Laser wavelength effect on nanosecond laser light reflection in ablation of metals

Abstract

Reflection of nanosecond laser pulses with different wavelengths (1.06 and 0.69 µm) in ablation of titanium in air is studied experimentally. The laser wavelength effect on reflection is essential at low laser fluence values. However, it becomes negligible for laser fluence values by about an order of magnitude higher than the plasma ignition threshold. We speculate that the disappearance of the wavelength effect is explained by counteracting processes of the laser light absorption in plasma, which increases with laser wavelength, and absorption in the surface layer, which decreases with increasing laser wavelength.

How the Physicochemical Properties of the Bulk Material Affect the Ablation Crater Profile, Mass Balance, and Bubble Dynamics During Single‐Pulse, Nanosecond Laser Ablation in Water

“…Hence, the target reflectivity or roughness of the pristine target surface seems to be less‐relevant in the high‐fluence regime where the cavitation bubble volumes are comparable for all materials except Al. This observation is further supported by Bevanides et al., who showed that the reflectivity drops significantly during ns‐ablation when the laser fluence is much higher than the ablation threshold [84] …”

“…However,r ecent studies have shown that the bulk material's reflectivity is of minor importance when the target is ablated with laser fluences far above the ablation threshold. [72,84] Since the incident laser fluence of 166 Jcm À2 used for ablation is two orders of magnitude higher than the ablation threshold (see Ta ble 1), it is concluded that differences in surface roughness can be neglected for the discussion of the SEM images. Nevertheless, the surface roughness is important concerning incubation effects at lower incident laser fluences, discussed in more detail in the cavitation bubble section of this work.…”

Incubation Effect of Pre‐Irradiation on Bubble Formation and Ablation in Laser Ablation in Liquids

“…With increasing pulse energy the ignited plasma becomes the driving force for the cavitation bubble as already discussed above. On the other hand, the reflectivity drops for laser ablation with nanosecond pulse duration when the fluence is far above the plasma threshold . This reduces both the energy loss and the incubation effects due to the reflectivity change induced by the roughness.…”

“…On the other hand, the reflectivity drops for laser ablation with nanosecond pulse duration when the fluence is far above the plasma threshold. [39] This reduces both the energy loss and the incubation effects due to the reflectivity change induced by the roughness. As shown in Figure 2a) right hand side, the first bubble induced at 10 mJ pulse energy is very similar for the Ag, Au and Ge target.…”

States and Properties of Metallic Systems at a Threshold Breakdown of the Through Holes Under Power Laser Action. Threshold Breakdown of Through Holes in Metal Foils by Powerful Laser Radiation (Part 1)

“…Affecting of powerful laser irradiation on metallic (dielectric and semiconductor) targets leads to formation of craters and holes, moving away of substance from a target -to the ablation [1][2][3][4][5][6][7][8][9][10][11][12]. The special role are here playing the different thermodynamic states -"solid, liquid, gas, plasma" in which substance consistently goes across.…”