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DESCRIPTIONAttosecond Metrology. A method for attosecond pulse characterisation. Adam Wyatt 1. Eadweard Muybridges Horse in Motion. Ian Walmsley 1 Laura Corner 1 A. Monmayrant John Tisch et al 2 Eric Cormier 3 Louis F. DiMauro 4. 1 Clarendon Laboratory, University of Oxford - PowerPoint PPT Presentation
Attosecond MetrologyA method for attosecond pulse characterisationAdam Wyatt1Ian Walmsley1Laura Corner1A. MonmayrantJohn Tisch et al2Eric Cormier3Louis F. DiMauro41Clarendon Laboratory, University of Oxford2Blackett Laboratory, Imperial College3Centre Lasers Intenses et Applications, Universite Bordeaux4Brookhaven National LaboratoryEadweard Muybridges Horse in Motion
OutlineMotivationAnalytic Representation of Optical PulsesSPIDER Generalisation & ImplementationHigh Harmonic GenerationXUV SPIDER VariantsResearch TasksConclusionOverview of presentation
MotivationSuccess of Femtoscience applications for AttosciencePump Probe Experiments Advanced Flash PhotographyTo capture event, need to have flash shorter than event.If exact detail of probe pulse known, pulse only needs to be comparable in duration to event in interest.Success of FemtoscienceApplications for AttoscienceTracking molecular motion in chemical reactions (femtochemistry)Detection & control of coherent processes.MicromachiningNobel Prizes!!!Tracking electronic motionSurface science????
Whats the problemWhy is it hard to characterise ultrashort pulsesDuration much shorter than detector response.Examples:
What are EM pulses?Superposition of CW EM Fields
What are EM pulses?Superposition of Few CW EM Fields Pulse Trains
What are EM pulses?Superposition of CW EM Fields Isolated Pulses
Characterising EM pulsesReal Field and Analytic Field EquationsComplex Temporal Electric FieldComplex Spectral Electric Field
Pulse CharacterisationWhat completely defines a pulseDirection basic toolsColour spectrometerArrival time interferometerDirect measurementsIndirect measurementsDuration ?Shape ?Pulse much shorter than detector response!Electric field envelopeCarrier frequencyPulse arrival timePulse spectrumFourier TransformAbsolute phase (CEO)Dispersive phaseAnalytic Electric Field Equations(In Angular Frequency and Time)
MethodsCurrent pulse characterisation methodsDifferent classes of characterisation methods and some examples1:1I. A. Walmsley & V. Wong, J Opt Soc Am B,13(11), 19962M. Beck et el, Opt Lett, 18(23), 19933R. Trebino et el, Rev Sci Inst, 68(9), 19974L. Gallmann et el, Opt Lett, 24(18), 1999
2 Beam InterferometeryGeneralised Interferometer Spectrum
Carrier FrequencyHow to extract the phase informationFourier Transform
What is needed for SPIDERSpectral ShearWww+WNyquist:Noise:Sampling Intervalw
Classic SPIDERExperimental Set-up
High Harmonic GenerationThe very basicsLaser distorts atomic potential.Electron wavepacket tunnels through barrier.Laser causes electron to oscillate back & forth.Collisions with atom causes re-ionisation.High energy photons emitted.LaserAtomElectronHigh energy photon
XUV SPIDERGenerating the shear in the XUVw01w02Example30fs driving pulses at 800nm W ~ 209 x1012 rad s-113nm corresponds to n = 611nm bandwidth at 13nm Dt = 275asShear at driving freq. = W / 61 dw = 1.2nm
XUV SPIDERSPIDER method for HHG radiation
SEA-XUV SPIDERSEA-SPIDER method for HHG radiationFourier Transform
SPIDER Adv.Comparisons of different techniques
Different SPIDER Adv.Comparison of XUV-SPIDER and SEA-SPIDER
Simulated ResultsSimulated HHG data and XUV SPIDER reconstruction31333537-15-10-50510Original and Reconstruction of Phase Of Harmonics Harmonic OrderPhase /radRescaled Harmonic SpectrumPhase from 800nm driving pulsePhase from 800.5nm driving pulseReconstructed Phase-10-8-6-4-20246810012345Temporal Profiles of Attosecond Pulse Trainstime /fsIntensity /arb. unitsFourier Transform Limited (FTL)Simulated ProfileReconstructed Profile31333537-15-10-50510Original and Reconstruction of Phase Of HarmonicsHarmonic OrderPhase /rad-10-8-6-4-20246810012345Temporal Profiles of Attosecond Pulse Trainstime /fsIntensity /arb. unitsRescaled Harmonic SpectrumPhase from 800nm driving pulsePhase from 802.5nm driving pulseReconstructed PhaseFourier Transform Limited (FTL)Simulated ProfileReconstructed Profile
Generating the carrier frequencyCan do need to improve!Fringes2D Fourier Transform
Generating the shearSome ideas still to be testedBi-Mirror / Knife edge4-f Knife edge / Full puls shapingAOPDF Pulse ShapingHard too large bandwidthLow power output (high losses)Easily implementedLimitationsOsc.AOPDFAmp.HCFHHGMetrology
Research TasksShown different driving pulses created sheared harmonics by numerically solving TDSE1 for single 30 fs pulse HHG. Frequencies must not differ by more than 2.5nm at 800nm.Shown max driving intensity ~ 1.7 x1014 Wcm-2.Shown can reconstruct across harmonics given signal with fringes.Shown SEA SPIDER also feasible for experimental parameters.Whats been done?1Data from simulations provided by collaborator E. Cormier, University of Bordeaux, France.
Research TasksWhat to do?Simulate HHG with two driving pulses directly (c.f. combing spectra from individual pulse simulations).Find optimal shear and time delay for typical noise parameters.Test XUV-SPIDER for shorter pulses (5 fs) via simulation.Test how different driving pulses can be.Test generating shear
ConclusionsApplications & motivation for Attoscience.Success of femtoscience.SPIDER technique. What is needed (carrier frequency & time delay)Conventional implementation.XUV SPIDER.How to create shear via HHG.Pros & Cons of SPIDER.Lots of good points, limited by creating sheared pulses.
Still more to doPromising outlook!What have we learnt?