The Sensing Characteristics of a Bragg Fiber Based Plasmonic Biosensor Using an As_2S_3 Chalcogenide Layer

摘要

The sensing performances of a four layer Bragg fiber based plasmonic biosensor for aqueous solutions using an As_2S_3 chalcogenide layer are investigated with an analytical method. In comparison with a previously considered fiber structure with a GaP layer, the new geometry has the advantages of a smaller value of the full width at half maximum and a larger value of the signal-to-noise ratio; however, the maximum of amplitude sensitivity is smaller when an As_2S_3 layer is used in the place of the GaP layer. If the thickness of the As_2S_3 layer is increased to the value for which it is quarter wavelength, the power fraction carried at the resonant wavelength by the core guided mode in the analyte layer becomes comparable with the value obtained in an optical fiber with the GaP layer, evidencing that the higher value of the refractive index for the GaP layer is compensated by a larger value of the thickness for the As_2S_3 layer. Taking into account the 0.04 photoinduced refractive index change obtained by illumination the chalcogenide As_2S_3 layer with a laser beam, the resonant wavelength is decreased by 0.128 nm and the loss for the core mode is increased by 41dB/cm.