Role of carrier-transfer in the optical nonlinearity of graphene/BiTe heterojunctions.

Two-dimensional (2D) topological insulators (TIs) have attracted a lot of attention owing to their striking optical nonlinearity. However, the ultra-low saturable intensity (SI) of TIs resulting from the bulk conduction band limits their applications, such as in mode-locking solid-state lasers. In this work, through fabricating a graphene/BiTe heterojunction which combines monolayer graphene and a BiTe nanoplate, the optical nonlinearities are analyzed.

Are graphene-BiTe van der Waals heterostructure-based saturable absorbers promising for solid-state Q-switched lasers?

This Letter compared the absorption characteristics of a homemade graphene-BiTe (G-B) van der Waals heterostructure to a BiTe topological insulator (TI) with a similar preparation method and number of layers. The results indicate that the G-B heterostructure can tremendously enhance the modulation depth and saturable intensity. In addition, a passively Q-switched laser at 1.