Fig. 1. (a) Schematic diagram of the pump-seed setup. A typical time profile of N2+ lasing amplified by different mechanisms is plotted. More details can be referred in the main text. (b) The typical N2+ lasing spectra measured under the pumping of the LP and PM pulses. (c) The dependence of the 391 nm lasing signal intensity on the angle θ.

Fig. 2. N2+ lasing signal as a function of the seed intensity for the cases of the LP and PM (θ=32°) laser excitation. The signal intensity in the case of LP has been multiplied a factor of 200 for a direct comparison.

Fig. 3. Measured time structures of N2+ lasing under the triggering of various seed intensities for the pumping of the (a) LP and (b) PM laser. The longitudinal axis in these two cases is normalized by the same value. (c) The retarded time τ as a function of the seed intensity for the PM laser.

Fig. 4. Simulated time profiles of 391 nm lasing at various seed intensities under excitation of the (a) LP and (b) PM laser. The insets show the corresponding lasing intensity as a function of the seed intensity for these two situations.

Fig. 5. Calculated lasing signal (I−I0)/I0 on a log scale as a function of β and the seed pulse area ϑ with T1,2=2.5  ps. The red and black dashed lines correspond to the amplification similar to the case of the LP and PM laser in Fig. 2.