Efficient extension and enhancement of high-order harmonics of He+ by combined laser pulses

Abstract

We theoretically study the interaction of a He+ ion with fundamental laser pulses and different combined laser pulses. For low laser intensity the cut-off energy is extended; however, for higher laser intensity the cut-off of the enhanced harmonics is extended under the combination of two fundamental laser pulses whose wavelengths are 800 nm and 394 nm, respectively. We investigate the yield of ionization as a function of peak laser intensity and find that the yield of ionization is different for low and higher laser intensity regimes. The efficient extension of cut-off energy of enhanced harmonics is demonstrated by a classical analysis.