The behaviour of sapphire under intense two-colour excitation by picosecond laser

Ultrashort pulse lasers are evidencing their benefits in the processing of transparent materials. Sapphire is one most attractive engineering materials today. It hard and, therefore, difficult to machine mechanically required shape. Laser dicing promising techniques for sapphire separation. Two-pulse two-colour irradiation was applied initiate free-shape cutting material. Two collinear laser beams with wavelengths 1064 and 355 nm, duration 10 ps inter-pulse delay 0.1 ns were combined induce intra-volume modifications (directional cracks) wafer The photon energy both well below band gap, various channels multi-photon excitation involved process. Significant enhancement modification area experimentally observed when intensities focused infrared ultraviolet within narrow ranges. We discuss resonant laser–sapphire interaction mechanisms, leading up four times higher material involving multiple photons energetic levels intrinsic defects band-gap. level schemes colour centres two-step absorption under intensive have been prepared.