Control of saturable absorption of topological insulator Bi2Se3 by electron and hole doping

In this work, few layers of Bi2Se3 is chemically treated, in which the AuCl3 solution is used for oxidation reaction to form p-doping, and BV solution (benzyl dichloride) is put to form n-doping to change material properties. We used pumpprobe system to verify the effect of doping on Bi2Se3 materials. In addition, the nonlinear saturable absorption of the material is also controlled. Through the I-scan test, we found that the saturable absorption has diverse responses to different wavelengths and doping conditions. By doping, the Fermi level of the material can be adjusted to control the saturable absorption of the material, which can be applied to the mode-locked laser. The weakened saturable light intensity can make the mode-locked pulse easier to generate.