etching processes. The static displacement profile of the micro-resonator under electrostatic load was measured by an optical interferometer. A model of a pinned–pinned beam with axial stress of 250MPa was used to fit the measured data. Two techniques based on scanning electron microscope (SEM) and atomic force microscope (AFM) were developed to characterize the resonant frequencies of different modes and quality factor of the resonator. The measured resonant frequencies match well with the calculated values with residual stress of 258MPa, providing additional insight into resonator model and ALD alumina material properties. The developed techniques can be applied to further size reduction of devices made with ALD methods. [Copyright &y& Elsevier]

Abstract: This paper reports on GaAs micro-resonators with torsional vibration modes. An analytical model is used to design better GaAs resonant {hhl} cantilevers. In particular geometry of (441) and (114) resonators are optimized for specific alignments of the cantilever. The temperature response of the resonance frequency is also given. A piezoresistive four-terminal element is used to sense changes in frequency induced by a mechanical input. Sensitivity and non-linearity of the transverse output voltage are studied for the two selected orientations showing that the (441) orientation is preferable. The cantilever is fabricated by micromachining. Hence, the simulator TENSOSIM is used to predict etching shapes at the opening of the mechanical structure and after subsequent etchings. Here, again results call for the choice of a (441) beam. Finally, performances of the final (441) micro-resonator and of the piezoresistive sensor are evaluated with a special emphasis on errors caused by misalignments or by some uncertainty about the angle of cut. This study shows that GaAs resonators with piezoelectric excitation and piezoresistive detection open up new sensors applications. [Copyright &y& Elsevier]

Abstract: An association of the finite-difference time domain (FDTD) method together with coupled mode theories (CMTs) has been applied to the study of the bistable properties of whispering gallery mode (WGM) micro-ring resonators. The semi-analytical results obtained are compared with numerical nonlinear full calculations (nonlinear FDTD). It is shown that CMTs allow a good quantitative description of the stationary and dynamical behaviors of the bistability in such micro-resonators. As an example, we treat the case of a polymer micro-ring in a symmetrical dual coupling configuration. [Copyright &y& Elsevier]