Sensing Performance of the Bragg Fiber- Based Plasmonic Sensors with Four Layers

We report the application of the analytical and finite element methods to the analysis of the sensing performance for the Bragg fiber-based plasmonic sensors having four layers. The advantages of an optical fiber with four (SiO2, GaP, gold, and H2O) layers are a very large value of the am- plitude sensitivity (3708.8 refractive index units (RIU)−1), large values of the loss (3091.0 dB/cm) and the power fraction P (0.36) at the loss matching point for the core mode in H2O, a small value of the full width at half maximum (19.4 nm), a smaller value (2.1 nm) of the difference Δλ between maximal amplitude sensitivity and resonant wavelengths, and a sym- metric line shape of the wavelength-dependent loss but a small spectral sensitivity (3236 nmRIU−1). A modification in the geometry of the fiber produces a significant change in the sensitivity and in the propagation parameters of the device. Thus, the advantages of another optical fiber with four layers are a very large value of spectral sensitivity ( nmRIU−1), large values of the amplitude sensitivity (2084.4 RIU−1), and the loss (3214.5 dB/cm) and the power fraction P (0.35), but the difference Δλ is large (8.6 nm) and the line shape for the wavelength dependence of the imaginary part of the effective index is asymmetric.