Characterization of laser processing of single-crystal natural diamonds using micro-Raman spectroscopic investigations

The application of lasers for processing diamond has revolutionized the diamond industry and its applications in microelectronics, microelectromechanical system (MEMS) and microoptoelectromechanical system (MOEMS) technologies. The process quality can be evaluated using spectroscopic techniques. In the present investigation, four different types of Q-switched solid-state lasers (with different beam parameters), namely, a lamp-pumped Nd: YAG laser operating at 1064 nm, a lamp-pumped Nd: YAG laser operating at second harmonically generated 532 mn, a diode-pumped Nd: YVO4 laser operating at 1064 mn and a diode-pumped Nd: YAG laser operating at 1064 mn, have been employed for the processing of a single-crystal, gem-quality, natural diamond. The main objective behind the selection of these lasers with different beam parameters was to study the effect of wavelength, pulse width, pulse energy, peak power and beam quality factor (M-2 factor) on various aspects of processing (such as microcracking, material loss and cut surface quality) and their relative merits and demerits. The overall weight loss of the diamond and formation of microcracks during processing have been studied for the above four cases. The characteristics of the graphite formed during processing, elemental analysis, surface morphology of the cut surface and process dynamics have been studied using micro-Raman spectroscopy and scanning electron microscopy (SEM). We observed that laser cutting of single-crystal diamonds used for industrial applications can be accomplished without microcracking or surface distortion using Q-switched Nd: YAG lasers. This allows direct processing without extensive postgrinding and polishing stages. Very efficient diamond processing is possible using diode-pumped lasers, which results in the lowest possible breakage rate, good accuracy, good surface finish and low weight loss. From the micro-Raman and SEM studies, it is concluded that the surface quality obtained is superior when diode-pumped Nd: YVO4 laser is used, owing to its extremely high peak power. The maximum graphite content is observed while processing with lamp-pumped Nd: YAG laser at 532 nm. An overall comparison of all the laser sources leads to the conclusion that diode-pumped Nd: YAG laser is a superior option for the efficient processing of natural diamond crystals. Copyright (c) 2006 John Wiley & Sons, Ltd.