QC 351 A7 no. 80 / This dissertation presents a theoretical investigation into the production, evolution, and asymptotic form of chirped pulses in homogeneously and inhomogeneously broadened laser amplifiers. Amplifier equations of motion are obtained in a form appropriate for dealing with such frequency-modulated pulses. The transient response of laser amplifiers to variously chirped Gaussian input pulses is studied parametrically using numerical solutions of the amplifier equations. The chirping mechanisms of the intensity dependence (Kerr effect) and the quadratic frequency dependence of the index of refraction are discussed briefly, as are the chirps produced by them and the amplification of Gaussian pulses in their presence. The amplifier whose host exhibits these dispersive effects is treated as a sequence of pairs of slices. One of each pair amplifies and exhibits the Kerr effect; the other has an index with a quadratic frequency dependence. This slice model is used to obtain steadystate pulses in both homogeneously and inhomogeneously broadened amplifiers whose host indexes have a quadratic frequency dependence. The steady-state pulse characteristics are determined as functions of amplifier parameters and the index curvature. The principal results are as follows: The homogeneously broadened amplifier responds predominately to the temporal character of a chirped input pulse whereas the inhomogeneously broadened amplifier response depends primarily upon the pulse spectrum. Of three important concepts (area theorem, echoes, and optical nutation) used to describe unchirped pulse amplification in inhomogeneously broadened media, only photon echo is useful when pulses are more than slightly chirped. The presence of the Kerr effect can produce significant chirps on large pulses. Amplification in the presence of the Kerr effect produces pulses strikingly similar to experimental results. Quadratic frequency dependence in the index has very little influence on most pulses in short amplifiers but has a cumulative effect in long amplifiers and laser oscillators. Chirped steady-state pulses exist in both homogeneously and inhomogeneously broadened amplifiers when the host index has such frequency dependence. In the homogeneously broadened case, they exist at relative gain levels dramatically below other theoretical predictions. They occur in the inhomogeneously broadened case only for the smaller index curvatures.

Introdução: A psoríase é uma doença inflamatória crônica com prevalência estimada em 2% da população mundial. As alterações ungueais estão presentes em cerca de 50% dos casos e chegam a acometer até 80% dos pacientes em algum momento da vida. Elas costumam ser resistentes aos tratamentos convencionais e possuir caráter recidivante. O laser de corante pulsado (LCP) tem surgido como alternativa terapêutica. Objetivos: Avaliar a eficácia do LCP na psoríase ungueal e o impacto do tratamento na qualidade de vida. Métodos: Para este estudo foram selecionados quatorze pacientes com diagnóstico de psoríase das unhas provenientes do ambulatório de Dermatologia do Hospital de Clínicas de Porto Alegre ou de clínicas privadas, tratados com aplicação do LCP com fluência de 6J/cm2 e duração de pulso de 0,45ms nas unhas acometidas em sessões mensais por três meses e uma nova visita, para seguimento, após 90 dias era realizada. A avaliação objetiva dos resultados foi realizada pelo índice de gravidade da psoríase ungueal (NAPSI) e avaliação subjetiva através de registro fotográfico das unhas acometidas na primeira e na terceira sessões e 90 dias após a última sessão. O índice de qualidade de vida para dermatologia (DLQI) foi respondido na primeira e 90 dias após a última sessão. Resultados: A mediana de melhora nas contagens do NAPSI total, do NAPSI do leito e do NAPSI da matiz ungueais foram, respectivamente, de 44,15% (P=0,002), 50% (P=0,033) e 65,1% (P=0,024). Os pacientes apresentaram também melhora significativa no DLQI após o tratamento, com mediana de 40%. Conclusões: O LCP pode ser considerado uma alternativa de tratamento para psoríase ungueal. / Introduction: Psoriasis is a chronic inflammatory disease with an estimated prevalence of 2% of the world population. The nail changes are present in about 50% of cases and affect up to 80% of patients at some point in life. Nail psoriasis is often refractory to conventional treatments. Pulsed dye laser (PDL) has emerged as an alternative therapy. Objectives: To evaluate the efficacy of PDL in nail psoriasis and the impact of treatment on quality of life. Methods: For this study, were selected eleven patients diagnosed with nail psoriasis from the Dermatology clinic of the Hospital de Clínicas de Porto Alegre or private clinics. PDL was applied in affected nails with fluency of 6J/cm2 and pulse duration of 0,45ms in monthly sessions for three months. A follow-up visit after 90 days was done. The outcome assesment was made by the Nail Psoriasis Severity Index (NAPSI) and photographic records in the basement, in the third session and in the follow-up. The Dermatology Life Quality Index (DLQI) was answered in the baseline and in the follow-up. Results: The median improvement in the scores of the overall NAPSI, nail bed NAPSI and nail matrix NAPSI were respectively 44.15% (P = 0.002), 50% (P = 0.033) and 65.1% (P = 0.024). The patients also had significant improvement in DLQI after treatment with a median of 40%. Conclusions: PDL can be considered an alternative treatment for nail psoriasis.

M.S. / Electrical Engineering / The efficient coupling between a semiconductor laser and a single-mode fiber is a key element for fully utilizing the single-mode fiber for the optical communication. In this thesis, the Gaussian beam approach is used for analyzing the coupling of a single-mode laser diode to a single-mode optical fiber by a microlens. Two analytical methods based on both the ABCD law and the diffraction theory are presented. The effect of a microlens on both the phase and amplitude of a Gaussian beam are discussed in detail. The presented analysis specifies the optimum coupling in terms of laser and fiber parameters and the laser to fiber distance. Furthermore, the coupling efficiencies achievable in hemispheric and etched conical microlenses systems are explicitly compared. The present analysis shows that a coupling efficiency as high as 62% is achievable with the optimal choice of laser and fiber parameters. Additionally, theoretically obtained coupling efficiency is compared with the experimental data for both butt and etched fibers.

M.S. / Electrical Engineering / Surface-emitting laser diodes are of interest for various applications such as monolithic two-dimensional arrays and optical interconnects for integrated optics. Therefore, it is essential to characterize these lasers. The farfield radiation pattern is one of the important characteristics of a laser diode. In this thesis the farfield of a surface-emitting laser diode with a turning mirror is modeled and measured. The computer simulation uses a rigorous theoretical expression for the field at the output mirror laser-air interface derived by Davies and Walpole and then using a modified form of the Kirchoff diffraction integral to generate the farfield. The computer modeling is done for both flat 45° and parabolic turning mirrors. Experimental data were also obtained for a surface-emitter with a 45° straight turning mirror. This mirror was fabricated using the focused ion beam micromachining technique developed at OGC. In the case of the parabolic turning mirror, the experimental results published by Liau and Walpole were used. A comparison of theoretical and experimental results for the two shapes of mirrors is also presented.

Graduation date: 1991

Thèse de doctorat : Electronique : Metz : 2006. / Thèse soutenue sur ensemble de travaux. Bibliogr. p. 137-144. Index des ill. p.13-15. Index des tables p. 17. Liste des acronymes p. 145-146.

Thesis (Ph. D.)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xv, 145 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Betty Lisle Anderson, Dept. of Electrical Engineering. Includes bibliographical references (p. 140-145).

Thesis (Masters)--California Institute of Technology, 1978. / Title from home page. Viewed 02/09/10. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references.

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