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This thesis presents the design, fabrication, and testing of novel MEMS pressure and temperature sensors fabricated on optical fiber end faces. A simple micromachining process compatible with MEMS was developed in fabricating sensors directly on optical fibers. The pressure sensor configuration involves anodic bonding of a piece of an extremely thin silicon wafer onto the fiber end face over a cavity etched in the central portion of the fiber end face. Final device diameter is thus the same as that of the optical fiber. The temperature sensor is based on anodically bonding a thin piece of silicon onto the fiber end face. The pressure sensors were fabricated on 400 µm diameter fibers while temperature sensors were fabricated on both 200 and 400 µm diameter fibers. Pressure measurements were made over the 14 to 80 psi range while temperature measurements were made over the 23 to 300 0 C range. Pressure sensor sensitivities of 0.1 mV/psi and 0.2 mV/psi were obtained. The pressure sensors were designed with cavity diameter d=150 µm, and cavity depth h=0.640 µm. Diaphragm thickness for the two sensors were t=7.1, and t=3.4 µm. Higher sensitivity was achieved by design of a sensor with the thinner diaphragm. A sensor array fabrication effort demonstrated that our micromachining process could be extended to simultaneous processing of an array of fibers. The temperature sensor was fabricated by bonding 3.1 µm thick silicon onto the fiber end face. An oxidant-resistant encapsulation scheme for the temperature sensor was proposed, namely aluminum coated silicon nitride (Al/Si 3 N 4). The uncoated side of silicon was bonded to a fiber end face using the anodic bonding method. The measured values of κ φ =λ m-1 dλ m /dT for capped and uncapped sensors were κ φ =(7.5±0.6)×10-5 / 0 C, and κ φ =(7.2±0.1)×10-5 / 0 C respectively. The measured κ φ value for the uncapped sensor is equal to that which was iii determined using the published material properties for crystalline silicon (κ φ 7.9×10-5 / 0 C) within measurement uncertainty. The micromachining process developed for micromachining fiber end faces along with the bonding of silicon to fiber end faces can be extended to fabrication of other MEMS based microoptic devices where fiber optic interrogation is advantageous. First of all, I want to thank my co-advisers Professors Joseph T. Boyd, and Howard E. Jackson for their invaluable guidance, and generous support throughout my thesis project. Their formative influence on my way of thinking about research will continue well beyond the completion of this thesis. I am indebted to Dr. Boyd for introducing me to an exciting thesis project in the area of Optical MEMS and supervising me in such a manner that enabled me to progress and learn in a timely manner. I feel fortunate in associating such a kind and good person. This thesis would not exist without Dr. Jackson, who accepted me as a doctoral student, at a very difficult time of my life, and who believed in my declaration of dedication. His professionalism, guidance, energy, humor...

PACS 73.40. Qv, Gallium nitride is known to have both piezoelectric and piezoresistive properties (A. D. Bykhovski et al., Appl. Phys. Lett. 68, 818 (1996) [1] and R. Gaska et al., Appl. Phys. Lett. 71, 3817(1997) [2]). GaN's inertness to corrosive chemicals and robustness to high temperature makes it a potential candidate for harsh environment pressure sensor applications. We report piezoresistive and piezoelectric gauge factor measurements done on n-GaN. Resistor structures were fabricated on 1×1018 cm -3 n-type doped 250 µm thick GaN and subject to three point bend tests. The gauge factor was measured to be 28 at room temperature. The sample was also heated to 125 °C and the gauge factor was measured to be 17. Metal-InsulatorSemiconductor capacitor structures were fabricated on 7×1016 cm -3 n-typed doped 2 µm thick GaN grown by MOCVD. Three point bend tests were done on the capacitors. The gauge factor was determined at both room temperature to be 167 and at 250 °C to be 104.

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We report in this paper the use of Si/PLZT technology in the fabrication of 2-D electrically and optically addressed spatial light modulators. First, a 12 x 12 electrically matrix addressed array was fabricated using simultaneous laser assisted diffusion and crystallization. Then, NMOS transistors exhibiting electron mobility of 550 cm(2)/V-s were fabricated in each unit cell of the matrix array and used to control the PLZT modulator. A dynamic range of 35:1 was achieved. A 16 x 16 optically addressed SLM array was also fabricated. In this case, to improve the optical sensitivity, a three-transistor CMOS detector-amplifier circuit was included in each unit cell of the array.