TY - JOUR
T1 - Transverse mode coupling and supermode establishment in a free-electron laser oscillator
AU - Pinhasi, Y.
AU - Gover, A.
PY - 1996/6/11
Y1 - 1996/6/11
N2 - A three-dimensional study of transverse mode evolution in a free-electron laser (FEL) oscillator is presented. The total electromagnetic field circulating in the resonator is represented as a superposition of transverse modes of the cavity. Coupled-mode theory is employed to derive a generalized 3-D steady-state oscillation criterion, from which the oscillator supermode can be found analytically in the linear gain approximation. The oscillator supermode, which is the eigenmode solution of the oscillator at steady-state, keeps its transverse profile and polarization after each round-trip. Relations between the oscillator supermode and the amplifier supermode are discussed. It is shown that they are identical only when the feedback process is entirely non-dispersive and non-discriminating. We employ a 3-D nonlinear simulation code based on the same transverse mode expansion to demonstrate the evolvement of transverse modes in the oscillator towards formation of a supermode in a simple example. The simulation shows that the steady-state result of the oscillation buildup simulation is identical to the supermode predicted by the analytical approach.
AB - A three-dimensional study of transverse mode evolution in a free-electron laser (FEL) oscillator is presented. The total electromagnetic field circulating in the resonator is represented as a superposition of transverse modes of the cavity. Coupled-mode theory is employed to derive a generalized 3-D steady-state oscillation criterion, from which the oscillator supermode can be found analytically in the linear gain approximation. The oscillator supermode, which is the eigenmode solution of the oscillator at steady-state, keeps its transverse profile and polarization after each round-trip. Relations between the oscillator supermode and the amplifier supermode are discussed. It is shown that they are identical only when the feedback process is entirely non-dispersive and non-discriminating. We employ a 3-D nonlinear simulation code based on the same transverse mode expansion to demonstrate the evolvement of transverse modes in the oscillator towards formation of a supermode in a simple example. The simulation shows that the steady-state result of the oscillation buildup simulation is identical to the supermode predicted by the analytical approach.
UR - http://www.scopus.com/inward/record.url?scp=0030164676&partnerID=8YFLogxK
U2 - 10.1016/0168-9002(95)01362-8
DO - 10.1016/0168-9002(95)01362-8
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AN - SCOPUS:0030164676
SN - 0168-9002
VL - 375
SP - 233
EP - 236
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
IS - 1-3
ER -