Attosecond technology meeting RAL: 7/12/2005
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Transcript of Attosecond technology meeting RAL: 7/12/2005
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
+
+
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The few-cycle driving The few-cycle driving laserlaser
30fs 800mW 1kHz
650-900nm 450mW
6.5fs 200mW
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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)
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The few-cycle driving The few-cycle driving laserlaser
Phase stabiliser
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Fast phase stabilisationFast phase stabilisation
A. Baltuska, et al., Nature 421, 611 (2003)
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-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
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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
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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
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High harmonic High harmonic generationgeneration
f=40cm mirror
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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
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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!)
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Fringes in harmonic spectraFringes in harmonic spectra
Latest fringe data (much cleaner and controllable)
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Atomic streak cameraAtomic streak camera
Drescher, Science,291 pg1923,2001
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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
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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)
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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
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MoSi mirror profileMoSi mirror profile
CXRO website
http://www.cxro.lbl.gov/
Wavelength (nm)
Mirror reflectivity
Mirror phase
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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
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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!
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New beamline!!!!!New beamline!!!!!
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AcknowledgementsAcknowledgements
Thanks to….
John,Jon and Roland
Joe Robinson
Andy Gregory and Peter Ruthven
All the other atto people!