irradiated laser pulse is also plotted with blue dotted line. It is clear that the critical
surface initially moves forward boring a hole in the pre-formed plasma with the
velocity of about 6% of the speed of light as evaluated from (7.4.3). Then, the
Doppler shift passes the null point after the peak of laser intensity, and the critical
surface moves backward. This means the solid density is too heavy for the laser
keeps the hole boring during the ps range. The Doppler shift obtained in 2D PIC
simulation is also plotted with yellow line, suggesting that the laser breaks up to
several filaments in the pre-formed plasma as shown below and the strongest
filament mainly contribute the hole boring.
2D PIC simulation is carried out to compare and analyze the experimental result.
Since the laser intensity distribution at the focused point is elongated in 2D space
with 4:1 ratio with the long side of 24 mm as seen in the inset in Fig. 7.19, this
0.08
0.06
0.04
SpecFROG data
2D PIC
Intensity (10 19 w/cm 2 )
Incident
intensity
Doppler shift interred
from laser absorption
location
0.02
0
0
1000
Δλ/λ
0
2000
t (fs)
3000
4000
5000
30
25
20
15
10
5
0
-0.02
-0.04
Fig. 7.18 Comparison of measured and simulated time history of spectral shift. Black solid line:
experimental data. Orange dashed line: central wavelength of specular 2ω spectrum in the 2D PIC
run. Purple triangles: expected Doppler shift inferred from motion of laser absorption point in the
2D PIC run. Blue dashed line: incident laser intensity profile. [Figure 2 in Ref. 14]
140
19.5
19
18.5
1.5
1
0.5
0
-0.5
-1
-1.5
-2
120
100n c
10n c
1n c
(a)
F e
logF e [W/cm 2 ]
100
log n/n c
100
y[μm]
24μm
P laser
z[μm]
120
80
80
Fig. 7.19 (a) Snapshot of
laser energy flux (P laser ),
electron density (contour
lines), and electron energy
flux (F e ) at the peak power
in the 2D PIC simulation.
The red dashed contours of
the electron density are at
t ¼ 0, and the blue contour
lines are at t ¼ 2.2 ps. The
inset is a typical on-shot
Titan vacuum focus laser
intensity profile. [Figure 3 in
Ref. 14]
258
7 Relativistic Laser and Solid Target Interactions
surface initially moves forward boring a hole in the pre-formed plasma with the
velocity of about 6% of the speed of light as evaluated from (7.4.3). Then, the
Doppler shift passes the null point after the peak of laser intensity, and the critical
surface moves backward. This means the solid density is too heavy for the laser
keeps the hole boring during the ps range. The Doppler shift obtained in 2D PIC
simulation is also plotted with yellow line, suggesting that the laser breaks up to
several filaments in the pre-formed plasma as shown below and the strongest
filament mainly contribute the hole boring.
2D PIC simulation is carried out to compare and analyze the experimental result.
Since the laser intensity distribution at the focused point is elongated in 2D space
with 4:1 ratio with the long side of 24 mm as seen in the inset in Fig. 7.19, this
0.08
0.06
0.04
SpecFROG data
2D PIC
Intensity (10 19 w/cm 2 )
Incident
intensity
Doppler shift interred
from laser absorption
location
0.02
0
0
1000
Δλ/λ
0
2000
t (fs)
3000
4000
5000
30
25
20
15
10
5
0
-0.02
-0.04
Fig. 7.18 Comparison of measured and simulated time history of spectral shift. Black solid line:
experimental data. Orange dashed line: central wavelength of specular 2ω spectrum in the 2D PIC
run. Purple triangles: expected Doppler shift inferred from motion of laser absorption point in the
2D PIC run. Blue dashed line: incident laser intensity profile. [Figure 2 in Ref. 14]
140
19.5
19
18.5
1.5
1
0.5
0
-0.5
-1
-1.5
-2
120
100n c
10n c
1n c
(a)
F e
logF e [W/cm 2 ]
100
log n/n c
100
y[μm]
24μm
P laser
z[μm]
120
80
80
Fig. 7.19 (a) Snapshot of
laser energy flux (P laser ),
electron density (contour
lines), and electron energy
flux (F e ) at the peak power
in the 2D PIC simulation.
The red dashed contours of
the electron density are at
t ¼ 0, and the blue contour
lines are at t ¼ 2.2 ps. The
inset is a typical on-shot
Titan vacuum focus laser
intensity profile. [Figure 3 in
Ref. 14]
258
7 Relativistic Laser and Solid Target Interactions