Controlling harmonic emission and attosecond pulse generation from H2+ by using an asymmetric few-cycle inhomogeneous laser field

The generation of the higher-order harmonics and attosecond pulses from H-2(+) driven by an asymmetric few-cycle inhomogeneous laser field has been theoretically investigated. It is found that (i) due to the asymmetric enhancement of the laser intensity in space, larger extensions of the harmonics with only one harmonic emission event from E (t) > 0 and E (t) < 0 can be found for the cases of positive and the negative asymmetric inhomogeneous fields, respectively. Moreover, due to the asymmetric inhomogeneous effect, the modulation of the harmonics, caused by the coupling of the two quantum paths can be decreased. (ii) As the polarization angle of the laser field increases, not only the intensities and the cutoffs of the harmonics are decreased, but also the modulation of the harmonics are enhanced. (iii) The contribution of the harmonic plateau can be controlled by changing the carrier-envelope phase of the laser field or by properly adding controlling pulses (e.g. adding a second controlling pulse with a longer wavelength or adding a half-cycle pulse). As a result, a supercontinuum with the bandwidth of 434 eV and a near-isolated 37 as pulse can be obtained. (C) 2017 The Physical Society of the Republic of China (Taiwan). Published by Elsevier B.V. All rights reserved.