Single attosecond pulse generation in an orthogonally polarized two-color laser field combined with a static electric field

Abstract

We investigate theoretic high-order harmonic generation and single attosecond pulse generation in an orthogonally polarized two-color laser field, which is synthesized by a mid-infrared (IR) pulse ($12.5$ fs, $2000$ nm) in the $y$ component and a much weaker ($12$ fs, $800$ nm) pulse in the $x$ component. We find that the width of the harmonic plateau can be extended when a static electric field is added in the $y$ component. We also investigate emission time of harmonics in terms of a time-frequency analysis to illustrate the physical mechanism of high-order harmonic generation. We calculate the ionization rate using the Ammosov-Delone-Krainov model and interpret the variation of harmonic intensity for different static electric field strengths. When the ratio of strengths of the static and the $y$-component laser fields is 0.1, a continuous harmonic spectrum is formed from $220$ to $420$ eV. By superposing a properly selected range of the harmonic spectrum from $300$ to $350$ eV, an isolated attosecond pulse with a duration of about $75$ as is obtained, which is near linearly polarized.