Generation of high-order harmonics using laser-produced rare-gas-like ions

Abstract

We report the first observation of high-order harmonic waves from rare-gas-like ions excited by a subpicosecond KrF excimer laser. At an intensity of ${10}^{15}$ W/${\mathrm{cm}}^2$, the highest orders of observed harmonics are the ninth (27.6 nm) in ${\mathrm{Li}}^{+}$, the eleventh (22.6 nm) in ${\mathrm{Na}}^{+}$, and the thirteenth (19.1 nm) in ${\mathrm{K}}^{+}$. The advantage of such ions as nonlinear media for extreme ultraviolet generation is discussed in relation to ionization potentials.