Sideband suppression in free-electron lasers using a grating rhomb

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · IEEE J. Quant. Electron.; (United States)

DOI:https://doi.org/10.1109/3.205· OSTI ID:7004784

Tokar, R L; McVey, B D; Goldstein, J C

In this paper the phase shift produced by a grating rhomb is included in free-electron laser (FEL) pulse calculations to investigate whether or not grating rhombs can be used to suppress the sideband instability. The idea is that because the group travel time through a rhomb is an increasing function of the laser wavelength, an FEL oscillator can be designed such that the optical pulse at a chosen central wavelength and the pulse of electrons overlap spatially when they enter the wiggler. Over many passes, light in a small bandwidth about the chosen wavelength receives the greatest amplification because it overlaps the electrons, and light at sideband instability wavelengths that does not overlap the electrons is suppressed by losses in the oscillator cavity. For a 5 m tapered wiggler like that planned for use in an experiment at the Boeing Aerospace Company, the range in rhomb dispersion and cavity loss that yields acceptable FEL performance is defined. At low values of cavity loss, for example 15 percent, a wide range of rhomb dispersion exists for which both the sideband instability is largely suppressed and the energy extracted from the electrons is high. At large values of cavity loss, for example 30 percent, a critical value for rhomb dispersion exists below which the laser pulse is compressed by the rhomb, leading to reduced energy extraction. As the rhomb dispersion is increased, the effect disappears and the energy extraction increases. The critical point is interplay of the positive chirp acquired by the laser pulse via the FEL interaction in the wiggler and the negative chirp added by the rhomb on each pass.

• Research Organization: Applied Theoretical Physics Div., Los Alamos National Lab., Los Alamos, NM (US)
• OSTI ID: 7004784
• Journal Information: IEEE J. Quant. Electron.; (United States), Journal Name: IEEE J. Quant. Electron.; (United States) Vol. 24:6; ISSN IEJQA
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
CALCULATION METHODS
CAVITY RESONATORS
CRYSTALS
ELECTRONIC EQUIPMENT
EQUIPMENT
FREE ELECTRON LASERS
GRATINGS
INSTABILITY
LASERS
OSCILLATORS
PHASE SHIFT
PULSES
RESONATORS
WAVELENGTHS