Coherent Soft-X-Ray pulses at multi MHz repetition rates using enhancement cavities

Abstract

Enhancement cavities are passive optical resonators which allow increasing the power of multi-MHz pulse trains by orders of magnitude. Generating high harmonics from enhanced pulses of an Yb-laser (λ =1040 nm) coherent XUV pulses with wavelengths down to 11.5 nm (108 eV) were obtained at a repetition rate of 78 MHz. Harmonics were coupled out of the cavity by a small hole in a mirror. With up to 5 kW of fundamental laser power in the cavity, average powers of 5.4 μWand 8 pW were measured at 38 and 11.5 nm respectively. New developments include scaling of fundamental laser powers in a cavity up to 670 kW and efforts aiming at the generation of attosecond pulses with multi-MHz repetition rates.