Double optical gating for generating high flux isolated attosecond pulses in the soft X-ray regime

Double optical gating (DOG) technique was implemented with a two-cycle, 1.7 µm driving field to generate isolated attosecond pulses in the 100–250 eV spectrum range. The strong ellipticity dependency of the high harmonics from the 1.7 µm driving field makes polarization based gating method very efficient. When a second harmonic (SH) field is introduced, complete gating can be achieved with less ionization from the leading edge of the driving field, which yields supercontinua with a pulse energy of 0.3 nJ. We perform an attosecond streaking measurement to confirm the generation of isolated attosecond pulses.