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 real profile. 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.

Autocorrelation Interferometric AC Intensity AC Single – shot AC Both F(t) and F’(t) are replica’s of the same function E(t)exp

Interferometric AC F(t) = E(t)exc[it+i(t)] I1() = |E(t)exc[it+i(t)] +E(t-)exc[i(t- )+i(t-)]|2dt I2() = |{E(t)exc[it+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

Interferometric AC

Limitions of AC Non-specific: one has assume a particular pulse shape. Returns only amplitude.

Full-field characterization of femtosecond pulses by spectrum and cross-correlation measurements OPTICS LETTERS / Vol. 24, No. 23 / December 1, 1999 J. W. Nicholson, J. Jasapara, and W. Rudolph F. G. Omenetto and A. J. Taylor

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

FROG Rev. Sci. Instrum., Vol. 68, No. 9, September 1997 R. 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.

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

FRPP: pump-probe FROG OPTICS LETTERS / Vol. 27, No. 13 / July 1, 2002 S. 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 1999 C. 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