Lithium niobate waveguide-integrated Bi2Te3/graphene heterojunction photodetector

We demonstrate an on-chip photodetector by integratinga graphene and topological insulator Bi2Te3 heterostruc-ture on a thin-film lithium niobate waveguide. Lithiumniobate on insulator (LNOI) waveguides are fabricated bythe photolithography-assisted chemical mechanical etchingmethod. The bismuth telluride (Bi2Te3) and graphene het-erostructure design provides enhanced photocurrent dueto the effective photocarrier generation. The lithium nio-bate waveguide-integrated Bi2Te3/graphene heterojunctionpresents a high absorption coefficient of 2.1 dB/μm. TheBi2Te3/graphene heterojunction photodetector exhibits aresponsivity of 2.54 mA/W without external bias at a 1.55 μmwavelength, which is enhancement of sevenfold as comparedto the pure graphene-based photodetector. The photodetec-tor has a 3 dB bandwidth of over 4.7 GHz. This work providesa potentially viable method for a self-powered, high respon-sivity, and fast response of the photodetector integrated withthe LNOI photonic platform.