Spatially dependent Raman gain by vortex beam in a four-level N-typed atomic system

An efficient scheme for controlling the spatial Raman gain is proposed in a cold atomic ensemble with a four-level N-typed configuration. The cold atoms are driven by the Laguerre–Gaussian (LG) vortex beams. Using experimentally achievable parameters, we identify the condition under which the topological charge (TC) allows us to manipulate the spatial distribution of the Raman gain spectra. Furthermore, we find that the spatial Raman gain can be effectively controlled via adjusting the relevant optical parameters. Subsequently, we show interesting optical properties of vortex-induced transparency(VIT) and vortex-induced gain (VIG) by controlling the probe absorption spectrum. Our scheme may provide a feasible approach for constructing novel vortex beams based on cold atomic ensemble.