Investigation of Au/ZnGeP2 Coated Optical Fibers as Potential Surface Plasmon Resonance Sensors

Fibre optic sensors, especially those which are based on surface plasmon resonance (SPR) have become a very well-researched field. Yet, due to the plethora of material choices available, it is still a nascent field of research. In this work, we have endeavoured to study the effectiveness and suitability of a fibre-based SPR sensor, with gold (Au) thin films along with
$ZnGeP_{2}$
or
$CdTe$
dielectric layers, using MATLAB software. Both dielectric materials are known to have very good optical properties, and also protect the gold layer from oxidation. Sensors with an Au layer and
$CdTe$
showed a reduction in sensitivity with an increase in dielectric thickness and are not recommended for sensing applications within the refractive index range considered. On the other hand, sensors with
$Au/ZnGeP_{2}$
showed increased sensitivity as the thickness of the dielectric layer increased. The detection accuracy and figure of merits of the sensor decreased with an increase in dielectric thickness because of the increase in FWHM. However, given the increase in sensitivity, this is an acceptable tradeoff and hence the SPR sensor with a 40nm Au layer and a 3nm
$ZnGeP_{2}$
layer, which showed a maximum sensitivity of 2916 nm/RIU, may be used as an ideal sensor for the given conditions.