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Degenerate Four Wave Mixing of Short and Ultrashort Light Pulses

Description: This dissertation presents experimental and theoretical studies of transient degenerate four wave mixing (DFWM) in organic dyes. Chapter 1 is an introduction to DFWM. Chapter 2 describes DFWM experiments that were performed in the gain medium of a dye laser. Chapter 3 presents the theory of DFWM of short pulses in three level saturable media. Chapter 4 presents DFWM experiments of femtosecond pulses in the saturable absorber of a passively modelocked ring dye laser. Chapter 5 presents the theory of DFWM of ultrashort pulses in resonant media.
Date: August 1984
Creator: McMichael, Ian C. (Ian Charles)
Partner: UNT Libraries

Absolute Photodissociation Quantum Yields for the NO3 Free Radical

Description: The nitrate free radical was photolyzed by a pulsed tunable dye laser between 470 and 685 nm, at 296 K, and in the presence of 10 torr N{sub 2}. The two product channels, NO + O{sub 2} and NO{sub 2} + O, were measured by resonance fluorescence of NO or of O. Absolute calibration of the method was achieved by in situ ultraviolet photolysis of NO{sub 2}, which yields both NO and O. With these data on photochemical yields, the photolysis coefficients for the two product channels at the surface of the earth with an overhead sun over wavelengths 470-700 nm are calculated to be j{sub 1}(NO + O{sub 2}) = 0.022 {+-} 0.007 s{sup -1} and j{sub 2}(NO{sub 2} + O) = 0.18 {+-} 0.06 s{sup -1}.
Date: January 1, 1980
Creator: Magnotta, Frank & Johnston, Harold S.
Partner: UNT Libraries Government Documents Department

An Optical Offgas Sensor Network Incorporating a HG Cavity Ringdown Spectrometer and IR Diode Lasers

Description: A multi-element cavity ringdown system was evaluated with the objective of developing an intelligent sensor network to be incorporated into the control systems for advanced coal combustion facilities. Using a combination of a YAG-pumped dye laser and a tunable NIR/IR laser a dual cavity was constructed and a labview program was developed to provide multi-channel, real-time data to permit the real-time monitoring of typical exhaust emission gases, (for example: CO{sub 2}, SO{sub 2}, and mercury) of concern to the next generation of coal-powered facilities.
Date: December 30, 2007
Creator: Miller, George P.
Partner: UNT Libraries Government Documents Department

Synthetic thrombus model for in vitro studies of laser thrombolysis

Description: Laser thrombolysis is the controlled ablation of a thrombus (blood clot) blockage in a living arterial system. Theoretical modeling of the interaction of laser light with thrombi relies on the ability to perform in vitro experiments with well characterized surrogate materials. A synthetic thrombus formulation may offer more accurate results when compared to in vivo clinical experiments. The authors describe the development of new surrogate materials based on formulations incorporating chick egg, guar gum, modified food starch, and a laser light absorbing dye. The sound speed and physical consistency of the materials were very close to porcine (arterial) and human (venous) thrombi. Photographic and videotape recordings of pulsed dye laser ablation experiments under various experimental conditions were used to evaluate the new material as compared to in vitro tests with human (venous) thrombus. The characteristics of ablation and mass removal were similar to that of real thrombi, and therefore provide a more realistic model for in vitro laser thrombolysis when compared to gelatin.
Date: July 1, 1998
Creator: Hermes, R.E. & Trajkovska, K.
Partner: UNT Libraries Government Documents Department

Measurements of the Lick Observatory Sodium Laser Guide Star

Description: The Lick Observatory guide star laser has provided a beacon sufficient to close the adaptive optics loop and produce corrected images during runs in 1996 and 1997. This report summarizes measurements of the wavefront quality of the outgoing beam, photoreturn signal from the sodium beacon, and radiance distribution of the guide star on the sky, and follows with an analysis of the impact of the laser on adaptive optics system performance.
Date: March 1, 1998
Creator: Gavel, D. T.
Partner: UNT Libraries Government Documents Department

Design of a protocol for combined laser hyperthermia-photodynamic therapy in the esophagus

Description: Photodynamic laser therapy (PDT) for esophageal cancer has recently been studied in animal and clinical trials. In several animal experiments a synergetic effect was found by simultaneously applying PDT and hyperthermia (HT). In this paper an optical fiber system is described which can be used in the esophagus for combined PDT with a 1 W dye laser and HT with a 15--40 W Nd-YAG laser. Phantoms were developed to simulate the geometry of the esophagus using cow muscle. The spatial-temporal temperature field during HT was measured. The results were compared with calculations using a coupled Monte Carlo laser transport/finite difference heat transport model using the LATIS computer program. Measurements and calculations yield a realistic description of the temperature distribution during HT under various experimental conditions. The LATIS program allows the prediction of the effects of blood perfusion for in-vivo situations. The results show that the perfusion has considerable influence on the temperature field, which must be considered for in-vivo applications.
Date: February 1, 2000
Creator: London, R A; Eichler, J; Liebetrudt, J & Ziegenhagen, L
Partner: UNT Libraries Government Documents Department

Laser dye technology

Description: The author has worked with laser dyes for a number of years. A first interest was in the Navy blue-green program where a flashlamp pumped dye laser was used as an underwater communication and detection device. It made use of the optical window of sea-water--blue for deep ocean, green for coastal water. A major activity however has been with the Atomic Vapor Laser Isotope Separation Program (AVLIS) at the Lawrence Livermore National Laboratory. The aim here has been enriching isotopes for the nuclear fuel cycle. The tunability of the dye laser is utilized to selectively excite one isotope in uranium vapor, and this isotope is collected electrostatically as shown in Figure 1. The interests in the AVLIS program have been in the near ultra-violet, violet, red and deep-red.
Date: September 1, 1999
Creator: Hammond, P R
Partner: UNT Libraries Government Documents Department

Design and performance of a laser guide star system for the Keck II telescope

Description: A laser system to generate sodium-layer guide stars has been designed, built and delivered to the Keck Observatory in Hawaii. The system uses frequency doubled YAG lasers to pump liquid dye lasers and produces 20 W of average power. The design and performance results of this laser system are presented.
Date: May 18, 1998
Creator: Friedman, H. W., LLNL
Partner: UNT Libraries Government Documents Department

Laser enhanced microwave plasma isotope separation. Final report, September 30, 1992--September 29, 1995

Description: The experimental research was to focus on laser excitation of a low abundance isotope and then ionize and separate the isotope of low abundance using a microwave/ECR discharge at 2.45 GHz. A small compact electron cyclotron resonance ion source, which uses permanent magnets, was constructed during this project. The dye laser was purchased and later an excimer laser had to also be purchased because it turned out that the dye laser could not be pumped by our copper laser. It was intended that the dye laser be tuned to a wavelength of 670.8 nm, which would excite {sup 6}Li which would then be preferentially ionized by the ECR source and collected with a charged grid. The degree of enrichment was to be determined using thermal ionization mass spectrometry. The final objective of this project was to assess the feasibility of this system to large-scale production of stable isotopes. However the funding of this project was interrupted and we were not able to achieve all of our goals.
Date: June 1, 1996
Creator: Brake, M.L. & Gilgenbach, R.M.
Partner: UNT Libraries Government Documents Department

Selective excitation of the yellow luminescence of GaN

Description: The yellow luminescence of n-type GaN has been studied with selective excitation using a combination of Ar ion and dye lasers. Narrower structures whose peak energies follow the excitation photon energy over the width of the yellow luminescence have been observed. Unlike the yellow luminescence excited by above band gap excitations, these fine structures exhibits thermal activated quenching behavior. We propose that these fine structures are due to emission occurring at complexes of shallow donors and deep acceptors which can be resonantly excited by photons with energies below the band gap. The activation energy deduced from their intensity is that for delocalization of electrons out of the complexes. Our results therefore suggest that there is more than one recombination channel (usually assumed to be due to distant donor-acceptor pairs) to the yellow luminescence in GaN.
Date: July 1, 1999
Creator: Colton, J. S.; Yu, P. Y.; Teo, K. L.; Weber, E. R.; Grzegory, I. & Uchida, K.
Partner: UNT Libraries Government Documents Department

First results of a polychromatic artificial sodium star for the correction of tilt

Description: This paper presents the first results of a joint experiment carried out at Lawrence Livermore National Laboratory during January, 1996. Laser and optical systems were tested to provide a polychromatic artificial sodium star for the correction of tilt. This paper presents the results of that experiment.
Date: March 6, 1996
Creator: Friedman, H.; Foy, R..; Tallon, M. & Migus, A.
Partner: UNT Libraries Government Documents Department

Laser systems for the generation of sodium layer guide stars

Description: Laser generated guide stars in the mesosphere at 90 km provide an effective beacon for adaptive optics schemes which compensate the effects of atmospheric turbulence. This report discusses the attributes of the laser systems which are desirable from a point of view of overall adaptive optics system performance and operation ease.
Date: March 5, 1996
Creator: Friedman, H.; Erbert, G.; Kuklo, T.; Salmon, T.; Thompson, G.; Wong, N. et al.
Partner: UNT Libraries Government Documents Department

Exciton annihilation studies in poly(p-phenylene vinylene)

Description: To verify the excitonic nature of the light-emitting state in PPV, fluorescence intensities and decay lifetimes were investigated as a function of excitation intensity. The results agree with the behavior predicted by the molecular exciton model. In particular, exciton-exciton annihilation causes the fluorescence intensity to saturate and the fluorescence lifetime to shorten at high exciton densities. In addition, the exciton annihilation, and thus diffusion, coefficients are found to be relatively large, even at low temperatures, indicating that exciton migration is important in PPV. These results indicate that the fluorescent (photoluminescent) state in PPV is excitonic in nature. The results argue against the band model where high mobility at reduced temperatures is not expected because the light-emitting species, neutral bipolarons, are associated with large lattice distortions.
Date: August 1, 1995
Creator: Valencia, V.S.; Kepler, R.G.; Jacobs, S.J.; Beeson, P.M. & Allemond, P.M.
Partner: UNT Libraries Government Documents Department

Production of high-value isotopically separated materials

Description: The purpose of this project was to complete the development of the laser systems and separator systems needed to investigate the potential for the economical separation of high value isotopes used in medical and industrial applications, then demonstrate this separation capability. The project was to focus on the isotopic purification of lead for use as solder in high- end electronics, and on the isotopic enrichment of thallium for medical applications. Ultimately the goal is to demonstrate the economical and technical viability of the technology for lead and thallium and to develop a more general capability for other possible isotope separation missions. Both lead and thallium are usefulapplications in this context because they require- dye lasers, solid- state lasers, and a frequency doubling capability of some of the lasers. This later capability allows access to the wavelength range 250 to 450 mn, with tunable, high- power and high repetition frequency lasers. Until recently, these wavelengths have been largely inaccessible in combination with these other laser characteristics. In addition, up to two new potential laser- isotope separation applications would be conceptually developed through a process of needs analysis and technical feasibility studies. Because of an unanticipated reduction in the size of the LDRD pool of funds, it was decided not to fully fund this project. However, enough funds were allocated to allow an orderly closeout of the project activities. Two key technical steps in the laser development were accomplished during the closeout phase, both of which are required for lead and thallium isotope separation. The first accomplishment successfully demonstrated the power scalability of a master- oscillator, power amplifier (MOPA) approach to a high- power Ti- sapphire laser host material. The net result output power produced, after a series of amplification stages, was about 50 W of tunable (red) laser light. In addition, ...
Date: February 25, 1999
Creator: Comaskey, B; Schneibner, K F; Shaw, M J & Wilder, J G
Partner: UNT Libraries Government Documents Department

Nonlinear dynamics of broad-band lasers

Description: Significant progress has been made in several areas. The source of mode-intensity fluctuations in a three-mirror, multimode dye laser has been identified in the typical operating regime well above threshold. It was found experimentally that deterministic four-wave mixing interactions are the underlying cause. We have also made new theoretical studies concerning the regime just above threshold and predicted that the mode fluctuations will be dominated by quantum noise in this regime. We have constructed a preliminary-design short-cavity dye laser in an attempt to enhance this quantum effect, and are now beginning to characterize its output. We have also constructed a Ti:Sapphire laser, and are beginning its study.
Date: February 1, 1990
Creator: Raymer, M.G.
Partner: UNT Libraries Government Documents Department

Trace surface analysis using ion and photon desorption with resonance ionization detection

Description: Surface Analysis by Resonant Ionization of Sputtered Atoms (SARISA) has demonstrated the ability to detect trace elements at concentrations below 100 ppt. Use of energetic primary ions to desorb surface species is uniquely suited for elemental surface analysis because the ratio between the number of incident energetic ions and the number of ejected surface atoms is easily quantifiable as the sputter yield. Molecular surface analysis by ion desorption does not possess this advantage, however. In this case, laser desorption followed by resonant or near resonant ionization is often a better analysis tool. Here the power of resonant ionization detection of desorbed species is demonstrated on hibonite samples (for elemental analysis) and on fullerene samples (for molecular analysis). 10 refs., 1 fig., 1 tab.
Date: January 1, 1991
Creator: Pellin, M.J.; Young, C.E.; Calaway, W.F.; Lykke, K.R.; Wurz, P.; Gruen, D.M. (Argonne National Lab., IL (USA)) et al.
Partner: UNT Libraries Government Documents Department