Imperial College London

Attosecond technology meeting Attosecond technology meeting RAL: 7/12/2005RAL: 7/12/2005

Imperial College XUV Attosecond Beamline:progress and results to date

Charles Haworth

Laser Consortium

Imperial College London

Supervisor: Dr. John Tisch

Imperial College London

Creation of isolated Creation of isolated attosecond pulsesattosecond pulses

t

inte

nsi

tyLong pulse

many recollisions

spectral comb

pulse train

t

Few-cycle pulse

single recollision of maximum energy

continuum

single pulse

in

ten

sity

+

+

Imperial College London

The few-cycle driving The few-cycle driving laserlaser

30fs 800mW 1kHz

650-900nm 450mW

6.5fs 200mW

Imperial College London

IR Pulse measurement IR Pulse measurement with FROGwith FROG

Experimental trace Retrieved trace

Retrieved temporal amplitude & phase Retrieved spectral amplitude & phase

Time (fs) Time (fs)

Wav

elen

gth

(nm

)

Wav

elen

gth

(nm

)

Wavelength (nm)Time (fs)

Imperial College London

The few-cycle driving The few-cycle driving laserlaser

Phase stabiliser

Imperial College London

Fast phase stabilisationFast phase stabilisation

A. Baltuska, et al., Nature 421, 611 (2003)

Imperial College London

-100 -75 -50 -25 0 25 50 75 1000.0

0.2

0.4

0.6

0.8

1.0

2.5bar - chirped 1.5bar

No

rmal

ised

inte

nsi

ty

Time (fs)

-100 -75 -50 -25 0 25 50 75 1000.0

0.2

0.4

0.6

0.8

1.0

No

rmal

ised

inte

nsi

ty

Time (fs)

5 10 15 20 25 30

1

2

3

4

5

6

No

. of

tim

es t

ran

sfo

rm li

mit

Pulse Duration (fs)

-100 -75 -50 -25 0 25 50 75 1000.0

0.2

0.4

0.6

0.8

1.0

No

rmal

ised

inte

nsi

ty

Time (fs)

-100 -75 -50 -25 0 25 50 75 1000.0

0.2

0.4

0.6

0.8

1.0

No

rmal

ised

inte

nsi

ty

Time (fs)

0 bar

Tunable pulse duration Tunable pulse duration

2.5 bar neon1.5 bar neon2.5 bar neon - chirpedPressure tuning of pulse duration

Adjustment of gas pressure in differentially pumped fibre permits the generation of near-transform-limited pulses in the range 7-30fs, with constant energy and alignment.

This provides clean pulses without significant satellites c.f. chirping maximum bandwidth, which introduces significant pulse distortion due to the modulated nature of the self-phase modulated spectrum.

FWHM = 28fsFWHM = 7fsFWHM = 18.5fsFWHM = 18.5fs

Imperial College London

High harmonic High harmonic generationgeneration

f=40cm mirror

Imperial College London

Harmonic spectrumHarmonic spectrum

Calculated harmonic spectra Measured harmonic spectra

Divergence

Wav

elen

gth

Incr

easi

ng h

arm

onic

ord

er

Incr

easi

ng h

arm

onic

ord

er

Divergence

46nm

12nm

Imperial College London

XUV SPIDERXUV SPIDER

Spatially encoded XUV SPIDER

Preliminary tests

Fringing observed in the harmonic signal from two spatially separated foci

We have observed very clear spatial and spectral fringes in the harmonic spectra

nozzle

plasma plasma

~100µm

Spatially Resolved HHG Spectra (initial

data!)

Imperial College London

Fringes in harmonic spectraFringes in harmonic spectra

Latest fringe data (much cleaner and controllable)

Imperial College London

Atomic streak cameraAtomic streak camera

Drescher, Science,291 pg1923,2001

Imperial College London

MoSi MirrorMoSi Mirror

Engineering the atomic streak camera for metrology of attosecond pulses

Developing methods of coring and mounting the MoSi multilayer mirror used as the XUV/IR delay stage.

Testing needle gas targets

X-ray UHV mirror mount for atomic streak camera

Imperial College London

Coring processCoring process

Cored two-part mirror

Have MoSi mirror from NTT Japan (13nm centre wavelength, 10 bilayers)

Tests indicate that core can be cut in-house with minimal damage to the substrate and coating

Damage occurs close to the cut and should not adversely affect focusing of either the XUV or infrared pulses.

core

cutting gap (kerf)

Imperial College London

Atto management Atto management meeting 09/05meeting 09/05

MoSi multilayer 2-part mirror for Atomic Streak Camera

Centre part mounted on stalk ready for attachment to piezo stage

Annular part mounted in UHV motorised mount

5mm

4mm

Imperial College London

MoSi mirror profileMoSi mirror profile

CXRO website

http://www.cxro.lbl.gov/

Wavelength (nm)

Mirror reflectivity

Mirror phase

Imperial College London

Neon HHG spectrum Neon HHG spectrum

Inte

nsity

(ar

b. u

nits

)

Wavelength (nm)

Lineout of harmonic spectrum

Reflected XUV spectrum

Wavelength

Pos

ition

3D surface plot of neon harmonicsIn

tens

ity

Imperial College London

Neon harmonics - Neon harmonics - ContinuumContinuum

300as pulse duration

Time

Inte

nsity

Wavelength

Pos

ition

3D surface plot of optimised neon harmonics In

tens

ity

Limited by MoSi mirror bandwidth!

Imperial College London

New beamline!!!!!New beamline!!!!!

Imperial College London

AcknowledgementsAcknowledgements

Thanks to….

John,Jon and Roland

Joe Robinson

Andy Gregory and Peter Ruthven

All the other atto people!