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13 May 1997 Ultrafast laser-induced structural changes in semiconductors
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We present experimentally determined values of the dielectric function of GaAs following femtosecond laser excitation. The data at photon energies of 2.2 and 4.4 eV show that the response of the dielectric function tot he excitation is dominate by changes in the electronic band structure and not by the optical susceptibility of the excited free carriers. The behavior of the dielectric function indicates a drop in the average bonding-antibonding splitting of GaAs following the excitation, which leads to a collapse of the band gap. The changes in the electronic band structure results from a combination of electronic screening, many-body effects, and structural deformation of the lattice caused by the destabilization of the covalent bonds. Broadband measurement of the dielectric function over the range 1.5-3.5 eV reveals ultrafast laser-induced heating at low fluence, disordering at intermediate fluence, and an ultrafast semiconductor-to-metal transition at high fluence.
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Eric Mazur, Eli N. Glezer, Li Huang, and John Paul Callan "Ultrafast laser-induced structural changes in semiconductors", Proc. SPIE 2966, Laser-Induced Damage in Optical Materials: 1996, (13 May 1997);

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