Plasmonic Waveguide Modulator Integrated with a Transferred Bi₂Se₃ Topological Insulator Film

We demonstrate a voltage-tunable plasmonic modulator that integrates a Bi₂Se₃ topological insulator thin film with a metal-dielectric plasmonic waveguide. The Bi₂Se₃ layer, transferred using a polymer-assisted method, enhances the modulation depth of the waveguide by enabling electrically driven carrier redistribution at the Au/Bi₂Se₃ interface, which perturbs the effective dielectric response of the shared Au plasmonic layer. With the Bi₂Se₃ film, the device demonstrates a significant output peak displacement in the transmission spectrum of up to 49.2 nm, along with an enhanced extinction ratio (ER) of 4.21 dB under an applied bias of 10 V for a 100 μm-long waveguide. These modulation effects are attributed to Au/Bi₂Se₃ interfacial carrier redistribution, carrier-induced modification of the shared Au plasmonic layer, possible Burstein-Moss-related absorption modification in Bi₂Se₃, and accumulated wavelength-dependent propagation loss. Our results suggest that the unique properties of Bi₂Se₃ offer a viable approach for broadband optical modulation, providing an alternative to conventional 2D materials like graphene. This work highlights the utility of topological materials for developing actively tunable components in integrated nanophotonic systems.