The application of a thyristor (a four-layer P1-N1-P2-N2 semiconductor structure) as an optical detector is explored. Based on laboratory experiments which demonstrated that this device produces a pulse-mode output to incident light, the thyristor is investigated by comparing the existing theory of static forward-biased operation to simulation results obtained using ATLAS by Silvaco, Inc. The results include identification of the holding point on the IV curve by simulating the junction potential across each junction as a function of current, and demonstration that impact ionization is not a critical factor in thyristor operation. A series of simulations were performed which show that the thyristor can be optimized for use as a detector by decreasing the emitter efficiencies by decreasing the doping in the P1 and N2 layers, or by increasing the doping in the P2 layer; the switching voltage can be controlled by selecting the doping and thickness of the N1 layer. A detector device was designed to allow further testing of the thyristor detector using the ABN CMOS process from AMI Semiconductor via the MOSIS service. The design of this device is discussed and simulated IV curves are presented.

This thesis presents analysis and characterization of performance of a newly designed, multicolor quantum well infrared photodetector (QWIP). Specifically, it focuses on a detector capable of detecting infrared emissions in the near infrared (NIR), mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR). Through photocurrent spectroscopy and performance analysis, this prototype detector can be classified and prepared for possible future use within the U.S. Armed Forces. Certain military applications require a highly accurate, reliable, sensitive, and multispectral infrared detector to identify targets and ensure mission success. By designing and fabricating a multicolor quantum well infrared photodetector, simultaneous detection of targets in the near infrared, mid-wavelength infrared and long-wavelength infrared is possible using only one detector. In addition, power and cooling requirements for quantum well infrared detectors makes them suitable for use in the field. / US Navy (USN) author.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 84-88). Also available via the Internet.

Thesis (M.S.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 109-111). Also available via the Internet.

Thesis (M.S.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaf 45). Also available via the World Wide Web.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2005. / Thesis Advisor(s): Gamani Karunasiri, Douglas Fouts. Includes bibliographical references (p. 73-74). Also available online.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006. / F. Levent Degertekin, Committee Chair ; David S. Citrin, Committee Member ; Paul E. Hasler, Committee Member ; Peter J. Hesketh, Committee Member ; Zhiping Zhou, Committee Member.

Near infrared (NIR) light detection has drawn substantial attentions in a variety of applications. NIR detectors prepared by the solution processable organic semiconductors and organic-inorganic hybrid material systems have the advantages for achieving flexible, light weight and large area NIR detection devices. The aim of this research work is to study the modulation of the photo-generated charge carriers in perovskite and polymer systems for attaining high performing solution-processable NIR phototransistors (PTs) and photodiodes (PDs). In the first part, an organo-lead halide perovskite/polymer bi-layer channel PT is discussed. Compared to the performance of the polymer only PTs, the PTs with a perovskite/polymer hybrid channel exhibit a profound broadband enhancement in photoresponsivity over the light wavelength range from UV to NIR. The improved performance in the hybrid perovskite/polymer PTs is closely associated with the efficient charge separation and transfer between the perovskite and polymer functional layers in the heterojunction. With the success in developing the bi-layer perovskite/polymer PTs, the enhancement in NIR detection is further realized in PTs by incorporating a bulk heterojunction (BHJ) channel. The BHJ channel is formed by blending NIR sensitive polymer donor with three different acceptor materials for enhancing exciton dissociation and charge separation efficiency. It is shown that the use of donor/acceptor BHJ greatly facilitates the dissociation of photo generated excitons. The efficient exciton dissociation helps to boost the utilization of the photo generated excitons, and thereby improves the photoresponsivity. Although the PTs with a BHJ channel possess high photoresponsivity, the photosensitivity of these NIR PTs is still less than satisfactory. The results reveal that a higher activation energy of charge carriers is favorable for a lower carrier density in the channel. While under NIR light illumination, the mobile charge carriers, created due to the dissociation of the photo generated excitons, result in a dramatic increase in carrier density in the active channel. The increase in carrier density under NIR illumination, gives rise to a higher channel current, thereby a higher photosensitivity. A pixel-less NIR imaging device based on light up-conversion from near-infrared to green is demonstrated. A polymer donor/non-fullerene acceptor BHJ serving as the NIR sensitive unit is integrated monolithically with a perovskite-based light emitting diode (LED) unit for achieving light up-conversion from NIR to visible light. The BHJ serves as an NIR sensitive hole injection layer in the perovskite LEDs. Therefore, the efficient electroluminescence in area where NIR-induced efficient charge injection occurs in the LEDs can be displayed clearly, producing the visible light image. The photoresponsivity of perovskite based UV-Visible-NIR photodiodes (PDs) is discussed in the last part of the thesis. A periodic nano-grating hole transporting layer (HTL), formed by the nano-imprinting, is adopted for enhancing the photoresponsivity of the PDs. Theoretical simulation reveals that the periodic nano-grating HTL helps to improve light absorption in the active layer, caused by the enhanced light in-coupling effect. In the meantime, the nano-grating HTL based PDs exhibit weak angular dependency as compared to that of the planar control ones which is appealing for wide angle light detections.

M.Eng. (Electrical and Electronic Engineering) / An in-fibre Bragg grating is a period perturbation of the refractive index of the core of an optical fibre, where the length of the grating is much longer than the period of the grating. These gratings reflect light in a narrow band around a certain optical frequency. This narrow band is shifted in wavelength when the element is strained and is an absolute measure of the strain state of the grating. One way to interrogate this type of sensor is by using it as a mirror of an optical fibre laser, therefby forcing the laser emission band to coincide with the resonant frequency of the grating. In this thesis a theoretical model was developed to describe the operation of optically pumped Er+-doped optical fibre lasers. An explicit expression for the ouput power for a Fabry Perot fibre laser, was derived for the first time. The intracavity power propagation was also solved numerically. An optical fibre laser consisting out of an Er+-doped optical fibre optically pumped at 980nm, was built. A multilayer dielectric stack mirror was deposited on the one fibre endpoint of the laser. The other reflector is an in-fibre Bragg grating with a peak reflectance of 94% at 1548.5nm and a bandwith of <O.3nm. The buildup of the output power of the laser during the deposition, showed good correlation with the predicted values. The length of the active fibre was also varied, and again the theory could correctly predict the output power as well as the laser pump threshold. A scanning type of Sagnac interferometer was investigated as a possible wavelength demodulation system for the fibre laser sensor. With some alterations this system shows merit as an inexpensive and effective way to monitor the wavelength shifts in in-fibre Bragg gratings.