Graphene-metal heterostructure for novel electro-optic modulator based on optical fiber Bragg grating device

Optical modulation is a key component in photonic systems, enabling precise control over light for applications in communication and sensing. In this work, we demonstrate a graphene–metal (Cu) heterostructure–integrated electro–thermo–optic modulator based on an optical fiber Bragg grating (FBG) device. Graphene nanoplatelets are deposited onto the surface of the FBG to provide a conformal, conductive, and thermally efficient interface, followed by copper electroplating to enable robust, solderable electrical contacts. Electrical current injected through the graphene–metal coating generates localized Joule heating, resulting in controlled modulation of the Bragg wavelength through thermo-optic and thermal expansion effects. Experimental results demonstrate Bragg wavelength shifts of up to ~1450 pm under low-frequency electrical modulation, with a quadratic dependence on the applied current, confirming thermally driven modulation. The integrated graphene–metal architecture provides a compact, scalable, and efficient approach for electrically tunable FBG devices suitable for sensing and fiber-optic modulation applications.