Influence of Oxide Overlayer on the Performance of a Fiber Optic SPR Sensor With Al/Cu Layers

Influence of different high-index oxide overlayers on the performance of a fiber optic SPR sensor coated with bimetallic layer of aluminum (Al)/copper (Cu) is reported. The oxides considered for the analysis are Al
₂
O
₃
, Al
₂
O
₃
, Al
₂
O
₃
, GeO
₂
, SnO
₂
, TeO
₂
, MgO, ITO, and ZnO, which on-coated over Al/Cu bimetallic layer causes an enhancement in electric field intensity at the oxide-analyte interface and increases the red shift in the resonance wavelength with the increase in the refractive index of the analyte solution. In addition, the figure of merit is also drastically improved. All the performance parameters are found to be different for different oxides. On the basis of comparison, the best possible oxide along with Al/Cu bimetallic layer and its requisite thickness is predicted. The sensor with Al/Cu/TeO
₂
is found to possess the best performance parameters. A fiber optic SPR sensor with coatings of Al/Cu/TeO
₂
layers over unclad core of the fiber is fabricated and its performance parameters are compared with the theoretically obtained values. Further, the sensitivity (5.98 μm/RIU) and the figure of merit (35.95) for 1.33 refractive index of the analyte are found to be better than those of previously reported sensors to the best of our knowledge.