characterization of short pulses

Ultrafast science Lund 2007

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. from pico-Joule to peta-Watt

• Physics of detection

• Choice of detector

• Linearity

• Sensitivity

• Spectral response

• Response time

• Damage


Spectral shape

• What do you need the spectrum for?• Sensitivity range.• Calibration of the spectrometer.• Dynamic range.• Optics on the way.• Fibber ”wave guides”.


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


Temporal profile:What for?

• Satellites: quality of amplification, quality of measurements

• Pulse duration: FWHM• Instrumental response function• Transform-limited pulse• Pulses of random shape


Electrical (direct) measurements of pulse duration:

not fast enough and (very) expensive.

• Photodiode: >10 ps (+fast Oscilloscope)• Streak Camera: 100 fs (?), ~1 ps


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


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


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


Interferometric AC


Limitions of AC

• Non-specific: one has assume a particular pulse shape.

• Returns only amplitude.


+

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


Frequennsy-resolved optical gating

FROG

Rev. Sci. Instrum., Vol. 68, No. 9, September 1997R. Trebino, K. W. DeLong, D. N. Fittinghoff, J. N. Sweetser,


FROG Rev. Sci. Instrum., Vol. 68, No. 9, September 1997R. Trebino, K. W. DeLong, D. N. Fittinghoff, J. N. Sweetser,


Single-shot FROG


FROG


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.


X-FROG: spectrally-resolved cross-correlation of an unknown pulse with the

reference pulse.

( ) '( ) ( )G F t F t dt


TADPOLE

Rev. Sci. Instrum., Vol. 68, No. 9, September 1997R. Trebino, K. W. DeLong, D. N. Fittinghoff, J. N. Sweetser,


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


Self-Referencing Spectral Interferometry for Measuring Ultrashort Optical Pulses

SPIDER

IEEE J Quant.Elctr. Vol. 35, No. 4, April 1999C. Iaconis, I.A. Walmsley


SPIDER


Advantages of SPIDER

• No moving parts• Direct reconstruction (>1kHz)• Noise immunity• Low sensitivity to detector spectral response• Precision and consistency mesures from data


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.


After SPIDER: ZAP-SPIDER


After SPIDER: SEA-SPIDER

E. M. Kosik and A. S. Radunsky I. A. Walmsley C. Dorrer OPTICS LETTERS Vol. 30, No. 3, 2005


After SPIDER: 2DSI

OPTICS LETTERS / Vol. 31, No. 13 / July 1, 2006 J. R. Birge, R. Ell, F. X. Kärtner

characterization of short pulses

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