Fig. 1. Schematic of experimental setup. The inset is the image of air plasma. The red dashed line is the position of the sample surface, and the white arrow indicates the direction of the laser pulse. The arrangements of the camera and spectrometer are set as an example of the exit surface damage. HWP, half-wavelength plate; PBS, polarized beam splitter; BS, beam splitter; EM, energy meter; FL, focus lens; FC, fiber collector; MO, microscope objective; TL, tube lens.

Fig. 2. Typical images of LPP on (a) the exit surface and (b) the input surface. Scanning electron microscope (SEM) morphologies of damage sites on (c) the exit surface and (d) the input surface.

Fig. 3. (a) Evolution of plasma size with laser energy on the input and exit surfaces, and (b) the ratio between the driving energy on both surfaces deduced by Sedov–Taylor scaling.

Fig. 4. Typical plasma emission spectra of bulk damage, exit surface damage, input surface damage, and air plasma from top to bottom. Lines superimposed on the bulk spectra are the fitted line and three Gaussian components. The wavelength range of the inset in the input surface spectra is 572–610 nm. The red arrow indicates the wavelength of 589.25 nm.

Fig. 5. Evaluated electron density and excitation temperature of exit and input surface LPPs.