Upload
lekhue
View
214
Download
0
Embed Size (px)
Citation preview
11th IUVSTA School on
Lasers in Materials Science - SLIMS 8-15 July 2012,
Isola di San Servolo, Venice, Italy
Institute of Thermophysics, Siberian Branch of RAS
Main research directions:
Heat- and mass-transfer in one- and two-phase systems and in the systems with phase transitions;
Hydrodynamic instabilities and turbulence;
Wave dynamics in liquid and gas flows;
Low-temperature plasmas;
Thermodynamic properties of matter;
Laser ablation.
Diamond Jubilee of UK governing by the Queen Elizabeth II
100-year Memorial of Titanic
Diamond Jubilee of the University of Southampton
Olympic and Paralympic Games – 2012 in London
Mechanisms of matter excitations and ablation with ultrashort laser pulses
Several examples of continuum modeling in application to laser ablation
Volume modification of transparent materials
Concluding remarks
Target
Laser
Scales of laser-affected regions:
- spot size ~10 μm – 1 mm;
- depth ~10 nm - few μm
(depending on laser focusing and absorption properties of an
irradiated material)
Density, thermal capacity, thermal conductivity, viscosity, mechanical properties (Young
modulus, plastic yield, tensile strength), etc.
Continuum:
Interatomic potential of interaction
Atomistic: Mesoscopic:
Combines features of macroscopic and
atomistic approaches
Stoneham et al. APA 69, S81 (1999)
Continuum shell model in application to nanotubes
Yakobson et al. Phys.Rev.Lett. 76, 2511 (1996)
Axial compression Bending
Torsion
Hachisu et al., Astrophys. J. 368, L27 (1991)
Sakagami & Nishihara,
Phys.Fluids B2, 2715 (1990)
From: Physicists joke (in Russian), Multiple editions since 1966.
Hydrodynamic modeling:
Similarity between space and “laboratory” astrophysics
Steel, λ = 780 nm, left: τ = 200 fs, F0 = 0.5 J/cm2; right: τ = 3.3 ns, F0 = 4.2 J/cm2. From: Chichkov et al. Appl. Phys. A 63, 109 (1996).
Sapphire, λ = 800 nm, τ = 200 fs, F0 = 4 J/cm2; “gentle” (left) and strong ablation phases. From: Stoian et al. Nucl. Instr. Meth. B 166-
167, 682 (2000).
I. Electronic excitation Metals: - absorption of laser light by free electrons
- - impact ionization
+
-
+
+
All materials: - electron photoemission
. )()()()(
av tntItIt
tne
k
ke
Typical experimental setup to study laser ablation of solids
+
-
-
Dielectrics and semiconductors:
- generation of free electrons
by photo-ionization;
-
- free electrons absorb laser radiation
- +
+ -
+ -
Eg
+
+
-
+
+
3. Ultrafast melting (only semiconductors)
+
- -
-
at t ≥ 400 fs after the dense plasma excitation
(A. Rousse et al. Nature 410, 65 (2001))
4. Thermal melting (picosecond time scale)
+
+
- +
+
+
+
+
- -
-
2. Electron-phonon coupling
Eg = 9 eV
Eex = 5.2 eV
Fused silica, 800 nm
+
-
+
+
- + +
+ -
+ -
Trapping with defect formation
Photo-recombination
Dielectrics Semiconductors
Auger recombination
Eg Eex
+ - +
+
+
+ -
Easier excitation by next pulses
Target
Laser
M
(1) Heating, (2) melting, (3) thermal vaporization
(4) phase explosion
Recoil pressure Hydrodynamic instabilities
(Lecture by Professor Miotello)
Electron-lattice thermalization time ~ 10-100 ps
Near-threshold fluences: (1) Spallation
(2) Coulomb explosion
Lecture by Professor Zhigilei
Two-temperature model
Kaganov et al. Sov. Phys. JETP 4, 173 (1957)
Anisimov et al. Sov. Phys. JETP 39, 375 (1974)
.r
lel
t
TT
t
T
)(
, )exp()()1()( 0
lel
ll
l
lee
ee
e
TTgz
TK
zt
TC
ztIRTTgz
TK
zt
TC
Lecture by Professor Miotello
Theory of elasticity
Yakobson et al. Phys.Rev.Lett. 76, 2511 (1996)
Continuum shell model
Axial compression Bending
Hydrodynamics Colombier et al. Phys.Rev.B 74, 224106 (2006)
Povarnitsyn et al. Appl. Surf. Sci. 253, 6343 (2007)
Torsion
Experimental evidence for CE in sapphire R. Stoian, et al.
Phys. Rev. B 62, 13167 (2000)
t 100 – 200 fs, l 800 nm
Normalized velocity distributions for O+ (open triangles) and O2+ (closed diamonds):
Momentum scaling
O+ O2+
E
Ions are emitted and accelerated by the
electric field.
This leads to the momentum scaling
Eeam
tEevm
Laser pulse
MPI Photo-
emission
free-electron
absorption
avalanche
absorption
and reflection
dynamics
electric
field
carrier
drift and
diffusion
Objects for modeling: Au, Si, Al2O3
Regimes: t = 15-100 fs, l = 800 nm
Rate equation (continuity)
Rate equation (continuity)
Poisson equation
Drude formalism
iejLSx
J
et
njj
jj, ,
1
Dj = kBTeej /e
E
x
en ni e
0
jjjjj neDEneJ
t
1
1
1111
0
*
in
n
n
nn
cr
eege
Continuity equation:
Poisson equation:
Complex dielectric
function:
).(,4,2
3
),,()(
2
le
l
l
ee
ee
le
e
e
e
e
TTgt
TC
e
TkKkC
txTTgx
T
en
J
t
TC
Si:
Two-temperature model:
).,()/1(
),(),(
2)2()(
0
ab
2
21
txPEEnCn
nEtxItx
nn
nnE
IE
IE
t
E
e
ie
eg
ia
aeggg
f
t
),(),()(
),( abph
6
6 txItxanhnn
nItxI
x ia
a
Al2O3:
),(),(),(2),( ab21 txItxatxIhnhntxIx
aa
Si:
Attenuation of the laser beam:
Metals (Au):
e
e
e
es
kT
eTAIR
kT
hF
h
kTcJ
exp1
3
3
2 20
33
2
2
Semiconductors (Si):
e
e
e
e
PE
free
PE
Au
AuPE
SiPEAus
kT
eTAIR
kT
hF
h
kT
l
lcJ
exp1
3
3
2
13
13
2
0
33
2
2
Dielectrics (Al2O3): )/exp()(2
1 6
6 lxnn
nInIPE
ha
ae
N.M. Bulgakova et al. Phys. Rev. B 69, 054102 (2004); Appl. Phys. A 81, 345 (2005) W. Marine et al. J. Appl. Phys. 103, 094902 (2008)
Photoemission:
-0,1 0,0 0,1 0,2 0,3
0
1
2
3
Silicon x 30
Gold x 100
Al2O
3
ni-n
e [10
21 c
m-3]
Time [ps]
Laser fluence (slightly above the threshold of ion observation in plumes): 4, 0.8, and 1.2 J/cm2 for Al2O3, Si, and Au, respectively
t = 100 fs
l = 800 nm
-0,1 0,0 0,1 0,2 0,3 0,4 0,5-10
-8
-6
-4
-2
0
Critical electric field
Ele
ctr
ic fie
ld [1
01
0 V
/m]
Time [ps]
w = 0E2/2
Wat = 0E2Vat/2
For sapphire:
Eth 51010 V/m
Number of emitted electrons:
Al2O3 - 6.2108
Si - 5.941011
Au - 8.21010
Maximums of the electric field: Al2O3 - 8.71010 V/m; Si - 1.4108 V/m;
Au - 9106 V/m
0
00at
0
)3(2
nTknE l
xth
Al2O3
0,1 1 100,0
0,2
0,4
0,6
0,8
1,0
Ne
Ar
He
Pt
K
Laser fluence [J/cm2]
0,01 0,1 1 100,0
0,2
0,4
0,6
0,8
1,0
Pt
Laser fluence [J/cm2]
Ablation threshold
1-atm air
Vacuum
1.08-atm Ne
K
Dependence on ionization
potential of the ambient gas
A.Y. Vorobyev, C. Guo: Appl. Phys. Lett. 86, 011916 (2005) Opt. Express 14, 13113 (2006)
DCBAe QQQQt
n
)eV(/exp
9
32 10
3
eAraee
eB
B TInnemThk
Q
ie
eBe
C nnTkm
eQ 2
2/9
10
)K(9
24 )K(/10155.2 11
eieD TnnQ
,0
iiB Q
dt
Tkdn
2/3
2/14 2
3
80
e
ieie
B
iT
TTnn
kM
eQ
,e
eBe Qdt
Tkdn
*)1()1( EQTkQIQQQ DeBCArBie
kQ
z
sc
t
sA
)()(
kQ
z
sc
t
sA
)()(
a
k
A nAJQ
)(),( ctzJ
ct zzzzs /)(1)(
R
ctzs
tttrrF
L
LL
)(
)/)(/exp(
0
22
0
22
0
Ar Pt
0
Vdiv
t
ˆ)( divpVVt
V
TdivVpdivUVdiv
t
U
mn m
nmn
x
V
,
, ,
n,m = 1 – 3, n ≠ m
z
TJJ
gt
100% ionization in the focal spot r = 50 μm and
z = 100 μm
z
r
M. Beresna et al. Appl. Phys. Lett.
98, 201101 (2011)
However, the mistery
of nanogratings stays uncovered
Pulse energy 39 μJ/cm2
Translation speed 50 μm/s
Repetition rate 100 kHz
Pulse energy 43 μJ/cm2
Translation speed 10 μm/s
Courtesy of Peter G. Kazansky, University of Southampton
tr
av
t
e
e
n
n
en
InIt
n
Multiphoton ionization Avalanche ionization
Trapping
exciton
E’
Re-excitation
)/()2( 5.0
Leff eEEmg
Keldysh parameter:
(ratio of time necessary to an electron to tunnel through the potential barrier to the period of the laser field)
At > 1 multiphoton ionization dominates; at < 1 tunneling
dominates.
≈ 1 at I ≈ 5×1013 W/cm2
2/2
0EcI at I ≈ 5×1013 W/cm2 E ≈ 2×108 V/cm
+ + +
+ + +
+ - - -
- - -
at the level ≤ 5×1013 W/cm2
Intensity clamping upon volume modification
.)(
2
1)()1(
2
)()1(2
"1
2
2
PI1
0
22
0
20
2
2
2
21
0
EE
EE
EEEE
EE
g
ec
t
RR
EWnTi
dtRffn
Tnik
t
ik
rrrT
k
i
z
t
tt
I. Non-linear Schrödinger equation (NLSE)
tr
e
l
a
ger
ePI
e
t
n
n
n
Emm
nW
t
n
2
/1)( EE
+ + +
+ + +
+ - - -
- - -
coupled with the rate equation for free carriers
NLSE is obtained from the Maxwell equations in assumption of beam propagation
II. Maxwell equations
+ + +
+ + +
+ - - -
- - -
Equation for the electric field accounting free carrier generation and associated processes
12 2
2 2
0 *2 2
0 *
1 4 8 | |rot (1 /(4 ))a
PI
D e Ei D j H W E E E
c t c c mc E
m nl
m
D E P P 2 2 2
2
0
1 | | ( ) | ( ) |4
nl r r
cP n n f E f R E t d Et t t
coupled with hydrodynamic model for free carriers
c
( v) vv
e
ei E
t m
t
PI
tr
W Wt
t
vj e
Time scale: laser pulse propagation through a glass
sample (several ps); NA = 0.45
Only a small part of the pulse front is efficiently absorbed within the beam
focus region. The rest parts of the beam “flow over” the generated electron plasma
with rather small absorption.
J. Appl. Phys., 101, 043506 (2007)
Phys. Rev. B, 77, 104205 (2008)
Appl. Phys. Lett., 94, 041911 (2009)
Absorption of the laser energy by electrons
Electron-lattice thermalization
Formation of steep temperature gradients
Generation of thermoelastic waves
Heat conduction cooling of the laser-affected region
I. NLSE or Maxwell equations
Spatial distribution of absorbed
energy temperature map
II. Models of thermoelastoplastics
“Frozen jets” and “bubble belts” Impact of polarization on
energy delivery into modification region
Impact of laser pulse tilt on waveguide writing
Formation and motion of micro/nanovoids in glass Nanogratings in glass
“There's Plenty of Room at the Bottom”, Richard P. Feynman
Interaction of ultrashort laser pulses with materials is a fascinating phenomenon that is rich in
physical content and opens new unprecedented opportunities for technological applications.
It requires consolidating knowledge of optics, solid state physics and chemistry, plasma physics,
thermodynamics, theory of elasticity and plasticity.
“Physics lesson” by Sergei Korsun
I hope you do not feel like this poor student under information bombardment
“All these is outrageous lie! They lost power at hbar in the Schrödinger equation and drew electrons instead of muons in air shower!”
From an Internet forum of Russian students
By Sean Carroll
Instead your critical view is very welcome!
Insitute of Thermophysics
SB RAS
Dr. Alexander Bulgakov
Dr. Igor Burakov
Dr. Yuri Shukhov
Students: Olga Bulgakova
Anton Evtushenko
Sergey Starinski
Maxim Shugaev
Lev Zakharov
Prof. Peter Kazansky Optoelectronics Research Centre, University of Southampton, UK
Dr. Vladimir Zhukov Institute of Computational Technologies SB RAS, Novosibirsk, Russia
Dr. Yuri Meshcheryakov Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
Prof. Eleanor Campbell Edinburgh University, UK
Dr. Arkadi Rosenfeld Max-Born-Institute, Berlin, Germany
Dr. Razvan Stoian Universite Jean Monnet, 42000 Saint Etienne, France
Dr. Anatoli Vorobyev Dr. Chunley Guo Rochester University, USA