Effects of carrier envelope phase on single shot XUV super

continuum generation

Mahendra Man Shakya, Steve Gilbertson, Chris Nakamura, Chengquan Li, Eric Moon, Zuoliang Duan, Janson Tacket, Shambhu

Ghimire and Zenghu Chang

200

Why do we need attosecond pulses?

Time

as psfs10-18 s 10-15 s 10-12 s

RotationVibrationCirculation

85 eV 135 ev

Attosecond pulse train

Single attosecond pulse (250 as)

BALTU KA et al., Nature 421, 611( 2003)

•Laser pulse: 5 fs, 0.75m

What Was Before reported?Single attosecond pulse at cutoff

Elaser

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

• 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 advantage of XUV single shot over f-2f

spectrometer ?

V. T. Platonenko and V. V. Strelkov J. Opt. Soc. Am. B 16, 435 (1999)

Left Circular Pulse

Right Circular Pulse

Td

e-

e-

e-

What is the polarization gating???

p

Ellipticity dependent pulse

L45°

e-pulse o-pulse

t= L( 1ve - 1

vo)

Bing ShanOct. 2003

Quartz Plate /4 Waveplate

Ellipticity-dependent pulse

Our Method: Generation of pulseswith a time-dependent ellipticity

Using Quartz plate

Opticaxis

Opticaxis

Z. Chang, PRA (2004)

Polarization gate width : Simplified Formula and Example

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.00.0

0.2

0.4

0.6

0.8

1.0

t=1.3 fs

p=8 fs

Td=15 fs

time (fs)

d

p

Tt

2

2.0 3.0

Major problem: Less number of photons

• Phase Matched Pressure.

• Small Diverging Angle of XUV

• Aluminum Filter Shield (Design)

Our Effort:

Our Design: Higher Efficiency

CCD1

MCP1

Gas Cell

Parabolic Mirror

Aluminum Filter

Retractable Mirror Diffraction

Grating

MCP2 nA

CCD2

Phase matching

35 40 45 50 55 600.0

0.2

0.4

0.6

0.8

1.0

1.28Jan06_Sun

No

rma

lize

d I

nte

nstiy

Photon Energy (eV)

5 Torr 15 25 35 45 55 65

Phase matched Plot

35 40 45 50 55 600.0

0.1

0.2

0.3

0.4

0.5

In

ten

sity (

arb

.un

it)

Photon Energy (eV)

5Torr 10Torr 15Torr 20Torr 25Torr 30Torr 35Torr 40Torr 45Torr 55Torr 60Torr

8Jan06_Sun

20Torr

30Torr

80Torr

125Torr

From phase matching pressure to phase mismatching pressure

8Jan05_Sun

35.65 38.75 41.85 45 48 51 54.25 57.35eV

55 Torr

60 Torr

Phase matching

0 20 40 60 80 100 1200.0

0.2

0.4

0.6

0.8

1.0 8Jan06_Sun

In

tens

ity (

rala

tive)

Pressure (Torr)

25th 27th 29th 31st 33rd

Measurement of half the diverging angle of the XUV beam

D=0.4cm

-10 -5 0 5 100.0

0.2

0.4

0.6

0.8

1.0

1/e2 = 3.5 mrads

No

rma

lize

d In

ten

sit

y

Divergence Angle (mrads)

8.1mrads

21.7mrads

Focus

1.35cm

Diffraction Grating

D=0.4cmW=1.3cm

W0

MCP1

Gas Cell

Parabolic Mirror

Aluminum Filter

Retractable Mirror Diffraction

Grating

MCP2 nA

CCD2

Measurement of half the diverging angle of the XUV beam

D=0.4cm

-10 -5 0 5 100.0

0.2

0.4

0.6

0.8

1.0

1/e2 = 3.5 mrads

No

rma

lize

d In

ten

sit

y

Divergence Angle (mrads)

8.1mrads

21.7mrads

Focus

1.35cm

Diffraction Grating

D=0.4cmW=1.3cm

W0

Single slit

Multi-slit

What do we expect to see with polarization gated input?? -spatial analogy

Single

electron – ion

Collision

Many

Electron-ion

Collision

-5.0 -2.5 0.0 2.5 5.0

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0(b)

Gate

Elli

ptic

ity

Ex (

Nor

mal

ized

)

Time (fs)

CE phase Zero Degree ( Double slits analogy)

-5.0 -2.5 0.0 2.5 5.0

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0(a)

Gate

Elli

ptic

ity

Ex (

Nor

mal

ized

)

Time (fs)

CE phase 90 Degree ( Single Slit analogy)

Linear and Long pulse ( 25fs) Harmonic spectrum

(Multi- Slits analogy)

35 40 45 50 55 600.0

0.2

0.4

0.6

0.8

1.0

Inte

nsi

ty (

arb

.un

it)

Photon Energy (eV)

Intensity2

Discrete harmonics with linear and long pulse(25fs) input

Linear and Short pulse (6fs) spectrum before polarization gating was applied

( Reduced Slit Number )

35 40 45 50 55 60

0.0

0.2

0.4

0.6

0.8

1.0

Inte

nsi

ty (

arb

.un

it)

Photon energy (eV)

Discrete but broad spectral width with linear 6fs input before gating( reduced slit analogy)

Super continuum with Polarization Gated input at 100 shots (Single Slit Analogy)

35 40 45 50 55 60

0.2

0.4

0.6

0.8

1.0

In

tens

ity (

arb.

unit)

Photon energy (eV)

Super continuum with polarization gated input at 100 shot (Single slit analogy)

Measurement of The Number of photons per pulse

Retractable Mirror

MCP1

Gas CellParabolic Mirror

Aluminum Filter

Diffraction Grating

MCP2 nA

CCD2

CCD1

e-nA

MCP2

Phosphor Screen

hν

Phosphor Screen

hν

MCP2

e-

nA

)8.1(04.0

8.0

)27(02.0

1.01063.5

30000

kVatAIT

HarmonicsthR

Q

G

TQRfGe

IN

Al

Al

AlAlrep

e-

20 30 400

1

2

3

4

5

-11.25o

11.25o

33.75o

56.25o

ce

=78.75o

Inte

nsity

(R

elat

ive)

Harmonic order

Effect of CE Phase Change on XUV Spectrum

22 24 26 28 30 32 34 36 380

100

200

300

400

500

600

700

Y

Axi

s T

itle

Harmonics

2’28”

2’20”

1’23”

1’06”

0’50”

0’35”

0’17”

0’0”

Single shot spectrum with CE phase unlocked

4Dec05_Sun

24 26 28 30 32 34 36 380

100

200

300

400

500

600

700

8002'11"

1'58"

1'38"

1'15"

0'55"

0'39"

0'21"

0'00"

Y

Axi

s T

itle

Harmonics

Single Shot Super continuum with CE Phase locked

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”.

Phosphor Screen

hν

MCP2

e-

nA

)8.1(04.0

8.0

)27(02.0

1.01063.5

30000

kVatAIT

HarmonicsthR

Q

G

TQRfGe

IN

Al

Al

AlAlrep

e-

Measurement of Number of photons per pulse

0

=1.3cm

D=?

Collimating mirror f = 1.5 m

Focusing mirror f = 250 mm

D=0.4cm

Required D is

D

fw0

z

zww

R

210

1.3 cm

Required D is

Required Beam Size to eliminate photon loss

w

z R02

1.3 cm

Measurement of half the diverging angle of the XUV beam

D=0.4cm

-10 -5 0 5 100.0

0.2

0.4

0.6

0.8

1.0

1/e2 = 3.5 mrads

No

rma

lize

d In

ten

sit

y

Divergence Angle (mrads)

8.1mrads

21.7mrads

Focus

1.35cm

Diffraction Grating

D=0.4cmW=1.3cm

W0