Emissão laser em meios espalhadores com ganho: estudos experimentais em soluções etanóicas e aquosas

• Autor(a) principal: Dominguez, Kelly Christian Tolentino
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/5714
• topic: Laser aleatório; Laser de corante; Nanopartículas; Espalhamento múltiplo; Random laser; Dye laser; Nanoparticles; Multiple scattering; CIENCIAS EXATAS E DA TERRA::FISICA

The approach of this thesis is study the laser emission from highly scattering media with gain with incoherent feedback. These systems are called of random lasers and diverge from the typical laser, because they can emit monochrome light with high intensity without a cavity. We detail several experimental studies in samples containing different rhodamines in solution containing TiO2 nanoparticles, which provide the feedback to lasing. The nanoparticles densities were chosen for random laser system remains in a diffusive regime. In this regime, the probability of the photon return to the starting point of incidence is unlikely; therefore the interference effects of waves associated to the photons can be neglected and the feedback is incoherent. We study de dependence of random laser threshold on both dye concentration C and scatterers density N. We showed that the dependence of random laser threshold on the nanoparticles density is a power law N-α, but the exponent α depends on the dye concentration. We used the novel random laser spectroscopy technique to study de binding energy between molecules in the dimers, our results agree very well with those found by other authors who used traditional methods. We also showed, by the first time, the random laser emission from aqueous solution containing rhodamines 6G and TiO2 nanoparticles, Sodium Dodecyl Sulfate (SDS) was added to dissolve the dye aggregates.