Self-amplified spontaneous emission: Difference between revisions
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Wise Badger (talk | contribs) m There was an imprecise statement: "Depending on the phase to each other..." which has been corrected with "Depending on the relative phase between electrons and photons..." The statement was incorrect because the energy gain or loss of the electrons depends on their interaction with the photons, not with each other |
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{{Short description|Laser technology}} |
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'''Self-amplified stimulated (or spontaneous) emission''' (SASE) is a process within a [[free-electron laser]] (FEL) by which a laser beam is created by the high-energy [[electron beam]]. The lasing starts up from the random microbunching (i.e., [[shot noise]]) on the electron beam instead of being coherently produced by an input seed [[laser]] source. This source is fully transversely coherent at saturation, but, because the radiation starts from random noise at many radiation wavelengths, the longitudinal coherence of the radiation is less than that of the amplifier case but better than that of spontaneous radiation. |
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'''Self-amplified spontaneous emission''' ('''SASE''') is a process within a [[free-electron laser]] (FEL) by which a laser beam is created from a high-energy [[electron beam]].<ref name="Kondratenko1980">{{cite journal|last1=Kondratenko|first1=A. M.|last2=Saldin|first2=E. L.|title=Generation of coherent radiation by a relativistic electron beam in an undulator|journal=Particle Accelerators|volume=10|year=1980|pages=207–216}}</ref><ref name="Milton2001">{{cite journal|last1=Milton|first1=S. V.|title=Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser|journal=Science|volume=292|issue=5524|year=2001|pages=2037–2041|issn=0036-8075|doi=10.1126/science.1059955|bibcode = 2001Sci...292.2037M|pmid=11358995|url=https://zenodo.org/record/1230806|doi-access=free}}</ref> |
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The SASE process starts with an electron bunch being injected into an [[undulator]], with a velocity close to the [[speed of light]] and a uniform density distribution within the bunch. In the undulator the electrons are wiggled and emit light characteristic of the [[undulator|undulator strength]] but within a certain energy bandwidth. The emitted photons travel slightly faster than the electrons and interact with them each undulator period. Depending on the relative phase between electrons and photons, electrons gain or lose energy (velocity), i.e. faster electrons catch up with slower ones.<ref>{{cite journal|journal=Physical Review Special Topics - Accelerators and Beams|year=2007|doi=10.1103/PhysRevSTAB.10.034801|title=Review of x-ray free-electron laser theory|last1=Zhirong|first1=H.|last2=Kwang-Je|first2=K.|bibcode = 2007PhRvS..10c4801H|volume=10|issue=3|pages=034801|doi-access=free}}</ref> Thereby the electron bunch density is periodically modulated by the radiation which is called [[microbunching]]. The structured electron beam amplifies only certain photon energies at the cost of kinetic energy until the system goes into saturation. SASE energy spectra show a [[shot noise|noise-like]] distribution of intense spikes on top of a lower-amplitude background. The micro-bunch structuring reduces the [[phase space]] available to the photons, thus they are also more likely to have a similar phase and the emitted beam is quasi-coherent. |
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This concept has been demonstrated at the [[SPring-8]] FEL in [[Japan]],<ref>{{Cite web|title=Spring-8 Webpage| url=http://www-xfel.spring8.or.jp/{{deadlink|date=October 2013}}|format= |accessdate=2007-12-21}}</ref> the Free electron LASer ([[DESY#Particle Accelerators, Facilities and Experiments at DESY|FLASH]]) in Hamburg and the [[SLAC National Accelerator Laboratory#LCLS|Linac Coherent Light Source]] (LCLS) at SLAC. |
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This concept has been demonstrated at the [[SPring-8]] FEL [[SACLA]] in [[Japan]], the Free electron LASer in Hamburg ([[FLASH]]) and the [[SLAC National Accelerator Laboratory#LCLS|Linac Coherent Light Source]] (LCLS) at SLAC.<ref name=EMMA2010>{{cite journal|last1=Emma|first1=P.|title=First lasing and operation of an ångstrom-wavelength free-electron laser|journal=Nature Photonics|year=2010|doi=10.1038/NPHOTON.2010.176|bibcode = 2010NaPho...4..641E|volume=4|issue=9|pages=641–647}}</ref> |
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==See also== |
==See also== |
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*[[Spontaneous emission]] |
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*[[List of laser articles]] |
*[[List of laser articles]] |
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{{Reflist}} |
{{Reflist}} |
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[[Category:Laser science]] |
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[[Category:Synchrotron radiation]] |
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Latest revision as of 05:21, 23 March 2024
Self-amplified spontaneous emission (SASE) is a process within a free-electron laser (FEL) by which a laser beam is created from a high-energy electron beam.[1][2]
The SASE process starts with an electron bunch being injected into an undulator, with a velocity close to the speed of light and a uniform density distribution within the bunch. In the undulator the electrons are wiggled and emit light characteristic of the undulator strength but within a certain energy bandwidth. The emitted photons travel slightly faster than the electrons and interact with them each undulator period. Depending on the relative phase between electrons and photons, electrons gain or lose energy (velocity), i.e. faster electrons catch up with slower ones.[3] Thereby the electron bunch density is periodically modulated by the radiation which is called microbunching. The structured electron beam amplifies only certain photon energies at the cost of kinetic energy until the system goes into saturation. SASE energy spectra show a noise-like distribution of intense spikes on top of a lower-amplitude background. The micro-bunch structuring reduces the phase space available to the photons, thus they are also more likely to have a similar phase and the emitted beam is quasi-coherent.
This concept has been demonstrated at the SPring-8 FEL SACLA in Japan, the Free electron LASer in Hamburg (FLASH) and the Linac Coherent Light Source (LCLS) at SLAC.[4]
See also
[edit]References
[edit]- ^ Kondratenko, A. M.; Saldin, E. L. (1980). "Generation of coherent radiation by a relativistic electron beam in an undulator". Particle Accelerators. 10: 207–216.
- ^ Milton, S. V. (2001). "Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser". Science. 292 (5524): 2037–2041. Bibcode:2001Sci...292.2037M. doi:10.1126/science.1059955. ISSN 0036-8075. PMID 11358995.
- ^ Zhirong, H.; Kwang-Je, K. (2007). "Review of x-ray free-electron laser theory". Physical Review Special Topics - Accelerators and Beams. 10 (3): 034801. Bibcode:2007PhRvS..10c4801H. doi:10.1103/PhysRevSTAB.10.034801.
- ^ Emma, P. (2010). "First lasing and operation of an ångstrom-wavelength free-electron laser". Nature Photonics. 4 (9): 641–647. Bibcode:2010NaPho...4..641E. doi:10.1038/NPHOTON.2010.176.
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