The generation of MHz isolated XUV attosecond pulses by plasmonic enhancement in a tailored symmetric Ag cross nanoantenna with a few-cycle laser

Within a few-cycle laser, the generation of MHz isolated extreme ultraviolet (XUV) attosecond pulses via nanoplasmonic field enhancement in silver nanostructures is theoretically investigated. Numerical techniques are employed to optimize nanoantennas and attain plasmonic field enhancement factors up to 270. In a volume of 15 × 15 × 30 nm−3 in the nanoantenna, the intensity could be enhanced to 1014 W cm−2 for high harmonic generation (HHG). Optimal conditions for the production of MHz isolated attosecond pulses of 140 attosecond duration via HHG have been identified. These findings open up the possibility for the development of a compact source of ultrashort XUV pulses with MHz repetition rates. Moreover, asymmetric cross HHG is proposed to control the polarizations, select the wavelengths by varying the ratio of silver nanoantennas and generate XUV pulses in both polarized directions. (paper)