An Optical Resonator For The Nist-NRL Free Electron Laser

A 9 m linear optical cavity will be used in the National Institute of Standards and Technology-Naval Research Laboratory free electron laser (NIST-NRL FEL). This FEL, which is driven by a racetrack microtron, is designed to lase from 0.2 to 10 /spl mu/m. The resonator must accommodate the large dynamic range in wavelength, low gain, high average power and coherent harmonic emission of the laser. The laser can be configured for maximum gain, as is necessary in the ultraviolet, or to minimize diffraction losses, as is necessary in the infrared. This is done by changing the length of the undulator and the radius of curvature of the cavity mirrors.