Thermal diffusion and thermoelastic bending are two consequences of heating generated on the sample surface. Both are employed in Open Photoacoustic Cell (OPC) technique to measure the thermal diffusivity of the sample. In this work, we explore the potential use of the OPC technique to study the effectiveness of thermoelastic bending process and thermal diffusion process on photoacoustic signal (S) generation in solids. More specifically, it is observed that if the thermoelastic bending process becomes more effective while the sample thickness is decreased, this information can be used to obtain a method to self-check the value of the thermal diffusivity parameter measured. The method is based on the measurement of the thermoelastic bending parameter as a function of the sample thickness (ls). The expected dependence of the thermoelastic bending parameter (C2) with the sample thickness, according to the theoretical model, is C2 ∝ ls−3. Our results for aluminum metallic samples give a C2 ∝ ls−2.8 dependence. Also, a thermal diffusivity value of αexp = (8.4 ± 0.3) × 10−5 m2/s was measured for metallic aluminum. This value is in good agreement when compared with the theoretical value αAl = 8.6 × 10−5 m2/s.

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Magnetic circular dichroism (MCD) of trivalent rare earth doped lithium niobate crystals is reported for the first time. Magneto-optical signals of Nd3+ and Yb3+ ions have been studied at 2 K as a function of the magnetic field strength up to 5 T. This study allows the identification of the Zeeman sublevels of these ions, which can be labeled by irreducible representations (Γ4, Γ5, or Γ6), so that the sign and allowance of transitions can be predicted. From the dependence of suitable MCD spectral lines on the magnetic field strength, the effective gyromagnetic factor of the ground state has been determined for both ions: (gNd)∥=1.4±0.1 and; (gYb)∥=4.7±0.1.

Um sistema fotodetector para a sua utilização em medidas quantitativas da irradiância ou potência de um feixe de luz laser precisa ter uma resposta linear. Dispositivos com essa finalidade podem ser adquiridos comercialmente, mas possuem custo elevado. Nesta comunicaçãoé proposta a construção de um sistema fotodetector a partir de um resistor dependente de luz (LDR), o qualé um elemento cuja respostaé não-linear. Nesse caso, para sua utilização necessitamos de uma calibração prévia do sistema. O desempenho do novo sistema em experiências de quantificação da potência da luz em condições estacionárias foi avaliada comparando o resultado da determinação da largura de um feixe de laser com perfil espacial gaussiano mediante a técnica da lâmina, com o obtido por um fotodetector comercial. Palavras-chave:óptica, LDR, fotodetector.A photodetector for using in quantitative measurements of the irradiance or power of a laser beam needs to have a linear response. Devices with this property can be acquired but usually they are expensive. In this paper we propose the construction of a photodetector that employs a Light Dependent Resistor (LDR), which has a nonlinear response. In this situation, for using such a photodetector it is necessary a previous calibration. The performance of the new system in experiments that need to quantify the radiant power in stationary conditions was evaluated by comparing the results of the measurement of the radius of a gaussian beam through the knife-edge technique, with the obtained with a commercial linear photodetector.

Articles you may be interested inEffect of pressure on the critical temperature of single-crystal Y0.95Pr0.05Ba2Cu3O7-δ with a specified planar defect geometry Low Temp. Phys. 40, 699 (2014); 10.1063/1.4894321 Optical properties and energy transfer processes of Ho3+/Er3+-codoped fluorotellurite glass under 1550nm excitation for 2.0μm applications J. Appl. Phys. 116, 033106 (2014); 10.1063/1.4890719 Effect of ionic-size change of the rare earth ion on the electrical properties of the hole doped double perovskite Gd 0.95 Sr 0.05 BaCo 2 O 5.5 AIP Conf. Proc. 1512, 924 (2013); 10.1063/1.4791342 Location of trivalent lanthanide dopant energy levels in (Lu0.5Gd0.5)2O3 J. Appl. Phys. 109, 123518 (2011); 10.1063/1.3597788 2.05 µm emission properties and energy transfer mechanism of germanate glass doped with Ho3+, Tm3+, and Er3+The absorption and emission spectra between the 4 I 15/2 and 4 S 3/2 multiplets of the Er 3ϩ ion in (Er 0.05 Y 0.95 ͒ 2 BaZnO 5 are recorded. From these spectra we have demonstrated the occupancy of two nonequivalent positions by the Er 3ϩ ion in the sample. Time decay measurement, emission versus temperature analysis, and selective site excitation were made to confirm our conclusion. From emission versus temperature for 4 S 3/2 → 4 I 15/2 transitions and from the selective site excitation, we were able to select the group of lines that belong to each site. In this article, we present a table with the energy-level values for the ground 4 I 15/2 and the excited 4 S 3/2 multiplets of the Er 3ϩ ion in each site.

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