As disclosed herein, in a first aspect, a device may comprise: an oscillator producing a light output on a beam path; a target material for interaction with light on the beam path at an irradiation site; a beam delay on the beam path the beam delay having a beam folding optical arrangement; and a switch positioned along the beam path and interposed between the oscillator and the beam delay; the switch closable to divert at least a portion of light on the beam path from the beam path, the switch having close time, t1 and the beam path having a length, L1, along the path from the switch to the irradiation site; with t1