1. FEL – opt. Laser cross-correlation Reinhard Kienberger 1,2,(3) 1 Institut für Photonik, Technische Universität Wien, Austria (Ferenc Krausz) 2 SPPS (April – end 2004, fellowship Austrian Academy of Sciences) 3 Max-Planck Institut für Quantenoptik, Garching / München, Germany SLAC-workshop XFEL 2004 July 28, 2004

2. 1.) Cross-correlation technique: Photo- / Auger Electrons Attosecond streak camera 2.) Sidebands at ‚long‘ pulses 3.) Chirped Pulse Laser Assisted Auger Decay Outline

3. Sampling a Pulse with Itself: Autocorrelation Beam splitter Delay line Detector PumpProbe Interaction medium Electrons, Photons Frustrated by low two-photon transition probability at X-ray photon energies

4. Measuring a Sub-Femtosecond X-Ray Pulse with Laser Light? Beam splitter Delay line Detector X-ray pulse Visible light wave Interaction medium Electrons, Photons Sampling must be performed by the laser field rather than the pulse envelope Hentschel et al., Nature 414, 509 (2001)

5. ExEx aperture and electronic lens microsphere- plate detector VIS / XUV X-Correlation: Principle of Excitation and Detection Ne 2s ElEl Time-of-flight tube U. Becker and D.A. Shirley, VUV and Soft X-ray Photoionization, p. 152 parallel geometry!! 2p

6. Ionization with an Isolated Attosecond Pulse Gas: Ne Electrons: 2p W b = 21.46 eV XUV cut-off energy: ~95 eV Mirror reflectivity bandwidth: ~9 eV (FWHM) Detection as in: Kienberger et al., Science 297, 1144 (2002) delay possible

7. The Measurement: Experimental Setup Pump laser pulse Duration  6 fs Energy  0.3 mJ Rep. rate = 1 kHz Iris Zr-filter on pellicle TOF Ne PZT Two-component Mo/Si multilayer mirror Reflectivity > 60% @ 90 eV Bandwidth  9 eV Ne Ionisation detector Ag-mirror M. Drescher et al., Science 291, 1923 (2001)

8. Photoelectron Acceleration/Deceleration

9.  x < T 0 /2 ‚Short‘ XUV Pulse

10. Sampling Field Oscillations ħωxħωx +10 eV -10 eV 0 ΔWΔW tDtD

11. -20 -10 0 1010 20 0 6121622 50 60 70 80 90 0 1 Delay tt [fs] Photoelectron kinetic energy [eV] electron counts [arb. u.] Vector potential, A (t) [fs MV/cm] L Complete measurement of a few-cycle light wave 2 4810141820 Goulielmakis et al., Science, accepted for publication

12. Incident X-ray intensity Mapping Time to Energy ħωxħωx instant of electron release ΔW(t7)ΔW(t7) ΔW(t6)ΔW(t6) ΔW(t5)ΔW(t5) ΔW(t3)ΔW(t3) ΔW(t2)ΔW(t2) ΔW(t1)ΔW(t1) ΔW(t4)ΔW(t4) Change in electron energy -500 as 0500 as Laser electric field t7t7 t1t1 t2t2 t3t3 t4t4 t5t5 t6t6

13. Optical Streak Camera, 1834

14. Electron Streak Camera

15. Incident X-ray intensity Optical-Field-Driven Streak Camera ħωxħωx with Attosecond Resolution instant of electron release Change in electron energy -500 as 0500 as Laser electric field 300 as 10 eV

16. “Streak image“ is highly sensitive to a (possible) temporal energy sweep of the electron emission and hence to a (possible) chirp of the XUV pulse Example: linearly-chirped sub-femtosecond pulse Field-free spectrum Kienberger et al., Nature 427, 817 (2004)

17. Full Characterization of a Sub-Femtosecond XUV Pulse “Streak images“ of photoelectrons emitted at adjacent field oscillation maxima of the probing field E L (t) Reconstructed temporal intensity profile and chirp of the XUV excitation pulse pulse duration 250 ± 8 as Kienberger et al., Nature 427, 817 (2004)

18. 1.) Cross-correlation technique: Photo- / Auger Electrons Attosecond streak camera 2.) Sidebands at ‚long‘ pulses 3.) Chirped Pulse Laser Assisted Auger Decay Outline

19.  x < T 0 /2 ‚Short‘ XUV Pulse

20.  x > T 0 /2 ‚Long‘ XUV Pulse

21. E L (t)=E a (t) cos(  L t +  ) xx  =  = 0 T0T0 WW -W-W  x / T 0 E a (t) I x (t) h x 0.1 0.3 1 calculations

22. E L (t) = A(t)cos(  L t +  ) T0T0 WW h x Cross-check: Attosecond Diagnostics measurement

23. Time window possible Solution

24. Expanding the time window Difference Frequency Generation 0.5 fs 10 - 50 fs Time window generally applicable e.g. XFEL

25. 1.) Cross-correlation technique: Photo- / Auger Electrons Attosecond streak camera 2.) Sidebands at ‚long‘ pulses 3.) Chirped Pulse Laser Assisted Auger Decay Outline

26. 3. Application: From Attosecond Diagnostics to Attosecond Spectroscopy W1W1 W2W2 WhWh W bind W kin dNdN dWdW 0 Photo-emission   x - duration of X-ray pulse Auger-emission   h - lifetime of core hole Sidebands versus Δt ΔtΔt Streak images

27. Snapshots of Electron Emission from Kr Following Core-Hole Excitation by a Sub-fs X-Ray Pulse M. Drescher et al., Nature 419, 803 (2002) Tracing core-hole decay directly in time

28. tt Time Kinetic Energy W0W0 -h +h Electron Signal Laser / Auger Wave Sidebands map electron wave packet SPPS: jitter!

29. Time-dependent sideband-area Drescher et al., Nature 419, 803 (2002) Laser-EUV Delay (fs) -200204060 Sideband Area (arb. u.) 0 1 2 3 4 Laser pulse  = 7.9  1 fs

30. Problem with time delay: At SPPS / LCLS: No intrinsic time lock laser – x-rays i.e. ‘jitter’ → single shot measurement

31. W1W1 W2W2 WhWh W bind W kin dNdN dWdW 0 Auger decayLaser assisted Auger decayChirped pulse Laser assisted Auger decay Auger electron bunch Laser pulse sidebands at ΔW = h laser Broadening of sidebands ~  x-ray (convoluted with Auger decay time) direct measure of x-ray pulse duration J. M. Schins et al., Phys. Rev. Lett. 72, 2180 (1994) T. E. Glover et al., Phys. Rev. Lett. 74, 2468 (1996) t chirp Position of sidebands measure of jitter

32. Laser X-rays Setup:

33. WW 0 -W b Kinetic Energy Ex(t)Ex(t) EL(t)EL(t) Why Auger Electrons? t Line must be narrower than 2 ħω Photoline would mimic bandwidth of x-ray pulse (very broad @SPPS)

34. Problems to be solved Small cross-section of inner electrons (@10 keV) ‘Low’ flux at SPPS → LCLS Detection of KLL Augers - high Energy TOF… The End

35. Atomic Transient Recorder: tomographic images of electron distribution Reconstructs the time-momentum distribution of atomic electron emission confined to T 0 /2 from “tomographic images“ recorded by a strong, phase-controlled light field Resolves the time evolution of atomic excitation and relaxation processes on an attosecond time scale by probing primary (photo) or secondary (Auger) electron emission, respectively.

36. Electric Field Scan Kienberger et al., Science 297, 1444 (2002)

37. Photon energy [eV] 859095100105 X-ray intensity [a.u.] 0.0 0.5 1.0 Mo/Si mirror reflectivity 0.0 0.1 0.2 0.3 X-ray pulse duration,  x < 0.5 fs Timing jitter of X-ray pulse:  t < 0.2 fs Absolute timing with respect to E L (t) Advanced as Pulse Measurement ħωxħωx Kienberger et al., Nature 427, 817 (2004) +10 eV -10 eV 0 ΔWΔW Grating-spectrograph Reflectance curve of mirror Electron-spectrum (after band filter!)

38. Streak Records of Sub-Femtosecond XUV Pulses Satellite NO satellite