NDLI: Optical Guiding In Planar-wiggler-based Free-electron Lasers

Content Provider	IEEE Xplore Digital Library
Author	Freund, H.P. Chang, C.L.
Copyright Year	1989
Description	Author affiliation: Science Applications International Corp. (Freund, H.P.)
Abstract	Optical guiding in a free-electron laser is studied. Previous analyses have typically concentrated on planar wiggler configurations using a wiggler-averaged orbit analysis. However, the interaction arises from the beating of the wiggler and radiation fields which produces both upper- and lower-beat waves. The upper-beat wave results in a slowly varying ponderomotive wave while the lower-beat wave introduces an oscillation at half the wiggler period which vanishes in the wiggler-average approximation. Indeed, the lower-beat wave cancels out entirely for a helical wiggler whether or not a wiggler average is performed. In contrast, the lower-beat wave is present in planar configurations and causes the power and phase of the wave to oscillate at half the wiggler period. We have speculated that this effect may result in an oscillation in the guiding of the signal. The three-dimensional, multimode waveguide code WIGGLIN has been adapted to treat the short-wavelength regime. The effect of the lower-beat wave upon the optical guiding can be studied in this way since no wiggler-average approximation is made in WIGGLIN. The analysis assumes the injection of a Gaussian mode for a master oscillator into the wiggler in synchronism with the electron beam. The Gaussian mode is assumed to be focussed down to the minimum spot size upon entry to the wiggler, and is then decomposed into the modes of a rectangular waveguide, which satisfy the boundary conditions. Results indicate that the optical guiding of the resultant signal is indeed oscillatory at one-half of the wiggler period. In addition, side lobes about the principal radiation signal are observed to grow which may adversely affect the bulk guiding of the wave. Implications of these results upon future FEL designs are discussed.
Starting Page	429
Ending Page	435
File Size	654415
Page Count	7
File Format	PDF
DOI	10.1109/FEL.1989.716046
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1989-08-28
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Laser theory Electron beams Free electron lasers Rectangular waveguides Electromagnetic waveguides Electron optics Boundary conditions Undulators Electron tubes Optical waveguides
Content Type	Text
Resource Type	Article

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