Fig. 1. Optical path of time-resolved shadow graphic imaging and calibration method of time-delay. (a) Optical path of time-resolved shadow graphic imaging; (b) plasma channels induced by femtosecond laser in fused silica under near zero time-delay

Fig. 2. Ultrafast dynamics of shock wave on surface of quartz glass. (a) Time-resolved shadowgraphs of femtosecond laser ablated silica glass when pump laser energy density is 0.16 J/cm²; (b) expansion distance of shock wave versus time-delay

Fig. 3. Relationship between micro-hole profile and pulse number under different time-delays. (a) 0.5 ns; (b) 1.5 ns

Fig. 4. Relationship between micro-hole aspect ratio and femtosecond laser pulse number