Measurement of the coherent harmonic emission from a free-electron laser oscillator

Abstract

We have measured the emitted energy and the spectral and temporal distributions of the first seven harmonics which are self-generated by the Mark III free-electron laser oscillator at Stanford University. The bandwidth scaling shows that current theory will have to be revised. We present our results and discuss the implications for using free-electron lasers as a source of tunable coherent extreme ultraviolet photon beams.