GIORDANO BRUNO CREPALDI DE SIMONE

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Optimized grain size distributions for maximum efficiency in neodymium doped powder random lasers
2017 - WETTER, N.U.; GIEHL, J.M.; BUTZBACH, F.; ANACLETO, D.; SIMONE, G. de; JIMENEZ-VILLAR, E.
We show that polydispersed powders can have much higher random laser output power and efficiency than monodispersed powders. A more than 50% slope efficiency is achieved by using highly doped Nd:YVO4 powders composed of average grains size of 50 μm and 10% volume fraction of grains below 1 μm. We demonstrate that the smaller particles, trapped between large particles, serve as gain centers whereas the large particles control the light diffusion into the sample. A detailed light diffusion analysis of the samples explains the observed differences.
Dependency of absorbed light in powders of Nd3+:YVO4 with different grain sizes and applied pressure
2017 - SILVA, DANILO A.A. da; WETTER, NIKLAUS U.; SIMONE, GIORDANO B.C. de
This work explores the relation between the absorption and reflectivity of several powders of Nd3+:YVO4 with different grain sizes. To do that, this powder was analyzed in a spectrometer with a calibrated integrating sphere. With that we obtained the reflectivity curve of the samples and calculated the ratio between the maximum of reflectivity and the maximum of absorption, which result in smaller grains absorbing more light.