Optical fiber optrodes are attractive sensing devices due to their ability to perform point measurement in remote locations. Mostly, they are oriented to biochemical sensing, quite often supported by fluorescent and spectroscopic techniques, but with the refractometric approach considered as well when the objective is of high measurement performance, particularly when the focus is on enhancing the measurand resolution. In this work, we address this subject, proposing and analyzing the characteristics of a fiber optic optrode relying on plasmonic interaction. A linearly tapered optical fiber tip is covered by a double overlay: the inner one - a silver thin film and over it - a dielectric layer, with this combination allowing to achieve, at a specific wavelength range, surface plasmonic resonance (SPR) interaction sensitive to the refractive index of the surrounding medium. Typically, the interrogation of the SPR sensing structures is performed, considering spectroscopic techniques, but in principle, a far better performance can be obtained, considering the reading of the phase of the light at a specific wavelength located within the spectral plasmonic resonance. This is the approach which is studied here in the context of the proposed optical fiber optrode configuration. The analysis performed shows the combination of a silver inner layer with a dielectric titanium oxide layer with tuned thicknesses enables sensitive phase reading and allows the operation of the fiber optic optrode sensor in the third telecommunication wavelength window.

基于金属氧化物薄膜材料在中波红外波段应用的需求，研究了含水状态的TiO2、HfO2、Ta2O5和Y2O34种金属氧化物薄膜在中波红外波段内（2.5~5 μm）光学常数的色散特性。利用电子束蒸发沉积技术，在超光滑的硅表面制备了4种氧化物薄膜，基于洛仑兹振子介电常数色散模型，通过透射率光谱反演计算了4种氧化物薄膜的光学常数。研究结果表明：4种氧化物均有少量的水分子、羟基，水含量从少到多的薄膜依次为TiO2、HfO2、Ta2O5和Y2O3，在远离水吸收的位置，消光系数从小到大的薄膜分别为TiO2、HfO2、Ta2O5和Y2O3；在电子束蒸发沉积工艺条件下，为了降低水的影响，TiO2和HfO2是中红外波段较为理想的金属氧化物薄膜材料。