Resonance enhancement of harmonics in metal plasmas using tunable mid-infrared pulses

The tuning of odd and even high-order harmonics along the resonances of laser-produced plasmas using an optical parametric amplifier of white-light continuum radiation (1250-1400 nm) and its second harmonic is reported. We demonstrate the enhancement of tunable harmonics in the regions of 27, 38, and 47 nm using tin, antimony, and chromium plasmas and discuss the theoretical model of this phenomenon.