Modelagem e caracterização de um dispositivo optoeletrônico baseado no fenômeno de ressonância de plásmons de superfície operando no modo de grade.

Abstract

In this work the development of a sensor system using the surface plasmons resonance phenomenon in the periodic grating is presented. In order to evaluate the influence of interface geometry on sensor sensitivity, a theoretical and practical study is performed to calculate the resonance curve at the periodic interface. The sensor system is designed from the construction of an optoelectronic device whose characterization in a multilayer structure allows it to be used to excite the surface plasmons. The device has a sensing region composed of a periodic grating with sawtooth profile with rounded edges. The analysis of the geometry of this structure was carried out through a theoretical study, which served as starting point in the mathematical approach and formulation of the problem. The solution was evaluated from a commercial computational tool, which uses the finite element method to solve the equations involved considering all the conditions adopted, whose results were validated through experiments. For the accomplishment of these experiments, three distinct devices were made, using the metal deposition process. The metals gold (Au), silver (Ag) and copper (Cu) were deposited in layers of nanometer scale forming a thin film of metal on the grating. Simulations and experimental tests were performed on each device built under the same conditions. Two types of studies were carried out from the incidence of light beam: the first varying the angle of incidence and the second, the wavelength of light. In both methods, the light had its direct incidence in the metallic grating aiming to reach a improve the sensitivity of the device. The results obtained by simulations and experiments, from light reflected by the periodic grating in order zero, were presented as curve models, whose axes: reflectivity times wavelength and reflectivity times incidence angle, demonstrated the reflectivity drop for a given wavelength range, or resonance angle. Applications of the sensor system proposed in this work were glimpsed for the detection of gases, more specifically condensed water vapor, being analyzed their efficiency and sensitivity in the detection of this compound.