Effects of carrier envelope phase
on single shot XUV super
continuum generation
200
Mahendra Man Shakya, Steve Gilbertson,
Chris Nakamura, Chengquan Li, Eric Moon,
Zuoliang Duan, Janson Tacket, Shambhu
Ghimire and Zenghu Chang
Why do we need attosecond pulses?
as
fs
ps
10-18 s
10-15 s
10-12 s
Time
Circulation
Vibration
Rotation
What Was Before reported?
Single attosecond pulse at cutoff
•Laser pulse: 5 fs, 0.75mm
Single attosecond pulse (250 as)
Elaser
85 eV
135 ev
Attosecond pulse train
BALTU KA et al., Nature 421, 611( 2003)
t
Our Goal
• To study dynamics of electron in atoms
and molecules using pump-probe
technique with the pulse as short as 25
attosecond (one atomic unit) generated
from plateau region of XUV spectrum.
• To Study effect of CE phase change on
the dynamics of electrons in atoms.
• To determine the absolute CE phase
from XUV Spectrum
What is the advantage of XUV
single shot over f-2f
spectrometer ?
• f-2f set up measures the relative CE
phase change .
• But it is possible to determine absolute
phase from XUV by investigating shot to
shot variation of CE phase with
polarization gated input.
What is the polarization gating???
e-
Right Circular Pulse
e-
p
e-
Td
Ellipticity dependent pulse
Left Circular Pulse
V. T. Platonenko and V. V. Strelkov J. Opt. Soc. Am. B 16, 435 (1999)
Our Method: Generation of pulses
with a time-dependent ellipticity
Using Quartz plate
Bing Shan
Oct. 2003
Optic
axis
L
45°
Optic
axis
1
1
t= L( ve
- vo
)

Ellipticity-dependent pulse
e-pulse o-pulse
Quartz Plate
/4 Waveplate
Polarization gate width : Simplified
Formula and Example
1.0
0.8
t 0.2  0.3
0.6
p
2
p=8 fs
Td=15 fs
Td

0.4
0.2
t=1.3 fs
0.0
-2.0
-1.5
Z. Chang, PRA (2004)
-1.0
-0.5
0.0
0.5
time (fs)
1.0
1.5
2.0
Major problem: Less number of
photons
Our Effort:
• Phase Matched Pressure.
• Small Diverging Angle of XUV
• Aluminum Filter Shield (Design)
Our Design: Higher Efficiency
Gas Cell
Parabolic
Mirror
Aluminum
Filter
Retractable
Mirror
Diffraction
Grating
CCD1
MCP2
nA
CCD2
MCP1
Phase matching
1.2
5 Torr
15
25
35
45
55
65
8Jan06_Sun
Normalized Intenstiy
1.0
0.8
0.6
0.4
0.2
0.0
35
40
45
50
Photon Energy (eV)
55
60
Phase matched Plot
8Jan06_Sun
Intensity (arb.unit)
0.5
5Torr
10Torr
15Torr
20Torr
25Torr
30Torr
35Torr
40Torr
45Torr
55Torr
60Torr
0.4
0.3
0.2
0.1
0.0
35
40
45
50
Photon Energy (eV)
55
60
From phase matching pressure to phase
mismatching pressure
20Torr
30Torr
55 Torr
80Torr
60 Torr
125Torr
eV 35.65
8Jan05_Sun
38.75
41.85
45
48
51
54.25
57.35
Phase matching
25th
27th
29th
31st
33rd
Intensity (ralative)
1.0
0.8
8Jan06_Sun
0.6
0.4
0.2
0.0
0
20
40
60
80
Pressure (Torr)
100
120
Normalized Intensity
Measurement of half the diverging angle of
the XUV beam
1.0
Focus
0.8
Gas Cell
Parabolic
0.6
Mirror
Aluminum
Filter
Retractable
Mirror
Diffraction Grating
Diffraction
Grating
8.1mrads
1/e = 3.5 mrads
2
0.4
21.7mrads
0.2
1.35cm
MCP2
nA
0.0
-10
-5
0
5
10
CCD2
Divergence Angle (mrads)
MCP1
W0
D=0.4cm
W=1.3cm
Normalized Intensity
Measurement of half the diverging angle of
the XUV beam
1.0
Focus
Diffraction Grating
0.8
8.1mrads
0.6
1/e = 3.5 mrads
2
0.4
21.7mrads
0.2
1.35cm
0.0
-10
-5
0
5
10
Divergence Angle (mrads)
W0
D=0.4cm
W=1.3cm
What do we expect to see with polarization
gated input?? -spatial analogy
Single
electronslit
– ion
Single
Collision
Many
Multi-slit
Electron-ion
Collision
1.0 (b)
1.0
0.5
0.5
0.0
0.0
-0.5
-0.5
-1.0
-5.0
-1.0
Gate
-2.5
0.0
Time (fs)
2.5
5.0
Ellipticity
Ex (Normalized)
CE phase Zero Degree ( Double slits analogy)
CE phase 90 Degree ( Single Slit analogy)
(a)
1.0
0.5
0.5
0.0
0.0
-0.5
-0.5
-1.0
-5.0
-1.0
Gate
-2.5
0.0
Time (fs)
2.5
5.0
Ellipticity
Ex (Normalized)
1.0
Linear and Long pulse ( 25fs) Harmonic spectrum
(Multi- Slits analogy)
Discrete harmonics with linear and long
pulse(25fs) input
Intensity (arb.unit)
1.0
Intensity2
0.8
0.6
0.4
0.2
0.0
35
40
45
50
55
Photon Energy (eV)
60
Linear and Short pulse (6fs) spectrum before
polarization gating was applied
( Reduced Slit Number )
Discrete but broad spectral width with linear
6fs input before gating( reduced slit analogy)
Intensity (arb.unit)
1.0
0.8
0.6
0.4
0.2
0.0
35
40
45
50
55
Photon energy (eV)
60
Super continuum with Polarization Gated
input at 100 shots (Single Slit Analogy)
Super continuum with polarization gated
input at 100 shot (Single slit analogy)
Intensity (arb.unit)
1.0
0.8
0.6
0.4
0.2
35
40
45
50
Photon energy (eV)
55
60
Measurement of The Number of photons per pulse
MCP2
Gas Cell
Phosphor Screen
Aluminum
Filter
N
Parabolic
Mirror
hν
e-
MCP2
eMCP2
Diffraction
I Grating
Ge f rep R Al Q T Al
nA
CCD1
MCP1
th
R Al 0.02 (27 Harmonics )
T Al  0.8
I  0.04 mA(at1.8kV )
Phosphor Screen
e-
 30000
G  5.3  10 6
Q  0.1nA
CCD2

nA
hν
Retractable
Mirror
Effect of CE Phase Change on XUV Spectrum
5
Intensity (Relative)
ce=78.75
o
4
56.25
o
3
33.75
o
11.25
o
2
1
-11.25
0
20
30
Harmonic order
40
o
Single shot spectrum with CE phase unlocked
2’28”
700
2’20”
600
1’23”
Y Axis Title
500
1’06”
400
0’50”
300
0’35”
200
0’17”
100
0’0”
0
22
24
26
28
30
32
Harmonics
34
36
38
Single Shot Super continuum with 4Dec05_Sun
CE Phase locked
800
2'11"
700
1'58"
Y Axis Title
600
1'38"
500
1'15"
400
0'55"
300
0'39"
200
0'21"
100
0'00"
0
24
26
28
30
32
Harmonics
34
36
38
Summary
• Dependence of the photon flux of
polarization gated high harmonics on the
target gas pressure was investigated.
• Highest number of photons was estimated
to be ~104 , which was enough to run single
shot experiment.
• We observed effect of CE phase on XUV
spectra, which could be applied as a
“phase meter”.
Measurement of Number of photons per pulse
MCP2
Phosphor Screen
N
hν
e-
e-
nA
I
Ge f rep R Al Q T Al
 30000
G  5.3  10 6
Q  0.1
th

0
.
02
(
Harmonics )
27
R Al
T Al  0.8
I  0.04 mA(at1.8kV )
Required Beam Size to eliminate photon loss
Collimating
mirror f = 1.5 m
D=?

Focusing mirror
f = 250 mm
Required D is
Required D is
D=0.4cm
1.3 cm
0
f
w0   
D
=1.3cm
  w0 2
zR 

w  w0  1 
1.3 cm


z 2
zR
Normalized Intensity
Measurement of half the diverging angle of
the XUV beam
1.0
Focus
Diffraction Grating
0.8
8.1mrads
0.6
1/e = 3.5 mrads
2
0.4
21.7mrads
0.2
1.35cm
0.0
-10
-5
0
5
10
Divergence Angle (mrads)
W0
D=0.4cm
W=1.3cm