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1 Introduction: The New Era of High Energy Lasers
Prospect of the Laser System Upgrading
of our present 6 atm CO2-HPA as well as possibility of increasing its operating
pressure up to 10 atm in order to amplify laser pulses as short as 1 ps (Sect. 2.2).
We are planning to realize these possibilities in te very near future since they do not
demand principal reassembling of present laser system. We also have some other
plans (for longer terms) for our system upgrading:
1. Investigating the possibility of using N2O:CO:N2:He mixtures in our CO2-HPA
instead of traditional CO2:N2:He ones. It should be noted that owing to lower
group of symmetry of N0 molecule if compared with CO2 neighboring
rotational-vibration transitions in the N2O molecule are located twice as close to
each other compared with CO2 molecule. Therefore, it is possible to realize
smooth gain spectrum of N2O molecule owing to pressure broadening of laser
transitions at the pressures of gas mixtures 5–6 atm, thus considerably
decreasing the level of pulsed high-voltage applied to the discharge chamber. It
should be also noted that utilization of such a gas mixture is many orders less
expensive compared with CO2 multiisotopic mixtures. Of course we understand
that it will not be an easy problem. Owing to the substantially higher attachment
of electrons to N2O molecules compared with that of CO2 the kinetics of the
SSVD in N2O mixtures strongly differs from that of CO2. However, we had
already realized SSVD in N2O gas mixtures of 1 atm pressure with record
values of SSVD active volume (20 Â 20 Â 125 cm3), efﬁciency (6.7%) and
light energy (465 J)  and have a good experience in investigation of kinetics
of SSVD in such gas mixtures.
2. We are sure that repetition rates of *60 Hz can be realized in our laser system.
All elements of our present MO scheme can operate at f * 60 Hz with reasonable upgrading. The e-beam gun utilized in our CO2–HPA can also operate
at such repetition rates if we provide more effective evacuation systems for
vacuum diode compared with present one (this necessity is caused by evaporation of graphite into the volume of the diode at each shot of the gun). All
elements of our DPPHVG (capacitors and spark gaps) can also operate at such
repetition rates; moreover, the spark gaps were elaborated to work at f < 100 Hz
in the gas flow mode of operation (in the present laser system, there is no need to
use this option but it can be put into operation easily). The main problem for
60 Hz operation of CO2–HPA is to provide gas flow mode of operation of the
discharge chamber. It will evidently demand its reassembling and modiﬁcation
or more probable construction of a new one. It should be noted that construction
of TEA-CO2 lasers with f up to 20 Hz and active volumes of 5–10 1 and
TEA-CO2 lasers with f up to 400 Hz and single pulse energy of *1 J.
3. The utilization of e-beam gun in laser systems demands a high vacuum pump
system (to provide 10−5 Torr). The presence of this system evidently substantially increases the weight and dimensions of CO2–HPA as well as making its
operation more complicated. It is also evident that additional problems will
occur when transitioning to high repirates. As such, we are now searching for
alternative systems of gas mixture preionization and one of the possible methods
is pulling electrons out of the barrier close-to-cathode discharge and into the
Wide Aperture Picosecond CO2 Laser System
discharge gap. We have a wealth of experience in utilizating this type of
preionization in TEA-CO2 discharge units with interelectrode spacing of up to
60 cm and we hope to use this for superatmospheric pressure gas mixtures .
If we are successful in this endeavor, this will considerably simplify the construction and operation of our CO2–HPA.
1. We have put a CO2 laser system in operation with high aperture (5 Â 5 cm2),
6 atm ampliﬁer, that generates a train of subnanosecond laser pulses with sum
energy of up to 5 J.
2. Our estimates based on scaling laws of SSVD stability with pressure indicate
that we can obtain SSVD in our CO2-HPA at P = 10 atm for interelectrode
spacing =4 cm, present gas mixture (CO2:N2:He = 10:5:85) and energy loading
densities >100 J/(l atm). Such a discharge unit can effectively amplify 10 lm
laser pulses as short as 1 ps.
3. There are no principal limits for upgrading our laser system to operate with
repetition rate *60 Hz. However, such a modiﬁcation of the setup will obviously demand solutions to a number of technical problems.
1. V.V. Apollonov, A.I. Artemyev, Yu.L. Kalachev, A.G. Suzdaltsev, A.M. Prokhorov, M.V.
Fedorov, Electrons acceleration by intence laser radiation ﬁeld in the presence of static
magnetic ﬁled. JETF 97(5), 1498–1510 (1990)
2. J. Amesson, F.K. Kneubuhl, Future laser-driven particle accelerators. Infrared Phys. 25,
3. S.A. Jamison, A.V. Nurmikko, Generation of picosecond pulses of variable duration at
10.6 lm. Appl. Phys. Lett. 33(7), 589–600 (1978)
4. P.B. Corkum, High-power, subpicosecond 10 lm pulse generation. Opt. Lett. 8, 514–516
5. P.B. Corkum, Ampliﬁcation of 10 lm Pulses in Multiatmosphere CO2 Lasers. IEEE,
J. Quantum Electron. QE-21, 216–232, (1985)
6. Z.A. Biglov, V.M. Gordienko, V.T. Platonenko, V.A. Slobodyanyuk, V.D. Taranukhin, SYu.
Ten, Generation and ampliﬁcation of phazemodulated picosecond pulses of 10 lm range.
Izvestiya AN USSR, Seriya Fizicheskaya 55, 337–341 (1991)
7. P.B. Corkum, C. Roland, High Energy Picosecond 10 lm Pulses. Proc. SPIE 664, 212–216
8. V.V. Apollonov, G.G. Baitsur et al., SSVD initiated by UV radiation and electrons of plasma
of spark discharge on the surface of dielectric (in Russian). Pis’ma v zhurnal telhnicheskoi
ﬁziki 14, 2107–2110 (1988)
9. A.G. Gordeichik, A.G. Maslennikov, A.A. Kuchinsky, V.A. Rodichkin, V.A. Smirnov, V.
P. Tomashevich, I.V. Shestakov, E.G. Yankin, Pulsed CO2 laser pumped by SSVD and
preionized by soft X-ray (in Russian), Kvantovaya Elektronika 18(10), 173–1175 (1991)
10. A.J. Alcock, P.B. Corkum, Ultra-fast switching of infrared radiation by laser produced
carrirers in semiconductors. Can. J. Phys. 57, 1280–1290 (1979)
11. P.E. Dyer, I.K. Perera, Pulse evolution in injection mode locked TE CO2 lasers. Appl. Phys.
23, 245–251 (1980)
12. P.B. Corkum, A.J. Alcock, Generation and ampliﬁcation of short 10 pm pulses. in Picosecond
Phenomena, Springer Series in Chemical Physics, ed. by C.V. Shank, E.P. Ippen, S.L.
Shapiro, vol. 4 (1978), p. 308–312
13. V.V. Apollonov et al., N2O laser pumped by SSVD. Kvantovaya Elektronika 16, 1303–1305
14. V.V. Apollonov et al, High-power CO2 and N2O lasers with SSVD pumping. J. Opt. Soc. Am.
B 8(2), 220 (1991)
Lasers for Industrial, Scientiﬁc
and Ecological Use
Abstract This chapter is based on a long-term experience of the development and
operation of lasers and contains tested technical solutions on designing separate
units as well on the laser on the whole. The best overall dimensions and operation
characteristics and the prospects of additional chemical pumping put AMT GDL in
the forefront among other powerful industrial lasers. High repetition rate
pulse-periodic regime of high power laser radiation generated by AMT GDL on the
level of >100 kW of average power is the most important step for effective
implementation of many different laser-based technologies of the time. The very
near future will highlight the total potential of high-energy lasers, which will be
used effectively for processing materials and for the solution of other important
challenges faced by future science and technology. However, today it is possible to
say that creation of megawatt high-repetition-rate P–P lasers with a large cross
section of the active medium will open up an avenue for their use in solving the
problems of launching small satellites with lasers, formation of super-long conducting channels in space and atmosphere, and cleaning of the near-Earth space
from space debris, etc. Hopefully, the mono-module disk laser will have a lot of
advantages in comparison with the many other lasers observed in the present
Introduction: The New Era of High Energy Lasers
So, the SDI age is over. The age that was very much influencing research and
development in the area of high power and high energy lasers. These days, we have
extremely strong demand for the development of very powerful lasers (>100 kW)
for civil applications . Now the modern level of laser technology development
makes laser methods of materials treatment more and more competitive. In particular, disregarding the higher price of the equipment applied, laser welding of
metals provides a signiﬁcant increase in productivity, a higher quality of the weld
practically without any following mechanical processing, and low residual stresses
© Springer International Publishing Switzerland 2016
V.V. Apollonov, High-Energy Molecular Lasers,
Springer Series in Optical Sciences 201, DOI 10.1007/978-3-319-33359-5_47
47 Lasers for Industrial, Scientiﬁc and Ecological Use
in the welded products. The world market of powerful industrial lasers (average
power level 1 Ä 15 kW) applied for cutting and welding of metal structures of
1 Ä 10 mm thick has been actively formed.
At the same time, there are a number of technical problems, the solution for
which is signiﬁcantly simpliﬁed by the application of industrial powerful lasers
(within the range of 50 Ä 100 kW). In particular, the areas of applications for
autonomous mobile technological laser complexes (AMT GDL) are the following:
• Cleaning the coast line from oil products following oil emergency overflow and
cleaning of water surface from oil layer including thin iridescent layer that can
not be effectively removed by any other methods;
• Remote cutting of metal and armored concrete constructions in a course of
demontage and emergency repair on nuclear power plants, oil and gas boring
wells, in a process of emergency work after an earthquake and other natural
disasters; cutting up ships and submarines to metal scrap;
• Remote treatment of large metallurgical chemical, mining equipment in the
course of assembling and repair;
• Special technologies for use at speciﬁc conditions of different productions such
as cutting of materials and metal constructions, welding and surface treatment;
• Operative struggle with ice-covering of port equipment, constructions and
• Laser-based decontamination of surfaces by peeling in a process of emergency
works after natural disasters and different accidents;
The upper level of estimation for output power of laser should be given by:
Á 0:75 Á v
1:26 v ỵ 0:126 v ỵ
1 ỵ p
The variables in the expression are given in: h—[cm]; W—[kW]; v—[cm/s];
G—[g/s]. In order to increase cut depth, a simultaneous increase of power and gas
flow rate are required and taking into account the losses, the power needed for
cutting the samples 35 cm thick should be %100 kW (v = 0.3 cm/s; G = 20 g/s).
There are several variants of high-energy laser beams application on removal of
a thin oil ﬁlm from the water surface, removal of the results of disasters, accidents
and catastrophes. In these cases, price and work expenses do not play the primary
role. The ﬁrst place is occupied with the requirements for the reliability of high
average power lasers; the overhaul period without putting additional components;
simplicity in service; and operation and ecological safety. More than this, as the
objects of operation are located outside workshops and far away from electric
power sources, one of the basic requirements for a powerful high energy laser for
such application is its mobility and full autonomy. As such, most attention had been
devoted to the discussions and experimental realizations of autonomous mobile
technological gas-dynamic laser (AMT GDL) .
Comparison of Some Types of Lasers …
Comparison of Some Types of Lasers That Can Be
Scaled up to the Average Power Level >100 kW
Among all types of lasers that can be scaled up to the average power level
50 Ä 100 kW, the following lasers can be taken for industrial applications:
Gas-dynamic CO2-laser (CO2 GDL),
Chemical oxygen-iodine laser (COIL);
Gas-discharge CO laser;
Let’s make a short comparison of the above-given lasers.
A CW chemical HF-laser can be rather powerful and effective but it is typical of
low pressure of the active medium (not exceeding several mm Hg) and a toxic
exhaust. Hence, on the ground, this laser can operate only with vacuum vessels,
which doesn’t satisfy the requirements of a long-term operation.
Intensive development in the latest period chemical oxygen-iodine laser (COIL)
does not seem attractive from the point of view of ecology and the exploitation of
SCT lasers satisfying the above-given requirements, although the potential of this
COIL-laser for the creation of other industrial lasers cannot be stressed highly
enough. This laser also has a rather low work pressure; its exhaust gases have
iodine vapors. Chemical means of the production of oxygen delta requires components difﬁcult in application (chlorine, alkali, hydrogen peroxide etc.) and rather
big chemical reactors. Gas-discharge method of the oxygen delta production does
not improve the situation signiﬁcantly and is yet to be developed perfectly. The
price of application of a COIL of such power is assumed by specialists to be
50 Ä 60 US$ per a kW h of laser, which makes is unproﬁtable.
A gas-discharge CO laser has a rather high efﬁciency (of the order of 40%).
However, for a long-term operation of the industrial CO laser with an open working
cycle and output power of 50 Ä 100 kW, a rather high consumption of cryogenically cooled CO and N2 (of the order of 3 Ä 4 tons/h) will take place. In
addition, the bulky store systems of the components, the system of laser
gas-dynamic pat cooling as well as complex high-power electric devices will be
required. The development of a neutralizing system, which provides ecologically,
permitted CO laser exhaust is of a certain difﬁculty. And the creation of an
industrial CO laser of similar power with the closed cycle in a mobile variant seems
problematic enough because of high consumption of liquid N2 for heat pick up from
its gas-dynamic path.
The application of gas-discharge CO2-lasers is discussed in two variants: open
and closed cycles. Disregarding a much lower efﬁciency comprised to a CO laser, a
gas-discharge CO2-laser of the closed cycle is simpler technologically than the
analogous CO laser since its gas-dynamic path is not cooled to cryogenic
47 Lasers for Industrial, Scientiﬁc and Ecological Use
temperature and heat dissipated by the laser can be removed by means of water heat
exchangers. Here the operation of a gas-discharge CO2-laser of the closed cycle is
fulﬁlled on the mixture of CO2:N2:HE with helium content of up to 50%, and the
mixture should be renewed in the amount of %1% per each one of its rounds over
the gas-dynamic path. Hence the laser with the power of %100 kW will consume
expensive helium for mixture renovation in the amount not less than 35–40 kg/h,
which makes its operation much expensive. This laser is a more complex than the
analogous one with an open cycle and of much higher weight and overall dimension. That’s why it’s more advantageous in operation under stationary conditions
with a long daily operation cycle where in the ﬁrst place the level of operation
expenses is. At the same time a gas-discharge CO2-laser of the open cycle is more
suitable for the SCT laser creation.
One of the variants of the mobile non-SSVD industrial CO2-laser of an open
cycle developed in Russia with the power of 50 kW, which operates on the mixture
of CO2 and the atmospheric air. This laser is designed for works on recovery after
accidents in oil and gas wells, operates from on-board components for 10 min and
weights 30 tons. For operation, it requires an external power source of ! 600 kW.
Work components of this laser consume:
• CO2 gaseous
• Fuel (aircraft kerosene)
• Cooling water
The laser is located on two vehicles and requires a powerful electric power
source (in the ﬁeld—a mobile electric station). As such, such a laser is not
acceptable for many areas of applications.
Mobile CO2-AMT GDL
The experience of the developments show that the best weight & overall dimensions with power levels 50 Ä 100 kW have gas-dynamic CO2-lasers (GDL). GDL
is not restricted by a stationary power source and does not require intermediate
transformers from heat energy into the electric one, it does not need additional
systems for spent gases exhaust into the atmosphere, it is rate easy in operation, is
highly reliable and has a long service time. All these factors, make GDL most
suitable for the creation of SCT laser of full value with the application of air as an
oxidizer and sowbelly-spread and low-toxica matter as aircraft kerosene (C12H22)
and toluene (C7H8).
Below can see list of technical parameters of AMT GDL based on reconstructed
Mobile CO2-AMT GDL
Output power, kW
Beam diameter, mm
Mode of operation
Angular divergence, rad
Laser fuel (toluene), kg/h
Engine fuel (kerosene), kg/h
Sucked air flow rate, kg/s
Bled off air flow rate, kg
Compressed air pressure, MPa
Time of continuous operation, min
Total service life, h
Power unit and laser device overall
Setup weight, kg
3 Á 10−4
3 Á 10−4
7000 Â 3000 Â 2500
400 Ä 500
7000 Â 2000 Â 3000
It follows from the list that the cost of 1 kW h of laser power in such AMT GDL
are not exceeding 15 US$, which is 4 times lower than for COIL.
It should also be noted that there is a possibility of a more complete reconstruction of RD-33 engine, which allows to bled off up to 14 kg/s of compressed air
under the pressure of 2.3 Mpa. Here the output power of AMT GDL with the same
operation expenses may reach 100 kW.
The AMT GDL is a module structure mounted in standard container. During the
development of this scheme the experience of the creation of autonomous electric
stations based on aircraft engines was applied. The container design allows providing its transportation by all types of vehicle as well as comfortable working
conditions for the personnel.
It is well know that the speciﬁc output in a GDL Wsp is determined by the
composition of the active medium at the input of the nozzle unit, its stagnation
temperature, T0, and pressure, p0, the dimension of the restricted section of the
nozzle, hcr, as soon as active area width l and optical resonator parameters. All these
parameters depend on each other.
The calculations of the speciﬁc power output, Wsp, of the industrial AMT GDL
were made assuming for the application of an unstable optical resonator. Speciﬁc
output for kerosene constitutes 5 and 7 kW/kg with the expansion ratio values of 15
and 23, respectively, and for toluene 7 and 9 kW/kg.
Table 47.1 gives output power values W for some variants of GDL creation.
47 Lasers for Industrial, Scientiﬁc and Ecological Use
Table 47.1 Output power values W for some variants of fuel for GDL
1300 Ä 1400
1400 Ä 1500
0.26 Ä 0.28
0.38 Ä 0.40
50 Ä 70
100 Ä 130
As it follows from the given data, the operation of industrial GDL requires the
source of compressed air with the pressure %1.7 Ä 2.3 Mpa and the flow rate of
10 Ä 14 kg/s. Such parameters can be provided by a specially designed compressor
driven by the gas-turbine engine (GTE). The advantage of such an approach is in
the possibility of optimization parameters of the air fed to the laser. For powerful
industrial GDL, operating under stationary conditions, the variant of GTE’s feeding
from a natural gas source can be discussed. This cuts the operation expenses in half.
At present, the structure on the basis of a serial aircraft engine appears to be
more prepared for application. Besides its compressor, it is able to give a portion of
the compressed air required for operation of the laser. In such a case, the aircraft
engine should not only be able to allow to be bled off the required air portion but
also to provide required pressure. A comparative analysis of aircraft engines produced in Russia showed that as a gas-turbine compressor unit of an industrial GDL,
a serial RD-33 engine, can be taken. The engine provides sucked airflow rate of up
to 80 kg/s and the degree of complete pressure increase pk % 22. As the studies
show, it is quite possible to bled off up to 9 kg/s of air heated to %700 K under the
pressure of %20 Mpa after a rather simple reconstruction of this engine .
An input ejector is positioned at the engine input, behind the low-pressure
turbine an output ejector is situated that provides the external air pumping through a
heat exchanger where heat pick up from the coolant system of units of the laser
module (flow part of optical resonator, diffuser, resonator mirrors etc.). The input
and output ejectors are of a lobe type because these devices simultaneously fulﬁl the
function of noise suppressors. In a high-pressure compressor, compressed air is fed
to the laser device, which is located behind the engine. The exhaust laser and engine
gases are sent to the common exhaust device.
The possibility of the application of GDL in the form of industrial laser imposes
a number of speciﬁc demands on the structure, which were not met by the developers of laser system before. First of all, this concerns the necessity of continuous
operation during 6–8 h under conditions of multiple switching OFF and ON with
the service life of at least a year without the replacing of any parts and units. This is
achieved by the application of materials capable of operation under the temperatures up to 1500 Ä 1600 K and the application of cooled structures.
Efﬁciency Increase of the AMT GDL …
Efﬁciency Increase of the AMT GDL by Additional
The further development of an idea lying in the basis of GDL has yielded
appearance of the so-called chemical GDL. The latter approach is based on the
optimization of the active medium parameters by the burning process control.
Altering the coefﬁcient a (deviation from stoichiometry) in the various stages of the
process, feeding the fuel, other components into corresponding areas of the combustion chamber, one may control the portion of chemical energy supplied in the
rotational levels and simultaneously decrease the temperature of gas immediately
before the nozzle array.
Investigations demonstrated signiﬁcant growth of speciﬁc energy characteristics
(in particular gain) compared with the conventional GDL; expected advantages of
AMT CGDL are also:
• Smaller consumption of gas and fuel components;
• The temperature of the working gas immediately before the nozzle array may be
decreased to 1000 Ä 1200 K, which essentially simpliﬁes the choice of the
materials, cooling of gas flow path; and the entire lifetime of the laser unit
• Due to essential lowering of working gas temperature, the extension ratio of a
nozzle and switch pressure of the diffuser (at atmospheric exhaust) may be
diminished; hence the blade becomes more manufacturable and of durable;
• Energy consumption, and weight-overall dimension become smaller signiﬁcantly.
High Repetitive Pulsed Regime of the AMT GDL
One of the ways of GDL operation mode control and optimization is based on use
of active intracavity optics. It enables modulation of transparency of the resonator
in the frequency range up to many tens of kHz (30–60 kHz) and thus to form the
required temporal modulation of laser radiation. This problem concerns with the
high power GDL is of an essential interest. The possibility to accomplish such a
mode of operation is considered in details .
New Approach to High Energy Lasers—
Mono-Module Disk Laser
The mono-module disk laser concept is an effective design for diode-pumped
solid-state lasers, which allows the realization of lasers with a super-high output
average power, having very good efﬁciency and excellent beam quality. Since the
47 Lasers for Industrial, Scientiﬁc and Ecological Use
ﬁrst demonstration of the principle in 1964, the output power of mono-module disk
lasers has been increased to the level of a few kW in continuous wave (CW) mode.
“Zig-Zag” disk laser geometry is not, in our opinion, promising for scaling up the
laser output. The scaling laws for the mono-module disk laser design show that the
limits for CW mode are far beyond 100 kW for the output power, and the energy
can be higher than 100 J in pulsed mode. Owing to efﬁcient porous cooling technology and possibility of suppressing ampliﬁed spontaneous emission (ASE),
mono-module disk lasers can operate in CW and pulse-periodic (P–P) regimes at
extremely high output powers.
It has long been customary that as new technologies emerge into the light,
potential users and experts start wondering whether these new technologies will
replace the old, well-established approaches to the solution of known problems.
When we look back at the time when the ﬁrst laser was created, it becomes clear
that each new and more advanced technology usually replaces the pre-existing and
well-proven technologies. However, a more differentiated and balanced assessment
of the many innovations in the ﬁeld of laser shows that there is no such thing as a
perfect design, or an ideal laser. There is always room for improvement and further
development. It is possible that in the near future a laser with disk geometry of the
active medium will become the dominant technology. However, despite this, a
number of existing laser technologies (with some exceptions, of course) will continue to improve for quite a long time. Based on these considerations, we must
continue to develop most types of lasers, each time clearly specifying their undeniable technological niche and knowing well their advantages and disadvantages.
High efﬁciency and excellent beam quality of disk lasers means that they can be
widely used in modern science and industry for a very large range of applications,
including treatment of the surface of dielectric materials in microelectronics, cutting, drilling, welding, polishing and cleaning of the surface, and other technological operations with superhard and fragile metals and composite materials, etc.
Pulse-periodic Q-switched disk lasers and high-average-power, mode-locked laser
systems ensure optimal conditions for ablation (sublimation) of a material.
A number of advantages of high repetition rate P–P lasers emitting short pulses, as
applied to a wide range of industrial technologies, is the basis of many modern
concepts of disk lasers. High-intensity light with an insigniﬁcant thermal lens effect
in the central highly loaded zone of the active medium has led to the lifting of
restrictions on the brightness of the pump diode. This has reduced the cost of laser
sources, and thus has signiﬁcantly improved the efﬁciency of electro-optical conversion, especially in the regime of high average powers. The power of the laser
source is varied by scaling the cross sectional area of the generated radiation. It
should be noted that its ratio to the thickness of the active material in disk geometry
is much larger than the ratio of the cross section of typical core elements of the
active medium to their length in any conventional solid-state laser system. This
eliminates the problems associated with nonlinear distortions of the geometry of the
active medium, and enables realization of super high peak and average powers of
laser sources with disk geometry and same parameters of radiation in the far-ﬁeld