Abstract
In this paper, we introduce a plasmonic structure-based fiber optics gas sensor using gold nano-particles on the end face. The proposed optical sensors are designed and evaluated to investigate the influence of the shape of the nano-particles. Evaluation techniques such as wavelength and peak sensitivities, full width at half maximum, and figure of merit are studied. By extension, we numerically study the macroscopic electric and magnetic field distributions and the microscopic polarization and current density in order to interpret the physical mechanism. The optical sensor based on nano-particles of classical spherical shape shows the highest wavelength sensitivity. However, it was motivating that the sensor based on nano-particles of the conical shape offers a better performance. It exhibits resonance wavelength and peak intensity sensitivities of 157 nm/RIU and 44 %/RIU, respectively, which give a higher overall sensitivity. In addition, it offers a narrow stable line width and high figures of merit.