Thermal and mechanical damage of GaAs in picosecond regime

An in-depth study of the single pulse and multiple pulse laser (35 ps, 10 H z and 1064 mn) damage for threshold fluence and greater fluence of GaAs (10 0) single crystal is presented. Damage which starts at a power 2 x 10(11) W /cm(2) in the form of pits occurs due to accumulation of laser induced micr oscopic defects. Effect of multiple pulse at first makes the pits more prom inent in the form of Ga emission. Then the topmost layer is removed. If the number of pulses is further increased new pits are formed in the new surfa ce (beneath the removed surface) and the above process is repeated. The the rmal model is sufficient to explain this morphology. However, for larger fl uences, a large cracking and fracture and the possibility of both Ga and As emission in different ratios suggest that mechanical damage is a dominant feature for hi-her fluences which arises due to generation of shock waves a nd rapid vaporization of material. Damage threshold has been calculated wit h the help of the thermal model given by Meyer et al. which is in good agre ement with our experimental results. (C) 2001 Elsevier Science Ltd. All rig hts reserved.