Resonance-enhanced high-order harmonic generation and frequency mixing in two-color laser field

The resonance-enhanced high-order harmonic generation and frequency mixing in two-color laser field are investigated theoretically in this paper. We found that, for the first time to our knowledge, in the investigation of high-order harmonic generation in two-color laser field, the atomic energy-level structure will greatly affect the efficiency of high-order harmonic generation. For a certain atomic level structure, in addition to the normal infrared driving laser field, a specially chosen high frequency and relatively low intensity laser field can greatly enhance the efficiency of high-order harmonic generation. In the investigation of high-order frequency-mixing, we found similar effects.