<p>Among the various physical systems considered for scalable quantum information processing (QIP), individually trapped ions or neutral atoms have emerged as promising candidates. Recent experiments using these systems have demonstrated the basic building blocks required for a useful quantum computer. In many of these experiments, precisely tuned lasers control and manipulate the quantum bit (qubit) represented in the electronic energy levels of the ion or atom. Scaling these systems to the necessary number of qubits needed for meaningful calculations, requires the development of scalable optical technology capable of delivering laser resources across an array of ions or atoms. That scalable technology is currently not available.</p><p>In this dissertation, I will report on the development, design, characterization, and implementation of an optical beam steering system utilizing microelectromechanical systems (MEMS) technology. Highly optimized micromirrors enable fast reconfiguration of multiple laser beam paths which can accommodate a range of wavelengths. Employing micromirrors with a broadband metallic coating, our system has the flexibility to simultaneously control multiple beams covering a wide range of wavelengths. </p><p>The reconfiguration of two independent beams at different wavelengths (780 and 635 nm) across a common 5x5 array of target sites is reported along with micromirror switching times as fast as 4 us. The optical design of the system minimizes residual intensity at neighboring sites to less than 40 dB below the peak intensity. Integration of a similar system into a neutral atom QIP experiment is reported where 5 individually trapped atoms are selectively manipulated through single qubit rotations with a single laser source. This demonstration represents the first application of MEMS technology in scalable QIP laser addressing.</p> / Dissertation

<p>Piezoelectric micromachined ultrasound transducer (pMUT) two-dimensional (2D) arrays have been proposed as an alternative to conventional bulk-PZT thickness-mode transducers for high frequency, forward-looking, catheter-based ultrasound imaging of the cardiovascular system. The appeal of pMUTs is based on several key advantages over conventional transducer technologies, including high operational frequencies, small element size, and low cost due to their microelectromechanical system (MEMS) silicon-based fabrication. While previous studies have demonstrated acoustic performance characteristics suitable for ultrasound image formation, pulse-echo B-mode imaging of tissue and tissue-like phantoms using 2D pMUT arrays small enough for forward-looking catheter-based applications have been demonstrated only at Duke University by Dausch et al.</p><p>Having demonstrated the suitability of 2D pMUT arrays for tissue imaging, an important step is to demonstrate effective design control. The frequency of operation is a fundamental component of transducer design. Previous modeling efforts for pMUT vibration have used classical/Kirchoff thin plate theory (CPT) or Mindlin thick plate theory, however pMUTs with geometric dimensions similar to those explored here, have not been modeled with experimental comparison to physical devices.</p><p>It is hypothesized that the frequency of vibration of pMUTs can be predictively modeled based on experimental data from various pMUT configurations. Experimental frequency results were acquired and used to develop an empirical model based on a modified Mindlin thick plate theory. This dissertation presents the development of the frequency design theory culminating in a set of predictive design equations for the frequency of vibration of 2D pMUT arrays aimed at improving their use in high-frequency, forward-looking, catheter-based ultrasound imaging applications.</p> / Dissertation

Laser ultrasonics has been used to measure the bending stiffness of paper products by measuring the dispersion of ultrasonic plate waves. In laser ultrasonics, ultrasound can be generated by absorption of pulsed laser spot while detection can be carried out by Laser Doppler Interferometry. The research presented in this paper describes a new method to detect ultrasonic plate waves using a recently developed acoustic transducer, more specifically an optical Micro ElectroMechanical System (MEMS) microphone with broadband capability. The MEMS device operates as a non-contact proximity probe placed less than ¼ a millimeter away from the plate. The signals are detected with a capacitive micromachined ultrasonic transducer (cMUT) in which the back electrode of the capacitive transducer on a transparent substrate is shaped as an optical diffraction grating. The displacement of the transducer membrane is determined using an optical interferometer. By applying voltage to deflect the membrane electrostatically, the detection sensitivity is kept at an optimum level. The main purpose of the research presented herein was to test this MEMSs ability to detect ultrasonic waves propagating through paper, to increase the signal-to-noise ratio (SNR), and to calibrate the device in order to quantify the limitations on sensitivity in the context of the detection of ultrasound in paper. Similar tests were conducted for comparison with a modified Mach-Zehnder Interferometer, a more traditional method used for laser ultrasonic detection, and its results are presented in this paper.

This study investigated the behavior of porous silicon gas sensors under exposure to CO, NO, and NH3 gas at the part per million level. Parameters of interest in this study included the electrical, environmental, and chemi-resistive performance associated with various porous silicon morphologies. Based upon the variability of preliminary results, a gas pulsing method was combined with signal processing in order to analyze small impedance changes in an environment of substantial noise. With this technique, sensors could be effectively screened and characterized. Finally this method was combined with various post-treatments in order to improve the sensitivity and selectivity of individual sensors.

This thesis reports on the use of sputter-deposited zinc-oxide as a transduction mechanism to actuate and sense single crystal silicon (SCS) microelectromechanical (MEMS) resonators. Low frequency prototypes of piezo-on-silicon resonators with operating frequencies in the range of hundreds of kHz were implemented using micromechanical single crystal silicon clamped-clamped beam resonators. The resonators reported here extend the frequency of this technology into very high frequency (VHF range) by using in-plane length extensional bulk resonant modes. This thesis outlines the design, implementation and characterization of high-frequency single crystal silicon (SCS) block resonators with piezoelectric electromechanical transducers. The resonators are fabricated on 4m thick SOI substrates and use sputtered ZnO as the piezo material. The centrally supported block resonators operate in their first and higher order length extensional bulk modes with high quality factor (Q). Measurement results are in good agreement with the developed ANSYS simulations.

The current tools for geometric analysis of micro-electromechanical systems (MEMS) are primarily limited to those of the semiconductor industry. These tools are suited for measuring entities that are two-dimensional in nature such as lines, circles, and planes. Hardware that is capable of collecting three-dimensional data is typically limited by the slope variations in the surfaces of the part, and cannot accurately capture information from steep sidewalls, particularly in parts fabricated using the LIGA micro-fabrication process. This research develops a methodology to qualify MEMS, by implementing a novel computer-aided inspection (CAI) software framework. This software platform uses data acquired from current MEMS inspection hardware, and applies newly developed analysis algorithms to geometrically characterize a part. This work implements algorithms for all the procedures typical to a CAI program (e.g., point-to-entity assignment, registration, and data analysis) in addition to new techniques suited for inspection of high aspect ratio MEMS. This methodology describes possible registration errors based on the type of geometries being analyzed and the type of data acquired. Analyses of multiple point clouds with the use of fiducial information are shown to provide a critical link between single point cloud analyses that has heretofore been unrealized.

Arguments for miniaturization of a thermal field-flow fractionation system ( and #956;-ThFFF) and fabrication of a micro-scale acoustic field-flow fractionation system ( and #956;-AcFFF) using similar methods was presented. Motivation for miniaturization of ThFFF systems was established by examining the geometrical scaling of the fundamental ThFFF theory. Miniaturization of conventional macro-scale ThFFF systems was made possible through utilization of micromachining technologies. Fabrication of the and #956;-ThFFF system was discussed in detail. The and #956;-ThFFF system was characterized for plate height versus flow rate, single component polystyrene retention, and multi-component polystyrene separations. Retention, thermal diffusion coefficients, and maximum diameter-based selectivity values were extracted from separation data and found comparable with macro-scale ThFFF system results. Retention values ranged from 0.33 to 0.46. Thermal diffusion coefficients were between 3.0ױ0-8 and 5.4ױ0-8 cm2/sec?? The maximum diameter-based selectivity was 1.40. While the concept of an acoustic FFF sub-technique has been around for decades, the fabrication methods have not been available until recently. The theory was developed in full including relating sample physical properties to retention time in the FFF system. In addition to the theory, the design and fabrication of the and #956;-AcFFF was presented. Design results from an acoustic modeling program were presented with the determination of the acoustic resonant frequency. The acoustic-based systems was designed around the model results and characterized by electrical input impedance, fluidic, plate height, polystyrene suspension retention, and polystyrene mixture separation studies. The and #956;-AcFFF system was able to retain a series of nanometer scale polystyrene samples. However, the retention data did not follow normal mode retention but did reveal the location of the steric inversion point for the power level used, around 200 nm. The results of the multiple component separation confirmed this results as the sample, which contained 110, 210, and 300 nm diameter samples, was not resolved but only broadened.

The objective of this research was to develop efficient, non-invasive separation systems for various biological and non-biological substances. One of the major technological pushes in modern bioanalysis instrumentation development is the realization of efficient, miniaturized bioanalysis systems. In this work, three sizes of micromachined electrical field-flow fractionation (m-ElFFF) systems, with complementary on-column electrical and optical detection modalities were fabricated to achieve this objective. Field-flow fractionation (FFF) technology is capable of fractionating (or separating) a wide variety of materials and is capable of hundreds of consecutive analysis runs using a single system. A highly promising sub-technique, particularly for the analysis of biological / biochemical materials, is electrical field-flow fractionation (ElFFF). In this work, microfabrication technologies were used to fabricate m-ElFFF systems that have smaller system volumes, require smaller sample volumes and have shorter run times than their macro-scale counterparts. Direct, on-column detection within the miniaturized separation device improved the resolution, decreased the band broadening, lowered the plate height, and shortened the overall analysis time. Also, the information obtained from these detection systems can be used to elucidate information on the electrical and physical characteristics of a sample. Therefore, complimentary on-column detection systems, were designed, fabricated and characterized. Additionally, the data from the two detection systems was compared and a quantitative correlation was performed, enabling the independent use of each detection system.

A micromachined magnetic field sensing system capable of measuring the direction of the Earths magnetic field has been fabricated, measured, and characterized. The system is composed of a micromachined silicon resonator combined with a permanent magnet, excitation and sensing coils, and a magnetic feedback loop. Electromagnetic excitation of the mechanical resonator enables it to operate with very low power consumption and low excitation voltage. The interaction between an external magnetic field surrounding the sensor and the permanent magnet generates a rotating torque on the silicon resonator disc, changing the effective stiffness of the beams and therefore the resonant frequency of the sensor. MEMS-based mechanically-resonant sensors, in which the sensor resonant frequency shifts in response to the measurand, are widely utilized. Such sensors are typically operated in their linear resonant regime. However, substantial improvements in resonant sensor performance can be obtained by designing the sensors to operate far into their nonlinear regime. This effect is illustrated through the use of a magnetically-torqued, rotationally-resonant MEMS platform. Platform structural parameters such as beam width and number of beams are parametrically varied subject to the constraint of constant small-deflection resonant frequency. Nonlinear performance improvement characterization is performed both analytically as well as with Finite Element Method (FEM) simulation, and confirmed with measurement results. These nonlinearity based sensitivity enhancement mechanisms are utilized in the device design. The complete magnetic sensing system consumes less than 200 microwatts of power in continuous operation, and is capable of sensing the direction of the Earths magnetic field. Such low power consumption levels enable continuous magnetic field sensing for portable electronics and potentially wristwatch applications, thereby enabling personal navigation and motion sensing functionalities. A total system power consumption of 138W and a resonator actuation voltage of 4mVpp from the 1.2V power supply have been demonstrated with capability of measuring the direction of the Earths magnetic field. Sensitivities of 0.009, 0.086, and 0.196 [mHz/(Hz and #903;degree)] for the Earths magnetic field were measured for 3, 4, and 6 beam structures, respectively.

Miniature microphones have numerous applications but often exhibit poor performance which can be attributed to the challenges associated with capacitive detection at small size scales. Optical detection methods are able to overcome some of these challenges although miniaturized integration of these optical systems has not yet been demonstrated. An optical interferometric detection scheme is presented and is implemented using micro-scale optoelectronic devices which are used primarily in fiber optic data transmission. Using basic diffraction theory, a model is developed and used to optimize the micro-optical system within a 1mm3 volume. Both omnidirectional and directional optical microphone designs are presented and a modular packaging architecture is assembled in order to test these devices. Results from the 2mm diameter omnidirectional optical microphone structure demonstrate a 26dBA noise floor. The biomimetic directional optical microphone, which has an equivalent port spacing of 1mm, demonstrates a noise floor of 34dBA. Additionally, these results demonstrate an array of two biomimetic directional optical microphones located on the same silicon chip and separated by less than 5mm. These results confirm the micro-optical detection method as an alternative to capacitive detection especially for miniaturized microphone applications and suggest that this method in its modular packaging architecture is competitive with industry leading measurement microphones.