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.
We report on measurements of high-order dispersion maps of an optical fiber, showing how the ratio between the third and fourth-order dispersion (β3/β4) and the zero-dispersion wavelength (λ0) vary along the length of the fiber. Our method is based on Four-Wave Mixing between short pulses derived from an incoherent pump and a weak laser. We find that the variations in the ratio β3/β4 are correlated to those in λ0. We present also numerical calculations to illustrate the limits on the spatial resolution of the method. Due to the good accuracy in measuring λ0 and β3/β4 (10 -3% and 5% relative error, respectively), and its simplicity, the method can be used to identify fiber segments of good uniformity, suitable to build nonlinear optical devices such as parametric amplifiers and frequency comb generators.
We present the modeling of optical amplifiers based on the transient population inversion in optically pumped graphene atop integrated waveguides. We discuss the design criteria and introduce our results in the optimization of this device.
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