Ultrafast light-matter interaction in transparent medium
The ultrafast interaction between high power laser light and plasma has been studied theoretically. The theoretical simulations are based on the nonlinear Schrödinger equation taking into account group velocity dispersion, diffraction, self-focusing and multiphoton absorption. The plasma is forme...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2012
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nasplib_isofts_kiev_ua-123456789-1182692025-06-03T16:28:47Z Ultrafast light-matter interaction in transparent medium Korovin, A.V. The ultrafast interaction between high power laser light and plasma has been studied theoretically. The theoretical simulations are based on the nonlinear Schrödinger equation taking into account group velocity dispersion, diffraction, self-focusing and multiphoton absorption. The plasma is formed during propagation of femtosecond laser pulse with high input power in transparent medium due to multiphoton ionization process. The induced plasma results in light scattering with formation of multiple cones. It was found that plasma forms cone region that is inverse to cones appearing from scattering of electromagnetic field. The Fourier transformation of temporal-spatial dependences of plasma density demonstrates formation of quasi-periodic structure for plasma waves. The author gratefully acknowledges financial support by the Deutsche Forschungsgemeinschaft (priority programme 1327 “Optically induced sub-100 nm structures for biomedical and technological applications”). 2012 Article Ultrafast light-matter interaction in transparent medium / A.V. Korovin // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 1. — С. 48-54. — Бібліогр.: 21 назв. — англ. 1560-8034 PACS 42.50.Ct https://nasplib.isofts.kiev.ua/handle/123456789/118269 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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The ultrafast interaction between high power laser light and plasma has been
studied theoretically. The theoretical simulations are based on the nonlinear Schrödinger
equation taking into account group velocity dispersion, diffraction, self-focusing and
multiphoton absorption. The plasma is formed during propagation of femtosecond laser
pulse with high input power in transparent medium due to multiphoton ionization
process. The induced plasma results in light scattering with formation of multiple cones.
It was found that plasma forms cone region that is inverse to cones appearing from
scattering of electromagnetic field. The Fourier transformation of temporal-spatial
dependences of plasma density demonstrates formation of quasi-periodic structure for
plasma waves. |
| format |
Article |
| author |
Korovin, A.V. |
| spellingShingle |
Korovin, A.V. Ultrafast light-matter interaction in transparent medium Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Korovin, A.V. |
| author_sort |
Korovin, A.V. |
| title |
Ultrafast light-matter interaction in transparent medium |
| title_short |
Ultrafast light-matter interaction in transparent medium |
| title_full |
Ultrafast light-matter interaction in transparent medium |
| title_fullStr |
Ultrafast light-matter interaction in transparent medium |
| title_full_unstemmed |
Ultrafast light-matter interaction in transparent medium |
| title_sort |
ultrafast light-matter interaction in transparent medium |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2012 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/118269 |
| citation_txt |
Ultrafast light-matter interaction in transparent medium / A.V. Korovin // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2012. — Т. 15, № 1. — С. 48-54. — Бібліогр.: 21 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT korovinav ultrafastlightmatterinteractionintransparentmedium |
| first_indexed |
2025-12-01T21:45:00Z |
| last_indexed |
2025-12-01T21:45:00Z |
| _version_ |
1850343958583967744 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 1. P. 48-54.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
48
PACS 42.50.Ct
Ultrafast light-matter interaction in transparent medium
Alexander V. Korovin
V. Lashkaryov Institute for Semiconductor Physics, NAS of Ukraine, 03028 Kyiv, Ukraine
E-mail: korovin@isp.kiev.ua
Abstract. The ultrafast interaction between high power laser light and plasma has been
studied theoretically. The theoretical simulations are based on the nonlinear Schrödinger
equation taking into account group velocity dispersion, diffraction, self-focusing and
multiphoton absorption. The plasma is formed during propagation of femtosecond laser
pulse with high input power in transparent medium due to multiphoton ionization
process. The induced plasma results in light scattering with formation of multiple cones.
It was found that plasma forms cone region that is inverse to cones appearing from
scattering of electromagnetic field. The Fourier transformation of temporal-spatial
dependences of plasma density demonstrates formation of quasi-periodic structure for
plasma waves.
Keywords: light-matter interaction, ultra-short laser pulse, multiphoton process,
transparent medium.
Manuscript received 15.12.11; revised version received 05.01.12; accepted for
publication 26.01.12; published online 29.03.12.
1. Introduction
In recent decades, extra high peak power laser pulses
allowing to obtain the extreme intensity of the
electromagnetic field in the focus of an ultra-short laser
pulses have led to a variety of new applications as well
as atmospheric analysis and remote sensing of molecules
[1], supercontinuum generation [2, 3], precise scalpels
for delicate eye surgery [4], driving sources for table-top
particle accelerators [5], etc. Also, one of the most
promising applications of ultrafast lasers is a
femtosecond-laser processing of transparent materials
such as glasses [6], crystals [7], and polymers [8]. This
versatile method allows obtaining arbitrary three-
dimensional microstructures using a highly focused
femtosecond laser beam through a local change in
refractive index of the host material. So, integrated
optical components can be directly inscribed into the
bulk of transparent materials by translating the sample.
In fused silica, different regimes of structural changes
can be observed [6] depending mainly on the energy
carried by the incident individual laser pulses. At low
energies, a homogeneous refractive index increase
occurs due to the rapid melting and quenching of the
glass. In contrast, at high pulse energies microexplosions
create permanent voids in the focal volume.
Interestingly, at intermediate energies, birefringent index
changes are induced. It has been shown that the
anisotropy is caused by self-organized structures with
subwavelength periodicity, the so-called nanogratings
[9] that are oriented perpendicular to the polarization of
the writing beam [10]. Since their discovery, much
attention has been given to use nanogratings for the
fabrication of microfluidic channels [11]. The control of
propagation dynamics, both spatial and temporal, is
crucial in these applications. This necessitates a
complete understanding of the physical processes that
govern the spatio-temporal dynamics of the intense
ultra-short pulse in the medium. The theoretical
description of laser-induced refractive index changes in
the interaction of high-intensity laser pulses with plasma
was considered by many authors [12-15]. The
spontaneous breakup of highly elliptical laser beams into
one- and two-dimensional arrays of light filaments was
studied in fused silica [16], where the multiple
filamentation process is initiated by random intensity
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 1. P. 48-54.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
49
modulation across the beam “amplitude noise”. Besides,
formation of filamentation was studied at propagation of
1-ps laser pulses in scattering medium (aqueous
suspension of 2-μm polystyrene microspheres) where
scattering was introduced through a stochastic diffusion
and diffraction term [17]. At present, it is reasonable to
say that understanding the interplay of various physical
processes over the extensive range of various parameters
like input power, pulse width, wavelength and repetition
rate is far from complete. This is largely due to the fact
that experimental conditions vary widely and models
used are not always comprehensive. Thus, the physics of
this problem needs further study.
In this paper, the numerical simulations of
propagation of ultra-short laser pulse in a transparent
medium are presented. The theoretical model of ultrafast
light-matter interaction is based on the nonlinear
Schrödinger equation with taking into account the group
velocity dispersion, diffraction, self-focusing and
multiphoton absorption as well as continuity equation
for the plasma density. Modelling ultra-fast light-matter
interaction was performed in 3D space with the spatio-
temporal Fourier transformation of electric field and
plasma density for transverse (relatively to laser pulse
propagation direction) coordinate. This spatio-temporal
Fourier transformation gives us information about light-
matter interaction because the peculiarities in such
transformation correspond to dispersion curves for
quasi-particles appearing at interaction between
plasmons and photons. Also, this transformation allows
us to observe formation of periodic or quasi-periodic
structures.
The paper is organized as follows. After
introduction, in Section 2 the fundamentals for
theoretical description of ultrafast light-matter
interaction were made. In Section 3, the numerical
results and discussions for simulation of ultra-short laser
pulse propagation in transparent medium (fused silica)
are presented. The final conclusions are presented in
Section 4.
2. Fundamentals
Modelling light interaction with matter in nonlinear
regime could be performed using Maxwell equations
with induced current when taking into account optical
Kerr effect as well as multiphoton and avalanche
ionization. The Maxwell equations in SI units could be
read
t
t
t
t ,
,
, RJ
RD
RHR
,
t
t
t
,
,
RB
RER ,
tt ,, RRDR , 0, tRBR , (1)
where the designations are commonly used.
In the case of isotropic media, relation between
electric displacement and electric field if taking into
account the optical Kerr effect can be written in the time
domain as follows
ttdtttgtt DEEE
23 . (2)
where ε is the permittivity for linear response and χ(3) is
the third-order nonlinear susceptibility,
tgttg Raman 1 with
tUtetg t
Raman 12
2
2
1
2
2
2
1 sin2
. Neglecting the
Raman response ( 1 ), Eq. (2) can be rewritten as
follows
tttt DEEE 23 . (3)
2.1. Multiphoton and avalanche ionization
The evolution equation for the electron density
reads [14]
ri
PI E
U
EW
t
22
. (4)
where τr is the electron recombination time, is the
coefficient of absorption due to inverse bremsstrahlung
that follows from the Drude model, and it could be
written as
22
0
00
22
0
0
0
2
0
2
0
2
0
11 c
c
atc
c
e
k
n
ek
, (5)
where k0 = n00/c = 2/ and 0 are the wave number
and frequency of the carrier wave, respectively, and n0 is
the medium refractive index in the case of linear
response, ρat = ε0µe (n00/e)2 – initial electron density in
the valence band, µe – reduced electron mass, c –
momentum transfer collision time. For usual materials,
plasma absorption is a decreasing function while plasma
defocusing is an increasing function of c. Thus, the
collision time characterizes a balance between plasma
absorption and plasma defocusing.
For the high-intense light propagating through
dielectric media with photon energy lower than the
energy gap in media, the multiphoton ionization gives its
contribution to free-electron generation, involving
transitions from the valence band to the conduction one
through the gap potential. For relatively weak fields, the
multiphoton ionization rate from Keldysh’s theory for p-
photon ionization can be approximated by [15]
)( at
p
pPI IIW , (6)
where p is the multiphoton (for p-photons) ionization
cross section.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 1. P. 48-54.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
50
The current density for avalanche and multiphoton
(p-photons) ionization in frequency domain takes the
following form
EEEj
12 p
atipU . (7)
So, the absorbed photons or plasma density
generation rates are defined from Eq. (7) in the
following form
.
ReRe
2
2
p
atp
ii UU
G
E
E
Ej
(8)
2.2. Initial conditions
To obtain ultra-intense laser pulse, high focusing is
needed. We describe focusing the laser pulse by using
linearly polarized Gaussian-like beams. So, the initial
electric field for laser pulse propagating along z-axis
could be presented in the following form [18]
..
2
exp
/1
€
,
2
0
cc
ziz
kr
tkzi
zzi
tE
tE
RR
e
r , (9)
where 2
00 /1)( zzwzw is the characteristic
transverse size of the beam in z-position and w0 is the
beam waist, /2
00 wnz is the Rayleigh range (2z0 is
the confocal parameter and 1
0/1 zzif is the
curvature of the wave at the distance z from the linear
focus), 0ziz is the complex radius of curvature and
ptt hsec or 2exp ptt is the
temporal pulse shape with the temporal half-width, p.
The typical numerical apertures and beam waists
measured with a low intensity femtosecond laser at
800 nm for various objectives could be found in [14].
The input laser power is pinin EP /2 , so the
light intensity could be read as 2
0
2
0 2 wPE in .
Generally, the focal spot could be approximated by
plane wave while outside of focal spot the spherical
harmonics give best approximation. More accurate
formula for linearly polarized Gaussian-like beams takes
the following form [19] in the case of diffraction angle
satisfying the condition 1/2/ 0000 kwzw
,
,
2
0
/
/
0
2
0
22
22
Oe
gefEzrE
tzzrkzi
zwr
x
(10)
0, zrE y , (11)
3
0
0
0 ,, OzrE
w
x
fizrE xz , (12)
where 00
2
00 /2/ wkwz – depth of focus in the
Rayleigh’s range, 0hsec tg – temporal pulse
shape, tkz – phase, p0 – characteristic
pulse width.
2.3. Nonlinear Schrödinger equation
In the framework of paraxial equation approximation,
the electric field, tzyxE ,,, , of the pulse propagating
along the +z-direction is presented using the envelope
function in the form
..,,,,,, 00 ccetzyxEtzyxE tzki , (13)
where tzyx ,,,E is the pulse envelope. For the cases of
the slowly-varying envelope approximation, the
propagation equation for the pulse envelope can be
reduced to the nonlinear Schrödinger (NLS) equation
from the wave equation using the well-known arguments
[12, 14, 15]. The NLS equation could be extended to
include the effects of ionization and the effects of the
influence of electron plasma on the pulse envelope and
takes the form
.E E
E
UEW
i
EE
t
i
c
in
E
yxt
i
k
i
t
E
t
Ei
z
E
iPI
c 2
2
0
2
0
0
2
2
2
2
2
00
3
3
32
2
2
2
1
1
2
1
1
2
2
(14)
Usually, E is normalized in the way when
2E
equals to the intensity of the pulse in W/cm2. The terms
with coefficients β2 and β3 take into account second- and
third-order group velocity dispersions (GVD),
respectively. The first-order GVD term is vanished for
the case of frame of reference moving with the group
velocity of the pulse. The subsequent term in the left-
hand side is the space-time focusing term in which the
transverse Laplacian leads to familiar diffraction effects.
The fourth term accounts for third-order nonlinear
effects due to the intensity dependent refractive index n2.
Self-focusing in space and self-phase modulation (SPM)
in time are direct consequences of this term [14, 15, 20].
The partial time derivative in the term causes self-
steepening, which leads to the formation of a shock front
in the pulse envelope. While SPM is responsible for
symmetric broadening of the pulse spectrum, self-
steepening causes an asymmetry in the spectrum [20].
The studies of Chiron et al.[12], Couairon et al.
[14] and Kumagai et al. [15] justify retaining only the
transverse Laplacian in the space-time focusing term for
longer pulse widths, 100 fs or longer, when it is of
interest to study only the spatio-temporal dynamics for
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 1. P. 48-54.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
51
pulses that are not in the few cycle limit. For the same
reason, we can ignore the third-order GVD, self-
steepening and Raman response. So, Eq. (14) can be
simplified to the following form
.E
E
UEW
EiEEkin
E
yxk
i
t
Ei
z
E
iPI
c 2
2
0
2
02
2
2
2
2
0
2
2
2
2
1
1
2
22
(15).
3. Numerical results and discussions
For simulations, we use the Gaussian pulse laser beam
with the operation wavelength equal to 800 nm
( 1
0 fs355.2 ) and duration = 150 fs. In this case,
deviation of the frequency is about =
13 fs10667.6 (following to the uncertainty relation)
that is 0.283% from 0. So, we can neglect dispersion in
optical constants due to slow frequency dependence in
this spectral region. In calculations, we use parameters
that are typical for propagation of a high-intense laser
pulse in fused silica (FS), and they are presented in
Table.
Table. Parameters used in simulations of the propagating
ultra-short laser pulse in fused silica.
The spatial distribution of the electric field intensity
and plasma density are presented in Fig. 1 for various
input laser energies. The calculations were made in 3D
space using Eqs. (1) and (4) for data from Table. At each
step in the z-direction, the electric field envelope is
determined from Eq. (1) using the split-step Fourier
method [21], while the electron plasma density is obtained
by second-order Runge-Kutta integration of Eq. (4). The
spatial distributions in Fig. 1 were calculated for the time
corresponding to the maximum electric field intensity in a
linear regime at the focal spot (z = 0 and t = 0 correspond
to position of this linear focal spot). The space step was
chosen equal to 0.065 µm. As we can see, the laser beam
is gathered while its intensity reach critical intensity
allowing effective multiphoton ionization (in the case of
fused silica, it is six-photon ionization). Excited electron
plasma leads to reducing the medium refractive index and,
as a result, electromagnetic field flows around region with
the low optical density. After region with electron plasma,
the electromagnetic field is gathered again. With
increasing the input laser beam energy, the number of
self-steepening (interchanging between flow around and
gathering of electromagnetic field) processes is increased,
too. Also, we clearly observe multiple cone formation
(from Fig. 1 the characteristic cone angles can be
determined as 13° for 0.135 J, 16° and 6° for 0.675 J,
and 30°, 16° and 10° for 1.35 J) in the electric field
intensity at laser power increasing and formation of
plasma cone (this cone angle is decreased from 25° down
to 20° at input energy increasing) with the vertex of a
cone opposite to vertex of a cone for electric field
intensity.
a)
Electric field intensity, 1013 W/cm2
z, m
x
,
m
-10 0 10 20
-2
0
2
0.5 1 1.5 2 2.5
Plasma density, 1021 cm-3
z, m
-10 0 10 20
0 0.2 0.4
b)
Electric field intensity, 1013 W/cm2
z, m
x
,
m
-10 0 10 20
-4
-2
0
2
4
1 2 3
Plasma density, 1021 cm-3
z, m
-10 0 10 20
0 0.2 0.4 0.6 0.8
c)
Electric field intensity, 1013 W/cm2
z, m
x
,
m
-10 0 10 20
-5
0
5
1 2 3
Plasma density, 1021 cm-3
z, m
-10 0 10 20
0 0.5 1
Fig. 1. Spatial distribution of the electric field intensity and
plasma density at propagation of an intense light pulse through
non-linear medium (fused silica) for various input light
energies: 0.135 (a), 0.675 (b) and 1.35 m (c) and for time
corresponding to the electric field intensity maximum in the
linear regime at the focal spot (t = 0).
Name Value Notatio
n
Unit
point number for x
discretization
512 Nx
point number for y
discretization
512 Ny
point number for t
discretization
256 Nt
first order dispersion
parameter
4.894 1 fs/m
second order dispersion
parameter
0.034 2 fs2/m
refractive index 1.4533 n0
non-linear refractive
index
3.75·10-
16
n2 (W/cm2)-1
initial electron density 2.1·1022 0 cm-3
multiphoton ionization
cross section
9.6·10-70 6 (W/cm2)-6/s
ionization energy 9 Ui eV
collision time 20 c fs
electron recombination
time
150 r fs
reduced electron mass 0.64 me
input energy 0.135 Iinput J
z points number 400 Nz
z-step 0.25 z m
pulse waist (for 40×
magnitude)
0.7 w0 m
distance from linear focus
and simulation start
position
15
d
m
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 1. P. 48-54.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
52
a)
x
,
m
time, fs
z = 10 m
-200 -100 0 100 200
-2
0
2
time, fs
-200 -100 0 100 200
x
,
m
z = 5 m
-2
0
2
x
,
m
Electric field intensity, 1013 W/cm2
z = 2.5 m
-2
0
2
0 1 2
Plasma density, cm-3
10
14
10
16
10
18
10
20
b)
x
,
m
time, fs
z = 10 m
-200 -100 0 100 200
-4
-2
0
2
4
time, fs
-200 -100 0 100 200
x
,
m
z = 5 m
-4
-2
0
2
4
x
,
m
z = 0 m
-4
-2
0
2
4
x
,
m
Electric field intensity, 1013 W/cm2
z = –5 m
-4
-2
0
2
4
0.5 1 1.5 2
Plasma density, cm-3
10
14
10
16
10
18
10
20
c)
x
,
m
time, fs
z = 10 m
-200 -100 0 100 200
-5
0
5
time, fs
-200 -100 0 100 200
x
,
m
z = 5 m
-5
0
5
x
,
m
z = 0 m
-5
0
5
x
,
m
Electric field intensity, 1013 W/cm2
z = –5 m
-5
0
5
0 1 2 3
Plasma density, cm-3
10
14
10
16
10
18
10
20
Fig. 2. Time evolution of light intensity and plasma density at z
position depicted in Fig. 1 at fixed position y = 0 for various
input light energies: 0.135 (a), 0.675 (b) and 1.35 m (c).
The temporal evolution of electric field intensity
and plasma density in plane y = 0 for laser beam
propagation in fused silica at various positions in
propagation beam direction corresponding to white
dashed lines in Fig. 1 for various input electromagnetic
energies are presented in Fig. 2. For the best contrast, the
plasma density is presented in the logarithmic scale.
Since Eq. (1) is written in the frame of reference moving
at the group velocity of the pulse, the real time axis
should be shifted by β1z.
This scattering of laser beams in the form of
multiple cones is connected with excitation of plasma
waves. To proof this, the Fourier discrete
transformations (FDT) of the electric field and plasma
density over both transverse coordinate and time are
presented in Fig. 3. This transformation allowed us to
see dispersion relations. Here, we can see formation of
a quasi-periodic structure with period about 0.14 µm in
the plasma density. Also, Fig. 3 demonstrates
formation of plasma waves and such wave could be
estimation following to the Bohm–Gross dispersion
relation, 2222 2/3 pleppl kv , where
eep mne 0
2 is the plasma frequency,
eeBe mTkv 2 – thermal speed of electrons, kpl –
electron plasma wave vector, kB – Boltzmann constant,
and Te – electron temperature. These dispersion curves
are presented in Fig. 3 by dashed lines. It was found
that the linear plasma response gives us quantitative
description of formation of plasma waves in the
nonlinear regime. For the case of 0.135 J laser pulse,
the electron temperature is changed from 106 K up to
6·106 K with the effective plasma density 1018 cm. For
the case of 0.675 J laser pulse, the electron
temperature is changed from 6·106 K down to 3·106 K
with the effective plasma density 1018 cm. For the case
of 1.35 µJ laser pulse, the electron temperature is
changed from 4·106 K up to 107 K with the effective
plasma density 1019, 1018 and 4·1018 cm. These values
agree in their order with the estimations made in [9]
and corresponding periodicity in plasma density is
about 0.14 µm. For periodic structure the Brillouin
zones are shown by dashed-dotted lines in Fig. 3 for
FDT of plasma density. The peculiarities in FDT of
electric field intensity could be estimated using the
dispersion relation for light waves propagating in
electron plasma (bulk plasmon polaritons):
222 / plppl knc , where kph is the light wave vector
and n – plasma refractive index. These dispersion
waves are presented in Fig. 3 by solid lines. For the
FDT of electric field intensity in Fig. 3, the value of
wave vector could be obtained from kx = kph sinθ,
where θ is the angle between kx and kz components of
the wave vector. For fitting, we used 15 angle that
corresponds to the angle between cone generatrices and
laser beam propagation direction. Also, there are some
lines with constant wave vectors in FDT of the electric
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2012. V. 15, N 1. P. 48-54.
© 2012, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
53
field intensity with unknown nature. The corresponding
lengths for these lines are 0.23, 0.17 and 0.14 m and
they still unchangeable in the case of input energy
changing (dotted lines in Fig. 3).
a)
, 1
/f
s
k
x
, 1/m
z = 10 m
0 10 20 30 40
0
0.5
k
x
, 1/m
0 10 20 30 40
, 1
/f
s
z = 5 m
0
0.5
FDT of electric field intensity, a.u.
, 1
/f
s
z = 2.5 m
0
0.5
FDT of plasma density, a.u.
b)
, 1
/f
s
k
x
, 1/m
z = 10 m
0 10 20 30 40
0
0.5
k
x
, 1/m
0 10 20 30 40
, 1
/f
s
z = 5 m
0
0.5
, 1
/f
s
z = 0 m
0
0.5
FDT of electric field intensity, a.u.
, 1
/f
s
z = –5 m
0
0.5
FDT of plasma density, a.u.
c)
, 1
/f
s
k
x
, 1/m
z = 10 m
0 10 20 30 40
0
0.5
k
x
, 1/m
0 10 20 30 40
, 1
/f
s
z = 5 m
0
0.5
, 1
/f
s
z = 0 m
0
0.5
FDT of electric field intensity, a.u.
, 1
/f
s
z = –5 m
0
0.5
FDT of plasma density, a.u.
Fig. 3. Coordinate-time Fourier discrete transformation for
electric field and plasma density from Fig. 2. Dashed lines
correspond to dispersion dependences for surface waves, solid
lines – for bulk plasmon polaritons, and dashed-dotted lines –
Brillouin zones.
4. Conclusions
In this paper, propagation of an ultra-short laser pulse
(150 fs) in transparent medium (fused silica) has been
studied in regime of high input powers (0.135, 0.675 and
1.35 J) using the nonlinear Schrödinger equation with
taking into account the group velocity dispersion,
diffraction, self-focusing (optical Kerr effect) and
absorption for multiphoton and avalanche ionization
processes as well as continuity equation for the electron
plasma density. The dynamic of interaction between the
laser pulse and electron plasma that is induced by this
pulse demonstrates complicated nature of ultrafast light-
matter interaction, where competition between self-
focusing and plasma defocusing processes leads to
formation of multiple cones for the electric filed
intensity and single cone formation for the plasma
density. Also, the Fourier transformations of spatio-
temporal dependences for the electric field and plasma
density demonstrate formation of a quasi-periodic
structure for plasma waves, which could help in
describing self-grating formation. Also, these Fourier
transformations demonstrate formation of plasma waves
and polaritons that could be estimated by using the linear
response approximation.
Acknowledgements
The author gratefully acknowledges financial support by
the Deutsche Forschungsgemeinschaft (priority
programme 1327 “Optically induced sub-100 nm
structures for biomedical and technological
applications”).
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