Investigation Of Stimulated Raman Scattering Using Short Pulse Diffraction Limited Laser Beam Near The Instability Threshold PDF Download
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| Release | : 2008 |
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Download Investigation of Stimulated Raman Scattering Using Short-pulse Diffraction Limited Laser Beam Near the Instability Threshold Book in PDF, ePub and Kindle
Short pulse laser plasma interaction experiments using diffraction limited beams provide an excellent platform to investigate the fundamental physics of Stimulated Raman Scattering. Detailed understanding of these laser plasma instabilities impacts the current inertial confinement fusion ignition designs and could potentially impact fast ignition when higher energy lasers are used with longer pulse durations (> 1 kJ and> 1 ps). Using short laser pulses, experiments can be modeled over the entire interaction time of the laser using particle-in-cell codes to validate our understanding quantitatively. Experiments have been conducted at the Trident laser facility and the LULI (Laboratoire pour l'Utilisation des Lasers Intenses) to investigate stimulated Raman scattering near the threshold of the instability using 527 nm and 1059 nm laser light respectively with 1.5-3.0 ps pulses. In both experiments, the interaction beam was focused into a pre-ionized He gas-jet plasma. Measurements of the reflectivity as a function of intensity and k[lambda]{sub D} were completed at the Trident laser facility. At LULI, a 300 fs Thomson scattering probe is used to directly measure the density fluctuations of the driven electron plasma and ion acoustic waves. Work is currently underway comparing the results of the experiments with simulations using the VPIC [K.J. Bowers, et at., Phys. Plasmas, 15 055703 (2008)] particle-in-cell code. Details of the experimental results are presented in this manuscript.
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| Release | : 1987 |
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Download Chapter 2 Book in PDF, ePub and Kindle
Transmission of a high intensity laser beam through the atmosphere can be affected by a variety of stimulated and parametric nonlinear processes. As a result, gain at other wavelengths will be generated along the propagation path of the beam. But the conversion of the original laser energy into other wavelengths is not the only result. Unless special measures are taken, the wavefront of the Raman shifted radiation will be determined by the turbulence in the atmosphere and by the aspect ratio of the gain medium. These processes will lead to beam divergences which can be significantly greater than the diffraction limit. As a result of these nonlinear processes, it will not be possible to efficiently propagate the beam unless proper measures are taken. Developing a quantitative model is especially important for determining the propagation characteristics of FEL laser pulses through the atmosphere. The objective of this research report is to present such a time dependent model for stimulated Raman conversion of short laser pulse propagating in the atmosphere and to calculate the threshold laser pulse energy and intensity for stimulated rotational Raman scattering as a function of wavelength, pulse width and beam diameter. 12 refs., 10 figs.
| Author | : Victor Distler |
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| Total Pages | : 0 |
| Release | : 2021* |
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Download Stimulated Raman Scattering in High-power Fiber Lasers Book in PDF, ePub and Kindle
This thesis contains investigations of stimulated Raman scattering (SRS) in high-power continuous wave fiber lasers with diffraction-limited beam quality. A high-power, narrow-linewidth Raman fiber amplifier is constructed and SRS-induced transverse mode instability (TMI) is experimentally observed in a passive fiber. Influential parameters (like the fiber length) on the TMI threshold are investigated. Additionally, the spectral linewidth of the Raman fiber amplifier is investigated. Furthermore, walk-off between the Stokes signal and the Raman pump signal was found to have a major influence on the amount of Stokes light created in high-power fiber oscillators. An analytical model quantifying this effect for high-power cw fiber lasers is developed.
| Author | : John Francis Reintjes |
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| Total Pages | : 213 |
| Release | : 1971 |
| Genre | : Raman effect |
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Download A Study of Transient Stimulated Raman Scattering and Self-Focusing in the Picosecond Time Regime Book in PDF, ePub and Kindle
The high intensities and short durations available in mode locked laser pulses have made possible the study of optical interactions with matter in entirely new regimes of intensity and time. Because of the large electric fields present in these pulses, third order susceptibilities can determine the dominant optical response of a medium. In addition, the extremely short durations of these pulses causes many nonlinear optical interactions to become transient, since the pulse is over before the medium can fully respond. In this report, a study of two third order processes, Stimulated Raman Scattering and self-focusing, with picosecond pulses is reported. A time of flight technique is used to study the propagation properties of a self-focused beam. These results are compared with recently developed transient theories of the self-focusing process which result from numerical integration of the self-focusing equations for both phase and amplitude. Many of the propagation and spectral properties of the self-focused pulses are successfully accounted for by the transient theory which predicts a region of stabilized duration and diameter in the tail of the pulse which is constant in form over many centimeters in the cell. Finally, the symmetry of experimental spectra is not fully accounted for in the transient theory, and additional explanations of this effect are proposed. The design and construction of a diffraction limited Nd:glass mode locked laser system with reproducible output pulses containing peak intensities of about 10 GW/sq cm is also described. (Author).
| Author | : R. Jeffrey Balla |
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| Total Pages | : 56 |
| Release | : 2000 |
| Genre | : Raman effect |
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Download Raman Shifting a Tunable ArF Excimer Laser to Wavelengths of 190 to 240 Nm With a Forced Convection Raman Cell Book in PDF, ePub and Kindle
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| Release | : 1980 |
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Download Stimulated Raman Scattering in Large Plasmas Book in PDF, ePub and Kindle
Stimulated Raman scattering is of concern to laser fusion since it can create a hot electron environment which can increase the difficulty of achieving high final fuel densities. In earlier experiments with one micron laser light, the energy measured in Raman-scattered light has been insignificant. But these experiments were done with, at most, about 100 joules of laser energy. The Raman instability has a high threshold which also requires a large plasma to be irradiated with a large diameter spot. Only with a long interaction length can the Raman-scattered light wave convectively grow to a large amplitude, and only in recent long pulse, high energy experiments (4000 joules in 2 ns) at the Shiva laser facility have we observed as much as several percent of the laser light to be Raman-scattered. We find that the Raman instability has a much lower intensity threshold for longer laser pulselength and larger laser spot size on a solid target.
| Author | : Chester J. Schuler |
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| Total Pages | : 126 |
| Release | : 1968 |
| Genre | : Lasers |
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Download Laser-induced Spontaneous and Stimulated Raman Scattering Book in PDF, ePub and Kindle
| Author | : D. P. Bortfield |
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| Total Pages | : 85 |
| Release | : 1967 |
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Download Investigation of Stimulated Raman Oscillators and Amplifiers Book in PDF, ePub and Kindle
The results of an investigation of several non-linear optical effects are presented. Main emphasis is on the study of stimulated Raman scattering and mode selective techniques for giant pulse lasers. Secondary studies of optical harmonic generation and bleachable dye lasers are also discussed. It is shown that the gain in a diffusely pumped stimulated Raman scattering amplifier behaves according to the theory developed by Hellwarth and that the gain anomaly observed in colinear amplifiers (and explained as a consequence of beam trapping of the input beam) is, in fact, not present. A study of the mode selective properties of a passive Q-switch reveals that mode selection occurs as a result of the slow buildup of oscillation in a passive Q-switched laser. The character of spatial and temporal amplitude fluctuations in a laser beam is related to the degree of mode selection employed and the effect of these fluctuations on stimulated Raman conversion is given. A discussion is presented of laser action in two polymethene dyes in glycerol solution pumped by a giant pulse ruby. The potential for laser action in these particular dyes was identified in a parallel Hughes program. (Author).
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| Total Pages | : 10 |
| Release | : 1990 |
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Download Stimulated Raman Scatter from Laser-produced Plasmas Book in PDF, ePub and Kindle
Stimulated Raman scattering in plasmas is a three-wave instability with important practical consequences for laser fusion. Most studies of this process to date have focused on its threshold. Even the linear-theory threshold poses interesting problems; and observed thresholds have been difficult to interpret. However, with increasing evidence that this instability often becomes absolute, it has become appropriate to examine saturation mechanisms as well. A number of such mechanisms are discussed here, one of which has been reported to have a chaotic regime. 26 refs., 4 figs.
| Author | : Satish Chand Abbi |
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| Total Pages | : 180 |
| Release | : 1967 |
| Genre | : Lasers |
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Download Stimulated Raman Emission and Self-focusing of a Laser Beam in Non-linear Media Book in PDF, ePub and Kindle
Stimulated Raman emission and self-trapping of optical beams in non-linear media are two distinct processes. The experiments reported in the paper are aimed at providing some additional experimental material prior to such a combined study of the two processes. The study gives an experimental investigation of stimulated Raman emission in the presence of self-focusing for several liquids. A theoretical treatment is given for the stimulated Raman emission and the self-focusing of intense optical beams. (Author).
