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Gas laser

About: Gas laser is a research topic. Over the lifetime, 4623 publications have been published within this topic receiving 48909 citations.


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TL;DR: In this article, the authors describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer.
Abstract: We describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer. High sensitivity for detection of resonance information is achieved by optical heterodyne detection with sidebands produced by rf phase modulation. Physical, optical, and electronic aspects of this discriminator/laser frequency stabilization system are considered in detail. We show that a high-speed domain exists in which the system responds to the phase (rather than frequency) change of the laser; thus with suitable design the servo loop bandwidth is not limited by the cavity response time. We report diagnostic experiments in which a dye laser and gas laser were independently locked to one stable cavity. Because of the precautions employed, the observed sub-100 Hz beat line width shows that the lasers were this stable. Applications of this system of laser stabilization include precision laser spectroscopy and interferometric gravity-wave detectors.

3,393 citations

Journal ArticleDOI
TL;DR: In this paper, the observation of photosensitivity in Ge-doped core optical fibers is reported. The photosensitivity is manifested by light-induced refractive index changes in the core of the waveguide.
Abstract: The observation of photosensitivity in Ge‐doped core optical fibers is reported. The photosensitivity is manifested by light‐induced refractive‐index changes in the core of the waveguide. Narrowband reflectors in a guide structure have been fabricated using this photosensitivity and the resulting DFB reflectors employed as laser mirrors in a cw gas laser in the visible.

2,294 citations

Journal ArticleDOI
TL;DR: The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers as mentioned in this paper.
Abstract: The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

494 citations

Journal ArticleDOI
TL;DR: Finite‐width light distributions in arterial tissue during Argon laser irradiation are simulated using the Monte Carlo method and the diverging light from a fiber penetrates tissue in a manner similar to collimated light.
Abstract: Finite-width light distributions in arterial tissue during Argon laser irradiation (476 nm) are simulated using the Monte Carlo method Edge effects caused by radial diffusion of the light extend +/- 15 mm inward from the perimeter of a uniform incident beam For beam diameters exceeding 3 mm the light distribution along the central axis can be described by the one-dimensional solution for an infinitely wide beam The overlapping edge effects for beam diameters smaller than 3 mm reduce the penetration of the irradiance in the tissue The beam profile influences the light distribution significantly The fluence rates near the surface for a Gaussian beam are two times higher on the central axis and decrease faster radially than for a flat profile The diverging light from a fiber penetrates tissue in a manner similar to collimated light

349 citations

Book
24 Apr 1995
TL;DR: In this paper, the authors presented a simplified model of the RF Discharge Constant Positive Plasma Potential Stochastic Heating of Electrons and Sheath Sheaths Experimental Current-Voltage Characteristics CVC and Normal Current Densities in the a-discharge (Theory and Numerical Simulation) The a-g Transition Parameters The y-Discharge The a -g Transition at Moderate and Low Pressures Coexistence of Two RF Modes in the Gap High-Pressure RF Capacitive Discharges RF Discharges with Coated Electrodes Low-Press
Abstract: Basic Principals of the RF Capacitive Discharge Excitation of an RF Discharge Electron Motion in an Oscillating Electric Field Electrodynamic Plasma Characteristics and Interaction with Oscillating Field Electron Production and Loss: Plasma Maintenance A Simplified Model of the RF Discharge Constant Positive Plasma Potential Stochastic Heating of Electrons RF Discharge Modes Moderate-Pressure RF Discharge Space Charge Sheaths Experimental Current-Voltage Characteristics CVC and Normal Current Densities in the a-Discharge (Theory and Numerical Simulation) The a-g Transition Parameters The y-Discharge The a-g Transition at Moderate and Low Pressures Coexistence of Two RF Modes in the Gap High-Pressure RF Capacitive Discharges RF Discharge with Coated Electrodes Low-Pressure RF Discharges and Asymmetry Effects Self-Bias in an Asymmetric Capacitively Coupled Discharge Correlations Between Plasma and Sheath Parameters in an Ambipolar Diffusion-Controlled Discharge Sheath Dynamics and Current Anharmonicity in an Asymmetric Discharge Current Anharmonicity in Asymmetric and Symmetric Discharges Battery Effect in an Asymmetric Discharge Plasma 'Nontransparency' and Fast Electron Response to RF Field and 'Oscillationless' Sheath Ions The Floating Potential The a-Sheath The Energy Spectrum of Ions Bombarding the Electrode Surface RF Discharge in Electronegative Gases Smooth a-g Transition and the g Mode Some Aspects of Stochastic Heating of Electrons Numerical Simulation of Low-Pressure RF Discharges Magnetron RF Discharge Experimental Methods and Measurements Voltage Measurements and Current-Voltage Characteristics Probe Measurement of Constant Space and Plasma Potentials Active DC Probing of an RF Discharge A Method for Studying the Transverse Discharge Structure Optical Methods for the Study of Spatial Discharge Structure Laser-Induced Fluorescence and Laser-Optogalvanic Spectroscopy Excitation and Control of an RF Discharge Application of RF Capacitive Discharges for Gas Laser Excitation and Plasma Technology RF Discharge and Gas Lasers: A Brief History Arguments in Favor of RF Laser Excitation Frequency Dependence of Discharge and Active Laser Medium Parameters Selection of Designs and Parameters of Transverse RF-Excited CO2 Lasers with Diffusional Cooling Optical Resonators of Waveguide and Slab RF CO2 Lasers High Flowrate CO2 Lasers Excited by RF and Combined RF-DC Discharges Lasers with Alternative Active Media Magnetic Stabilization of Slab Discharges Plasmachemical Technology References Index

341 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20219
202029
201923
201824
201740
201640