We propose a waveguide integrated plasmonic platform in order to deliver excitation power to and collect signal
efficiently from a nanoantenna. The system consists of a silicon waveguide with an integrated nanoantenna and a fiber
spot size converter. The nanoantenna is designed to have a broad resonance around 1.5 microns with an estimated
surface enhanced Raman scattering (SERS) enhancement of 6 orders of magnitude and collection efficiency up to 80%.
The device is fabricated on a silicon-on-insulator (SOI) wafer. The proposed and fabricated device can be used in
applications such as on-chip SERS spectroscopy, infrared spectroscopy and gas sensing.
We report hybrid polymer actuator arrays based on environmentally responsive hydrogel and actuatable optical
microstructures that are designed to reversibly switch optical properties in response to the environment. Arrays of
micrometer scale plates were patterned by deep reactive ion etching of silicon which served as master structures for
replica molding in polydimethylsiloxane (PDMS). UV-curable epoxy was cast in a metal-sputtered PDMS mold to
transfer a thin metal film onto each microplate to form a micromirror array. Polyelectrolyte hydrogel, such as
poly(acrylamide-co-acrylic acid), was patterned on the micromirror array and acted as an artificial muscle, bending the
micromirrors in response to the change in humidity or pH. Such hybrid systems showed reversible switching between
high transmittance (low reflectivity) and low transmittance (high reflectivity) without the aid of external power. Our
design of hybrid actuated optics opens a broad avenue for developing environmentally responsive adaptive and active
Suspended silicon based nanostructures for optomechanic applications have been successfully fabricated using the
Hydrofluoric acid (HF) vapor phase etching technique. In this paper, we demonstrate the fabrication of parallel silicon
waveguides with a cross section of 250nm x 220nm, and photonic crystal nanobeam cavities with an air gap as small as
50nm between these released structures. The waveguides have been suspended over a distance of more than 75um.
Stiction is a major issue for releasing structures with gaps in the order of tens of nanometers. At the same time, the
process has to be gentle due to the small dimensions of the structures involved in the release process. HF vapor etching
technique was successfully utilized to etch the 2um thick thermally grown sacrificial silicon oxide layer. This process
has an high yield as no liquid is in contact with the structures being released, thus eliminating any kind of liquid flow
which typically proves to be a potential destruction source for such small structures. This HF vapor phase etching is a
simple and controllable process which completely eliminates the requirement of any kind of sophisticated drying
techniques needed with conventional wet etching.
When imaging schemes such as Magnetic Resonance Imaging are applied to nano-scale samples, the practical resolution is often limited by noise due to the difficulty of detecting a signal from a small number of nuclear or electronic spins. In this paper we discuss the potential for improving resolution by using optically detected magnetic resonance imaging such as optical Raman excited ESR transitions. Comparisons will be made between magnetic field gradients vs ac Stark gradients and optical Raman vs. direct microwave spin excitations. To make the analysis more concrete we will use nitrogen-vacancy (NV) defect centers in diamond as a test system.
In this work, preliminary analysis and testing of a thermoelectric compact shape memory alloy (TEC-SMA) actuator prototype will be presented. The prototype testing process will result in detailed feasibility assessment and quantification of the operational specification ranges for the TEC-SMA actuator. The actuators' potential for compactness and miniaturization will be assessed and quantified, however for the initial work presented in this paper, the prototype will not be optimally compact. The presented actuator prototype is a solid-state, thermoelectric SMA actuator that utilizes directly the thermoelectric effect for cooling an SMA element. The preliminary experimental setup consists of an SMA strip in close contact with Thermoelectric Modules (TEM)s for cooling, coupled with an LVDT, a load cell, and thermocouples to characterize and optimize the actuator bandwidth, stroke, length, output power and energy density based on SMA actuation cycles. Preliminary experimental results are presented based on the described setup for 0.5 <i>Hz</i> and 1.0 <i>Hz</i> actuation frequencies. A significant conclusion form this study is the need for power modulation for TEMs and SMA actuators for optimal performance of the TEC-SMA actuator.
Advances in active materials and smart structures, especially in applications of Shape Memory Alloys (SMA) as vibration isolation devices requires modeling of the pseudoelastic hysteresis found in SMAs. In general SMA hysteresis has been modeled either through constitutive models based on mechanics and material parameters or through system identification based models that depend only on input-output relationships, most popular being the Preisach Model. In this work, a basis is set forth for studying the effect of SMA pseudoelasticity on the behavior of vibrating systems. A Preisach Model is implemented to predict the component level pseudoelastic response of SMA spring elements. The model is integrated into a numerical solution of the non-linear dynamic system that results from the inclusion of Shape Memory Alloy components in a dynamic structural system. The effect of pseudoelasticity on a dynamic system is investigated for various loading levels and system configurations and the importance of large amplitude motion is discussed. Promising results are obtained from these investigations and the application of these studies to experimental work in progress by the authors is briefly discussed.
Advances in smart materials and structures technology, especially in applications of Shape Memory Alloys (SMA) as actuators and vibration isolation devices require understanding of the nonlinear hysteretic response found in SMAs. SMA hysteresis can be modeled either through constitutive models based on physical material parameters or through models based on system identification. In this work, a simplified material model for the pseudoelastic response of SMAs is presented, suitable for vibration isolation applications. Response obtained from the simplified model is compared with the response obtained from an existing thermodynamic constitutive SMA model and the results from the two models are found to match well. The computation time required by the simplified model was approximately seven times faster compared with the thermodynamic constitutive model. The simplified model is utilized to simulate a single degree of freedom mass-SMA system where the SMA acts as a passive vibration isolation device, showing a substantial reduction in displacement transmissibility.