Fig. 1. Schematic of the experimental setup: HWP, half-wave plate at 800 nm; L1, plano-concave lens (f1=−75  mm);L2, plano-convex lens (f2=200  mm); L3, concave mirror with Al coating (f3=125  mm).

Fig. 2. (a) Filament-induced breakdown spectra of Al under different polarizer angles of −15°, 15°, 45°, 60°, and 105°. −25° was corresponding to the polarization plane of the laser beam. The energy before L1 was 6.22 mJ, and the pulse duration was 30 fs. (b) Integration range used to calculate the integral intensity of Al I 396.152 nm and its background.

Fig. 3. Comparison of polarization dependence of relative intensity, original intensity, and background intensity of the Al atomic line (Al I 396.152 nm) together with the polarization of the incident laser beam.

Fig. 4. Spectral intensity of the Al atomic line (original data), background, and relative intensity as a function of the polarizer angle after inserting a half-wave plate before the telescope system.