Fig. 1. Experimental setup of pulse discharge when laser is injected in water

Fig. 2. Schematic diagram of interaction between laser and electric field

Fig. 3. Changes of electron densities in plasma channel for injected laser energy of 50 mJ. （a） 0 ns;（b） 5 ns;（c） 10 ns

Fig. 4. Distribution of electron density at z axis in plasma channel for injected laser energy of 50 mJ

Fig. 5. Change of electron density in plasma channel for injected laser energy of 80 mJ. （a） 0 ns;（b） 5 ns;（c） 10 ns

Fig. 6. Distributions of electric field intensity in laser leading-in plasma channel. （a） 0 ns;（b） 5 ns;（c） 10 ns

Fig. 7. Effect of spot size on electron density in plasma channel. （a） 0.1 mm; （b） 0.2 mm; （c） 0.3 mm

Fig. 8. Effect of spot size on electron density in plasma channel (z axis）

Fig. 9. Effect of laser incident position on electron density in plasma channel