Fig. 1. Pump-probe shadow imaging device

Fig. 2. Air plasma at the material surface

Fig. 3. Propagation of Gaussian beam when the focus is 100 μm inside the material

Fig. 4. Effects of the microstructure formed by the first 219 pulses irradiating the material on propagation and ionization of subsequent individual pulses when the focus is on the quartz surface. (a) 20×, NA=0.4; (b) 40×, NA=0.6

Fig. 5. Propagation of the 220th pulse when the focusing condition is 20× and the focal point is at the quartz surface

Fig. 6. Propagation of the 220th pulse when the focusing condition is 20× and the focal point is 100 μm inside the quartz

Fig. 7. Color number density distribution of free electrons. (a) Focal point is at the quartz surface; (b) focal point is 100 μm inside the quartz

Fig. 8. Time distribution of maximum electron number density when the focusing condition is 20×. (a) Focal point is at the quartz surface; (b) focal point is 100 μm inside the quartz

Fig. 9. Shaded diagrams of the propagation process of the 220th pulse when focusing condition is 40× and the focal point is at the quartz surface

Fig. 10. Shaded diagrams of the propagation process of the 220th pulse when focusing condition is 40× and the focal point is 100 μm inside the quartz

Fig. 11. Variation of maximum electron number density with time when the focusing condition is 40×. (a) Focal point is at the quartz surface; (b) focal point is 100 μm inside the quartz

Fig. 12. Propagation and ionization of the pulse when the focus is different locations (20× focus). (a) Propagation and ionization images of the pulse at 498 fs; (b) crater morphology formed by the first 220 pulses

Fig. 13. Propagation and ionization of the pulse when the focus is different locations (40× focus). (a) Propagation and ionization images of the pulse at 498 fs; (b) crater morphology formed by the first 220 pulses

Fig. 14. Common process problems and transient ionization images in processing V-shaped microstructures. (a) Microcracking problem in processing sapphire V-shaped structures; (b) induced streak problem in processing SiO₂

Fig. 15. Common process problems and transient ionization images in processing inverted trapezoidal microstructures. (a) Cracking problem in processing diamond inverted trapezoidal structures; (b) fragmentation problem in processing SiC inverted trapezoidal structures