Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Agrawal, Brij ; Kim, Jae Jun. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: High Energy Laser (HEL), beam control, Fast Steering Mirror (FSM), two axis gimbal, stabilization, video tracking, feedforward control, adaptive filter. Includes bibliographical references (p. 69). Also available in print.

The goal of this research work is to develop and analyze Quantum Dot (QD) lasers aimed at improving high power performance which is crucial for numerous scientific, military and industrial applications. Fundamentally two dissimilar types of lasers are investigated: namely bipolar electron-hole laser and unipolar quantum cascade laser. Planar quantum well (QW) laser diodes are already well-established as commercially available high power semiconductor lasers. However these lasers are unable to deliver power greater few 10's of watts due to reduction in efficiency at longer cavity lengths. This limitation arises from inherent optical losses tied to the two-dimensional density of available states in QWs. A novel approach is proposed here to circumvent this limitation by introducing self-assembled QDs into the laser cavity which due to their delta-like discrete density of states promise to reduce the optical losses by at least an order of magnitude, hence allowing cavity length to increase proportionally. Detailed analysis based on harmonic oscillator model and solution at quasi-equilibrium condition reveal that total internal losses as low as 0.05 per cm⁻¹ can be achieved in a QD laser enabling it to deliver 50 watts of power from each bar while maintaining efficiency close to 90%. In order to take full advantage of the discrete atom-like behavior, it is also of utmost importance to reduce the inhomogeneous broadening of the dot distribution originating from size fluctuation. Experimental data of ultra narrow linewidth InAs quantum dots having linewidth of only 22 meV is presented. Research attempt has been taken to integrate these narrowly distributed dots into a workable structure. Preliminary data shows that these dots are extremely sensitive to the laser material which calls for careful optimization of the entire structure. As for the unipolar QCL, it is shown that internal absorption caused by phonon emission of electrons in a planar quantum cascade laser represents a possible limitation to the maximum operating efficiency. Possibility of reducing this absorption is explored and it is optimistically asserted that introducing QDs into the gain stage of a QCL can eliminate this internal loss mechanism, thus greatly improving high power operating characteristics.

The remainder of this thesis considers the longitudinal coherence of the copper vapour laser, and describes the design and initial performance of a narrow bandwidth dye laser for use with a CVL. Careful construction of a grazing-incidence grating arrangement similar to that of Littman has resulted in a laser which is particularly simple to align and which promises ease of tuning over a wide range. Operation confined to a single longitudinal mode has been demonstrated, corresponding to single shot bandwidths below IGHz, but instabilities caused by vibration and uneven dye flow broaden the time-averaged width to around 3GHz. Suggested improvements have not yet been implemented.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 96-99). Available also in a digital version from Dissertation Abstracts.

Recent advances in the development of high power short pulse laser systems has opened a new regime of laser plasma interactions for study. The thesis is presented in two parts. In Part I, we consider the implications of these high power laser pulses for the interaction with a uniform underdense plasma, with particular regard to plasma-based accelerators. We present a scheme for the resonant excitation of large electrostatic Wakefields in these plasmas using a train of ultra-intense laser pulses. We also present an analysis of the resonant mechanism of this excitation based on consideration of phase space trajectories. In Part II, we consider the transition from linear Resonance Absorption to nonlinear absorption processes in a linear electron density profile as the intensity of the incident radiation increases and the scale length of the density profile decreases. We find that the electron motion excited by an electrostatic field exhibits some extremely complicated dynamics with bifurcations to period doubling and chaotic motion as the strength of the driving field is increased or the density scale length is decreased. We also present some results obtained from particle simulations of these interactions.

No description available.

The free electron laser (FEL) is among the latest technologies of interest to the U.S. military, in particular, the Navy. In naval applications, FEL laser would serve as a self-defense weapon system, protecting the ship from an array of threats including anti-surface cruise missiles and small boats. This system's potential range and deep magazine makes it ideal as point defense against incoming missiles. Its inexpensive cost of only a few dollars per engagement and multi-mission capability makes this future weapon system superior to the short-range missile-defense systems employed today. The most powerful FEL is currently located in Jefferson Lab, operating at 10 kW, two orders of magnitude short of the 1 MW power level required for weapons application. This thesis will describe the components and theory of operation of the FEL, as well as analyze two competing designs for the next step in the evolution of the future weapon system, the 100 kW FEL, proposed by Brookhaven and Los Alamos National Labs. Due to advances in NPS simulation techniques for the amplifier configuration, a more in depth analysis including the effects of electron beam tilt and shift is performed for the first time on these proposed designs.

No description available.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, December 1997. / Includes bibliographical references. Also available on the Internet.