Simulación del campo electromagnético generado sobre sustratos SERS basados en micro-estructuras recubiertas con metales usando el método computacional FDTD

Este trabajo estudia la amplificación del campo electromagnético que se produce sobre sustratos SERS (Surface Enhanced Raman Spectroscopy) basados en microestructuras piramidales recubiertas de metal (Au, Ag y Cu) al incidir en ellas un haz de luz monocromático, proceso conocido como efecto SERS. Este estudio se realizará utilizando el método computacional FDTD (Finite-Difference Time-Domain) y el software comercial Lumerical (Lumerical Solutions Inc. Ansys). Para ello se simulará una micro-pirámide de PMMA (polimetilmetacrilato) recubierta por un metal que se irá variando, al igual que se modificarán sus dimensiones: tamaño de base y grosor de la capa de metal. Finalmente se analizarán los resultados obtenidos para concluir qué material y que dimensiones proporcionan la máxima amplificación del campo electromagnético, y, por tanto, de la señal SERS. <br /

Experimental Investigation of the Dielectric Constants of Thin Noble Metallic Films Using a Surface Plasmon Resonance Sensor

Gold and silver have an extremely low refractive index value of about 0.04 in the visible to near infrared (NIR) regions, and this induces a relative error of about 50% in refractive index measurements. This can lead to a large uncertainty in the imaginary part of the dielectric constants. A large difference exists between the experimental results and the classic models. The surface plasmon resonance (SPR) sensors, which use tens of nanometer thick noble metal film as the sensing layer, show ultra-high sensitivity (reaching 10&minus;8 RIU) in this spectral range. As the spectral sensitivity and amplitude of SPR curves depend on the thickness and the dielectric constant of the sensing layer, we obtained high precision optical constants of the noble metal film using a multi-wavelength angle-modulated SPR sensing technology. The dielectric constant inferred from the parameters of the SPR curves, rather than from the refractive index and absorption ratio of noble metals, introduced a relative error within 10% of the resonance angle measurement. The measurement results demonstrate that the dielectric constants of gold and silver nano-films are more consistent with the widely used experimental results than with the classical theoretical model and always fall in the upper half of the imaginary part of the uncertainty range in the spectra of 500&ndash;900 nm