| Unconventional Laser Guide Stars and Wavefront Correction of Blue Starlight |
28 MAY 2002 |
10 pages |
| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERING
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 | In this project we established by theory and experiment (1) that a 1/ 4 Joule, 20 ns, ultraviolet laser pulse could create (near 20 km altitude) a return signal to the transmitting telescope that would appear, for 20 ns, to have a brightness temperature of millions of degrees, and thus serve as a guide star for high-order corrections of blue starlight, (2) that a much lower energy (approx. one hundred ... |
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| Studies of Optical Beam Phase Conjugation and Electromagnetic Scattering Process |
17 JUN 97 |
27 pages |
| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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| In this project we have performed both experimental and theoretical studies of nonlinear optical beam interactions in a variety of media. During this reporting period we have (1) extended our set of exact focused-pulse solutions of Maxwell's equations in vacuum, (2) discovered a new two-photon resonance in the fullerene C60, (3) measured excited- state cross-sections in protonic-doped bis-benzothiazole (4) developed a nonlinear interferometer which measures phase, as well as magnitude, ... |
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| Studies of Optical Beam Phase Conjugation and Electromagnetic Scattering Process |
30 MAR 94 |
28 pages |
| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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| In this project we have performed both experimental and theoretical studies of optical beam phase-conjugation and of electromagnetic scattering and propagation with intense optical fields. During the reporting period we have: (1) demonstrated that atomic vapors require fewer photons to perform optical wave mixing that any other medium examined to date; (2) sowed theoretically that a one-joule broadband optical pulse, whose carrier wavelength is one micron, can impart nearly one ... |
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| Studies of Optical Beam Phase-Conjugation and Electromagnetic Scattering Process |
05 MAY 92 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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 | In this project we have performed both experimental and theoretical studies of optical beam phase-conjugation and of electromagnetic scattering and propagation with intense optical fields. We have: (1) made measurements of high- power four-wave mixing in many new polymers synthesized at USC to characterize their nonlinear optical properties; (2) made what we believe is the first observation of nonexponential attenuation of a weak optical beam in a homogeneous (highly scattering) ... |
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| Studies of Optical Beam Phase-Conjugation and Electromagnetic Scattering Process |
06 MAR 91 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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| This project performed both experimental and theoretical studies of optical beam phase-conjugation and of electromagnetic scattering and propagation with intense optical fields. We have: (1) made the first determination of the nonlinear optical index of air and of common gases throughout the visible; (2) established the threshold beam intensities required to produce nonlinear effects in plasma; (3) measured the linear and nonlinear refractive indices of many new optical polymers; (4) ... |
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| Optical Beam Phase-Conjugation and Electromagnetic Scattering Process with Intense Fields |
09 MAY 88 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERING
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| This project performed both theoretical and experimental studies of optical beam phase-conjugation and electromagnetic scattering processes with intense optical fields. New bounds are established on the power and energy required to perform useful wave mixing in certain classes of nonlinear media. New physical processes are discovered for optical beam phase conjugation. The first complete physical characterizations of monopolar and bipolar photorefractive crystals is performed. Keywords: Optical beam phase conjugation; Nonlinear ... |
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| Instrumentation for High Speed Phase Conjugation |
05 APR 88 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERING
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| With this equipment grant we have established and instrumented an optical laser source at 1.06 microns and three harmonics, with the added capability of a tunable dye laser pumped at any of these harmonics. Pulse lengths are available from 10 to 10(5) picosecond. Maximum pulse energy is 0.4 J at 1.06 microns in 4 nsec. First measurements on new optical polymers show them to be promising as stable room-temperature nonlinear ... |
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| Phase Conjugation Scaling for High Energy Lasers |
30 MAY 85 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERING
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| Phase conjugation of both continuous and pulsed 10.6 micron lasers by stimulated Brillouin backscattering (SBB) has been attempted. Because of various technical difficulties, conclusive evidence of SBB was not found. However, theoretical studies in this project supported further the promise of SBB for obtaining diffraction-limited beams from high power infrared lasers. Several novel schemes for realizing 10 micron waveguides of several meters length were explored experimentally. Keywords: High energy lasers; ... |
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| Electromagnetic Scattering Processes at Resonances and with Intense Fields |
JUN 81 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF PHYSICS
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| To be able to interpret and predict the nature of the electromagnetic radiation that is scattered by matter from a strong incident monochromatic wave whose frequency is at or near a resonance of the scattering medium. The problems attacked include those that arise in mode-locking, saturable adsorption, saturation spectroscopy, high-energy optical amplifiers, infrared-laser window failure, optical image and frequency converters, optical computers, and coherent optical adaptive techniques. (rrh) |
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| Raman-Induced Kerr Effect Studies. |
10 JUN 1980 |
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| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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| The Raman-Induced Kerr Effect, developed at U.S.C. is a new form of laser spectroscopy which is beginning to find wide application as a remote diagnostic sensor of fast (picosecond to nanosecond) transient shocks, explosions, and plasma arcs. |
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| Laser-Induced Damage in Optical Materials. |
FEB 1974 |
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| Authors:
Concetto R. Giuliano; Robert W. Hellwarth; HUGHES RESEARCH LABS MALIBU CALIF
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| The report contains the results of damage experiments performed at 0.694 and 1.06 micrometer using well-controlled Q-switched ruby and Nd:YAG lasers. Materials studied at 1.06 micrometer are proustite (Ag3AsS3) and lithium niobate (LiNbO3). Surface damage thresholds were measured for proustite for different conditions of pulse repetition rate and pulse duration. A discussion of the theories of optical avalanche breakdown is presented in which doubts are raised as to whether 'intrinsic' ... |
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| Damage Threshold Studies in Laser Crystals. |
SEP 1972 |
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| Authors:
Concetto R. Giuliano; Donald F. DeBois; Robert W. Hellwarth; LaVerne D. Hess; Gerald R. Rickel; HUGHES RESEARCH LABS MALIBU CALIF
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| The report contains a cumulative summation of a three-year experimental and theoretical program on laser induced damage in ruby and sapphire at 6943 A. Both bulk and surface damage were studied, using a well-characterized single transverse and longitudinal mode Q-switched ruby laser and amplifier. Temporal studies of the development of internal damage tracks using a high speed streak camera have been correlated with self-focusing theory with good agreement and constitute ... |
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| Damage Threshold Studies in Laser Crystals: Surface Damage, Prevention of Self-Focusing. |
JAN 1972 |
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| Authors:
Concetto R. Giuliano; Robert W. Hellwarth; Gerald R. Rickel; HUGHES RESEARCH LABS MALIBU CALIF
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| Initial experimental results on laser induced surface damage are discussed. The dependence of surface damage threshold on the distance between the focusing lens and sample indicates that surface damage for sapphire is a power density phenomenon. It is also pointed out that the exit surface damage threshold for sapphire is not connected with any nonlinear processes taking place deep within the bulk of the material, such as self-focusing. The relationship ... |
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| Damage Threshold Studies in Laser Crystals: Beam Intensity Profile and Self-Focusing. |
JAN 1971 |
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| Authors:
Concetto R. Giuliano; Donald F. DuBois; Robert W. Hellwarth; Gerald R. Rickel; HUGHES RESEARCH LABS MALIBU CALIF
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| The results of a number of experiments are presented which were aimed at detailed characterization of the spatial profile of the laser beam both before and after amplification. Revised values of previous damage thresholds are presented as well as the results of measurements of damage threshold as a function of lens focal length. In other experiments, the time evolution of the damage tracks in ruby and sapphire was studied using ... |
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| Damage Threshold Studies in Laser Crystals: Experimental and Theoretical Results in Ruby and Sapphire. |
JUL 1970 |
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| Authors:
Concetto R. Giuliano; Robert W. Hellwarth; LeVerne D. Hess; Gerald R. Rickel; HUGHES RESEARCH LABS MALIBU CALIF
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| The results of a number of experiments are presented as well as a summary of the theoretical work. Bulk damage thresholds for several ruby and sapphire samples from different sources are presented. The problem of surface damage is discussed, and qualitative comparisons between entrance and exit surface damage are made. Differences between the gross characteristics of bulk damage in ruby and sapphire are presented and discussed. The dependence of damage ... |
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| DAMAGE THRESHOLD STUDIES IN LASER CRYSTALS. |
JAN 1970 |
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| Authors:
Concetto R. Giuliano; Robert W. Hellwarth; LaVerne D. Hess; Gerald R. Rickel; HUGHES RESEARCH LABS MALIBU CALIF
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| In the report a mode-controlled giant pulse laser oscillator and amplifier are described. The oscillator employs a temperature-controlled resonant reflector, a dye Q-switch laser and a 2 mm aperture to assure single mode operation. The result of preliminary threshold measurements on a few different ruby samples are presented. Equations which describe the propagation of the gaussian mode are examined in order to answer some important questions concerning focusing inside dielectric ... |
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Reports by Author
