High-brightness Metal Vapour Lasers: Volume I: Physical Fundamentals and Mathematical Models

542 Pages·2017·65.36 MB·English

by  V. M. Batenin, V. V. Buchanov, A. M. Boichenko, M. A. Kazaryan, I. I. Klimovskii, E. I. Molodykh

High-brightness
Metal Vapour
Lasers
Vol. 1 Physical Fundamentals
and Mathematical Models
High-brightness
Metal Vapour
Lasers
Vol. 1 Physical Fundamentals
and Mathematical Models
V. M. Batenin, V. V. Buchanov, A. M. Boichenko
M. A. Kazaryan, I. I. Klimovskii, E. I. Molodykh
CRC Press
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Contents
Foreword 1
Notations, indexes and abbreviations 7
Introduction 13
1 Devices and methods for producing metal vapours 22
1.1. First designs of metal vapour lasers 22
1.2. Self-heated lasers 23
1.2.1. Thermal regime of discharge laser tubes 23
1.2.2. Design of structures with self-heating laser tubes 25
1.3. The explosive method for producing metal vapours 29
1.4. Pumping laser systems 31
1.5. The flow of fine particles as the active medium of
metal vapour lasers 34
1.6. Methods for affecting the output characteristics of lasers 37
1.7. Laser cells for copper vapour lasers with a transverse discharge 39
1.8. Laser tubes with a hollow cathode 43
1.9. Modified cells for gas discharge lasers 46
1.10. Laser cells pumped by electron beams 51
1.11. Metal vapour salts lasers 58
1.11.1. Methods for introducing metal atoms into the working zone 58
1.11.2. Gas discharge tubes 59
1.11.3. Methods for producing vapours for hybrid metal vapour lasers 62
1.12. The principles of calculating the thermal regime of emitters 64
2 Excitation circuit and its effect on the lasing
characteristics of self-heating copper vapour lasers 73
2.1. Electrical characteristics of the discharge 77
2.2. Distribution of electrical energy consumed by a rectifier
in different elements of the charger and discharge circuits 78
2.3. Effect of the charging circuit on the lasing characteristics
of self-contained lasers 78
2.4. Influence of the discharge circuit on the lasing characteristics
of self-contained lasers 81
2.5. Features of the thyratron in pulse-periodic copper vapour lasers 92
3 Excitation circuits of self-contained lasers 105
3.1. Discharge circuits that increase the steepness of the leading
edge of the voltage pulse on electrodes of gas discharge tubes 105
vi Contents
3.2. Excitation circuits with pulse transformers 110
3.3. Thyratron excitation units with higher excitation pulse
repetition frequency and increased switching capacity 115
3.4. Excitation units with Blumlein circuits 124
3.5. Excitation units reducing the effect of cataphoresis on
the loss of working metal from GDT 127
3.6. Thyratron–thyristor excitation drive units 128
3.7. Generators of dual pulses and excitation pulse trains 132
3.8. Excitation pulse generators on tacitrons and vacuum triodes 134
3.9. Excitation circuits of pulse-periodic lasers with
dischargers as switches 136
3.10. Excitation circuits with semiconductor switches 139
3.11. Methods for controlling the characteristics of metal
vapour lasers 145
3.12. Prospects for the development of excitation pulse generators
of self-contained lasers 149
4 Repetitively pulsed self-contained lasers 154
4.1. The history of research of repetitively pulsed metal vapour
lasers 154
4.2. The radial inhomogeneity of the plasma parameters in the
repetitively pulsed self-contained lasers 162
4.2.1. The heterogeneity of the temperature distribution of gas 163
4.2.2. Heterogeneity of prepulse density distributions of the
concentration of the atoms of inert gas and working metal
in the ground state 166
4.2.3. The heterogeneity of prepulse electron concentration
distribution 167
4.2.4. The heterogeneity of prepulse electron temperature distribution
and concentration of metastable atoms 169
4.2.5. The heterogeneity of the distribution of plasma parameters
during the excitation pulse 170
4.3. The gas temperature in repetitively pulsed copper vapour
lasers 172
4.4. The results of measurements of concentrations of
metastable and resonance-excited atoms of working metal
in lasers at self-contained transitions of metal
atoms 183
4.5. The concentration and temperature of electrons in self-
contained lasers 195
4.5.1. The concentration and temperature of the electrons
during the excitation pulse 195
4.5.2. Concentration and temperature of electrons in the
interpulse interval in lasers with a GDT of small
Contents vii
diameters (d < 2 cm) 199
p
4.5.3. Concentration and temperature of electrons in large-diameter
GDTs 207
4.6. The concentration of atoms of the working metal in
self-contained lasers 211
5 The results of analytical studies of self-contained lasers 228
5.1. The characteristics of the lasing pulse of the self-contained
lasers 229
5.2. Lasing characteristics of copper vapour laser 235
5.3. Analytical solution of the characteristics of lasing pulse
of copper vapour lasers with the development of ionization
taken into account 242
5.4. The influence of self-absorption of stimulated emission
on the lasing characteristics 249
5.5. Similarity relations for pulsed metal vapour lasers 253
6 Numerical studies of pulsed metal vapour lasers 260
6.1. Physical and mathematical formulation of the problem 261
6.2. The calculated dependences of the coefficients,
cross sections, rate constants and frequencies of elementary
physical processes 265
6.3. Methods of solution, software and results of numerical
experiments 275
6.4. Copper vapour laser 289
6.4.1. Monopulse operating mode of a copper vapour laser
with a Maxwellian electron energy distribution function 289
6.4.2. Calculation of single-pulse operating mode a of copper vapour
laser with the non-Maxwellian electron energy
distribution function 291
6.4.3. Frequency operating mode of a copper vapour laser with neon
in the mixture 281
6.4.4. Operation of a copper vapour laser at high buffer gas pressure 304
6.4.5. A parametric study of the effect of initial data on the
energy characteristics of a CVL 314
6.5. Europium vapour laser 320
6.6. Optimization of parameters of metal vapour lasers 332
7 Numerical modeling of repetitively pulsed copper vapour
lasers taking into account the heterogeneity of distribution
of plasma parameters (inhomogeneity of discharge) over
the cross section of the gas discharge tube 345
7.1. The place and role of model studies of repetitively pulsed
copper vapour lasers, taking into account the radial
inhomogeneity of the plasma parameters [1–6] in a number
viii Contents
of other numerical studies of such lasers 345
7.2. The results of numerical studies of repetitively pulsed
CVLs, assuming uniform distribution of plasma parameters
over the cross section of the GDT [1–3] 347
7.3. Typical radial distributions of the prepulse plasma parameters
in the repetitively pulsed copper vapour lasers 356
7.4. The equations for calculating the lasing characteristics
in the conditions of inhomogeneous distribution of plasma
parameters over the cross section of the GDT 358
7.5. Dynamics of lasing in a radially inhomogeneous active
medium of a copper vapour laser 361
7.6. Effect of radial inhomogeneity of the plasma parameters
on the efficiency and specific lasing energy and efficiency
of the CVL 365
7.7. Effect of the excitation pulse shape on the lasing
characteristics of a CVL 371
7.8. Lasing characteristics of repetitively pulsed CVLs 374
7.9. Comparison of the results of calculations [4–6] and
experiment 385
7.10. Self-consistent models, taking into account radial
inhomogeneities 392
8 Simulation of copper vapour lasers. Kinetically
enhanced lasers 397
8.1. Introduction 397
8.2. The kinetic model 397
8.3. The electron distribution function 400
8.4. Restrictions on pulse repetition rate 416
8.5. Lasers with modified kinetics (kinetically enhanced lasers) 444
8.5.1 Additions of hydrogen 445
8.5.2. Hydrogen chloride additives 479
8.6. Formation of high-quality radiation of the copper vapour
laser in the master oscillator–amplifier system 510
8.6.1. The dependence of the additional power, taken from
the amplifier, on the pump power 520
Index 529
Foreword
The lasing at self-contained transitions of metal atoms was achieved
for the first time in lead vapours [1] in 1965, at the transition between
the resonant level 6p7s 3P01 and one of the levels 6p2 1D2 of the basic
configuration, at a wavelength of 722.9 nm. Since then, many studies
have been published that contain the results of research and development
of lasers on self-contained transitions of metal atoms. Moreover, in the
meantime numerous attempts have been made (see [2–7]) in some way
to summarize the results of studies carried out by different groups,
primarily in the USA and the former USSR.
12 years has passed since the publication of the monograph [6],
which made at that time a significant contribution to the development
of research and development of the self-contained metal vapour lasers.
During this time the investigations were almost completed of the
physical processes taking place in the active medium of self-contained
lasers and determining their lasing parameters; mathematical models
of these lasers were developed with different degrees of accuracy
so that it was possible to transfer from physical investigations to
numerical experiments in order to determine the optimum operating
conditions as regards the efficiency or the mean lasing power of the
self-contained lasers; new methods of development of these lasers
have been formulated. Constant interest in the lasers at self-contained
transitions of metal vapours has been maintained by the extensive
possibilities of using them in solving various applied problems.
The last and relatively successful attempt for the collective
generalization of the results of investigations of self-contained lasers
is a collection of the Proceedings of the International Scientific School:
Pulsed metal vapour lasers, organised in 1995 at the St. Andrews
University (Scotland) under the supervision of NATO. The proceedings,
published for this scientific school [8], provides quite complete