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We measure the adhesion energy of gold using a micromachined cantilever beam. Stress and stiffness of the beam are characterized by measuring the spectrum of mechanical vibrations and the deflection due to external force. We induce stiction between the beam and a nearby surface, employing capillary forces to determine the adhesion energy ␥. The obtained value ␥ϭ0.06 J/m 2 is a factor of 6 smaller than that predicted by idealized theory. This discrepancy may arise from surface roughness or an adsorbed layer intervening between the contacting surfaces in these mesoscopic structures. Casimir force, in addition to its fundamental interest, also plays an important role in the fabrication and operation of microelectromechanical systems ͑MEMS͒. This technology allows fabrication of a variety of on-chip fully integrated sensors and actuators with a rapidly growing number of applications. One of the principal causes of malfunctioning in MEMS is stiction, namely, the collapse of movable elements into nearby surfaces, resulting in their permanent adhesion ͑for a review, see Refs. 6 and 7͒. This can occur during fabrication, especially due to capillary forces present during drying of a liquid from the surface of the sample, or during operation.8 It was argued recently that the Casimir effect is often an important underlying mechanism causing this phenomenon. 9Here we report our experimental study of surface-surface interactions using micromachined Au cantilevers. In particular, we focus upon the extreme manifestation of the Casimir interaction, namely, adhesion between surfaces and the associated energy of this process. Traditionally, adhesion energy was studied experimentally by applying external forces to bulk materials and measuring the resultant contraction and/or cleavage.10 For these experiments the adhesion is associated with the perfectly smooth and clean internal surfaces of the bulk material. On the other hand, in many practical applications and in particular for MEMS devices surfaces are not ideal. In the present experiment we study this case by measuring adhesion between surfaces that may have some roughness and/or adsorbed contamination. These imperfections may alter the surfaces' properties, thus leading to a modified adhesion energy.The structures we use are designed to allow straightforward and unambiguous interpretation of our results. We use bulk micromachining ͑rather than surface micromachining͒, in which the substrate is completely removed beneath the sample. This greatly simplifies the boundary conditions of the electromagnetic field in the vicinity of the sample. Moreover, we avoid using multilayered structures, since their internal stresses generally play an important role and theoretical modeling is thus more difficult. We use metallic rather than semiconductor structures to minimize the possibility of parasitic bound surface charge attraction.After characterizing the mechanical properties of the beam, we induce stiction between the beam and a nearby electrode. The shape of the beam after adhesion a...

Two-photon loss mechanisms often accompany a Kerr nonlinearity. The kinetic inductance exhibited by superconducting transmission lines provides an example of a Kerr-like nonlinearity that is accompanied by a nonlinear resistance of the two-photon absorptive type. Such nonlinear dissipation can degrade the performance of amplifiers and mixers employing a Kerr-like nonlinearity as the gain or mixing medium. As an aid for parametric amplifier design, we provide a quantum analysis of a cavity parametric amplifier employing a Kerr nonlinearity that is accompanied by a two-photon absorptive loss. Because of their usefulness in diagnostics, we obtain expressions for the pump amplitude within the cavity, the reflection coefficient for the pump amplitude reflected off of the cavity, the parametric gain, and the intermodulation gain. Expressions by which of the degree of squeezing can be computed are also presented.

Abstract-We employ optical diffraction to study the mechanical properties of a grating array of suspended doubly clamped beams made of Au. The device allows application of electrostatic coupling between the beams that gives rise to formation of a band of normal modes of vibration (phonons). We parametrically excite these collective modes and study the response by measuring the diffraction signal. The results indicate that nonlinear effects strongly affect the dynamics of the system. Further optimization will allow employing similar systems for real-time mechanical spectrum analysis of electrical waveforms.[756]

We demonstrate a controlled dephasing experiment via exploiting a unique entangled interferometer-detector system, realized in an electronic mesoscopic structure. We study the dephasing process both from the which path information available in the detector and, alternatively, from the direct effect of the detector on the interferometer. Detection is possible only due to an induced phase change in the detector. Even though this phase change cannot actually be measured, strong dephasing of the interferometer took place. The intricate role of detector's noise and coherency are investigated.

Nonlinear elastic effects play an important role in the dynamics of microelectromechanical systems (MEMS). A Duffing oscillator is widely used as an archetypical model of mechanical resonators with nonlinear elastic behavior. In contrast, nonlinear dissipation effects in micromechanical oscillators are often overlooked. In this work, we consider a doubly clamped micromechanical beam oscillator, which exhibits nonlinearity in both elastic and dissipative properties. The dynamics of the oscillator is measured in both frequency and time domains and compared to theoretical predictions based on a Duffing-like model with nonlinear dissipation. We especially focus on the behavior of the system near bifurcation points. The results show that nonlinear dissipation can have a significant impact on the dynamics of micromechanical systems. To account for the results, we have developed a continuous model of a geometrically nonlinear beamstring with a linear Voigt-Kelvin viscoelastic constitutive law, which shows a relation between linear and nonlinear damping. However, the experimental results suggest that this model alone cannot fully account forall the experimentally observed nonlinear dissipation, and that additional nonlinear dissipative processes exist in our devices.

Nanomechanical resonators having small mass, high resonance frequency and low damping rate are widely employed as mass detectors. We study the performances of such a detector when the resonator is driven into a region of nonlinear oscillations. We predict theoretically that in this region the system acts as a phase-sensitive mechanical amplifier. This behavior can be exploited to achieve noise squeezing in the output signal when homodyne detection is employed for readout. We show that mass sensitivity of the device in this region may exceed the upper bound imposed by thermomechanical noise upon the sensitivity when operating in the linear region. On the other hand, we show that the high mass sensitivity is accompanied by a slowing down of the response of the system to a change in the mass.