The increasing demand for precise chemical and biological sensing has led to the development of highly efficient plasmonic optical fiber sensors. Therefore, it is essential to optimize and match the operating wavelength region of both the optical fiber configuration and localized surface plasmon resonance of nanoparticles (NPs). This can be achieved by developing NPs that can reach resonance at near-infrared wavelengths, where refractive index sensitivity is enhanced, and silica optical fibers have lower losses. High aspect-ratio bimetallic Au@Ag nanorods and different side-polished fiber structures are tested using numerical simulations. The selected optical fiber configuration was based on a side- polished fiber with a 1 mm polished section. It is compared power losses and power at the NP interface for two configurations: a step-index single-mode fiber (SMF) with core/cladding diameters of 8.2/125 µm and a multimode graded-index fiber (GIF) with 62.5/125 µm at various polishing depths. The results showed that the best performance for both configurations was achieved at similar polishing depths, namely 59.5 and 55.2 µm for the SMF and GIF, respectively. The optical impact of retardation effects due to the proximity with the fiber structure were also observed, which caused a reduction in sensitivity from 1750 nm/RIU to 1500 nm/RIU and a red-shift of
Optical microbubble resonators are among the highest sensitivity optical sensors. In the context of its application in the detection of water micro contaminants, in portable systems, their interrogation must be made by tracking the resonant wavelength peak position with the highest accuracy possible, at a reasonable cost. In this work different laser sources and scanning methods were tested and compared, aiming the development of a portable prototype. Each tunable laser source, was evaluated using a C2H2 Gas cell, which provided an absolute wavelength reference. Light transmitted through the cell was recorded using a photodetector and a software controlled feedback loop, enabling locking into selected reference peaks. Three distinct scanning methods were tested and compared for each laser source: large and short-range laser scanning and external waveform dithering, from which minimum standard deviations of 20, 0.18, and 0.07 pm, were obtained, respectively.
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