Rare earth-activated 1-D photonic crystals were fabricated by RF-sputtering technique. The cavity is constituted by an Er3+-doped SiO2 active layer inserted between two Bragg reflectors consisting of ten pairs of SiO2/TiO2 layers. Scanning electron microscopy is employed to put in evidence the quality of the sample, the homogeneities of the layers thickness and the good adhesion among them. Near infrared transmittance and variable angle reflectance spectra confirm the presence of a stop band from 1500 nm to 2000 nm with a cavity resonance centered at 1749 nm at 0° and a quality factor of 890. The influence of the cavity on the ⁴I₁₃/₂ -->⁴I₁₅/₂ emission band of Er3+ ion is also demonstrated.

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The study of the differences between ordered and disordered materials (in the hundreds of nanometer length- scale) is a central topic for a better understanding of light transport phenomena in photonic media. In this work we report on an experimental and theoretical study of light transmission in disordered one dimensional photonic structures, where the disorder is introduced by a random variation of layer thicknesses. We found that the ran- dom photonic structure exhibits a dramatic decrease of the overall light transmission in the range 350–1200 nm with respect to the corresponding periodic photonic crystal. This study envisages the use of disordered one dimensional photonic structures for the realization of broad band filters for many applications, from sensing to photo- and thermo-voltaics

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International audienceIn this paper, we numerically investigate the fluorescence decay of Tm-doped tellurite glasses with different dopant concentrations. The aim is to find a set of data that allows the prediction of material performance over a wide range of doping concentrations. Among the available data, a deep investigation of the reverse cross-relaxation process (3 F 4 , 3 F 4 ,→ 3 H 6 , 3 H 4) was not yet available. The numerical simulation indicates that the reverse cross-relaxation process parameter can be calculated by fitting the slow decaying 3 H 4 fluorescence tails emitted when the pump level is almost depopulated. We also show that the floor of the 3 H 4 decay curve is indeed related to a second exponential constant, half the 3 F 4 lifetime, kicking in once the 3 H 4 level depopulates. By properly fitting the whole set of decay curves for all samples, the proposed value for the reverse cross-relaxation process is 0.03 times the cross-relaxation parameter. We also comment on the measurement accuracy and best setup. Excellent agreement was found between the simulated and experimental data, indicating the validity of the approach. This paper therefore proposes a set of parameters validated by fitting experimental fluorescence decay curves of both the 3 H 4 and 3 F 4 levels. To the best of our knowledge, this is the first time a numerical simulation has been able to predict the fluorescence behavior of glasses with doping levels ranging from 0.36 mol% to 10 mol%. We also show that appropriate calculations of the reverse cross-relaxation parameter may have a significant effect on the simulation of laser and amplifier devices

We report on the realization and characterization of a high performance, compact magnetometer based on a magnetoresistive sensor and working in the range ±600 T. The output is provided both numerically and by means of a field-proportional voltage. Spurious offset effects are suppressed by flipping the film magnetization at a frequency of 100 kHz, 2 / 3 orders of magnitude higher than in conventional applications. The design allows for a field resolution of 20 nT, low output noise density, and high precision and accuracy ͑relative full-scale uncertainty of about 500 ppm͒.