characterization of short pulses
DESCRIPTION
Characterization of short pulses . A. Yartsev. What is good to know about short pulses?. Energy of each pulse Average power Spectrum Spatial distribution Temporal profile Satellites Duration Shape . Energy/Power measurements. fro m pico-Joule to peta-Watt. Physics of detection - PowerPoint PPT PresentationTRANSCRIPT
Ultrafast science Lund 2007
Characterization of short pulses.
A. Yartsev
Ultrafast science Lund 2007
What is good to know about short pulses?
• Energy of each pulse• Average power• Spectrum• Spatial distribution• Temporal profile
– Satellites– Duration– Shape
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Energy/Power measurements. from pico-Joule to peta-Watt
• Physics of detection
• Choice of detector
• Linearity
• Sensitivity
• Spectral response
• Response time
• Damage
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Spectral shape
• What do you need the spectrum for?• Sensitivity range.• Calibration of the spectrometer.• Dynamic range.• Optics on the way.• Fibber ”wave guides”.
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Beam profile
• Assume Gaussian?– Measure power through calibrated pinholes– Blade-edge method
• Measure real profile.– 2-D detector: CCD matrix– 1-D array detector– Linearity of response
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Temporal profile:What for?
• Satellites: quality of amplification, quality of measurements
• Pulse duration: FWHM• Instrumental response function• Transform-limited pulse• Pulses of random shape
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Electrical (direct) measurements of pulse duration:
not fast enough and (very) expensive.
• Photodiode: >10 ps (+fast Oscilloscope)• Streak Camera: 100 fs (?), ~1 ps
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All-optical methods
• Time from distance: 1 fs 0.3 m• Math: correlation function
– determines F(t) if G() is measured and F’(t) is known.
( ) '( ) ( )G F t F t dt
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Autocorrelation
• Interferometric AC• Intensity AC• Single – shot AC
• Both F(t) and F’(t) are replica’s of the same function E(t)exp
( ) '( ) ( )G F t F t dt
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Interferometric AC• F(t) = E(t)exc[it+i(t)]
• I1() = |E(t)exc[it+i(t)] +E(t-)exc[i(t- )+i(t-)]|2dt
• I2() = |{E(t)exc[it+i(t)] +E(t-)exc[i(t- )+i(t-)]}2|2dt
• First order AC: I1(=0)/I1() = 2• Second order AC: I2(=0)/I2() = 8
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Interferometric AC
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Interferometric AC
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Limitions of AC
• Non-specific: one has assume a particular pulse shape.
• Returns only amplitude.
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+
Spectrum
Full-field characterization of femtosecond pulses by spectrum
and cross-correlation measurements
OPTICS LETTERS / Vol. 24, No. 23 / December 1, 1999J. W. Nicholson, J. Jasapara, and W. RudolphF. G. Omenetto and A. J. Taylor
( ) '( ) ( )G F t F t dt
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Frequennsy-resolved optical gating
FROG
Rev. Sci. Instrum., Vol. 68, No. 9, September 1997R. Trebino, K. W. DeLong, D. N. Fittinghoff, J. N. Sweetser,
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FROG Rev. Sci. Instrum., Vol. 68, No. 9, September 1997R. Trebino, K. W. DeLong, D. N. Fittinghoff, J. N. Sweetser,
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Single-shot FROG
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FROG
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Limitions of FROG
• Requirements on set-up: linear detector response, step size, S/N.
• Delay-scanning technique.• Measures 2D characteristic – long.• Non-specific: needs a (complicated) retrival
to get pulse. • Does not always converge.
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X-FROG: spectrally-resolved cross-correlation of an unknown pulse with the
reference pulse.
( ) '( ) ( )G F t F t dt
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TADPOLE
Rev. Sci. Instrum., Vol. 68, No. 9, September 1997R. Trebino, K. W. DeLong, D. N. Fittinghoff, J. N. Sweetser,
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FRPP: pump-probe FROG
OPTICS LETTERS / Vol. 27, No. 13 / July 1, 2002S. Yeremenko, A. Baltuˇska, F. de Haan, M. S. Pshenichnikov, D. A. Wiersma
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Self-Referencing Spectral Interferometry for Measuring Ultrashort Optical Pulses
SPIDER
IEEE J Quant.Elctr. Vol. 35, No. 4, April 1999C. Iaconis, I.A. Walmsley
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SPIDER
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Advantages of SPIDER
• No moving parts• Direct reconstruction (>1kHz)• Noise immunity• Low sensitivity to detector spectral response• Precision and consistency mesures from data
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Limitions of SPIDER
• Has to be optimised for a particular time-and spectral range.
• Requires calibration.• Very sensitive to delay between pulses –
sensitive to alignment.
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After SPIDER: ZAP-SPIDER
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After SPIDER: SEA-SPIDER
E. M. Kosik and A. S. Radunsky I. A. Walmsley C. Dorrer OPTICS LETTERS Vol. 30, No. 3, 2005
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After SPIDER: 2DSI
OPTICS LETTERS / Vol. 31, No. 13 / July 1, 2006 J. R. Birge, R. Ell, F. X. Kärtner