Carrier envelope phase measurement of multi-cycle mid-infrared field and its application on attosecond pulse generation

A method for the carrier envelope phase (CEP) measurement of the multi-cycle mid-infrared field has been theoretically presented by using the CEP dependence of the harmonic cutoffs. It shows that by properly adding a CEP-known few-cycle near-infrared pulse to the multi-cycle mid-infrared field, the CEP dependence of the harmonic cutoffs from the combined field become much more distinct in comparison with those from the single mid-infrared field, which provides a route to a new CEP measurement technique. Further, by properly controlling the combined field, three supercontinua of 230, 242, and 266 eV with less modulation can be obtained. Finally, by selecting the generated harmonics, a series of sub-35 as pulses in the X-rays region can be produced.