JULIA MARIA GIEHL
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Artigo IPEN-doc 24396 Polydispersed powders (Nd3+:YVO4) for ultra efficient random lasers2018 - WETTER, NIKLAUS U.; GIEHL, JULIA M.; BUTZBACH, FELIX; ANACLETO, DANILO; JIMENEZ-VILLAR, ERNESTORandom lasers hold the potential for cheap, coherent light sources that can be miniaturized and molded into any shape with several other added benefits such as speckle-free imaging; however, they require improvements specifically in terms of efficiency. This paper details for the first time a strategy for increasing the efficiency of a random laser that consists in using smaller particles, trapped between large particles to serve as absorption and gain centers whereas the large particles control mainly the light diffusion into the sample. Measurements of backscattering cone, sample absorption, reflection, and laser emission are used to determine the samples’ transport mean free path, fill fractions, laser efficiency, and the average photon path lengths inside the scattering medium for backscattered pump photons. A record slope efficiency of 50% is reached by optimizing pump photon diffusion and absorption in a powder pellet composed by a polydispersed particle size distribution (smaller particles between bigger ones) from a grinded and sieved 1.33 mol% yttrium vanadate doped with neodymium crystal with mean particle size of 54 μm.Artigo IPEN-doc 23094 Optimizing grain size distribution in Nd:YVO4 powder pellets for random laser action with high efficiency2017 - WETTER, NIKLAUS U.; JIMENEZ-VILLAR, E.; GHIEL, JULIA M.; BUTZBACH, FELIX; TAYRA, VICTORWe demonstrate a volumetric random laser with an optical efficiency of 15%. We use a 1.33 mol% Nd:YVO4 crystal, grind it and mix the particles into ten different size distributions with mean particle sizes ranging from approximately 10 micrometers to 100 micrometers. After pressing into pellets, each of the ten groups has its transport mean free path calculated from the distribution spectra and experimentally measured by means of its backscattering cone. We then calculate the fill fractions of each sample. The pellets are diode-pumped at 806.5 nm. Linewidth narrowing and output power are measured as a function of absorbed pump power. 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. By optimizing diffusion and gain we achieve high slope efficiency.Resumo IPEN-doc 20368 Rhodamine-doped aerogel random laser2014 - MIRANDA, ADRIANA R. de; PECORARO, EDISON; RIBEIRO, SIDNEY J.L.; GIEHL, JULIA M.; WETTER, NIKLAUS U.Resumo IPEN-doc 20369 Focusing light through a scattering medium under the influences of laser instability2014 - REIJN, SAARA-MAARIT; GESKUS, DIMITRI; GIEHL, JULIA M.; MIRANDA, ADRIANA R. de; WETTER, NIKLAUS U.Artigo IPEN-doc 20365 Rhodamine-doped aerogel random laser2014 - MIRANDA, ADRIANA R. de; PECORARO, EDISON; RIBEIRO, SIDNEY J.L.; GIEHL, JULIA M.; REIJN, SAARA-MAARIT; WETTER, NIKLAUS U.Artigo IPEN-doc 20372 Relationship between coherent backscattering cone and the study of the random laser emission of Ndsup(3+):YVOsub(4) powders changing the particle size and applied pressure2014 - GIEHL, J.M.; MIRANDA, A.R.; REIJN, S.M.; BUTZCHAND, F.; WETTER, N.U.Artigo IPEN-doc 19606 Random laser generation in rhodamine-doped aerogel2013 - MIRANDA, ADRIANA R. de; PECORARO, EDISON; RIBEIRO, SIDNEY L.; GIEHL, JULIA M.; REIJN, SAARA M.; WETTER, NIKLAUS U.