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Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2008

Air Force Institute of Technology

Plasma and Beam Physics

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

Electronic State Distributions Of Y Ba2Cu3O7-X Laser Ablated Plumes, Patrick D. Kee Sep 2008

Electronic State Distributions Of Y Ba2Cu3O7-X Laser Ablated Plumes, Patrick D. Kee

Theses and Dissertations

The application of spectral and imagery diagnostics to YBa2Cu3O7 (YBCO) laser-ablated plumes was systematically studied to determine their effectiveness for process control. Emission signatures were collected for plumes created by ablating bulk YBCO with a pulsed laser source. A KrF (λ=248 nm) laser source operating at 4-10 J/cm2 at a 4-10 Hz pulse repetition frequency was used to ablate a bulk YBCO target at O2 background pressures ranging from 50 to 400 mTorr. Emission spectra were collected over the 500 to 860 nm bandpass at distances from the target ranging from 31.4 to …

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Characterizing Effects And Benefits Of Beam Defocus On High Energy Laser Performance Under Thermal Blooming And Turbulence Conditions For Air-To-Ground Engagements, Scott N. Long Jun 2008

Characterizing Effects And Benefits Of Beam Defocus On High Energy Laser Performance Under Thermal Blooming And Turbulence Conditions For Air-To-Ground Engagements, Scott N. Long

Theses and Dissertations

This dissertation makes contributions towards knowledge of optimizing of laser weapon performance when operating in the air-to-ground (ATG) regime in thermal blooming conditions. Wave optics modeling techniques were used to represent laser weapon performance in a high fidelity sense to allow progress to be made toward improving lower-fidelity scaling laws that can be used in systems level analysis which has need for better representations of thermal blooming. Chemical-oxygen iodine laser (COIL) based weapon systems that operate near the ground will experience thermal blooming due to atmospheric absorption if output power is sufficiently high. The thermal lens in the ATG case …

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Demonstration Of A Strategy To Perform Two-Dimensional Diode Laser Tomography, Ryan N. Givens Mar 2008

Demonstration Of A Strategy To Perform Two-Dimensional Diode Laser Tomography, Ryan N. Givens

Theses and Dissertations

Demonstration of a strategy to perform two-dimensional diode laser tomography using a priori knowledge from symmetry arguments and computational fluid dynamic (CFD) calculations is presented for a flat flame burner. The strategy uses an optimization technique to determine flame diameter and location using a vector quantization approach. Next, the variance in a training set, produced from CFD calculations, is captured using principal components analysis. The information in the training set allows interpolation between beam paths resulting in temperature and density maps. Finally, the TDLAS temperature and density maps are shown to agree with traditional thermocouple measurements of the flat flame …

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Modulation Response Of Twin Optically Coupled Diode Lasers, Eric M. Golden Mar 2008

Modulation Response Of Twin Optically Coupled Diode Lasers, Eric M. Golden

Theses and Dissertations

Diode lasers are useful in military and commercial applications that have strict requirements for size, weight and power. This includes the use of diode lasers in optoelectronic and photonic integrated circuits, which can lead to new technologies in optical communications and optical interconnects in high performance computing systems. For these systems to be effective, the diode laser must be modulated at frequencies beyond current limits which are typically a few GHz. This barrier can be broken by optically coupling a diode laser with a similar laser. A set of single mode rate equations models the dynamics of twin optically coupled …

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Production And Characterization Of Femtosecond-Laser-Induced Air Plasma, David R. Armbruster Mar 2008

Production And Characterization Of Femtosecond-Laser-Induced Air Plasma, David R. Armbruster

Theses and Dissertations

The purpose of this research was to produce, characterize, and optimize laser induced air plasma as a preliminary step in using the plasma as a source of terahertz radiation. An 800 nanometer, 50 femtosecond, 0.75 Watt, pulsed Ti:Sapphire laser system was used as the source infrared beam. A beam expander was used to expand the beam to a diameter of approximately 6.5 mm, and the beam was focused through a 25 mm focal length achromatic lens to produce laser-induced plasma in ambient air. A 40 kHz ultrasonic transducer was used to detect the plasma. A second harmonic generation crystal was …

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Ultrafast Spectroscopy Of Mid-Infrared Semiconductors Using The Signal And Idler Beams Of A Synchronous Optical Parametric Oscillator, Richard M. Derbis Mar 2008

Ultrafast Spectroscopy Of Mid-Infrared Semiconductors Using The Signal And Idler Beams Of A Synchronous Optical Parametric Oscillator, Richard M. Derbis

Theses and Dissertations

Mid-Wave Infrared (MWIR) semiconductors are of use to the Air Force for several applications. Ultrafast spectroscopy can be used to better quantify the effectiveness of semiconductor opto-electronic devices. The objective of this thesis was to improve the procedure for taking ultrafast, time-resolved measurements of photoluminescence from MWIR semiconductors. Previous work has used a mode-locked titanium sapphire (Ti:Saph) laser to excite the semiconductor sample and to upconvert the photoluminescence from the semiconductor. Work completed in this thesis improved on the techniques developed during previous work. A synchronous Optical Parameter Oscillator (OPO) will be used to convert the Ti:Saph laser (0.830 µm) …

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Measuring Dispersion In Laser Cavity Mirrors Using White-Light Interferometry, Allison S. Goodspeed Mar 2008

Measuring Dispersion In Laser Cavity Mirrors Using White-Light Interferometry, Allison S. Goodspeed

Theses and Dissertations

Terahertz radiation is an emerging field that has far reaching applications. There is a need for portable and affordable terahertz sources that may be used for detection of structural weaknesses in aerospace composites. One possibility for terahertz generation is a femtosecond Cr:LiSAF laser. However, controlling intracavity dispersion is necessary in order to get the ultrashort pulses needed to generate terahertz radiation. This research measures dispersion of the chirped femtosecond intracavity mirrors by employing white-light interferometry and explains the theory behind the curve-fitting process used to calculate dispersion. To compensate for the narrow reflectivity band of the mirrors, a CaF2 …

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