High-power pulse recirculation in a stable pseudo-confocal geometry.

A stable pseudo-confocal geometry for recirculation injection by nonlinear gating (RING) of high-energy ultrashort pulses is demonstrated. Implementation of RING in this robust geometry will benefit the development of ultrabright light sources based on inverse Compton scattering by increasing their efficiency. A detailed cavity analysis is presented, and a cavity enhancement factor of 17 has been experimentally observed.