Abstract
We present an efficient scheme for generation of an isolated attosecond (as) pulse based on the combination of two well-known methods: polarization gating method plus a method based on using two colors (). The first uses a pulse whose ellipticity is small within a very short time interval (called a polarization gating). By adding a second pulse whose frequency is a half-frequency (midinfrared) of the first pulse, we extend significantly the cutoff frequency, as well as the width of the supercontinuum harmonic spectrum. The high-order harmonic generation is calculated using the strong-field approximation theory. As a result, an isolated 42-as pulse is generated directly by superposing the hundreds of harmonics. To explain the mechanism of the ultrashort attosecond generation, we perform the semiclassical three-step model simulation and wavelet time-frequency transform of the harmonic spectra.
- Received 2 May 2014
DOI:https://doi.org/10.1103/PhysRevA.90.025401
©2014 American Physical Society