Simultaneous Second Harmonic Generation and multiphoton excited photoluminescence in anatase TiO2 nano powders

Second Harmonic Generation (SHG) and Multiphoton Excited Photoluminescence (MEPL) are observed in retro-reflection mode from a 22 nm diameter anatase TiO2 nanoparticle powder. Depth intensity profiles obtained by scanning the fundamental beam focal point through powder surface into its volume for energy of incident photons tuned around band-gap 3.2 eV. Evidence appearance both SHG MEPL is presented, their relative contribution depending on conditions photo-excitation, particular wavelength depth location. dominates at photon energies matching whereas below above clearly seen. exhibiting rising edge determined laser focusing decreasing extinction multiphoton scattering strongly differ between MEPL, being far narrower than that MEPL. Re-absorption emitted light occurs due to spectral proximity with band gap but excitation further suggests intrinsic difference two processes responsible contrasted profiles. This combined study where occur presents perspectives photonic properties materials.