Topological charge measurement in a four-level single layer graphene system

Abstract

In this letter we have proposed a four-level graphene monolayer system for identifying the topological charge of Laguerre–Gaussian light. Here, we have shown that due to the four-wave mixing mechanism in the monolayer graphene system, a weak signal beam can be generated due to quantum coherence and interference effect. We have discussed the spatially dependent linear absorption spectrums of the weak probe and new generated signal beams via quantum mechanical density matrix formalism. We have found that by numbering the spot areas of the probe and signal beams, one can realize the topological charge of the Laguerre–Gaussian beam interacts by monolayer graphene system. Moreover, we have realized that for some topological charge the new generated signal beam can be amplified in the graphene system.