Emissão laser aleatório em sílica mesoporosa SBA-15 dopada com Rodamina B

• Autor(a) principal: Prado, Marcus Vinícius Alves
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/jspui/handle/riufs/14727
• topic: Física; Laser aleatório; Sílica mesoporosa; SBA-15; Rodamina B; Retroalimentação incoerente; Sintonização da emissão; Random laser; Mesoporous silica; Rhodamine B; Incoherent feedback; Emission tuning; CIENCIAS EXATAS E DA TERRA::FISICA

Random laser is a phenomenon in which feedback provided by a scattering medium promotes the amplification of light by means of the stimulated emission. With that in mind, we investigated powder samples of mesoporous silica SBA-15 doped with Rhodamine B in this work. Herein, the organic dye acts as the gain medium, while the SBA-15 silica structure has a double role. On the one hand, it provides the light scattering needed to achieve feedback in the system. Besides that, the silica high surface area, especially within the pores, makes this material an excellent host for the adsorption of dyes. In the experiments, the fluorescence spectra of two samples with distinct loads of Rhodamine B were measured. The powder was excited by 8 ns pulses of the second harmonic of a Nd:YAG laser. The experimental setup allowed the control of the incident power on the samples. In such manner, the characterization procedure consisted in analyzing the emission peak intensity and spectral width as a function of the excitation fluence. This experiment was repeated with different values for the laser spot diameter, thus, it was confirmed the existence of random laser emission with incoherent feedback in both samples. To the best of our knowledge, this phenomenon has never been reported for this system before. In both cases, a minimum value for the oscillation threshold was achieved around 50 MJ/mm2. However, for excitation spot diameter smaller than 1 mm, the higher the amount of Rhodamine B, the lower was the threshold. In addition, with the combination of different excitation conditions and the dye concentration, it was possible to tune the emission wavelength over a range greater than 5 nm. This was done by exploiting the reabsorption processes that take place on the system, whose dependence with the formation of the organic molecules aggregates was discussed. Hence, we concluded that the studied material has a huge potential in the development of tunable solid-state random lasers.