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Top1. Introduction
To fulfill the ever increasing demands of miniaturized features in the manufactured components or parts, a number of material processing methods have been developed and are being applied to manufacture complex shaped and high accurate products in micro domain. Amongst these methods, laser material processing methods are promising and effective tools that can efficiently be applied to process a wide range of materials ranging from metals, ceramics, composites, glass, quartz and many more (Steen, 2010). Laser materials processing is given high importance when conventional thermo-chemo-mechanical processes are ineffective in processing a particular material. Lasers processing offers several distinguished advantages which include one-step direct and locally confined machining, no induced mechanical stresses on machined surface, green and clean technology, elimination of secondary operations, less material wastage as chips and less cycle time (Islam & Campbell, 1993; Roessler, 1989). Among the various types of lasers available, pulsed Nd:YAG lasers and excimer lasers provide unique features during processing of difficult-to-cut materials, especially ceramics and composites (Quintero et al., 2001). The working principle of laser beam machining (LBM) is that a high intense laser beam is irradiated on the workpiece surface, due to which the irradiated zone gets extreme high temperature upto the material’s melting and vaporization temperature (Dubey & Yadava, 2008). The molten material is removed by high pressurized flow of gases (air or neutral) creating small size of crater on the machining surface. The development of laser material processing has been started three decades ago including intensive research activities in the area of drilling, cutting, grooving, marking and surface modifications (Steen, 1989; Wilson & Hawkes, 1987). However, to create micro-dimensional features on difficult-to-machine materials, in-depth researches have been started 15 years back (Masuzawa & Toenshoff, 1997; Ehmann, 2005; Dornfeld et al., 2006). Recently, laser micro-machining processes have been given much attention to manufacture miniaturized components for integrating these micro-parts in various applications in biomedical, electronics, automotive, chemical and aerospace areas (Pantelis & Psyllaki, 1996; Forget et al., 1989).