Spatial Control of Recollision Wave Packets with Attosecond Precision

We propose orthogonally polarized two-color laser pulses to steer tunneling electrons with attosecond precision around the ion core. We numerically demonstrate that the angles of birth and recollision, the recollision energy, and the temporal structure of the recolliding wave packet can be controlled without stabilization of the carrier-envelope phase of the laser, and that the wave packet’s properties can be described by classical relations for a point charge. This establishes unique mapping between parameters of the laser field and attributes of the recolliding wave packet. The method is capable of probing ionic wave packet dynamics with attosecond resolution from an adjustable direction and might be used as an alternative to aligning molecules. Shaping the properties of the recollision wave packet by controlling the laser field may also provide new routes for improvement of attosecond pulse generation via high harmonic radiation.

Figure 1

Time structure of the recolliding electron wave packet (recollision current) as seen by the ion. The thick, full line depicts argon in an 800 nm laser field in $x$, $\kappa =2$, ${\varphi }_{\mathrm{CE},x}=0$, ${\varphi }_{\mathrm{CE},y}=0.4\pi$, $I_x=I_y=2.5\times {10}^{14}\mathrm{W}/{\mathrm{cm}}^2$. The thick, dotted-dashed line shows the same but for ${\varphi }_{\mathrm{CE},x}=-0.4\pi$, ${\varphi }_{\mathrm{CE},y}=0$. The thin, dotted current was created by linearly polarized light, ${\varphi }_{\mathrm{CE},x}=0$, $I_x=4.34\times {10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ in argon. Pulse durations 5 fs (FWHM). The intensities correspond to constant ionization yield. The inset shows the recollision current for ${\mathrm{H}}_2$ with the molecular axis orthogonal to the laser polarization in linearly polarized 800 nm laser light, 4 cycles (FWHM), peak intensity $2\times {10}^{14}\mathrm{W}/{\mathrm{cm}}^2$.

Figure 2

Birth and recollision angle of the wave packet discussed in Fig. 1: (a) Temporal structure of the ionizing part (light shaded area) and the returning ionizing part (dark shaded area) of the wave packet and the generating laser field in $x$ (black line) and $y$ (gray line) over absolute time. (b) Temporal structure (black line) and probe angle (gray line) over time of flight. (c) Birth (gray lines) and recollision angles (black lines) over absolute time. The thick lines depict the numerical data, the thin lines are calculated by relations for a point charge (see text). (d) Birth angle for a wave packet born at $t_b=-47$ (full line) and recollision angle of that wave packet (dashed line) at a recollision time of $t_r=20$ over the ratio $\gamma$, both calculated for a point charge (see text).