Attosecond laser pulse synthesis using bichromatic high-order harmonic generation

Abstract

We analyze the dynamical symmetries and the selection rules relevant to the process of production of high-order harmonics as a result of irradiating an atom with strong, continuous bichromatic laser radiation of similar frequencies $\ensuremath{\omega}$ and $\ensuremath{\omega}+\ensuremath{\delta}\ensuremath{\omega}$. We show that when the two laser frequencies are close to one another (small $\ensuremath{\delta}\ensuremath{\omega}$), the spectrum becomes very dense and new selection rules are obtained. Such a dense spectrum of harmonics could be a source for the production of attosecond light pulses. We demonstrate our results numerically on a one-dimensional model Hamiltonian of a Xe atom and show how a pulse of length $700\text{\ensuremath{-}}\mathrm{as}$ could be produced.