Hong-Dan Zhang

3–5 μm AgGaS2 optical parametric oscillator with prism cavity

Employing a coated right-angled sapphire prism as the OPO cavity mirror, AgGaS2 type-I singly resonant optical parametric oscillator was demonstrated experimentally, which was pumped by a ns 1.064 μm Nd:YAG laser. Continuously tunable 2.35 to 5.27 μm radiation without changing cavity mirrors and maximum output energy 0.58 mJ per pulse are recorded.

Controlling the contributions to high-order harmonic generation from different nuclei of N2 with an orthogonally polarized two-color laser field*

The generation of high-order harmonic and the attosecond pulse of the N-2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model. We show that the control of contributions to high-order harmonic generation (HHG) from different nuclei is realized by properly selecting the relative phase. When the relative phase is chosen to be phi= 0.4 pi, the contribution to HHG from one nucleus is much more than that from another. Interference between two nuclei can be suppressed greatly; a supercontinuum spectrum of HHG appears from 40 eV to 125 eV. The underlying physical mechanism is well explained by the time-frequency analysis and the semi-classical three-step model with a finite initial transverse velocity. By superposing several orders of harmonics, an isolated attosecond pulse with a duration of 80 as can be generated.

High-order harmonic generation of CO2 with different vibrational modes in an intense laser field*

We apply the strong-field Lewenstein model to demonstrate the high-order harmonic generation of CO2 with three vibrational modes (balance vibration, bending vibration, and stretching vibration) driven by an intense laser field. The results show that the intensity of harmonic spectra is sensitive to molecular vibrational modes, and the high harmonic efficiency with stretching vibrational mode is the strongest. The underlying physical mechanism of the harmonic emission can be well explained by the corresponding ionization yield and the time–frequency analysis. Finally, we demonstrate the attosecond pulse generation with different vibrational modes and an isolated attosecond pulse with a duration of about 112 as is generated.