Coherent continuum extreme ultraviolet radiation in the sub-100-nJ range generated by a high-power many-cycle laser field.

High-energy coherent continuum radiation is generated by the interaction of rare gases with a high-power many-cycle laser field, utilizing the interferometric polarization gating technique. A narrow temporal gate is formed in the laser pulse within which the extreme ultraviolet (XUV) emission is restricted. An analytical expression for the gate function is derived. A super-XUV continuum down to 15 nm, broad enough to support synthesis of single pulses of 260 as duration and a few tens of nanojoule energy, has been measured. These results directly challenge the perspectives of single-attosecond pulse XUV-pump-XUV-probe applications.