Fig. 1. Snapshot of spatial distribution of the normalized light intensity of two parallel incident seed lasers with different initial phase difference of (a)–(c) , (d)–(f) and (g)–(i) at different times. The arrows in the left-column panels represent the Poynting vector of the lasers.

Fig. 2. Snapshots of spatial distribution of the electron density (a)–(c) and the current density (d)–(f) at different times for two parallel incident seed lasers of (a), (d) , (b), (e) and (c), (f) , respectively. Here, the current density is normalized by and .

Fig. 3. Snapshot of spatial distribution of the normalized light intensity at different times using two external guiding lasers of initial phases advancing compared to seed lasers (i.e., ) with the incidence angle of ((a)–(c), case 2) and ((d)–(f), case 3), respectively. The initial phase difference of the seed lasers is .

Fig. 4. Snapshot of spatial distribution of the normalized light intensity at different times using two external guiding lasers of initial phases advancing compared to seed lasers (i.e., ) with the incidence angle of ((a)–(c), case 4) and ((d)–(f), case 5), respectively. The initial phase difference of the seed lasers is .

Fig. 5. Snapshot of the normalized electron density for from case 1 to case 4, and for and in case 5.

Fig. 6. (a) The axial profile of laser intensity along the direction and (b) the transverse profile at the position corresponding to the peak intensity when the merged light is strongest in the five cases. For comparison, the black lines in (a) and (b) give the axial and transverse profiles of the seed laser. (c) The highest energy conversion efficiency from all incident lasers to the merged light, and (d) the temporal evolution of the energy conversion efficiency from all incident lasers to the electrons in the five cases.

Fig. 7. Dependence of the peak intensity of the merged light on (a) the intensity of the incident seed laser , (b) the transverse separation distance of the two seed lasers, (c) the incidence angle of the guiding laser and (d) the normalized electron density of plasma .