All Photonic Isolator using Atomically Thin (2D) Bismuth Telluride (Bi2Te3)

Abstract

Here we have demonstrated two-dimensional (2D) Bi2Te3 capable of showcasing broadband Kerr nonlinear optical response, which can be utilized for nonreciprocal light propagation in passive photonic isolators. The self-induced diffraction patterns generated at various wavelengths (650 nm, 532 nm, and 405 nm) in the far field are investigated to calculate the nonlinear refractive index (n2) and third-order nonlinear susceptibility χ_total^((3) ) of the synthesized 2D Bi2Te3 using SSPM (Spatial Self-Phase Modulation) Spectroscopy method. 2D-Bi2Te3 exhibits a significant nonlinear refractive index on the order of ≈10−4 cm2 W−1, which is higher than that of graphene. The laser-induced hole coherence effect accounts for the significant magnitude of third-order nonlinear susceptibility χ_monolayer^((3) ) (in order of × 10-7 e.s.u.). The surface engineering method is applied to realize a fast-response photonic system. Bader charge analysis (ab-initio experiment) was performed to probe interaction between 2D Bi2Te3 and different solvent molecules. Leveraging the enhanced Kerr nonlinearity of 2D Bi2Te3, a nonlinear photonic isolator that disrupts time-reversal symmetry has been successfully demonstrated, enabling unidirectional light propagation. This demonstration of the photonic isolator shows Bi2Te3 as a novel 2D material, expanding its potential applications across multiple photonic devices, including detectors, modulators, and switches.