Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Fabrication and Process Development for an Integrated Optical MEMS Microsystem in Indium Phosphide(2013) Siwak, Nathan Paul; Ghodssi, Reza; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation presents the design, fabrication, and evaluation of the first monolithically integrated MEMS resonant sensor system realized in the InP-InGaAs material family. The integration of a MEMS sensor along with the facilitating optical interrogation platform provides for increased manufacturing scalability, sensitivity, and reduced measurement noise and device cost. The MEMS device presented in this dissertation consists of an Indium Phosphide (InP) cantilever waveguide resonator whose displacement is measured optically via a vertically integrated laser diode and waveguide photodetector. All three major components of the sensor were integrated in a single 7.1 µm thick molecular beam epitaxy (MBE) epitaxial growth, lattice matched to an InP substrate. Full fabrication of the integrated MEMS device utilizes 7 projection lithography masks, 4 nested inductively coupled plasma (ICP) etches, and over 60 discrete processing steps. This dissertation focuses on the integration design and the development of specific III-V semiconductor fabrication processes in order to completely fabricate and realize these devices, including specialized ICP etching steps and a MEMS undercutting release etch. The fabricated devices were tested and characterized by investigating the separate component subsystems as well as the total combined system performance. Investigation of device failure and performance degradation is performed and related to non-idealities in the device fabrication and design. A discussion of future work to improve the performance of the system is presented. The work in this dissertation describing the successful fabrication process and analysis of such a complex system is a milestone for III-V based optical MEMS research and will serve as the groundwork for future research in the area of optical MEMS microsystems.Item Monolithic In-Plane Tunable Optical Filter(2008-08-11) McGee, Jonathan Adam; Ghodssi, Reza; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis presents the development of a Micro-Electro-Mechanical System (MEMS) monolithic in-plane tunable optical filter in both Indium Phosphide and Silicon. By placing one mirror of a waveguide-based Fabry-Perot interferometer on an electrostatically-actuated beam, a tunable filter is constructed. This is the first demonstration of a waveguide-coupled MEMS tunable optical filter in any material system. Filters with a tuning range of 40 nm from a wavelength 1550 nm with a linewidth of 35 nm are demonstrated. Future work will concentrate on improving the filter's optical characteristics, limited by etch-induced facet roughness, and integration with active photonic devices.Item Indium Phosphide MEMS Cantilever Waveguides with Integrated Readout for Chemical Sensing(2007-11-26) Siwak, Nathan Paul; Ghodssi, Reza; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis presents the development towards an integrated, monolithic, micro-electro-mechanical system (MEMS) cantilever waveguide resonator chemical sensor using the III-V semiconductor indium phosphide (InP). Waveguide cantilevers with resonant frequencies as high as 5.78 MHz, a quality factor of 340, and a sensitivity of 4.4x10^16 Hz/g are shown for the first time in this system. The first demonstration of vapor detection using the sensor platform is performed utilizing an organic semiconductor Pentacene absorbing layer. Vapors are measured from mass shifts of 6.56x10^-14 and 7.28x10^-14 g exhibiting a mass detection threshold of 5.09x10^-15 g. The design, fabrication, and testing of an integrated waveguide PIN photodetector with an In0.53Ga0.47As absorbing layer is reported. Dark currents as low as 8.7 nA are measured for these devices. The first demonstration of a resonating cantilever waveguide measurement is also performed using the monolithically integrated waveguide photodiodes with uncertainty of less than ± 35 Hz. Finally, a future outlook is presented for this monolithic InP sensor system.