Development of high power laser ablation process for polycrystalline diamond polishing: Part 1. Fundamental understanding of PCD ultra-short pulsed laser ablation

Diamond exhibits incredible chemical and mechanical properties. Utilization of diamond for industrial applications has universally spread thanks to the discovery of its industrial synthesis and the enhancement of its properties by its formation under a polycrystalline form, named polycrystalline diamond composite (PCD). For industrial production PCD bulk material has to pass through several complex processes from leaving the belt press down to be polished as a wafer with a mirror-finished surface. Especially the polishing process is an extremely laborious method originally discovered to polish diamond gemstones hundred years ago. Laser ablation has repeatedly been proven to be a cost efficient process for industrial purposes. Elaboration of new ablation processes for PCD manufacturing is increasing supported by the continuous improvement of ultra-short lasers and their high performances. The ambition of this project is to develop an alternative polishing process of PCD wafers by ultra-short laser ablation achieving better performances than traditional mechanical polishing. This paper presents a relationship between material related properties of various PCD grades and performance of ultra-short laser ablation process at low laser average power. Specifically, this paper demonstrates the high impact of the pulse duration on the ablation rate, the dependence of the optimal fluence for highest ablation rate on the PCD composition and the effect of fluence on diamond graphitization through Raman spectroscopy analysis.