关键词：传感器；纳米结构阵列；探测器；拉曼散射；仿真
摘 要：During the project, we have investigated the linear and nonlinear response of two dimensional gold square-nanopatch arrays. We have shown that these arrays exhibit very narrow resonances corresponding to the formation of leaky modes associated with surface plasmons at the air/metal interfaces. The experimental measurements have confirmed the spectral behaviour predicted by the simulations and emphasized that fabrication tolerances, such as the roughness, do not noticeably affect the performance of the device since they broaden and shift slightly the plasmonic resonances. Then the potential sensitivity of the device has been experimentally derived by evaluating the spectral shift when an extremely small change of the refractive index is induced at the top surface of the sensor, leading to sensitivity values up to 1000 nm/RIU and a corresponding Figure of Merit (FOM) of 222 RIU-1 (FWHM of the resonance is only 4.5 nm). Moreover, we have shown a new, more intuitive path to detect variations of refractive index from colour changes. We compared the diffracted spectra of the same sample with air and an IPA solution on top, registering a significant change in the sample colour. This observation can be also quantified in terms of sensitivity, leading to S = 121 nm/RIU and FOM = 6 RIU-1 (FWHM of the measured spectra is equal to 20 nm). Furthermore, such observation method allows establishing numerous other properties of the foreign compound such as its thickness or evaporation time, paving the way for new, yet unexplored plasmonic sensor devices. Finally the nonlinear response of the periodic arrays has been investigated and the effect of the geometrical parameters on the Surface Enhanced Raman Scattering signal has been analyzed.