A graphene–PDMS hybrid overcoating enhanced fiber plasmonic temperature sensor with high sensitivity and fast response

Abstract

A high-sensitivity and fast-response fiber-optic plasmonic temperature sensor is developed by coating graphene and polydimethylsiloxane (PDMS) onto an optical-fiber based plasmonic interface. The sensor is composed of a side-polished-fiber for light excitation and readout, a gold layer to excite surface plasmon resonance (SPR), graphene layers to enhance the SPR effect and accelerate the sensing response, and a PDMS layer acting as a thermo-optical responsive material. It is found that the number of graphene layers exhibits positive enhancement on the sensitivity toward the refractive index (RI) until 4 layers, and further increasing the number of layers leads to a decreased sensitivity. The four-layered graphene could improve the sensitivity of the RI sensor by 33% and the temperature sensitivity by 21.9% after overcoating the PDMS layer, increasing the temperature sensitivity from 1.28 nm °C⁻¹ for the SPR sensor with a PDMS layer to only 1.56 nm °C⁻¹ for the graphene–PDMS based sensor. Furthermore, the graphene layers shorten the response time of the temperature sensor by more than one order of magnitude, i.e., from 65 to 6 s. It is believed that the multilayer graphene/PDMS structure can be further exploited for optimizing other temperature sensors in terms of sensitivity and response time.