Four Wave Sum Difference Non‐Linear effects with X‐ray Lasers in a Gas Jet Plasma

Progress in a four‐wave sum difference frequency generation scheme to convert quasi‐coherent soft X‐ray radiation to shorter wavelengths, using a plasma medium is discussed. Experimental results and calculations involving the Ne‐like Ni XRL (λXRL = 0.023 μm) mixed in phase‐matched mode with a Nd:glass laser at the second harmonic (λOPT = 0.52 μm) in a Na‐like Argon plasma are presented. A 25 mm single slab target of Ni pumped with ∼ 200 J of energy from 5 optical beams has routinely produced ∼ 5 mJ of XRL energy at 23.1 nm. The XRL was split and recombined with the Nd:glass laser in the Na‐like Ar plasma. Considerations for phase matching the XRL and optical beams in the ionized gas jet are also discussed.