Fig. 1. Spatial profiles of the single reference Gaussian beam (case A) and the SG beams with the same electric field ratio of 8∶2 and different beam radius ratios of 1∶3 (case B), 1∶4 (case C), 1∶5 (case D), 1∶6 (case E)

Fig. 2. Variation of (a) beam diameter and (b) ionization probability at r=0 with different total energies, 1.0E0, 1.5E0, 2.0E0and 2.5E0 for the SG incident beam as a function of propagation distance z (the SG beam corresponds to case C in Fig. 1)

Fig. 3. Variation of (a) beam diameter and (b) ionization probability at r = 0 as a function of propagation distance z for the different types of beams with the total energy of 2.0E0 (the SG incident beam corresponds to case C in Fig. 1)

Fig. 4. Variation of the diameter of the plasma channel as a function of propagation distance z. (a) Single Gaussian incident beams G1, G2, G3, and the SG incident beam as case C in Fig. 1, with total energy of 2.0E0 for all types; (b) SG incident beams with the different total energies of 1.5E0, 2.0E0 and 2.5E0

Fig. 5. Variation the integral ionization density of overall space, 10, 20 and 30 μm diameters as a function of propagation distance z with all total energy of 2.0E0. (a) Single Gaussian incident beam G1; (b) SG incident beams (the SG incident beam corresponds to case C in Fig. 1)