We demonstrate a proof of concept of a novel and compact integrated mechano-optical sensor for H(2) detection based on a microcantilever suspended above a Si(3)N(4) grated waveguide. The fabricated devices are mechanically and optically modeled and characterized. Sensing operation of the sensor is demonstrated with 1% H(2) in N(2). The error in detection of the cantilever bending induced by absorption of H(2) is estimated to be approximately 10 nm. Significantly improved sensitivity (down to ∼33 pm) is expected for reduced initial bending of the microcantilever. The simulation and experimental results are in good agreement and provide a good guideline for further optimization of the sensor.
SynonymsMicroactuators; MicroElectroMechanical systems; Micromachines Definition MEMS actuators are a type of MicroElectroMechanical System (MEMS) that convert energy into motion. MEMS are systems that integrate mechanical and electrical components with dimensions on the order of micrometers. Therefore, the typical motions achieved by MEMS actuators are on the order of micrometers as well. Overview MEMS are systems that integrate mechanical and electrical components with dimensions on the order of micrometers. Though the concept of MEMS has existed since the 1960s, due to the advent of microfabrication techniques for miniaturizing electronic components, the term MEMS was not coined until 1986. Professors Jacobsen and Wood from the University of Utah devised this terminology in the course of writing a proposal to the Defense Advanced Research Projects Agency (DARPA) [1]. The term was then disseminated via a National Science Foundation (NSF) report, the Utah-held IEEE MEMS workshop in 1989, the IEEE/ASME Journal of MEMS, and subsequent DARPA MEMS funding solicitations. Since its inception, this term has gained wide acceptance as a catchall for microdevices in general.MEMS actuators are a specific class of MEMS that convert energy into motion. The mechanisms by which energy is converted into motion are typically physical or chemical. Motion of the MEMS actuator can be used for positioning, open and closing valves, characterization of energy conversion processes, switching, and material characterization at the micro/nanoscale. A commercial application for positioning with MEMS actuators is that of Texas Instruments Digital Micromirror Device (DMD), wherein micromirrors are positioned (rotated) in order to direct light to create images in projectors for display applications. Opening and closing of (micro) valves is important for microfluidics and lab-on-achip applications. MEMS actuators can be configured to be energy storage devices or to detect quantities pertaining to energy conversion. Radio Frequency (RF) MEMS make use of MEMS actuators to create resonators for use in filters, reference oscillators, switches, switched capacitors, and varactors. Finally, MEMS actuators are commonly used to study material responses at the micro-and nanoscales. They are used to apply mechanical forces to materials in order to characterize their material properties mechanically.Fabrication of MEMS actuators typically occurs via top-down fabrication methods. These methods begin with a larger piece of material, typically Si, and then shape the Si into the form of an actuator. Most MEMS actuators are extrusions of a 2-D pattern that are transferred into the Si via a photolithographic process. Three common methods by which MEMS actuators are fabricated are: Surface Micromachining, Silicon on Insulator (SOI) Surface Micromachining, and Single Crystal Reactive Etching and Metallization (SCREAM). Other processes exist, but many are a hybrid processes based in one of the prior mentioned processes.This discussion of Basic MEMS Actuators will...
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The concept of utilizing second order nonlinear optical processes to mimic third order nonlinearities, in particular the optical Kerr effect, is discussed. Nonlinear organic materials with their large second order nonlinearities offer definite advantages for the implementation of such concepts. As a demonstration, we present both experimental and numerical results in the two important telecommunication windows on a DAN single crystal core fiber originally designed for efficient second harmonic emission in the Čerenkov geometry at 820 nm.When third order nonlinear phenomena are investigated in non-centrosymmetric materials, two successive (cascaded) second order processes can contribute to the intrinsic third order response for some effects. (1) As early as 1967, Ostrowskij predicted that cascading could play a prime role in self-action processes or any of the geometries involving the mixing of four degenerate waves.(2) The two contributions which lead to intensity-dependent effects for a single input beam are shown schematically in Figure 1. The presence of the so-called cascaded nonlinearities can interfere with and even mask the direct or intrinsic third order effects. In the early days of nonlinear optics such interference effects were reported in studies of nonlinear phenomena in GaAs.(3,4) Cascading has also been used to calibrate the third order nonlinear susceptibility of reference materials such as α-quartz whose nonlinearities are in turn are used as references for Third Harmonic Generation evaluations of nonlinearities in fused silica etc.(5) In general cascading in bulk materials has not led to a large intensity-dependent refractive mdex.(6-9) However, recent advances have produced both new organic second order materials with large nonlinearities as well as new methods of phase-matching existing materials in waveguides utilizing the large nonlinear coefficients normally not available for phase-matching bulk crystais.(10-]3) This has led to new experiments in bulk organic materials as well as in waveguides/5,14-16) The low powers expected in waveguides have led to a number 0097-6156/95/0601-O509$12.00/0
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