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Free-Electron Lasers

#A-1901


Free-Electron Lasers (FEL) Exploiting Media with a Periodically Modulated Refractive Index (MPMRI)"

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics
  • PHY-PFA/Particles, Fields and Accelerator Physics/Physics
  • PHY-PLS/Plasma Physics/Physics

Status
3 Approved without Funding

Registration date
07.10.2010

Leading Institute
A.I. Alikhanyan National Science Laboratory, Armenia, Yerevan

Collaborators

  • Thomas Jefferson National Accelerator Facility, USA, VA, Newport News\nUniversity of British Columbia / Department of Chemistry, Canada, BC, Vancouver\nMax-Planck-Institut für Kernphysik, Germany, Heidelberg\nTexas A&M University / Department of Physics, USA, TX, College Station\nMax-Born-Institut für Nichtlineare Optik und Kurzzeitspectroskopie, Germany, Berlin

Project summary

The project is aimed towards theoretical and experimental investigation of Free-Electron Lasers (FEL) Exploiting Media with Periodically Modulated Refractive Index (MPMRI).

A specific scheme of MPMRI FEL, suggested in [1-2], will be used as a basis for further investigations.

Free-Electron Lasers are powerful, tunable, coherent sources of radiation, which are used in scientific research, plasma heating, condensed matter physics, atomic, molecular and optical physics, biophysics, biochemistry, biomedicine etc. FELs today produce radiation ranging from millimeter wavelengths to ultraviolet, including parts of spectrum in which no other intense, tunable sources are available. This field of modern science is interesting from the point of view of fundamental research and very promising for further applications.

Creation of compact inexpensive sources of radiation operating efficiently in visible, UV, or soft X-ray domains is one of the most important directions in the development and investigation of Free-Electron Lasers. A short-wavelength radiation can be generated by a FEL using either a high-energy (multi-GeV) electron beam or undulators with a short period. One way of constructing short-period undulator-like media can be related with using MPMRI. MPMRI can be considered as a kind of a volume diffraction grating. The following two types of MPMRI have been proposed: (1) a gas-plasma medium with periodically varied density or degree of ionization [1] and (2) a spatially periodical solid-state superlattice-like (SLL) structure, which can be composed, e.g., of a series of layers of different materials with different refractive indices (see Ref. [2] and references therein). Note that a closely related but simpler effect of a stimulated transition emission was observed experimentally [3] in a scheme similar to that suggested in [1-2] but without media modulation. Coherent radiation from bunched electrons and prebunched FEL in far-infrared and the millimeter wavelength regions were reported in [4] (Shibata et al), ultrabroadband terahertz source and beamline based on coherent transition radiation are investigated in [4] (Casalbuoni et al), characterization and mitigation of coherent-optical-transition-radiation signals from a compressed electron beam are reported in [4] (Lumpkin et al). The spontaneous radiation in multilayer systems is investigated in soft X-ray region [4] (Yamada et al), in EUV region [4] (Andre et al), in soft X-ray and EUV regions [4] (Nasonov et al) and in soft X-ray region [4] (Gevorkian, Verhoeven).

Our calculations indicate that the gain achievable in SLL FEL can be rather high. Qualitatively, this result is explained by a large mean permeability of SLL structures, εav >1, which makes phase velocities of many low-order Partial Plane Waves(PPW) smaller than the light speed c. For this reason, the resonance electron velocity is rather low too (electrons are only weakly relativistic), which provides conditions for a higher electron response for the electromagnetic wave to be amplified.

In [2] amplification in MPMRI FEL is studied in the regime of a large modulation. The conditions for realization of the large-modulation regime in a superlattice-like medium are established. The maximized gain, the corresponding saturation field and efficiency, as well as the optimal electron energy and propagation direction are determined. It is shown that the large-modulation regime makes it possible to extend significantly the operation frequency domain of the FEL employing a low-relativistic electron beam. Relationship with the Cherenkov and stimulated resonance-transition-radiation FELs is discussed.

Our calculations showed that MPMRI FEL is an attractive source of coherent radiation in infrared to UV range. It combines compact size and relatively high gain with tunability typical for Free-Electron Lasers. The physics behind its operation, which is a volume analog of the Smith-Purcell effect, is quite fascinating. There is a number of open questions which relate both to experimental implementation of the scheme and to its extensions to new materials with periodically modulated refractive index and to new operational regimes. In the framework of this proposal we plan to continue this work.

As a resume, the large-modulation regime in SLL FEL can provide an opportunity to construct a compact low-electron-energy free-electron laser operating in various spectral domains, including rather short wavelengths. The size of such an amplifying system can be rather small compared to the typical size of FEL with undulators [5,6]. This related mainly to a possibility of creating and using in MPMRI FELs with a rather small period, whereas in undulators, typically, is about several centimeters.

The theoretical and experimental work in the frame of this project will be carried out in collaboration with Prof. Christoph H. Keitel from German Max-Plank Institute (Heidelberg), Prof. Wilhelm Becker from the Berlin Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy, Burgess Distinguished Prof. Marlan O. Scully and Prof. Yu. V. Rostovtsev from Texas A&M University and Dr. E. Shapiro from Canadian University of British Columbia (Vancouver).

Experiments are planned to be done in Yerevan Physics Institute (YerPhI) (Armenia). The existing experimental equipment includes the microtron providing electron energies up to 5 Mev. Earlier this accelerator was used to make the first experiment on microtron-based FEL in the range of wavelengths 30-40 [7,8]. As for collaboration on FEL between Moscow General Physics Institute and Yerevan Physics Institute, it has rather old traditions [9-16, 20-25,28].

A group of highly qualified specialists is created for performing the project. The personnel of this project has a great experience and high level of proficiency in the proposed field of research. They are the authors of numerous publications concerning the mentioned problems and relevant issues of the project. The results of our research carried out together with scientists from the A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia, and with our collaborators from other countries were presented in papers [15-37], and are reported at 32 International Conferences. This is a nice example of cooperation between former Soviet Union scientists with foreign collaborators under ISTC sponsorship according to ISTC goals.

Since 2003 ISTC supports Free Electron Laser researches in the Yerevan Physics Institute by funding the projects A-820 and A-1602. Thanks to this support. Owing to the ISTC support we became permanent participants of:

  • International Laser Physics Conferences LPHYS (2004 – Trieste, Italy, 2005 – Kyoto, Japan, 2006 – Lausanne, Switzerland,2007 – Leon, Mexico, 2008 – Trondheim, Norway, 2009 – Barcelona, Spain, 2010 - Foz do Iguaçu, Brazil),
  • Central European Workshop on Quantum Optics CEWQO (2008 – Belgrade, Serbia, 2009 – Turku, Finland, 2010 - St. Andrews, Scotland, UK),
  • Winter Colloquium on the Physics of Quantum Electronics, PQE (2007,2008,2009,2010, Snowbird, Utah, USA),
  • International Particle Physics Conference(2009 – PAC Vancouver, Canada, 2010 – IPAC, Kyoto, Japan).


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