Fig. 1. Time-space evolution of (a) $N$, (b) $T_{e}$, (c) $T_{h}$ and (d) $T_{l}$ in Ge irradiated by laser pulse whose duration, wavelength and fluence are 100 fs, 620 nm and $0.1~\text{mJ}/\text{cm}^{2}$, respectively.

Fig. 2. Time evolution of (a) $N$, (b) $T_{l}$ (c) $T_{e}$ and (d) $T_{h}$ in Ge at different depths.

Fig. 3. Time-space evolution of the value of $T_{h}/T_{e}$. The pulse duration and fluence is 100 fs, and $0.1~\text{mJ}/\text{cm}^{2}$, respectively.

Fig. 4. Spatial evolution of $T_{e}$, $T_{h}$ and $T_{h}/T_{e}$ (right axis) at (a) 0.21, (b) 0, (c) 0.2, (d) 1.0, (e) 2.5 and (f) 8.0 ps.

Fig. 5. Time evolution of (a, c, e) $N$ (b, d, f) $T_{l}$ in Ge irradiated by laser pulses (a,b) with different durations and same intensity $I_{0}$ ($798~\text{MW}/\text{cm}^{2}$); (c, d) with different durations and same fluence ($0.1~\text{mJ}/\text{cm}^{2}$) and (e,f) with different energy densities and same duration (100 fs).

Fig. 6. Variation of the maximum value of $N$ with increasing fluence. The fluence is increased by the two ways: path A (increasing intensity in the case of fixed pulse duration) and path B (increasing pulse duration in the case of fixed intensity).

Fig. 7. Time evolution of (a) $N$ and (b) $T_{l}$ in Ge irradiated by double pulses, where the interval between them is 100 fs, the duration of the first pulse is 50 fs and that of the second one is 50, 70 and 100 fs, respectively; time evolution of (c) $N$ and (d) $T_{l}$ in Ge irradiated by the double pulses, where the duration of them are both 50 fs, and the interval between them is 50, 100, 200 and 400 fs, respectively.