Broadband ultrafast spatial self-phase modulation for topological insulator Bi2Te3 dispersions

Ultrathin topological insulator bismuth telluride (Bi2Te3) nanosheets with uniform hexagonal nanostructure have been synthesized by cost-effective solvothermal method. Broadband spatial self-phase modulation phenomena of these topological insulator nanosheets have been observed with 400 nm, 800 nm, and 1070 nm ultrafast lasers. The experimental results suggest that this coherent light scattering is due to the broadband, ultrafast, and large third-order optical nonlinearity of Bi2Te3. With the pulsed laser excitation, the nonlinear refractive index (n2) of Bi2Te3 dispersion solution was measured to be ∼10−12 m2/W, and the third-order nonlinear susceptibility ∼10−7 esu. Our work may provide an inroad for developing the nonlinear optical applications based on topological insulators.