Single-shot characterization of sub-15fs pulses with 50dB dynamic range A. Moulet 1, S.Grabielle 1, N.Forget 1, C.Cornaggia 2, O.Gobert 2 and T.Oksenhendler 1 1 FASTLITE, Centre scientifique d’Orsay Bât.503, Orsay, France 2 DSM/IRAMIS/SPAM/ATTO, CEA Saclay, Saclay, France

2010 ICUILConference, Watkins Glen 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 ~50dBMeasurement of coherent contrast “Self-referenced spectral interferometry”, T.Oksenhendler et al., APB 99, p1-6 (2010),

2010 ICUILConference, Watkins Glen Spectral interferometry Two delayed pulses: I(t) Pulse 1 Pulse 2 t  I(  ) Spectral interference pattern:

2010 ICUILConference, Watkins Glen Spectral interferometry DC termAC term Quadratic equation Both pulses are completely characterized if one spectral phase is known. A reference pulse is needed, with: - flat phase - broader spectrum if

2010 ICUILConference, Watkins Glen Creation of a reference pulse ? Spectral domain before XPW Time 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

2010 ICUILConference, Watkins Glen XPW filtering Spectrometer Birefringent plate Polarizer Replica generation Main pulse extinction Polarizer SRSI experimental setup BaF 2,1mm “Self-referenced spectral interferometry”, T.Oksenhendler et al., APB 99, p1-6 (2010), 110mm Spectrometer 260mm Iris Polarizer Focusing mirror XPW crystal Calcite plate Focusing mirror Input pulse replica Reference (XPW) pulse

2010 ICUILConference, Watkins Glen Experimental results Consistency check with the XPW spectrum enlargement and cleaning CEA laser and hollow core fiber: 810nm, 160nm, 10  J, 1kHz Input spectral amplitude and phase reconstruction F.T -1 DCAC

2010 ICUILConference, Watkins Glen Experimental results: cross-check with SPIDER ≈12 fs Hollow-core fiber (Ar, 2 bar) Amplified Ti:Sa laser DazzlerSRSI SPIDER Feedback -210fs 2 were added by Dazzler to compensate for the dispersion of the optics of the SRSI device

2010 ICUILConference, Watkins Glen 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.

2010 ICUILConference, Watkins Glen Dynamic range – time domain Measured I(t) FTL I(t) Artifacts ? Pulse duration FWHM = 14.5fs FTL FWHM = 14.6fs Another day, another pulse duration…

2010 ICUILConference, Watkins Glen 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)

2010 ICUILConference, Watkins Glen 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

2010 ICUILConference, Watkins Glen 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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2010 ICUILConference, Watkins Glen 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:

2010 ICUILConference, Watkins Glen Spectrum discrepancy

2010 ICUILConference, Watkins Glen Fourier Transform treatment - 1  I() F.T  Numerical filter, centering  F.T -1  t 0 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() ()()

2010 ICUILConference, Watkins Glen Fourier Transform treatment - 2  I() F.T -1  0 t 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()

2010 ICUILConference, Watkins Glen 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

2010 ICUILConference, Watkins Glen 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) Error (%) <10% Large chirps must be removed before measurement

2010 ICUILConference, Watkins Glen Experimental results with a Ti:S amplified laser F.T -1  Numerical filter, centering, FT  800nm, 40nm, 2mJ, 100Hz

2010 ICUILConference, Watkins Glen Spectrum reconstruction accuracy Measured spectrum (dashed red) and reconstructed spectrum with SRSI calculation (blue)