Optical Beam Quality in Free-Electron Lasers

The mode quality of the output of free-electron lasers (FELs) is near the diffraction limit. In this paper, we analyze the optical mode quality in FELs using the M 2 parameter, which is a measure of the size and divergence of the optical beam. We calculate M 2 in two ways: 1) by a direct integration...

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Bibliographic Details
Published in:IEEE journal of quantum electronics 2009-03, Vol.45 (3), p.218-222
Main Authors: Sprangle, P., Freund, H.P., Hafizi, B., Penano, J.R.
Format: Article
Language:English
Subjects:
Beam characteristics: profile, intensity, and power
spatial pattern formation
Beam propagation
Beams (radiation)
Diffraction
Divergence
electromagnetic simulation
Electromagnetism
electron and ion optics
Exact sciences and technology
Free electron lasers
Fundamental areas of phenomenology (including applications)
Laser modes
Laser optical systems: design and operation
Mathematical analysis
mode quality
Numerical analysis
Optical beams
Optical diffraction
Optical saturation
Optics
Oscillators
Particle beam measurements
Physics
Quantum electronics
Radiation by moving charges
Saturation
Size measurement
Unity
Wave optics
Wave propagation, transmission and absorption
Wavelength measurement
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Summary:The mode quality of the output of free-electron lasers (FELs) is near the diffraction limit. In this paper, we analyze the optical mode quality in FELs using the M 2 parameter, which is a measure of the size and divergence of the optical beam. We calculate M 2 in two ways: 1) by a direct integration over the transverse mode structure and 2) by allowing the mode to expand beyond the wiggler and analyzing the divergence. A numerical analysis is conducted using the MEDUSA simulation code that shows that M 2 , as expected, is near unity at saturation but increases with the higher order mode content if the interaction proceeds past saturation.
ISSN:0018-9197
1558-1713
DOI:10.1109/JQE.2009.2012508