An effective anti-oxidized strategy for ultra-narrow band absorber as plasmonic sensor

An effective strategy to avoid the Ag oxidized problem of the ultra-narrow band grating absorbers as sensors was proposed and demonstrated theoretically by introducing a thin Al2O3 layer above the upmost Ag grating layer. We theoretically and numerically study the influence of the Al2O3 layer on the plasmoinc absorbers. The resonant wavelength of the sensor is easily tunable via geometrical scaling of the Ag grate structure and thickness of the Al2O3 layer. The introduced Al2O3 layer does not influence the underlying mechanism of the ultra-narrow absorber, so it remains the high sensitivity of the Ag-based plasmonic absorbers by keeping the sensitivity 507 nm/RIU and FOM about 160. The introduced anti-oxidized layer is an effective and harmless anti-oxidized strategy, which has great potential to improve the performance of sensors in practical applications.