Fig. 1. Schematics of laser ablation in liquid. (a) Typical physical and chemical processes during laser ablation in liquid^[45]; evolutions of(b) light filaments^[46], (c) plasma^[47], and (d) cavitation bubble^[48] during laser ablation in liquid

Fig. 2. Schematics of transient observation technology of femtosecond laser ablation in liquid. (a) Transient absorption spectroscopy^[101]; (b) time-resolved liquid phase photoelectron spectroscopy^[102]; (c) time-resolved liquid phase X-ray diffraction spectroscopy^[103]; (d) transient imaging of liquid phase by ICCD^[104]; (e) liquid phase pump probe imaging^[105]; (f) liquid phase 4D electron microscope^[98]

Fig. 3. Transient observation results of light filament evolution during laser ablation in liquid^[88]. (a) Optical path diagram of interference imaging for femtosecond laser ablation in liquid; (b) evolution images of laser excitation region in water at pulse intensities of 0.26 μJ (left) and 0.4 μJ (right) with pulse propagating from left to right

Fig. 4. Transient observation results of solvated electron evolution during laser ablation in liquid. (a) Transient absorption spectra of excited solvated electrons in water and D₂O with different delay time in 450 nm‒5.5 μm probe range, with excitation wavelengths represented by vertical arrow^[122]; (b) upper left is schematic of liquid three-pulse photoelectron spectroscopy on top left and other images are photoelectron spectra measured in different solvents using 700 nm pump and 270 nm probe pulses with time resolution of 80 fs^[99]

Fig. 5. Transient observation results of plasma evolution during laser ablation in liquid. (a) Spectral line evolution results of Al and AlO during femtosecond laser ablation of γ-Al₂O₃ in liquid are detected by time-resolved spectroscopy, the upper picture is broad-spectrum plasma emission spectrum, the middle picture is high-resolution spectra of Al under different delays, and the lower picture is high-resolution spectra of AlO under different delays^[92]; (b) plasma density maps based on single-pulse laser induced breakdown spectrum and double-pulse laser induced breakdown spectrum for laser ablation of titanium in liquid^[128]; (c) ICCD is used to detect plasma luminescence intensity images during laser ablation of titanium target in liquid, the upper panel shows optical emission image observed at ambient pressure of 0.1 MPa , the middle panel shows optical emission image observed at ambient pressure of 0.5 MPa, and the lower panel shows relationship between optical emission intensity and external ambient pressure^[129]; (d) the upper panel shows time-resolved images of laser ablation in liquid under different solutions and magnetic field conditions, and the lower panel shows plasma intensity decay results with time under different conditions^[130]

Fig. 6. Transient observation results of bubble evolution during laser ablation in liquid. Shadow images of YAG pulsed laser ablation of titanium target in liquid after different delay time of (a) 0.7 μs, (b) 10 μs, (c) 90 μs, (d) 185 μs, (e) 225 μs, and (f) 2400 μs^[132]; (g) time-resolved shadowgraphs of laser-induced bubble production in water under different hydrostatic pressures with corresponding delay time at bottom of each image^[93]