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Pan R, Zapolnova E, Golz T, Krmpot AJ, Rabasovic MD, Petrovic J, Asgekar V, Faatz B, Tavella F, Perucchi A, Kovalev S, Green B, Geloni G, Tanikawa T, Yurkov M, Schneidmiller E, Gensch M, Stojanovic N. Photon diagnostics at the FLASH THz beamline. JOURNAL OF SYNCHROTRON RADIATION 2019; 26:700-707. [PMID: 31074433 PMCID: PMC6510192 DOI: 10.1107/s1600577519003412] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 03/11/2019] [Indexed: 05/30/2023]
Abstract
The THz beamline at FLASH, DESY, provides both tunable (1-300 THz) narrow-bandwidth (∼10%) and broad-bandwidth intense (up to 150 uJ) THz pulses delivered in 1 MHz bursts and naturally synchronized with free-electron laser X-ray pulses. Combination of these pulses, along with the auxiliary NIR and VIS ultrashort lasers, supports a plethora of dynamic investigations in physics, material science and biology. The unique features of the FLASH THz pulses and the accelerator source, however, bring along a set of challenges in the diagnostics of their key parameters: pulse energy, spectral, temporal and spatial profiles. Here, these challenges are discussed and the pulse diagnostic tools developed at FLASH are presented. In particular, a radiometric power measurement is presented that enables the derivation of the average pulse energy within a pulse burst across the spectral range, jitter-corrected electro-optical sampling for the full spectro-temporal pulse characterization, spatial beam profiling along the beam transport line and at the sample, and a lamellar grating based Fourier transform infrared spectrometer for the on-line assessment of the average THz pulse spectra. Corresponding measurement results provide a comprehensive insight into the THz beamline capabilities.
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Affiliation(s)
- Rui Pan
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | - Ekaterina Zapolnova
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | - Torsten Golz
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | | | | | - Jovana Petrovic
- Vinca Institute of Nuclear Sciences, Belgrade, Serbia
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | - Vivek Asgekar
- Department of Physics, S. P. Pune University, Pune, India
| | - Bart Faatz
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | - Franz Tavella
- SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Andrea Perucchi
- Elettra – Sincrotrone Trieste SCpA, 34149 Basovizza, Trieste, Italy
| | - Sergey Kovalev
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Bertram Green
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | | | | | - Mikhail Yurkov
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | - Evgeny Schneidmiller
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
| | - Michael Gensch
- German Aerospace Center (DLR), Institute of Optical Sensor Systems, Rutherfordstraße 2, 12489 Berlin, Germany
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Nikola Stojanovic
- Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany
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Lang P, Song X, Ji B, Tao H, Dou Y, Gao X, Hao Z, Lin J. Spatial- and energy-resolved photoemission electron from plasmonic nanoparticles in multiphoton regime. OPTICS EXPRESS 2019; 27:6878-6891. [PMID: 30876264 DOI: 10.1364/oe.27.006878] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/21/2019] [Indexed: 05/27/2023]
Abstract
Spatial-resolved photoelectron spectra have been observed from plasmonic metallic nanostructure and flat metal surface by a combination of time-of-flight photoemission electron microscope and femtosecond laser oscillator. The photoemission's main contribution is at localized 'hot spots,' where the plasmonic effect dominates and multiphoton photoemission is confirmed as the responsible mechanism for emission in both samples. Photoelectron spectra from hot spots exponentially decay in high energy regimes, smearing out the Fermi edge in Au flat surface. This phenomenon is explained by the emergence of above threshold photoemission that is induced by plasmonic effect; other competing mechanisms are ruled out. It is the first time that we have observed the emergence of high kinetic energy photoelectron in weak field region around 'hot spot.' We attribute the emergence of high kinetic energy photoelectron to the drifting of the liberated electron from plasmonic hot spot and driven by the gradient of plasmonic field.
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