An improved model for nanosecond pulsed laser ablation of metals

Abstract

A model is presented for the ablation of metals by nanosecond laser pulses, based on one-dimensional heat flow with temperature dependent material properties. A numerical optical calculation is introduced to account for laser beam absorption in the target, utilizing established matrix methods for electromagnetic plane wave propagation in multi-layered media. By including the effects of reflection from the dielectric-metal interface, the fall in reflectivity of aluminum during nanosecond laser pulses above the phase explosion threshold is found to be approximately twice that calculated in previous works. A simulated shielding coefficient is introduced to account for reflection and absorption of the incident laser beam by the ablation products. With these additions to foregoing models, good agreement between calculated and published experimental ablation data is attained for aluminum, both in terms of ablation threshold and depth. An investigation is subsequently carried out into the effects of laser wavelength, pulse duration and target thickness on the phase explosion threshold of aluminum.

Near field diffraction of cylindrical convex gratings

“…The behavior of this kind of grating has been already analyzed in previous works [9,10]. On the other hand, rotary encoders with the grating engraved by laser ablation [11,12] on the external curved side of a steel cylinder have recently been developed [13][14][15]. It has been demonstrated that gratings engraved by nanosecond laser ablation on steel substrates act like amplitude gratings due to their surficial roughness [16,17].…”

“…It corresponds to the same parameters as figure 2, but takes into consideration polychromatic light with Δλ = 50 nm and lateral size μ = a 10 m. For completeness, other particular cases corresponding to finite monochromatic sources and punctual polychromatic sources are analyzed and shown in the appendix. They are obtained from equation (12). These cases are of interest in other configurations of optical rotary encoders.…”

A study of surface swelling caused by graphitisation during pulsed laser ablation of carbon allotrope with high content of sp3bounds

“…It has been shown that the absorption of a significant fraction of the laser energy by the plasma that is created above the surface is an important phenomenon during nanosecond laser ablation [34], [35]. Including plasma absorption can lead to significant improvement of model predictions [36,37,38,39]. In this context, using the method developed for graphite ablation by Bulgakova et al [40], the plasma absorption is estimated using the total optical thickness of the ablation plume Λ such that…”

Smoothed Particle Hydrodynamics (SPH) modelling of transient heat transfer in pulsed laser ablation of Al and associated free-surface problems

“…In order to understand and further improve the process parameters, different modelling approaches have been developed either analytically [5][6][7][8][9][10][11][12][13][14][15], or numerically [13,[16][17][18][19][20][21]. Conventional numerical modelling methods such as finite elements (FE), finite difference (FD) and finite volume (FV) may not be able to predict complex processes when multiple materials and phases are interacting due to the connected mesh that describes the computational domain.…”

“…Due to the fact that all the elements in the mesh are connected to each other and cannot leave the mesh, the splashed particles in laser cutting, drilling and ablation cannot be observed in such methods. Some authors [21][22][23] simulated the protrusion formed by the laser ablation/machining by deleting the elements that have their temperatures greater than the boiling temperature. However, such approach fails to provide information on the behaviour of ejected material.…”