RESUMO
The finite element method (FEM) was used to investigate the optical-mechanical behavior of a Fabry-Perot Interferometer (FPI) composed of a capillary segment spliced between two sections of standard optical fiber. The developed FEM model was validated by comparing it with theory and with previously published experimental data. The model was then used to show that the absolute strain on the host substrate is usually smaller than the strain measurement obtained with the sensor. Finally, the FEM model was used to propose a cavity geometry that can be produced with repeatability and that yields the correct absolute strain experienced by the host substrate, without requiring previous strain calibration.
RESUMO
Materials presenting high optical nonlinearity, such as materials containing metal nanoparticles (NPs), can be used in various applications in photonics. This motivated the research presented in this paper, where morphological, linear and nonlinear optical characteristics of gold NPs on the surface of bulk soda-lime glass substrates were investigated as a function of nanoparticle height. The NPs were obtained by annealing gold (Au) thin films previously deposited on the substrates. Pixel intensity histogram fitting on Atomic Force Microscopy (AFM) images was performed to obtain the thickness of the deposited film. Image analysis was employed to obtain the statistical distribution of the average height of the NPs. In addition, absorbance spectra of the samples before and after annealing were measured. Finally, the nonlinear refractive index (n2) and the nonlinear absorption index (α2) at 800 nm were obtained before and after annealing by using the thermally managed eclipse Z-scan (TM-EZ) technique with a Ti:Sapphire laser (150 fs pulses). Results show that both n2 and α2 at this wavelength change signs after the annealing and that the samples presented a high nonlinear refractive index.
Assuntos
Compostos de Cálcio/química , Ouro/química , Nanopartículas/química , Nanopartículas/ultraestrutura , Óxidos/química , Refratometria/métodos , Hidróxido de Sódio/química , Adsorção , Vidro/química , Luz , Modelos Lineares , Teste de Materiais , Dinâmica não Linear , Espalhamento de Radiação , Propriedades de SuperfícieRESUMO
The width of the depletion region in fused-silica samples thermally poled during various periods of time is investigated experimentally with four previously reported characterization techniques in an attempt to unify their findings. Although all measurements give a similar width of the depletion region, it is shown that the determination of the profile of chi(2) is also required for a good estimate of the nonlinearity induced by poling.