High-Power Lasers and Laser Plasmas / Moshchnye Lazery I Lazernaya Plazma / Мощные Лазеры И Лазерная Плазма

248 Pages·1978·11.193 MB·English

by  N. G. Basov (auth.), N. G. Basov (eds.)

HIGH-POWER LASERS AND LASER PLASMAS
MOSHCHNYE LAZERY I LAZERNA YA PLAZMA
MOIll,HbIE JIA3EPbI II JIA3EPIJAH TIJIA3MA
The Lebedev Physics Institute Series
Editors: Academicians D.V. Skobel'tsyn and N.G. Basov
P. N. Lebedev Physics Institute, Academy of Sciences of the USSR
Recent Volumes in this Series
Volume 35 Electronic and Vibrational Spectra of Molecules
Volume 36 Photodisintegration of Nuclei in the Giant Resonance Region
Volume 37 Electrical and Optical Properties of Semiconductors
Volume 38 Wideband Cruciform Radio Telescope Research
Volume 39 Optical Studies in Liquids and Solids
Volume 40 Experimental Physics: Methods and Apparatus
Volume 41 The Nucleon Compton Effect at Low and Medium Energies
Volume 42 Electronics in Experimental Physics
Volume 43 Nonlinear Optics
Volume 44 Nuclear Physics and Interaction of Particles with Matter
Volume 45 Programming and Computer Techniques in Experimental Physics
Volume 46 Cosmic Rays and Nuclear Interactions at High Energies
Volume 47 Radio Astronomy: Instruments and Observations
Volume 48 Surface Properties of Semiconductors and Dynamics of Ionic Crystals
Volume 49 Quantum Electronics and Paramagnetic Resonance
Volume 50 Electroluminescence
Volume 51 Physics of Atomic Collisions
Volume 52 Quantum Electronics in Lasers and Masers, Part 2
Volume 53 Studies in Nuclear Physics
Volume 54 Photomesic and Photonuclear Reactions and Investigation Methods with Synchrotrons
Volume 55 Optical Properties of Metals and Intermolecular Interactions
~ Volume 56 Physical Processes in Lasers
Volume 57 Theory of Interaction of Elementary Particles at High Energies
Volume 58 Investigations in Nonlinear Optics and Hyperacoustics
Volume 59 Luminescence and Nonlinear Optics
Volume 60 Spectroscopy of Laser Crystals with Ionic Structure
, Volume61 Theory of Plasmas
Volume 62 Methods in Stellar Atmosphere and Interplanetary Plasma Research
Volume 63 Nuclear Reactions and Interaction of Neutrons and Matter
Volume 64 Primary Cosmic Radiation
Volume 65 Stellarators
Voh. . me 66 Theory of Collective Particle Acceleration and Relativistic Electron Beam Emission
Volume 67 Physical Investigations in Strong Magnetic Fields
Volume 68 Radiative Recombination in Semiconducting Crystals
Volume 69 Nuclear Reactions and Charged-Particle Accelerators
Volume 70 Group-Theoretical Methods in Physics
Volume 71 Photonuclear and Photomesic Processes
Volume 72 Physical Acoustics and Optics: Molecular Scattering of Light; Propagation of Hypersound; Metal Optics
Volume 73 Microwave-Plasma Interactions
Volume 74 Neutral Current Sheets in Plasmas
Volume 75 Optical Properties of Semiconductors
• Volume 76 Lasers and Their Applications
Volume 77 Radio, Submillimeter, and X-Ray Telescopes
\ Volume 78 Research in Molecular Laser Plasmas
Volume 79 Luminescence Cen ters in Crystals
Volume 80 Synchrotron Radiation
, Volume 81 Pulse Gas-Discharge Atomic and Molecular Lasers
Volume 82 Electronic Characteristics and ElectrC;lll-Phonon Interaction in Superconducting Metals and Alloys
Volume 83 Theoretical Problems in the Spectroscopy and Gas Dynamics of Lasers
Volume 84 Temporal Characteristics of Laser Pulses and Interaction of Laser Radia tion with Matter
Volume 85 High·Power Lasers and Laser Plasmas
Volume 86 Superconductivity
Volume 87 Coherent Cooperative Phenomena
Volume 88 Cosmic Rays in the Stratosphere and in Near Space
Volume 89 Electrical and Optical Properties of III-IV Semiconductors
Proceedings (Trudy) of the P. N. Lebedev Physics Institute
Volume 85
High -Power Lasers and
Laser Plasmas
Edited by
N. G. Basov
P. N. Lebedev Physics Institute
Academy of Sciences of the USSR
Moscow. USSR
Translated from Russian by
J. George Adashko
New York University
CONSULTANTS BUREAU
NEW YORK AND LONDON
Library of Congress Cataloging in Publication Data
Main en try under title:
High-power lasers and laser plasmas.
(Proceedings (Trudy) of the P. N. Lebedev Physics Institute; v. 85)
Translation of Moshchnye lazery i lazernaia plazma.
Includes bibliographical references and index.
I. Laser plasmas. 2. Laser beams. 3. Lasers. I. Basov, NikolaI Gennadievich, 1922- II.
Series: Akademiia nauk SSSR. Fizicheskiiinstitut. Proceedings;v. 85.
QCI.A4114 vol. 85 [QC718.5.L3] 530'.08s [530.4'4] 78-794
ISBN 978-1-4684-1634-3 ISBN 978-1-4684-1632-9 (eBook)
DOI 10.1007/978-1-4684-1632-9
The original Russian text was published by Nauka Press in Moscow in 1976 for the Academy
of Sciences of the USSR as Volume 85 of the Proceedings of the P. N. Lebedev Physics
Institute. This translation is published under an agreement with the Copyright Agency of
the USSR (V AAP).
© 1978 Consultants Bureau, New York
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N. Y. 10011
All rights reserved
No part of this book may be reproduced, stored in a retrieval sytem, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
CONTENTS
Stimulated Mandel'shtam - Brillouin Scattering
Lasers
V. V. Ragul'skii
Introduction . . • • • . • • • . • • . • . • . • . • . • • . • . . • . • . . • . . • . • • . • . • • . . . . . 1
Chapter I
Conditions for Obtaining Stationary Lasing with Stimulated Scattering of Light. . . . . 4
§ 1. Influence of Intensity, Energy Density, and Exciting-Radiation Pulse
Duration on the Laser Operation. • . . . . . . . . . . . . . . • . • . . • . . . . . 4
§ 2. Experimental Verification of the Conditions for Stationary Lasing . . • . • • 6
Chapter II
Gains and Line Widths for 5MBS in Gases 10
Chapter III
Single-Frequency 5MBS Ring Laser . • • • • . . • . . . . . . . . . • . . • • • . • . • • . . . • • 14
§ 1. Feasibility of Effective Conversion of Pump Radiation. • . . . . • • • . . . . . 14
§ 2. Single-Frequency 5MBS Laser. . • • . . • . . . . . • • • . • . . . • . • • • . . . . . 15
Chapter IV
Operation of 5MBS Amplifier in the Saturation Regime. • . • . . . . . . . . . • • • • . . • . 20
§ 1. Characteristics of 5MBS Amplifier in the Stationary Regime. • • • • . • . • • 20
§ 2. Experimental Investigation of Amplifier Operation in the Saturation
Region. • • • . . . . . . . . • . • • • . . . . • • . • . . . . . . . . • . • • • • . . • . . 22
Chapter V
Q Switching by 5MBS . . . . . . • • . . . . . . . • . • • . . . . • • • . . . . . . . • • . . . . . . . . 24
§ 1. Lasing Dynamics. • . . . . . . . . . . • . . . . . . • • . . . • • . . • . . . • • • . . . . 24
§ 2. Conditions under Which Q Switching Is Possible . • • . • . . . . . . . • • . • • • 28
§ 3. Experimental Verification of the Q-Switching Conditions. • • • • • • . . . . . . 29
Chapter VI
Inversion of the Exciting-Radiation Wave Front in 5MBS. . • . • • • • . . . • • . . . • . . . 30
§ 1. Comparison of the Wave Fronts of the Exciting and Scattered Light with
the Aid 'of a Phase Plate . • . . . • • . • • . . • • . . . . • • • . . • . • • • . • • • 30
§ 2. Influence of the Structure of the Exciting Radiation Field on the Shape of
the Scattered-Light Front. • . • • • . • . . . . . . . . • . • • . • . . . . • . . . . 33
§ 3. Compensation for the Phase Distortions in an Amplifying Medium with the
Aid of a "Brillouin Mirror" . • • . . . . . . • . . • . • • • . . . . • • . . . . • • . 35
Chapter VII
5MBS in the Case of Exciting Radiation with a Broad Spectrum 37
Appendix
Experimental Technique • . • . . . • . . . . . • . . . . . • . • • • . . . . . • • • • • • . • . • • • . 41
§ 1. Divergence Measurement Procedure. . • • • . . . • • • . • . • • • • . . • • • • • • 41
§ 2. Cell for Optical Investigations of Compressed Gases. • • . • • . • • . . . • • • 42
v
vi CONTENTS
§ 3. Faraday Decoupler. . • . . . . . . • . . . . . . . . . . • . . • . . . . 43
§ 4. Single-Mode Ruby Laser with Pulse Duration 60 nsec. . • . • 43
§ 5. Single-Mode Ruby Laser with Pulse Duration 60-200 nsec. . 45
§ 13. Fabry - Perot Etalon with 46-cm Base. • • • • • • • • • . • • • • • • • • • • • • . • 45
Literature Cited . • • • • • • • • • • . • • • • . • • • . • • . • • • • • . • • . • • • • • • • • . . • • • 46
Compressed-Gas Lasers
V. A. Danilychev, O. M. Kerimov, and 1. B. Kovsh
Introduction 49
Chapter I
Electroionization Method of Exciting Compressed-Gas Lasers. . • . • . . • • • • . 52
§ 1. Mechanism of Current Flow through the Active Medium of an
Electroionization Laser • • • • • . • • • • • • . • . • . • . . • • . • • • • • 54
§ 2. Experimental Technique • • • • • . • . . • • • . • • • . • • . • • • . • • . . . . 58
2.1. Construction of Laser Chambers • . • . • . . . • • • . • • • • • • • • • • 58
2.2. Optical Resonators. . . . • • • • • • • • • • • • • • • • • • . • • • • . • • • • . . 63
2.3. Measurements of Laser Parameters. . • • • . . • . • • . . . • . • • . • • • 65
§ 3. Electric Characteristics of Active Medium. • • • • • • • • • • • • • • • • • • • . • 68
3.1. Calculation of the Characteristics of the Discharge Excited by the
Electroionization Method. • • • . • • . • . . . . • . • • • • . . • • . . . • • . . • • 68
3.2. Experimental Investigation of a Nonautonomous Discharge Initiated in a
Compressed Gas by an Intense Electron Beam - Discussion of Results 73
Chapter II
Electroionization CO2 High-Pressure Laser. • . • . . • • • • • • . • • • • • • • • • • • 84
§ 1. Kinetics of Population of Working Levels; Gain of Active Medium of
Electroionization CO2 Laser .•.•.•. ~ • . • • . • . . • • • • • • . . • • • • • 86
§ 2. Threshold Characteristics, Output Energy, Power, and Efficiency of
Laser; Divergence of the Radiation. • . • . . . • • . . . . . • . • • • . . 89
§ 3. Gain Spectrum of Electroionization COz Laser . . • . • . . . . . . • . . . 97
§4. Relaxation of Upper Laser Level at High Pressures. • • • • . • • . . • • 104
§ 5. Operating Regimes of Electroionization CO2 Lasers. • • . • . . • • • • • 109
Chapter III
High-Pressure Gas Lasers Using Other Working Media. • • • • . • • • • • • . • • • • • • • 112
§ 1. Electroionization CO Laser. • • • • • . • • • • . • • • • • • • • • • • • • • • • . • • • 114
§ 2. Laser Operating with Compressed Xenon and Ar:Xe Mixture. • . • 118
§3. Ultraviolet High-Pressure Laser Using the Mixture Ar:N2 . . • • . 124
Conclusion .••••.•..• 127
Appendix
Theory of Current Flow through an Ionized Gas .• 128
Literature Cited .•.....••••••••••.•.•• 142
Experimental Investigation of the Reflection and Absorption
of High-Power Radiation in a Laser Plasma
O. N. Krokhin, G. V. Sklizkov, and A. S. Shikanov
Chapter I
Reflection of Laser Radiation from a Plasma (Survey of the Literature) 147
CONTENTS vii
§ 1. Experimental Conditions Realized in Research on Laser-Plasma
Parameters . • • . • . . . . • • • • • . . • . . • • . . • . • • • • • • • • • • • • • • . 148
§ 2. Energy Composition of the Reflected Radiation; Anomalous Character
of the Interaction of Laser Radiation with a Plasma in a Wide Range of
Flux Densities ... " ....... " ..................... " " " . 149
1 •
§ 3. Spectral Composition of Reflected and Scattered Radiation • • • • • • • • • • • 156
Chapter II
Investigation of the Absorption of Laser Radiation in Thin Targets. • • • • • • • • • • • • 161
§ 1. Experimental Setup ••••• ~ •••••••••••..•••.•••.••••• ~ • . . • 161
§ 2. Multiframe Schlieren Photography in, Ruby-Laser Light; Spatial
Resolution .......... " ......... 163
GO •• " ••• " " •• " ••••• lit • • •
§ 3. Determination of the Time of Bleaching of a Thin Target . • . . • . . • • . • . 164
§4. Investigation of the Dynamics of Motion of Shock Waves in the Gas
Surrounding the Target; Absorbed Energy. • . . • • • . • . . • • • • • . • • • 167
§ 5. Discussion of Results. • • • • • • . . . . . . . . • • . . . . • • . • . . . • • • • . . . . 169
Chapter III
Reflection of Laser Radiation from a Dense Plasma. . . • • • • . • . • . . • • • • • • . . • . 170
§ 1. Experimental Setup . . . • . • • . . • . . . . • . . . . • • • . • . • • • • . • • • . • • . 170
§ 2. Behavior of the Coefficient of Reflection of Laser Radiation from a Plasma
in the FlUX-Density Interval 101°_1014 W/cm2 •• • • • • • • • • • • • • • • • • 171
§3. Dependence of the Reflection Coefficient on the Time; Plasma Probing
by R uby-Laser Radiation. • • • • • • . • • • • . . . . • • • • . . • • . • • • • . • • 176
§ 4. Oscillations of Reflected Radiation with Time. . • . • • . . • . • • . . • • • • • • 178
§ 5. Directivity of Reflected Radiation. . . • • • . . • • • • • • • • • . • • • • • • • . • • 180
Chapter IV
Generation of Harmonics of the Heating-Radiation Frequency in a Laser Plasma 182
§ 1. Investigation of the Generation of the Second Harmonic of the Heating
Radiation in a Laser Plasma; Dependence on the Flux Density;
Variation with Time. • • • • • • • . • • • • • • • • • • • • • • • • • • • • • . • . . • 182
§ 2. Generation of 3/2wO Line. • . • • . . • . • . . . • • . • . • • • • • • • • • • • • . • • • 185
Chapter V
Anisotropy of X Rays from a Laser Plasma. • • • • • • . • • . . • . . • • • . . • • • • • • • • 186
§ 1. Procedure of Multichannel Measurement of Continuous X Radiation . • . . . 186
§ 2. Investigation of the Directivity of the X Rays . • . • . • • • . . . . • • . • • • • . 187
§ 3. Possibility of Measuring the Electron" Temperature" of a Laser Plasma
by the" Absorber" Method. • • • • • • . . • . . . • • • • . • • • • • . • . . . • . . 189
Literature Cited . . . . • • . . . . • . • . . . • • . . • . • . . . • • . . . . . . . . • . . • . • • . • • 191
Experimental Study of Cumulative Phenomena in a Plasma
Focus and in a Laser Plasma
V. A. Gribkov, o. N. Krokhin, G. V. Sklizkov, N. V. Filippov,
and T. I. Filippova
Introduction . . " . . " . . . . . . . . . . . . " " . . " 197
lit " " • • • • • " • • • III • • • " • • • • " g
Chapter I
Procedure of High-Speed Interferometric Investigation of a Nonstationary
Dense Plasma .. 198
/OJ g • " ••• 0 " •••• " • " •• lit " " " •• " " •• g •• " " •••• " •• " • •
§ 1. The Maximum Information Obtained by Optical Laser Research
Method s. " . . . . . " " " " . . . 198
0 " • • " lit " III " • " • • • • " • • • • • • " " " lit • " •
§ 2. High-Speed Laser Setup for Interferometric Investigations of a Plasma
Focus and Cumulative Laser-Plasma Configurations. • • • • • • • • • • • . 199
viii CONTENTS
§ 3. Synchronization Methods. . • • . . . . . . • • • . . . . . • . • • • • . • • • • • • . • . 200
§ 4. Discussion of the Applicability of Laser Interferometry and Interpretation
of the Interference Patterns. • . . . • . . . . . . . . • • . . • • . • • • . . • . • . 201
Chapter II
Investigation of Cumulative Stage of Plasma Focus . . . . . . . . . . • . . . . • . • • . . • . 204
§ 1. Parameters of the" Plasma Focus" 1'1stallation. . . . . . . • . • . . . . . . . • . 204
§ 2. Results of Reduction of the Interference Patterns of the First Contraction
of the Plasma Focus. . . • . . . . • . . . • . • • . . . . • . . • . • . • . . . . . • • 204
§ 3. Intermediate Phase . . . . • . • . • • • . • . . . . • • . . • • • . • • • . . • . • • . • . 209
§ 4. Second "Contraction" of Plasma Focus . . . . • . • . . • • . • . • . • • • . • . . . 211
§ 5. Concluding Stage. . . . . . . • • . • • . • . • • • . • • . • . . . . . • . . . • • • . . • . 213
Chapter III
Discussion of Results of Experiments with Plasma Focus. . . . . • . • . . . . • . • • • . . 214
§1. First "Contraction" ..••••••••.......••..•....••••••.•• 214
§ 2. Intermediate Phase .•.•.••.•.....••. 218
§ 3. Second "C ontraction" ..............•.••....•.•••••.•... 221
§ 4. Neutron Emission from Plasma Focus ... 223
Chapter IV
Investigations of Cumulative Laser Plasma . • . . . . . . . . . . • . • • • • . . • • • . . . • . 224
§ 1. Experimental Setup . . • . . . . . . . . • • • . . . . . . . . . . . . . • . . . • • • . 225
§ 2. Collision of Two Laser Flares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
§ 3. Quasi-cylindrical Cumulation of Laser Pla,sma. • . . • . . . . • . • . . . . . . • 226
§ 4. Investigation of X Rays from a Cumulative Laser . . . . • . . . . • . . . . . . . 229
§ 5. Probe Studies of Laser Plasma . • . . . . . . • . • . . . . . • • • . . • • • . • • . . 230
Chapter V
Discussion of Experimental Results 231
§ 1. Collision of Flares ....•..• 231
§ 2. Cone Cumulation .•..... 231
Conclusion .•.. 237
Literature Cited 238
STIMULATED MANDEL'SHT AM-BRILLOUIN
SCATTERING LASERS
V. V. Ragul'skii
The generation and amplification of light in stimulated Mandel'shtam-Brillouin scattering (SMBS) are
investigated. The conditions necessary for effective operation of 5MBS lasers, amplifiers, and modula
tors are ascertained. The possibility of conversion, with efficiency close to 100"70, of the pump radiation
in lasers and amplifiers at diffraction divergence of the generated light is demonstrated experimentally
and theoretically. To choose the optimal medium for the construction of the laser devices, the gains
and line widths of a number of compressed gases are determined. The influence of the width of the
spectrum of the exciting radiation on the stimulated scattering is investigated. It is shown that the wave
front of the light scattered by 5MBS can be inverted relative to the front of the exciting radiation. This
effect is used to compensate for the phase distortions in the amplifying medium.
INTRODUCTION
The high intensity and coherence of laser light makes it possible to observe numerous
nonlinear effects, particularity different processes of stimulated scattering of light. Soon after
the invention of the laser, stimulated Raman scattering (SRS) was observed [1], followed by
stimulated Mandel'shtam - Brillouin scattering (SMBS) [2]. A number of other types of stimu
lated scattering were discovered later [3-8]. As is well known, in these processes the intensity
of the scattered light increases nonlinearly with increasing intensity of the exciting radiation
and can become comparable with the latter [9]. As a result, stimulated scattering can be used
for an effective conversion of the laser frequency, as well as to change other characteristics
of its radiation, such as the spatial distribution, the divergence, the width of the spectrum, etc.
Since 5MBS is the dominant scattering process in many media [10], it is useful to consid
er the possiblities of constructing laser devices on its basis. The present article is devoted
to a study of this question.
Mandel's htam - Brillouin scattering is due to fluctuations of the dielectric constant as a
result of pressure fluctuations (sound waves) [11]. If the electric field intensity of the exciting
radiation is large, then this field (together with the field of the scattered light) causes, on ac
count of the electrostriction effect, an increase in the intensity of the sound wave. This in
crease leads to an increase of the intensity of the scattered light, which in turns causes an in
crease of the pressure fluctuations. As a result, the intenSity of the scattered light increases
nonlinearly as it propagates in the scattering medium. This is precisely the effect known as
stimulated Mandel'shtam -Brillouin scattering.
Stimulated Mandel'shtam-Brillouin scattering has been the subject of a tremendous num
ber of works. The reader can find detailed information in the review of Starunov and Fabelinskii
[12] (see also [13] and [14]). We present here only the principal relations describing this phenom-
1
2 V. V. RAGUL'SKII
enon. According to Tang's theory [15], in the case of a stationary regime the interaction of
plane monochromatic waves of the exciting and scattered light traveling opposite to each other
in an active medium is described by the equations
~ = gI (x)., (x),
dd:Yx = gI (x):J (x), (1)
where I and :J are the intensities of the exciting and scattered radiations; the scattered radia
tion propagates in the direction +x (0 :s x:s l). The gain g is determined by the parameters of
the scattering medium:
(2)
where v is the frequency of the exciting light, p is the density of the scattering medium, £- is
its dielectric constant, n is the refractive index, v is the speed of sound in this medium, and c
is the speed of light in vacuum. The position of the center of the gain line is given by the
expression
2vn . e
VB V - -c V Sill -2 ' (3)
where e is the scattering angle.
The line width 0))0 is determined by the damping of the hypersound in the active medium:
0)) 0 = 1/ (21fT s ), where T s is the hypersound damping time.
If I varies little over the length of the scattering region (i.e., there is no saturation), we
obtain from (1)
:J (I) = :J (0) egIl•
(4)
Equations (1) are valid also for the saturation regime; the corresponding solution is given in
Chapter IV. Equation (2) pertains to scattering through 180°. In scattering through an arbitrary
angle e, the gain at the maximum of the line is equal to [16]:
(5)
Prior to the performance of the investigations described in this article, there were only
few known publications on 5MBS lasers. The experimental studies [17-20] were devoted to the
lasing spectrum at different angles between the axis of the laser cavity and the beam of the
exciting radiation. The lasing threshold and the output power were determined [21]. Studies
were made also of the competition in such lasers between the 5MBS and the SRS processes [19,
22]. The initial lasing period was analyzed theoretically by Yariv [23]. He has shown that the
intensity of the generated radiation increases exponentially in time if the lasing is only on the
first Stokes component of the 5MBS and there is no saturation. Stationary lasing on several
components was theoretically considered in [24]. Its authors took into account saturation, but
the analysis was carried out only for the case when the exciting radiation coincides in frequen
cy with one of the resonator modes. This case has not yet been realized in experiment.
The papers cited above constitute the entire literature on 5MBS lasers. We note that the
experiments yielded a low « 1%) efficiency of conversion of the pump radiation into laser radia
tion. The cause is apparently the nonstationary regime of the operation of the described lasers.