Generating isolated attosecond pulse by a dual optical gating scheme
- PDF / 1,388,883 Bytes
- 8 Pages / 595.276 x 785.197 pts Page_size
- 102 Downloads / 237 Views
THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
Generating isolated attosecond pulse by a dual optical gating scheme Gao Chena and Ning Su School of Science, Changchun University of Science and Technology, Changchun 130022, P.R. China Received 12 May 2020 / Received in final form 22 July 2020 / Accepted 16 September 2020 Published online 1 October 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. Based on the theory of strong field approximation, we simulate the high harmonic and attosecond pulse generation from helium atom irradiated by a dual optical gating pulse composed of an orthogonally polarized field and a second harmonic pulse. The orthogonally polarized field consists of two linearly polarized pulses with a certain time delay, orthogonally polarized directions and 7 fs pulse duration. If the pulse that occurs first is called the driving pulse, the delayed pulse is called the gating pulse. The dual optical gating pulse is realized by adding a linearly polarized second harmonic pulse in the direction of the driving pulse of an orthogonally polarized field. It is found if the time delay between the driving pulse and the gating pulse and the phase difference between the second harmonic pulse and the driving pulse are reasonably adjusted, the high order harmonic generation spectra with higher efficiency and supercontinuum bandwidth can be obtained. After the inverse Fourier transform, an isolated short pulse with 124 as pulse duration can be obtained. Compared with the double optical gating scheme proposed by Chang et al., this experimentally relatively easy-to-operate scheme, on the one hand, overcomes the restrictions on the pulse width and intensity of the incident drive pulse, and on the other hand, avoids the atomic pre-ionization caused by the laser cycles before the polarization gate which is not conducive to the harmonic phase matching.
1 Introduction The isolated attosecond pulses have become one of the attractive frontier topics in recent years because they can track and control the motion of electrons in media such as atoms, molecules, clusters and solids [1,2]. At present, high harmonic generation (HHG) [3,4] and free electron laser [5,6] are two feasible methods to obtain isolated attosecond pulse sources. The free electron laser equipment is huge and expensive. HHG is the only effective means for obtaining the isolated attosecond pulses in the laboratory due to their tabletop size, high spatial and temporal coherence. HHG mainly comes from the extremely nonlinear interaction of ultrashort intense laser pulses with atomic or molecular targets, even solid targets. The process can be explained by the semi-classical three-step model [7]. First, the electron tunnels through a barrier formed by an atomic or molecular potential and a laser electric field, and then the ionized electron obtains energy in the laser field. Finally, when the electric field is reversed, the electrons pulled back to the vicinity of the parent ion have
Data Loading...
