Single-shot characterization of sub-15fs pulses with 50dB dynamic range A. Moulet 1, S.Grabielle 1,...
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Transcript of Single-shot characterization of sub-15fs pulses with 50dB dynamic range A. Moulet 1, S.Grabielle 1,...
Single-shot characterization of sub-15fs pulses with 50dB dynamic range
A. Moulet1 , S.Grabielle1, N.Forget1, C.Cornaggia2, O.Gobert2 and T.Oksenhendler1
1FASTLITE, Centre scientifique d’Orsay Bât.503, Orsay, France2DSM/IRAMIS/SPAM/ATTO, CEA Saclay, Saclay, France
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Self-Referenced Spectral Interferometry
SRSI is a recently demonstrated self-referenced pulse measurement technique with unique properties:
• single-shot (spectrum and phase are measured)
• achromatic (third order, degenerate NL effect)
• collinear (no beam splitting, totally collinear)
• compact footprint (A5)
• accurate: no calibration step, analytical
Time-dependent intensity dynamic range of ~50dB
Measurement of coherent contrast
“Self-referenced spectral interferometry”, T.Oksenhendler et al., APB 99, p1-6 (2010),
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Spectral interferometry
Two delayed pulses:I(t)
Pulse 1
Pulse 2
t
I()
Spectral interference pattern:
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Spectral interferometry
DC term AC term
Quadratic equation
Both pulses are completely characterized if one spectral phase is known. A reference pulse is needed, with:- flat phase- broader spectrum
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~~ EE if
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Creation of a reference pulse ?
Spectral domain
before XPWTime domain
Spectral domain
After XPW
I(t)
t
I() ()
Modulated spectrum
Spectral phase
I(t)
t
XPW
XPW pulse
Input pulse
XPW active media
Broader spectrum
Flatter phase
I() ()
Broader spectrum
Flatter phase
XPW can be used as reference pulse
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XPW filtering
Spectrometer
Birefringent plate
Polarizer
Replica generation Main pulse extinction
Polarizer
SRSI experimental setup
BaF2,1mm
“Self-referenced spectral interferometry”, T.Oksenhendler et al., APB 99, p1-6 (2010),
110m
m
Spectrometer
260mm
Iris IrisPolarizer
Polarizer
Focusingmirror
XPW crystal
Calcite plate
Focusingmirror
Input pulse replica
Reference (XPW) pulse
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Experimental results
300 350 400 4500
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1
SR
SI S
pectr
um
(u.a
)
Frequency (THz)
Consistency check with the XPW spectrum enlargement and cleaning
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1
Frequency (THz)
Sp
ectr
al in
ten
sity (
u.a
)
Input spectrumXPW spectrum
CEA laser and hollow core fiber: 810nm, 160nm, 10J, 1kHz
340 360 380 400 4200
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Frequency (THz)
Spectr
al in
tensity (
u.a
)
340 360 380 400 420-3
-2
-1
0
1
2
3
Spectr
al phase (
rad)
Input spectralamplitude and phase reconstruction
-1500 -1000 -500 0 500 1000 1500
10-4
10-3
10-2
10-1
100
Time (fs)
Tem
pora
l In
tensity (
u.a
.)
F.T-1
DC AC
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Experimental results: cross-check with SPIDER
-50 -25 0 25 500.0
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1.0
Time (fs)
Tem
pora
l Int
ensi
ty (
u.a.
)
SRSISPIDER
340 360 380 400 4200
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1
Frequency (THz)
Spe
ctra
l int
ensi
ty (
u.a)
340 360 380 400 420-3
-2
-1
0
1
2
3
Spe
ctra
l pha
se (
rad)
SRSI PhaseSPIDER Phase
≈12 fs
Hollow-core fiber (Ar, 2 bar)
Amplified Ti:Sa laser
Dazzler SRSI
SPIDER
Feedback
-210fs2 were added by Dazzler to compensate for the dispersion of the optics of the SRSI device
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300 320 340 360 380 400 420 440 460-80
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-60
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-10
0
10
Frequency (THz)
Nor
mal
ized
spe
ctra
l int
ensi
ty
Dynamic range – spectral domain
Dynamic range of spectrometer
~25dB
Dynamic range of the measurement
>50dB
XPW
Input
Spectral range of validity of the measurement (~200nm)
Spectral amplitude ( intensity) is measured on a broader spectral support than that of the pulse’s.
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Dynamic range – time domain
-400 -200 0 200 400-60
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-30
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0
Time (fs)
Nor
mal
ized
tim
e in
tens
ity
FWHM=14.51fsFWHM=14.59fs
Measured I(t)
FTL I(t)
Artifacts ?
Pulse duration FWHM = 14.5fs
FTL FWHM = 14.6fs
Another day, another pulse duration…
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-400 -200 0 200 400-60
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0
Time (fs)
Nor
mal
ized
tim
e in
tens
ity
FWHM=14.51fsFWHM=14.59fs
Dynamic range – time domain
Number of illuminated pixels (~512)
SNR of the CCD detector (~25dB)
For a measurement limited by shot-noise, the expected time dynamic range is:
=52dB
Expected dynamic range
Effect of residual spectral phase
Measured I(t)
FTL I(t)
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Dynamic range – time domain
To check the validity of the phase measurement and assess the dynamic time range: compensation of residual phase oscillations with the pulse shaper:
Expected dynamic range
Before feedback
After feedback
=34.6fs =19.3fs
FTL=18.6fs
=14.6fs =14.6fs
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Conclusions and prospects
Sub-15fs pulses were characterized by SRSI and results were cross-checked with SPIDER measurements
Assessed time dynamic range over ±400fs: 50dB
Std. dev. is more relevant than FWHM pulse duration for fine compression: high order phase really matters
Using spectrometers with cooled multiline CCD detectors, single-shot characterization with dynamic ranges as large as 85 dB on a picosecond scales could be reached.
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Our new product
Thank you for you attention
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Spectrum
Taking residual XPW phase into account: iterative algorithm
Interferogram
Spectral complex amplitude
Time complex amplitude
XPW phase
Phase difference+
FT
Spectral phase approximation
First approximation:
Hope:
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340 360 380 400 4200
0.2
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1
Frequency (THz)
Spe
ctra
l int
ensi
ty (
u.a)
340 360 380 400 420-3
-2
-1
0
1
2
3
Spe
ctra
l pha
se (
rad)
SRSI PhaseSPIDER Phase
335 345 355 365 375 385 395 405 415 4250.0
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0.9
1.0
Frequency (THz)
Spe
ctra
l Am
plitu
de (
a.u.
)
335 345 355 365 375 385 395 405 415 425-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
Spe
ctra
l Pha
se (
rad)
Spectrum discrepancy
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Fourier Transform treatment - 1
I()
F.T
Numerical filter, centering
F.T-1
t0
I(t)
C.Froehly, A.Lacourt, J.C.Vienot: J. Opt. (Paris) 4, 183 (1973) L.Lepetit, G.Chériaux, M.Joffre: J. Opt. Soc. Am. B 12, 2467 (1995)
t
I(t)
0
I() ()
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Fourier Transform treatment - 2
I()
F.T-1
0t
I(t)
C.Froehly, A.Lacourt, J.C.Vienot: J. Opt. (Paris) 4, 183 (1973) L.Lepetit, G.Chériaux, M.Joffre: J. Opt. Soc. Am. B 12, 2467 (1995)
Numerical filter
t
I(t)
0
F.T
I()
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• Bandwidth:
• Time range:
• Pulse complexity:
• Dynamic range:
Limitations ?
Spectral broadening is required
(spectral resolution)
Spectrometer bandwidth
Dispersion of crystals~160nm FWHM
Birefringent delay
~±400fs FWHM
Resolution of the spectrometer
Extinction ratio of polarizers
Dynamic of the spectrometer
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SRSI properties
• achromatic: the XPW effect is automatically phase-matched (collinear and degenerated 3nd order NL effect)
• single beam: no beam splitting, totally collinear
• single shot: spectrum and phase are measured for the same interferogram
• accurate: analytical, no calibration/integration step
• but… requires XPW broadening required
Retrieval error with a gaussian pulse (FWHM = 20 nm)
Err
or
(%)
<10%
Large chirps must be removed before measurement
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Experimental results with a Ti:S amplified laser
F.T-1
Numerical filter, centering, FT
800nm, 40nm, 2mJ, 100Hz
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Spectrum reconstruction accuracy
Measured spectrum (dashed red) and reconstructed spectrum with SRSI calculation (blue)