Real-time control of ultrafast laser micromachining by laser-induced breakdown spectroscopy

Abstract

Ultrafast laser micromachining provides many advantages for precision micromachining. One challenging problem, however, particularly for multilayer and heterogeneous materials, is how to prevent a given material from being ablated, as ultrafast laser micromachining is generally material insensitive. We present a real-time feedback control system for an ultrafast laser micromachining system based on laser-induced breakdown spectroscopy (LIBS). The characteristics of ultrafast LIBS are reviewed and discussed so as to demonstrate the feasibility of the technique. Comparison methods to identify the material emission patterns are developed, and several of the resulting algorithms were implemented into a real-time computer control system. LIBS-controlled micromachining is demonstrated for the fabrication of microheater structures on thermal sprayed materials. Compared with a strictly passive machining process without any such feedback control, the LIBS-based system provides several advantages including less damage to the substrate layer, reduced machining time, and more-uniform machining features.

Selective pulsed laser stripping of TiAlN erosion-resistant coatings: Effect of wavelength and pulse duration

“…This advantage becomes particularly interesting when coatings with uneven thicknesses are to be etched. In order to better assure such selectivity or end point detection, it is very suitable to apply in situ monitoring by analyzing the optical emissions emanating from the plasma plume indicative of atomic and/or molecular species [20,21].…”

Tailored Ultrafast Pulses for Selective Energetic Residue Sampling

“…Instead of using ns laser pulses, fs laser pulses were substituted to see if the amount of substrate entrained in the plasma could be reduced. Plasmas formed from an ultrafast laser pulse, ~100 fs, are generated by a different mechanism than plasmas formed from longer laser pulses (2); fs laser pulses deposit energy into the sample surface more efficiently (3,4). The use of laser pulses from the fourth harmonic of the Nd:YAG (266 nm) was also studied.…”

Evaluation of laser-induced thin-layer removal by using shadowgraphy and laser-induced breakdown spectroscopy

“…Several methods of detecting the acoustic waves and plasma spectrum during the thin-layer removal have been investigated [1][2][3]. Here, the acoustic waves have been measured by a microphone and a laser-beam-deflection probe [2,[4][5][6].…”

“…The OD energy-conversion efficiency changes when the ablated material changes, since a thin layer is already removed and the ablation of the substrate takes place. The second type of the method for monitoring the removal of thin layers is laser-induced breakdown spectroscopy (LIBS) [3,[8][9][10] that enables the spectrum analysis of the plasma emission generated during the laser-material interaction. In such a way, the identification of the elemental composition of the material being ablated is possible [11].…”