Optimization of Graphene on D-Fiber Saturable Absorbers

The graphene-light interaction in a waveguide can be optimized through the waveguide design. In the case of nonlinear optical devices, such as saturable absorbers, this optimization requires knowledge of the actual intensity that quantifies the nonlinear interaction with a waveguide mode. In this work we propose parameters that correctly quantify the strength of saturable absorption. We show that the graphene on D-fiber saturable absorber can be characterized through the absorption coefficient and a properly defined saturation power for each mode. We analyze the dependence of the graphene-light interaction on the geometrical parameters, chemical potential, number of graphene layers, and input power. The results show a wide variation of the graphene absorption with the design, which offers potential for polarizers with large polarization extinction ratios and saturable absorbers with low saturation powers. As a function of the number of layers, the interaction is maximized for five layers, and we predict a reverse saturable absorption effect for higher number of layers. The parameters introduced here to quantify the nonlinear graphene-light interaction can be applied to other waveguide structures and other 2D materials.