Femtosecond laser plasma: review of investigation and calculational model
Review of experimental and theoretical investigation of physical processes in femtosecond laser plasma is presented. Such effects, as X-ray and electric-magnetic wave emission, high energy electron and ion beams are described. It isshown that ultrashort laser pulse with duration comparable to period...
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irk-123456789-795312015-04-03T03:02:13Z Femtosecond laser plasma: review of investigation and calculational model Bugrov, N. Kholod, S. Zaharov, N. Plasma dynamics and plasma wall interaction Review of experimental and theoretical investigation of physical processes in femtosecond laser plasma is presented. Such effects, as X-ray and electric-magnetic wave emission, high energy electron and ion beams are described. It isshown that ultrashort laser pulse with duration comparable to period of wave oscillation (lessthan a few femtoseconds) is absorbing by inner electronsin contrast to absorption of more lasting laser pulses by outer electrons. The problem of mathematical modelling of these processes and corresponding computer code development is observed. Technological applications, such as production of high power X-ray and particles plasmassources, laser precision shaping and machining of different materials are discussed. Представлено огляд експериментальних і теоретичних досліджень фізичних процесів, що відбуваються у фемтосекундній лазерній плазмі. Описано такі ефекти, як рентгенівське й електромагнітне випромінювання, високоенергетичні електронні й іонні пучки. Показано, що ультракороткий лазерний імпульс тривалістю, порівнянною з періодом коливання хвилі (меншою ніж декілька фемтосекунд), поглинається внутрішніми електронами, на відміну від більш тривалих імпульсів, що поглинаються зовнішніми електронами. Розглянуто задачу математичного моделювання цих процесів і створення відповідного комп'ютерного коду. Обговорено технологічні аспекти, такі, як створення могутніх джерел рентгенівського випромінювання і плазми, формування лазерного пучка й обробка різних матеріалів. Представлен обзор экспериментальных и теоретических исследований физических процессов, происходящих в фемтосекундной лазерной плазме. Описаны такие эффекты, как рентгеновское и электромагнитное излучение, высокоэнергетичные электронные и ионные пучки. Показано, что ультракороткий лазерный импульс длительностью, сравнимой с периодом колебания волны (меньшей, чем несколько фемтосекунд), поглощается внутренними электронами, в отличие от более продолжительных импульсов, которые поглощаются внешними электронами. Рассмотрена задача математического моделирования этих процессов и создания соответствующего компьютерного кода. Обсуждены технологические аспекты, такие, как создание мощных источников рентгеновского излучения и плазмы, формирование лазерного пучка и обработка различных материалов. 2005 Article Femtosecond laser plasma: review of investigation and calculational model / N. Bugrov, S. Kholod, N. Zaharov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 94-95. — Бібліогр.: 4 назв. — англ. 1562-6016 PASC 52.38.-r; 52.38.Mf; 52.38.Ph; 52.50.Jm http://dspace.nbuv.gov.ua/handle/123456789/79531 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Plasma dynamics and plasma wall interaction Plasma dynamics and plasma wall interaction |
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Plasma dynamics and plasma wall interaction Plasma dynamics and plasma wall interaction Bugrov, N. Kholod, S. Zaharov, N. Femtosecond laser plasma: review of investigation and calculational model Вопросы атомной науки и техники |
| description |
Review of experimental and theoretical investigation of physical processes in femtosecond laser plasma is presented. Such effects, as X-ray and electric-magnetic wave emission, high energy electron and ion beams are described. It isshown that ultrashort laser pulse with duration comparable to period of wave oscillation (lessthan a few femtoseconds) is absorbing by inner electronsin contrast to absorption of more lasting laser pulses by outer electrons. The problem of mathematical modelling of these processes and corresponding computer code development is observed. Technological applications, such as production of high power X-ray and particles plasmassources, laser precision shaping and machining of different materials are discussed. |
| format |
Article |
| author |
Bugrov, N. Kholod, S. Zaharov, N. |
| author_facet |
Bugrov, N. Kholod, S. Zaharov, N. |
| author_sort |
Bugrov, N. |
| title |
Femtosecond laser plasma: review of investigation and calculational model |
| title_short |
Femtosecond laser plasma: review of investigation and calculational model |
| title_full |
Femtosecond laser plasma: review of investigation and calculational model |
| title_fullStr |
Femtosecond laser plasma: review of investigation and calculational model |
| title_full_unstemmed |
Femtosecond laser plasma: review of investigation and calculational model |
| title_sort |
femtosecond laser plasma: review of investigation and calculational model |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Plasma dynamics and plasma wall interaction |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79531 |
| citation_txt |
Femtosecond laser plasma: review of investigation and calculational model / N. Bugrov, S. Kholod, N. Zaharov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 94-95. — Бібліогр.: 4 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-06T03:33:05Z |
| last_indexed |
2025-07-06T03:33:05Z |
| _version_ |
1836866901281603584 |
| fulltext |
FEMTOSECOND LASER PLASMA: REVIEW OF INVESTIGATION
AND CALCULATIONAL MODEL
N. Bugrov, S. Kholod, N. Zaharov
CIPT DM RF, Russia
Review of experimental and theoretical investigation of physical processes in femtosecond laser plasma is presented. Such
effects, as X-ray and electric-magnetic wave emission, high energy electron and ion beams are described. It is shown that ultrashort
laser pulse with duration comparable to period of wave oscillation (less than a few femtoseconds) is absorbing by inner electrons in
contrast to absorption of more lasting laser pulses by outer electrons. The problem of mathematical modelling of these processes
and corresponding computer code development is observed. Technological applications, such as production of high power X-ray
and particles plasmas sources, laser precision shaping and machining of different materials are discussed.
PASC 52.38.-r; 52.38.Mf; 52.38.Ph; 52.50.Jm
PROCESSES OF INTERACTION OF LASER
RADIATION WITH SUBSTANCE
The increasing amount of the works devoted to femtosecond
laser plasma physics in last time, indicate to new achievements
in this area, both regarding to theoretical researches, and
regarding to development of applied problems.
Effects of interaction of ultrashort laser radiation with the
condensed environment can be illustrated by following circuit.
Thermal particles
to 2 keV
Fast electrons
1 keV – 20 MeV
Soft X-rays
100 eV – 2 keV
Hard X-rays
2 keV – 1 MeV
Fast ions
10 MeV
Laser pulse absorption
and reflection
At interaction of a intense (q = 1016-1020 W/cm2)
femtosecond laser pulse with condensed matter, the thin layer
of solid density plasma (~ 0,1-1 mm), cold ions and hot
(more 1 keV) electrons is formed. Therefore it is necessary to
take into account mechanisms of plasma formation and
absorption of laser radiation in this layer of plasma.
PLASMA OPTICAL PROPERTIES
Researches show [1], that absorptive ability formed near-
surface plasmas depends on intensity, length of a wave and
polarization of laser radiation, angle of its falling on a target
and characteristics of the target. The value of absorption
coefficient is from 20 % to 60 % and has the maximum for the
p-polarized laser radiation falling under a angle ∼ 60°. So, at
fig.1 the dependence of reflection coefficient Al-plasma versus
angle of laser pulse falling is shown.
GENERATION OF X-RAY RADIATION
Fast electrons, due to the big length of free run, are
capable to penetrate into cold target area before front of a
thermal wave. Thus, as bremsstrahlung at collision with
cold ions, as ruled radiation at knocking-out of electrons
from K-shells is formed.
The bremsstrahlung turns out as a continuum in an
interval 0,1 keV – 1 MeV and depends on laser intensity
and parameters of plasma whereas radiation from K- and
other internal nuclear shells can have energy 1 – 100 keV
and depends on nuclear number of a target [2].
Soft X-ray emission occurs both in lines, and in a continuous
spectrum of bremsstrahlung, and can occupy time, much
greater (~ 20 times), than duration of a laser pulse. For
example, in experiments with the XeCl-laser (λ = 0.308 µm,
q = 1017 W/cm2) and metal targets, X-ray pulses with energy
more than 200 eV and duration about 7 ps have been received,
whereas duration of a laser pulse was equal 500 fs.
Al
0
0,2
0,4
0,6
0,8
1
0 20 40 60 80
Θ°
R
1
2
Fig. 1. Reflection coefficient of Al-plasma versus angle of
laser pulse falling (q = 2,5∙1015 W/cm2, λ = 0,248 µm,
τp = 200 fs, 1 – s-polarization, 2 – p-polarization, lines –
calculation, points – experiment)
Generation of hard X-ray is carried out during of the
most laser pulse inside of a small angle from a direction of
fast electrons movement. The output of hard X-ray
depends on charging number of target atoms as Z3/2 (see
figure 2) while the temperature of electronic component
formed in plasma poorly depends on structure of a target
and at intensity of laser radiation and is ~ 4 keV for q~
1016 W/cm2 and various materials: from Si (Z = 14) up to
Te (Z = 73).
0
3
6
9
12
15
18
0 20 40 60 80
Ζ
8,7 keV
13 keV
15 keV
20 keV
Si Fe
G
aA
s
Pd Ta
Fig. 2. Dependence of X-ray output from charging number
of target atoms
ELECTROMAGNETIC PULSE GENERATION
Taking off from a target fast electrons create
electromagnetic fields which aspire to return them back.
94 Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. 2. P. 94-95№
Electron’s movement in the self-coordinated
electromagnetic fields outside of a target can lead to dipole
radiation of an electromagnetic wave with ultrashort
duration. In [3] performed calculations for factor of fast
electron energy transformation to electromagnetic wave
10-1 – 10-3 and spot radius r0 = 5 – 20 µm. The main part of
electrons is locked by an electric field in area with the
characteristic size about 1 micron near to an irradiated
surface. Most high energy electrons overcome the
specified area and are turned back to a target at the further
movement. Thus the part from them achieves a surface and
is absorbed by it.
Result of such non-uniform (along an axis 0z)
movements of electrons is generation of an
electromagnetic wave. In a considered case there are all
necessary conditions for dipole radiation.
GENERATION OF FAST PARTICLES BEAMS
At laser pulse interaction with the condensed matter the
fast ions beam is formed. The main mechanism is an
acceleration of ions by induced electrostatic fields in plasma
of targets. Thus fast electrons will move into vacuum and
accelerate ions by means of ambipolar fields. The
calculations [1] show, that at increase of femtosecond laser
intensity more than 1017 W/cm2 the ponderomotive pressure
of a laser beam starts to exceed pressure of plasma, and ions
get a component of speed directed into solid.
ENERGY DISTRIBUTION
The part of the laser energy, expended to formation of
electronic and ionic beams, X-ray and electromagnetic
radiation, is estimated for various parameters of a laser
pulse. It is shown that the factor of transformation of laser
radiation to fast electrons is about 10 % and ~ 1-3 % of
laser energy are capable to be transformed to energy of
ions. The factor of conversion of laser radiation to soft X-
ray can achieve 2 %, and to hard X-ray – 0,1 %. In turn,
the factor of transformation of energy of fast electrons in
dipole electromagnetic wave can achieve 10 %.
It is experimentally established [4], that the ionic beam is
defined at first by atoms of the impurity on a material
surface (the pollution, adsorbed gases: C+, C+2, H+).
ULTRAFAST LASER PULSE ABSORPTION
Process of absorption of laser pulses which duration τp,
comparable to the period of a laser electromagnetic wave
(less several femtoseconds) has quantum character. The
main influence in this case, renders such parameter, as the
ratio of laser pulse duration to a cycle time of electron on
an orbit τp/τe (Fig.3). The value τp/τe is less, the probability
of absorption of radiation quantum by electron is less.
Therefore practically only nearest to a nucleus electrons
can interact with ultrashort laser pulses. The exhaustive
model of such abnormal absorption of radiation till is not
developed now.
0
0,2
0,4
0,6
0,8
1
0 0,5 1 1,5 2
τ p /t e
P abs
Fig. 3. Probability of absorption of 1 fs laser pulse by
electrons of carbon
TECHNOLOGY APPLICATIONS
Examples of technology applications are drilling ultra
small apertures, precision processing of surfaces, creation
of ultra-thin films, production of high power X-ray and
particles plasmas sources.
REFERENCES
1. V.M. Velichko, V.D. Urlin, B.P. Yakutov //
Kvantovaya electronika. 2000, v.30, № 10, p.889-895.
2. A.A. Andreev, A.I. Zapysov, A.V. Tcharuhshev,
V.E.Yashin // Izvestiya AN. Seriya fizicheskaya, (63),
1999, p. 1239.
3. I.A. Litvinenko, V.A.Lykov // Pis’ma v ZhTF. 1998,
v.24, N5, p. 84-88.
4. P.L. Shkolnikov, A. E. Kaplan, A. Pukhov et al. // Appl.
Phys. Lett. 1997, v.71, p.3471.
ФЕМТОСЕКУНДНАЯ ЛАЗЕРНАЯ ПЛАЗМА: ОБЗОР ИССЛЕДОВАНИЙ И ВЫЧИСЛИТЕЛЬНАЯ МОДЕЛЬ
Н. Бугров, С. Холод, Н. Захаров
Представлен обзор экспериментальных и теоретических исследований физических процессов, происходящих в
фемтосекундной лазерной плазме. Описаны такие эффекты, как рентгеновское и электромагнитное излучение,
высокоэнергетичные электронные и ионные пучки. Показано, что ультракороткий лазерный импульс
длительностью, сравнимой с периодом колебания волны (меньшей, чем несколько фемтосекунд), поглощается
внутренними электронами, в отличие от более продолжительных импульсов, которые поглощаются внешними
электронами. Рассмотрена задача математического моделирования этих процессов и создания соответствующего
компьютерного кода. Обсуждены технологические аспекты, такие, как создание мощных источников
рентгеновского излучения и плазмы, формирование лазерного пучка и обработка различных материалов.
ФЕМТОСЕКУНДНА ЛАЗЕРНА ПЛАЗМА: ОГЛЯД ДОСЛІДЖЕНЬ І ОБЧИСЛЮВАЛЬНА МОДЕЛЬ
М. Бугров, С. Холод, М. Захаров
Представлено огляд експериментальних і теоретичних досліджень фізичних процесів, що відбуваються у
фемтосекундній лазерній плазмі. Описано такі ефекти, як рентгенівське й електромагнітне випромінювання,
високоенергетичні електронні й іонні пучки. Показано, що ультракороткий лазерний імпульс тривалістю,
порівнянною з періодом коливання хвилі (меншою ніж декілька фемтосекунд), поглинається внутрішніми
електронами, на відміну від більш тривалих імпульсів, що поглинаються зовнішніми електронами. Розглянуто
задачу математичного моделювання цих процесів і створення відповідного комп'ютерного коду. Обговорено
95
технологічні аспекти, такі, як створення могутніх джерел рентгенівського випромінювання і плазми, формування
лазерного пучка й обробка різних матеріалів.
96
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