Gain-guided X-ray free-electron laser oscillator

摘要

The X-ray free-electron laser oscillator (XFELO) has recently come to be reconsidered as a promising candidate for producing high-brightness, fully coherent pulses in the hard X-ray regime. This letter proposes a gain-guided XFELO scheme, without the need for the external focusing elements that are required in a conventional configuration. Self-consistent theoretical analysis and three-dimensional numerical simulation results verify that the X-ray transverse mode in such an "unstable" cavity is stable and robust owing to electron beam gain-guiding. The output pulse energy and the transverse and longitudinal coherence are comparable to those from conventional XFELOs. This promising scheme is expected to contribute significantly to the construction and operation of a real XFELO. Published by AIP Publishing.