High power lasers have got established as a tool of unprecedented precision and power and are finding usage in a wide spectrum of material processing applications e.g. laser cutting, welding, drilling, marking, scribing, surface hardening, surface alloying and cladding, surface texturing, shock peening, forming, micro-machining, and rapid manufacturing. The special properties of the laser beam, namely the low beam divergence, high power and wide range of pulse duration, from continuous wave (CW) down to sub-picoseconds (<10~(-12)s) have been exploited in these processing applications. Due to the low divergence the laser beam can be focused with the help of a lens to a spot of a very small diameter, typically of the order of the laser wavelength; resulting in a very high laser power density at the focal plane. Thus, when a high power laser beam is focused at the surface of any material, the material at the focal point undergoes heating, melting, evaporation, and ablation depending upon the laser power density.
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