When an X-ray Free- behaves like a Laser

Ivan Vartaniants

Photon Science, DESY, Hamburg, Germany NRNU, ‘MEPhI’, Moscow, Russia

Ivan Vartaniants | Coherence 2018, Port Jefferson, June 26, 2018 | Page 1 Hanbury Brown and Twiss Interferometry Hanbury Brown and Twiss interferometry

Telescopes measuring correlations of light from Sirius

From G. Goldhaber, Proc. Int. Workshop on Correlations and

Multiparticle production (CAMPOleg Gorobtsov - LESIP | HBT FLASH| IV), 201 World7| Page 3 Scientific (1991) Hanbury Brown and Twiss experiment

Sirius 2 퐼 퐫ퟏ 퐼 퐫ퟐ 푔 퐫ퟏ,퐫ퟐ = 퐼 퐫ퟏ 퐼 퐫ퟐ

퐼 퐫ퟏ 퐼 퐫ퟐ Mixer Sirius angular size: 0.0063” 퐼 퐫ퟏ 퐼 퐫ퟐ Average over coincidence measurements Hanbury Brown and Twiss, Nature 1956 Hanbury Brown and Twiss, Nature 1957 Quantum optics

Glauber has formulated: The source to be coherent, has to be coherent in all orders of correlation function Nobel prize: 2005 N-th order correlation function:

(푛) 퐼 푥1 …퐼(푥푛) 푔 푥1, … , 푥푛 = = 1 퐼 푥1 … 퐼 푥푛

Special case, 1-st order correlation function:

(1) 퐸 푥1 퐸(푥2) 푔 푥1, 푥2 = 퐼 푥1 퐼 푥2 R. Glauber, Phys. Rev., 131, 2766 (1963) Laser sources and chaotic sources Chaotic sources (Gaussian Statistics)

τ 푔 2 퐫 퐫 = 1 + 푐 ∣ γ ∣2 ퟏ, ퟐ 푇 12

tc : coherence time T: pulse duration

tc/T high at FELs

F.T. Arecchi et al., Phys. Lett. (1966) E. Ikonen, Phys. Rev. Lett. (1992) X-ray Free-Electron

Ivan Vartaniants | Nanoscale interdisciplinary research: , , biology, mathematics, April 25-27, 2017 | Page 7 XFEL sources

FLASH at DESY LCLS at Stanford 2005 2009

Ivan Vartaniants | Nanoscale interdisciplinaryFERMI research: at physics, Elettra chemistry, biology, mathematics, April 25-27, 2017 | Page 8 2011 European XFEL (started its user operation on September 1-st, 2017)

European XFEL

Ivan Vartaniants | Nanoscale interdisciplinary research: physics, chemistry, biology, mathematics, April 25-27, 2017 | Page 9 SASE FEL principle

SASE (self-amplified spontaneous emission)

in phase with e.m.-wave are retarded (“emit ”), electrons with opposite phase gain energy (“absorb photons”)

 longitudinal charge density modulation (“micro-bunching”)

with periodicity equal to λphot

 self-amplification of spontaneous emission due to increasingly coherent emission from micro-bunches (like point charge)

Ivan Vartaniants | Nanoscale interdisciplinary research: physics, chemistry, biology, mathematics, April 25-27, 2017 | Page 10 What are the 1-st order coherence properties of X-ray free-electron lasers?

I. A. Vartanyants & A. Singer, ''Coherence Properties of Third-Generation Sources and Free-Electron Lasers'', Synchrotron Light Sources and Free-Electron Lasers. Editors: E. Jaeschke, S. Khan, J.R. Schneider and J.B. Hastings Springer International Publishing Switzerland (2016), pp.821-863. Young’s double slit experiment

Thompson& Wolf, JOSA 47, 895 (1957) LCLS, transverse coherence

I. Vartaniants, et al., Phys. Rev. Lett. 107, 144801 (2011). FLASH, transverse coherence

Eph=155eV (λ=8.0 nm) Epulse=0.2 mJ Tpulse=100 fs

Nominal focus : 10-20 µm FWHM Pinhole separations up to 15 μm Destructive regime A. Singer, et al., Optics Express 20, 17480 (2012) Transverse coherence at FELs ~ 80-90% Basic question:

Whether XFEL’s are really laser-like sources according to Glauber’s definition? Hanbury Brown - Twiss Interferometry at FELs

A. Singer et al., Phys. Rev. Lett. 111, 034802 (2013) O. Gorobtsov et al., Phys. Rev. A 95, 023843 (2017) O. Gorobtsov et al.,Sci. Rep. 8, 2219 (2018) O. Gorobtsov et al., Nat. Commun. 9, 4498 (2018) Collaboration with W. Wurth group and FLASH Intensity-Intensity Correlation Measurements at FLASH l=5.5 nm Bunch charge 0.6 nC Pulse Energy 100 mJ

t ~ 1/Dn τ c 푔 2 퐫 퐫 = 1 + 푐 ∣ γ ∣2 ퟏ, ퟐ 푇 12 FLASH, PG2 beamline, (March,2012) Second Order Correlation Measurements

30 mm -4 DE/E=0.8∙10 x2 x1

2 퐼 푥1 퐼 푥2 푔 푥1,푥2 = 퐼 푥1 퐼 푥2 Second Order Correlation Measurements Exit slit: 30 mm

Coherence length: lc=0.93 mm Single longitudinal mode! Beam size: 0.45 mm Degree of coherence: 76% Second60 mm Order Correlation Measurements Exit slit: 60 mm Second150 m mOrder Correlation Measurements Exit slit: 150 mm Second300 m mOrder Correlation Measurements Exit slit: 300 mm Second500 m mOrder Correlation Measurements Exit slit: 500 mm

What is the origin of the 2-nd maximum? Second order correlation measurements

G. Baym, Acta Physica Polonica 29, 1839 (1998) Second500 m mOrder Correlation Measurements 500 mm

τ 푔 2 퐫 퐫 = 1 + 푐 ∣ γ ∣2 ퟏ, ퟐ 푇 12 Pulse duration

T=31±21 fs

A. Singer et al., Erratum PRL 117, 239903 (2016) Hanbury Brown and Twiss interferometry in mode at LCLS

O. Gorobtsov et al., Sci. Rep. 8, 2219 (2018) Collaboration with LCLS Diffraction experiment at LCLS

Measurements of Polysterene 420 nm Polysterene 160 nm response of colloidal crystals to IR laser irradiation

Beamline: XPP : 1.5498 A Bandwidth: 10-4 Repetition rate: 120 Hz Pulse duration: 42 fs (?) Focus size: 50 um Distance: 10 m Pixel size: 110 um Intensity: 109 ph/pulse

Oleg Gorobtsov | HBT FLASH| 2017| Page 32 N. Mukharamova et al., Appl. Sci., 7, 519 (2017) Bragg dance

Shot-to-shot changes in the Bragg peak intensity

Oleg Gorobtsov | HBT FLASH| 2017| Page 33 Intensity-intensity correlation function

2 푔 푥1, 푥2 = Polysterene 160 nm Polysterene 420 nm 퐼 푥 퐼(푥 ) = 1 2 퐼(푥1) 퐼(푥2)

Oleg Gorobtsov | HBT FLASH| 2017| Page 34 Simulated intensity-intensity correlation function

One beam Intensity (rms): 1.6 mm Two beams Coherence length: 10 mm Secondary beam:10% of intensity Background noise: 2% Position difference: 1.5 mm Our analysis has shown that pulse duration is about 11-12 fs instead of expected 40 fs provided by machine

Oleg Gorobtsov | Diffraction-based Hanbury Brown and Twiss interferometry on x-ray free-electron laser | 2017 | Page 35 Different configurations

Single source&beam Separated sources

Secondary beams Jitter

Oleg Gorobtsov | HBT FLASH| 2017| Page 36 O. Gorobtsov, et al., Phys. Rev. A 95, 023843 (2017) HBT experiments at SASE FELs

Our results demonstrate definitely that SASE

XFELs statistically behave as chaotic sources

and not as a fully coherent sources!

What about seeded FELs?

First and Last Name | Title of Presentation | Date | Page 37 Hanbury Brown and Twiss interferometry at the externally seeded FERMI source

O. Gorobtsov et al., Nat. Commun. 9, 4498 (2018) Collaboration with W. Wurth group and FERMI HBT experiment at FERMI

Layout of experiment at the seeded FEL FERMI HBT experiment at FERMI

g(2) -1 Seeded =0.03

g(2) -1 SASE =0.1

Seeded and SASE mode correlation functions and spectra HBT experiment at FERMI

(2) Single g -1 =0.02 pulse

Multiple g(2) -1 pulses =0.07

Seeded mode single and multiple pulses analysis Summary

Seeded FEL source FERMI statistically behaves as a real laser-like source according to Glauber’s definition

Still open question! What is the statistical behavior of self-seeded XFEL pulses?

We hope to clarify this question at European XFEL! Future of HBT interferometry Cherenkov Telescope Array

CTA Telescopes in Southern Hemisphere Cherenkov Telescope Array Cherenkov Telescope Array

Optical images of the “stars” Second-order optical coherence reconstructed from intensity surface measurements interferometry

Laboratory experiments Summary

Application of high-order correlation functions for imaging Quantum imaging with incoherently scattered light from a free-electron laser

R. Schneider et al., Nature Phys. 14, 126 (2018) Quantum imaging using high order correlations

Scheme of experiment at FLASH

Nine source separation vectors of a benzene-like mask generating six Fourth-order correlation scheme independently radiating incoherent light sources

CollaborationOleg Gorobtsov | Diffraction-based with Hanbury Brown J. and von Twiss interferometry Zanthier on x-ray free group-electron laser | 2017(Uni. | Page 50Erlangen) Quantum imaging using high order correlations

Single-shot speckle pattern and SEM image and quantum protocol experimentally derived fourth- reconstruction of the artificial benzene order intensity correlation molecule function

Oleg Gorobtsov | Diffraction-based Hanbury Brown and Twiss interferometry on x-ray free-electron laser | 2017 | Page 51 Ghost Imaging at X-ray Free-Electron Lasers

Y. Y. Kim et al., Phys. Rev. Lett. (2018) (in review); arXiv:1811.06855 What is Ghost Imaging

L2 L1 Bucket Sample X-ray Beam

Diffuser Splitter (source) Reference L3

Indirect imaging by correlation of 푀 1 a) Photons that pass through the sample and are 푇 (푥, 푦) = (퐵 − 퐵 )퐼 (푥, 푦) 퐺퐼 푀 푗 푗 measured by bucket detector 푗=1 b) Photons which never pass through the sample and are measured by the pixel detector TGI : Ghost Image M : # of frames

Bj : Bucket signal Ij(x,y) : Reference Image First and Last Name | Title of Presentation | Date | Page 53 Why we need Ghost Imaging

Advantages:

a. Developing of quantum imaging protocol

b. Reducing radiation dose on the sample

c. Turbulence robustness (i.e. tolerance to noise)

First and Last Name | Title of Presentation | Date | Page 54 Experiment at FLASH

Detector images Setup I (Diffuser+Splitting unit) 1

3 Setup II 2 (Diffuser + Transmission 1 Grating)

1 Setup III (Transmission Grating + Diffuser)

FLASHFirst and Last Name experiment, | Title of Presentation | Date March | Page 55 2018 Samples & Diffuser Sample Design 1) Single bar 2) Double bar 3) DESY logo

0.2 mm E : 92.5 eV (13.4nm)

Thickness Transmission Material (nm) (I/I0) 100 0.2e-2 Co 300 0.1e-7

0.5 mm 0.2 mm 1 mm

Diffuser

• 400 nm SiO2 colloidal particle ~17 mm ~17

12.5 mm First and Last Name | Title of Presentation | Date | Page 56 Ghost Imaging Procedure

Ʃ Time-average Time-average

Correlation

First and Last Name | Title of PresentationGhost | Date Imaging | Page 57 Bucket detector Best Result – Set-up II (position 2)

An average image at Ghost imaging Line profile of the the bucket detector reconstruction structure (average of ~40 000)

First and Last Name | Title of Presentation | Date | Page 58 Outlook

- Our experiments show that SASE FELs behave as chaotic sources and externally seeded FELs as laser-like sources - It allows to explore nonclassical states of light, perform quantum imaging and ghost imaging experiments; coherent control experiments

R. Schneider et al., Oleg Gorobtsov | HBT FLASH| 2017| Page 59 Nature Physics (2018) S. Usenko et al., Nature Comm. (2017) Coherent X-ray Scattering and Imaging Group at DESY

Present members: Former members: • A. Zozulya (now@XFEL) • S. Lazarev • N. Mukharamova • A. Mancuso (now@XFEL) • Y-Y. Kim • R. Khubbutdinov • O. Yefanov (now@CFEL) • R. Dronyak • D. Lapkin • L. Gelisio • J. Gulden (now@FH-Stralsund) • D. Assalauova • U. Lorenz (now@Uni. Potsdam) • A. Singer (now@Cornell Uni.) • R. Kurta (now@XFEL) • I. Besedin (now@MISR) • P. Skopintsev (now@PSI) • A. Shabalin (now@UCSD) • D. Dzhigaev (now@PETRA III) • O. Gorobtsov (now@Cornell Uni.) • I. Zaluzhnyy (now@UCSD) • M. Rose

Oleg Gorobtsov | HBT FLASH| 2017| Page 60 Acknowledgements

Former members of the group: Group of W. Wurth:

• A. Singer • G. Mercurio • U. Lorenz • F. Sorgenfrei • O. Gorobtsov

Present members of the group: FERMI:

• Young Yong Kim • K. Prince • L. Gelicio • L. Gianessi • M. Kiskinova • F. Capotondi

FLASH, LCLS, FERMI teams We have open PostDoc positions!

Thank you for your attention!