High-order harmonic generation in a narrow spectral range

It is proposed to use the two-component pumping of atoms by a strong low-frequency field and a high-frequency ultrashort pulse for the generation of high-order harmonics. For a fixed relative phase of the pumping fields, high-order harmonics are generated in a rather narrow spectral range. The interaction of atoms with the two-component field also determines the limiting efficiency of high-order harmonic generation. The effect can be reversed for the enhancement of high-order harmonics by using additional high-frequency pump radiation.