Nonadiabatic propagation effect for generating isolated sub-100 as pulses in the high-order harmonic plateau.

A robust scheme is proposed to generate an isolated sub-100 as pulse by using a 5fs/800nm driving pulse in combination with a macroscopic propagation effect. We demonstrate that one of the generated attosecond bursts in the high-order harmonic plateau can be efficiently dominant only when both the gas pressure and the gas cell length are properly chosen. We also show that this method can relax the dependence on the stabilization of the carrier-envelope phase (CEP) of the driving pulse. A single sub-100as pulse with only 10as duration variation can be produced even for about 50% fluctuation of the CEP. Under optimized conditions, an isolated 60as pulse can be directly generated without any additional phase compensation.