Quantum path selection in high-order harmonic generation from aligned molecules

We theoretically investigate high-order harmonic generation (HHG) from aligned N-2 molecules with a driving field composed of two-color circularly polarized laser pulses. It is shown that the combination of N-2 molecules and the waveform-controlled laser field allows us to select either long or short quantum path, depending on molecular alignment angles, while in atom Ar, two paths show comparable contribution to HHG. The selection of single quantum path in aligned N-2 molecules leads to an ultrabroad and smooth XUV supercontinuum, giving rise to isolated attosecond pulses generation. Moreover, we can control the intensity ratio of two attosecond pulses by adjusting the molecular alignment angles, providing an opportunity for attosecond pump-probe technique. (C) 2014 Optical Society of Americ