Tunable diode laser spectroscopy and the Beer-Lambert relation has been used to measure the absorption of water vapor both in an absorption cell and in a shock tube. The purpose of this thesis is to develop a laser diagnostic capable of determining species concentration. The correlation between species concentration and absorption is known, and if one is known the other can be calculated. A diode laser was obtained which has a tunable range of 1325.7 - 1400.8 nm and is centered at 1384 nm. An experimental setup was created in which the laser was used to obtain absorption spectroscopy data for water vapor within two separate scenarios- in an absorption cell and in a shock tube. A model was constructed which enabled the calculation of the Voigt profile which in turn was used to determine the absorption coefficient and ultimately enable the utilization of absorption spectroscopy principles to determine species concentration and/or absorption percentage. The experiments for the absorption cell were performed at room temperature. Twenty runs were performed and the average error for all runs was less than one percent. Three runs were performed for the shock-tube experiments. The absorption was calculated at three times- prior to the arrival of the shock, after the incident shock passed, and after the reflected shock passed. The temperatures for these conditions were 296K, 1060K, and 2000K respectively. These experiments showed reasonable agreement with theoretical calculations.

This thesis utilized the characteristics of the external cavity system including the wavelength tuning and the multi-channel output, and using the Quantum Confined Stark Effect (QCSE) by adding the bias on the electro-absorption modulator to build a new method of the Q-switched modulation .The method made the wavelength tuning and multi-channel output of high speed Q-switched external cavity semiconductor laser with the colinear output come true . The system of the external cavity semiconductor laser with the electro-absorption modulator making of the VCSEL with the wavelength 850nm and 830nm could be modulated to 63ns . The tuning range could be up to 0.9nm . Each of the channel would be separated into 0.2nm . We could obtain the two channels output by using the double electro-absorption modulators on the specific position .The distance of the wavelength is 4.61nm.

Abstract Two kinds of unsaturated polyesters¡¦ prepolymers were synthesized via two steps. For the hard segment, isophthalic acid was reacted with 1,2-propanediol first, then maleic anhydride was added to yield a copolyester with Tg around 13

Abtract In this thesis, our purpose is to improve the refractive index models for direct-gap semiconductors. For refractive index spectrum of direct-gap compound semiconductors, most experimental data is available only bellow the bandgap absorption edge. For used in the optimum design of eltro-optic devices, such as waveguide, electro-absorption modulator and Mach-Zehnder interferometer. We have to utilize a little experimental data to extend refractive index spectrum to near and just above the band-gap edge. We have known that square of refractive index ( ) is dielectric constant ( ), so we decompose the dielectric constant ( ) into the part of band-to-band absorption and another part of single-oscillator high energy absorption. For the part of band-to-band absorption, we added broadening parameter ( ) and used Kramers-Kronig relation to transform the absorption coefficient into dielectric constant. For another part of single-oscillator high energy background absorption, we first cut the absorption part form experimental data and then use Sellmeier¡¦s equation to fit the residue data. Finally, recombine all equations and extend refractive index spectrum to near and just above the band-gap edge. We successfully built whole model and confirm our model with GaAs. The calculation result on GaAs shows an excellent agreement with the reported experimental data. Furthermore, We apply our model to direct-gap binary¡Bternary and quaternary compounded materials and extend our model to near and just above the band-gap edge very well.

The key feature of the Integrating Cavity Absorption Meter (ICAM) is that it produces an isotropic illumination of the liquid sample and thereby dramatically minimizes scattering effects. The ICAM can produce an effective optical path length up to several meters. As a consequence, it is capable of measuring absorption coefficients as low as 0.001 m-1. The early version of the ICAM was used previously to measure the absorption spectrum of pure water over the 380-700 nm range. To extend its range into the ultraviolet, several modifications have been completed. The preliminary tests showed that the modified ICAM was able to measure the absorption of pure water for the wavelength down to 300 nm. After extensive experimental investigation and analysis, we found that the absorption of Spectralon® (the highly diffusive and reflective material used to build the ICAM) has a higher impact on measurements of absorption in the UV range than we had expected. Observations of high values for pure water absorption in the UV, specifically between 300 and 360 nm, are a consequence of absorption by the Spectralon®. These results indicated that even more serious modifications were required (e.g. Spectralon® can not be used for a cavity in the UV). Consequently, we developed a new diffuse reflecting material and used fused silica powder (sub-micron level) sealed inside a quartz cell to replace the inner Spectralon® cavity of the ICAM. The new data is in excellent agreement with the Pope and Fry data (380-600 nm) and fills the gap between the 320 nm data of Quickenden and Irvin and 380 nm data of Pope and Fry. We present definitive results for the absorption spectrum of pure water between 300 and 600 nm.

The technology of high-power light-emitting diodes (LEDs) is mature. In this study, the LEDs were aged through high temperature to understand the packaging failure mechanisms under lasting lighting. The Tracepro optics simulation software is also applied to analyze the radiation pattern decay caused by curvature variation and material aging. In the experiment procedure, the LEDs of three manufactures were placed in aging ovens in three different temperatures set at 95¢J, 85¢J, and 65¢J. The experiment results showed that the LED failures were the lens and silicon gel yellowing, silicon gel carbonization, lens slightly chapping, silicon cracks, bubbles generated between lens and silicon gel, and chip damage induced reverse current increase during the aging experiment. We observed the failure mechanism in reduction of optical power at 90%, 80%, 70%, 60%, 50% original power. Furthermore, the failure mechanisms of different from the manufactures is also compared in this work. The LED packages have long lifetime without silicon gel carbonization. In simulation study, a gap of lens deformation showed a reduction at -60¢X~-40¢X and 40¢X~60¢X of the radiation pattern. The LED modules also showed that the silicon gel and PC absorption coefficient increased. Material absorption coefficient increased more in the short wavelength showed 149mcd at ¡Ó60¢X of the radiation pattern.

"none"

Thèse doctorat : Acoustique : Villeurbanne, INSA : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 151-160.

Thesis (Ph. D.)--University of Michigan, 1923.

Thesis (Ph. D.)--University of Rochester, 1948. / Each part preceded by half-title not included in the foliation (3 leaves). Reproduced from type-written copy. Bibliography: leaves 56-58.