TWO COLOR OPERATION AT THE FERMI SEEDED FEL: ONE SEED PULSE One - PowerPoint PPT Presentation

TWO COLOR OPERATION AT THE FERMI SEEDED FEL: ONE SEED PULSE One seed pulse –> two color “zero-delay” FEL pulses using the split undulator scheme 2 colors Seed pulse (344 nm) H9 of 344nm (38 nm) MOD radiators DS possible applications in FWM H8 of 344nm (43 nm) 38 Wavelength (nm) 43 One seed pulse –> two color “zero-delay” FEL pulses using the two-stage FEL2 Pulses 1 st stage Pulse 1 st stage 2 nd stage H(7x3) and 2 nd stage 1 st stage H7 Seed pulse MOD radiators MOD radiators DS DS possible applications in pump-probe experiments (when combined with an appropriate split-and-delay stage)

SPLIT AND DELAY PADReS delay line Courtesy of E. Principi FEL-stimulated transient grating “mini-TIMER”@DiProI … and soon maxi-TIMER @EIS-TIMER beamline Courtesy of F. Bencivenga Bencivenga et al. , Nature 2015

TWO COLOR OPERATION AT THE FERMI SEEDED FEL: TWO SEED PULSES Two color seed pulses –> two color FEL pulses inside the FEL bandwidth Two FEL pulses (max wavelength Two seed pulses separation below 1%) H7 + tunability inside the FEL gain bandwidth 260.4nm 261.8nm 37.4nm 37.2nm MOD radiators DS modulator bandwidth (1/N) time 4me!delay!!<!800!fs ! 4me!delay!!<!800!fs ! E. Allaria et al., Nat. Commun. , 2013 K–B focusing 100 3,000 optics Pump ccd pixels Online spectrometer 50 Undulator ∆ t FEL amplifier 0 0 39 40 41 42 Twin FEL pulses 100 1,000 Probe probing structural ccd pixels C C D 50 d e t e Twin seed c t o r ∆ t laser pulses dynamics in solid Θ Pump 0 0 Θ Probe 39 40 42 samples using 100 3,000 Pump probe low - F ccd pixels ∆ t Ti dispersive 37.1 37.2 37.3 37.4 37.5 1 µ m diffraction grating 50 � (nm) 0 37.0 0 39 40 42 37.1 100 37.2 15,000 � (nm) Pump probe 37.3 ccd pixels high - F 37.4 50 37.5 37.6 0 0 –500 0 500 1,000 1,500 2,000 2,500 39 40 41 42 Delay (fs) Angle

TWO COLOR OPERATION AT THE FERMI SEEDED FEL: TWO SEED PULSES Two color seed pulses –> split undulator scheme Two FEL pulses wide tunability Two seed pulses H14 of 261nm (18 nm) 23nm 18nm 261nm 255nm radiators MOD DS τ!<!800!fs ! τ!<!800!!fs ! H11 of 255nm (23 nm) E. Ferrari et al., Nat. Commun. , 2016 probing demagnetization dynamics in magnetic compounds

EXOTIC TWO COLOR SCHEMES AND FULL SPECTRO-TEMPORAL SHAPING OF FEL PULSES AT FERMI

BUNCHING IN A SEEDED FEL Dispersive!sec4on!strength! Seed!laser!envelope! b n ( t )~J n [ − nBA ( t )]exp{ in [ φ s ( t ) + φ e ( t )]} Bessel!func4on! Electron!energy!profile! Seed!phase! Energy' Bunching!envelope!! FEL!temporal!profile! φ s ( t ) + φ e ( t ) FEL!phase! Time'' The!FEL!pulse!can!be!shaped!through!the!manipula4on!of!the! seed!envelope!A(t)!and!phase!!!! φ s ( t )

FEL PULSE ENVELOPE Bunching!at!the! nth !harmonic! b n ( t )~J n [ − nBA ( t )]exp{ in [ φ s ( t ) + φ e ( t )]} Amplitude'profile !

FEL SPECTRUM Bunching!at!the! nth !harmonic! b n ( t )~J n [ − nBA ( t )]exp{ in [ φ s ( t ) + φ e ( t )]} Amplitude'profile ! Phase'profile !

SEEDED FELs AS SELF-STANDING SOURCES FOR X-RAY PUMP – X-RAY PROBE EXPERIMENTS moderate dispersive strength λ " FEL'intensity ' 9me ' Spectrum ' wavelength '

SEEDED FELs AS SELF-STANDING SOURCES FOR X-RAY PUMP – X-RAY PROBE EXPERIMENTS moderate dispersive strength strong dispersive strength λ " λ 1" λ 2" FEL'intensity ' 9me ' Spectrum ' wavelength ' G.!De!Ninno #et#al., !!PRL ,#2013#

GENERATION OF TRANSFORM LIMITED FEL PULSES Amplitude'profile ! Phase'profile !

EXPERIMENTAL DEMONSTRATION Compensated'chirp' Strong'chirp' Theory! Experiment! First!demonstra4on!of!the!possibility!to!generate!a!transform[limited!FEL!pulse! Gauthier et al., PRL , 2015

GENERATION OF TIME-DELAYED PHASE-LOCKED PULSES Two phase-locked seed pulses generate two phase-locked FEL pulses: Twin#seed#pulses# Twin#FEL#pulses# τ # Laser#pulse# τ# D ISPERSIVE ! MODULATOR ! RADIATOR ! SECTION ! spectrometer# to#beamlines# e [ !beam!! µ[controlled!! birefringent!plate! Interferogram Twin'seeds'?' e + 'beam'interac9on' Δϕ FEL "="2k"π" τ # Spectral intensity Δϕ FEL "="(2k+1)"π" Δϕ SEED" wavelength Control the phase difference between the carrier waves of the two time-delayed FEL pulses. Gauthier et al., PRL , 2016

TIME-DELAYED PHASE-LOCKED PULSES: EXPERIMENTAL RESULTS Sequence'of'single?shot'spectra ' Interferograms'vs.'phase'varia9on ' Step!phase!varia4on! Δϕ FEL "="2π"/5.67 # Δϕ FEL" +"2π tuning of the twin-seed phase phase stability: λ FEL /12 RMS precise control of the twin-FEL phase locking in phase better than 15 attoseconds Possible applications: nonlinear coherent transient interferometry and spectroscopy, spectral holography, quantum state holography, highly resolved spectroscopy, … Gauthier et al., PRL, 2016

“ZERO-DELAY” PHASE-LOCKED PULSES FOR COHERENT CONTROL Phase locking between two harmonics of the seed, controlled by means of an electron phase shifter. 2w = 31.5nm w = 63nm Proof[of[principle!experiment:!! Two[path!quantum!interference!experiment!(Brumer[Shapiro).! Interferences!between!2!pathways!for!Ne!ioniza4on:! Ioniza4on!of!Ne!with!1!photon!at!2w! vs. !2!photons!at!w.! K.!C.!Prince! et#al.,#Nature#Photonics ,!2016!

THERE ARE MANY MORE THINGS YOU CAN DO IN THE TEMPORAL DOMAIN BY USING AN EXTERNAL SEED TO TRIGGER THE FEL EMISSION...

BUT LET’S SWITCH TO THE TRANSVERSE PLANE...

FUL DESCRIPTION OF THE FEL RADIATION MECHANISM 3D FEL theory: Eigenmode expansion of the radiation field: eigenmode growth rate At saturation the fundamental (TEM 00 ) mode, which has the highest growth rate, dominates. E.!L.!Saldin,!E!.A.!Schneidmiller!and!M.!V.!Yurkov,! New#J.#Phys., !2010!

ORBITAL ANGULAR MOMENTUM (OAM) OF LIGHT Optical vortices, i.e., helically phased beams with a field dependence , carry orbital angular momentum* Classically: Analogy with quantum mechanics: *Allen et al., Phys. Rev. A, 1992 image by Ebrahim Karimi

SO, WHAT CAN WE DO WITH OPTICAL VORTICES? Visible wavelengths: XUV and X-rays: • H. He et al. , Direct Observation of • M. van Veenendaal et al. , Prediction Transfer of Angular Momentum to of Strong Dichroism Induced by X Absorptive Particles from a Laser Rays Carrying Orbital Momentum , Beam with a Phase Singularity , Phys. Phys. Rev. Lett. 98 , 157401 (2007). Rev. Lett. 75 , 826 (1995). • A. Picón et al. , Photoionization with • M. P. J. Lavery et al. , Detection of a orbital angular momentum beams , Spinning Object Using Light’s Orbital Opt. Express 18 , 3660 (2010). Angular Momentum , Science 341 , 537 (2013). • A. S. Rury et al. , Examining resonant inelastic spontaneous • A. Jesacher et al. , Shadow Effects in scattering of classical Laguerre- Spiral Phase Contrast Microscopy , Gauss beams from molecules , Phys. Rev. Lett. 94 , 233902 (2005). Phys. Rev. A 87 , 043408 (2013). • J. Wang et al. , Terabit free-space data transmission employing orbital angular momentum multiplexing , Nature Photonics 6 , 488 (2012).

HOW CAN WE GENERATE OAM? Using optical elements, e.g., a spiral phase plate: image by Ebrahim Karimi Not practical at XUV and X-ray wavelengths and FEL intensities in situ generation preferred

WHAT CAN WE DO AT FERMI? Use a phase-mask to modify the transverse profile of the seed: Using a 4-quadrant staircase-like phase Use a spiral phase plate as the phase- modulation of the seed: mask? It doesn‘t work!

MICROBUNCHING CONSTRUCTION IN THE MODULATOR Formation of microbunching in Modification of the transverse the modulator: transverse seed profile using a phase profile at a) the fundamental mask: (260 nm) and b) 7th harmonic (37 nm)

EVOLUTION OF THE RADIATION PROFILE Evolution of the FEL power and Transverse radiation profile in bunching factors ( I beam = 1 kA, the undulator (7th harmonic) P seed = 1 GW, normalized emittance = 5 x 10 -6 m) P.R. Ribi č et al. , PRL 112, 2014

EXPERIMENTAL (ALMOST) DEMONSTRATION seed transverse intensity FEL intensity profile profile Shaping FEL radiation in the transverse plane is much more difficult compared to shaping in the temporal domain!

WHAT HAVE WE JUST LEARNED? • compared to synchrotrons FELs produce more poweful (orders of magnitude higher peak brilliance) and shorter (femtosecond) pulses with laser-like properties • self seeding and HGHG improve FEL performance (spectral brightness, central wavelength and pulse energy stability) • different schemes for SASE and seeded FELs can deliver two color pulses with tunable properties for pump-probe experiments • HGHG offers full control over the spectro-temporal and spatial properties of FEL light

Acknowledgements: Giovanni De Ninno, Elettra/UNG David Gauthier, Elettra FERMI comissioning team Giorgio Margaritondo, EPFL