Multiphoton interactions in rutile

Abstract

Laser-induced photoluminescence and photoconductivity in rutile crystal are described. Nd:YAG laser photons were employed which have energies of 1.16 eV (1.06 μm). This energy is just slightly more than ⅓ of the TiO2 band gap. Intensities between 105 and 106 W/cm2 were employed. The photoconductivity is shown to be produced by competing single- and two-photon events. The first-order and second-order photoconductivity cross sections are found to be 3.6 × 10−26 cm2 and 1.54 × 10−50 cm4 sec, respectively. A thermoluminescence study revealed traps with thermal ionization energies between 0.4 and 0.9 eV below the conduction band. Traps with photoionization energies ~1 and ~2 eV below the conduction band are believed to be responsible for the observed results and may or may not be due to alumina impurities known to exist in the samples.