Variable-Wiggler Free-Electron-Laser Oscillation

Abstract

A tapered-wiggler free-electron-laser oscillator has been operated above threshold at the wavelength of 1.57 \ensuremath{\mu}m. The laser was operated with 0%, 1%, and 2% tapers in energy, achieving laser efficiency of 0.4%, 1.1%, and 1.2%, respectively. The efficiency of the 2% taper was three times the untapered case.