Enhancement of many high-order harmonics via a single multiphoton resonance - art. no. 013820

In the strong-field regime a single multiphoton resonance can enhance many harmonics of the fundamental laser frequency simultaneously. We demonstrate that an alkali-metal atom driven by an intense, ultrafast midinfrared puls e is an ideal system for observing this effect by calculating the response of potassium atoms to radiation that is nearly three or five photon resonan t with the 4s-4p transition. We find that all the harmonics through at leas t the 17th are enhanced over a wide range of intensities, and that the reso nance width of the enhanced harmonics is governed by the lifetime of the mu ltiphoton resonance.