Influence of Induced Ripples on Optical Properties of Graphene: Density Functional Theory

In the present work, we theoretically investigated the optical properties of a rippled graphene monolayer. We induced ripples on the graphene monolayer by applying different uniaxial and biaxial strain. Five optical properties were reported: dielectric function, absorption coefficient, reflectivity, optical conductivity, and refractive index. Two types of incident light were considered, i.e., polarized light and unpolarized light. Inducing ripples on the graphene monolayer remove constrains on electron transitions. Such electron transition is not allowed in planar graphene under certain light polarization. While new peaks evolve in the optical absorption spectrum, other peaks disappear. We detected a prominent peak in the absorption spectrum located around 1.2 eV. Besides, absorption peaks originated as a consequence of inter-band transitions and they reveal a red-shift with increasing strain. We detected that intensity, width and energy position of the peaks are sensitive to the deformation created in the planar graphene monolayer. We presented that different optical graphene properties were determined by the direct inter-band electron transitions.