Azimuthal modulation of electromagnetically-induced transparency by using asymmetrical Laguerre-Gaussian beams

Abstract: Recently, the generation and detection of structured light field have drawn a great deal of attention, due to their importance in high-capacity optical data storage and quantum technology. In this letter, we explore the azimuthal modulation of optical transparency in a four-level double-V type quantum system near a plasmonic nanostructure. A Laguerre-Gaussian beam and the interaction of the system with free-space vacuum modes have been employed to create the phase-dependent absorption of a non-vortex probe field. First, we demonstrate how to identify the azimuthal index associated with the conventional LG beam via measuring the probe absorption so that the phase information of such a beam gets encoded on the spatially-dependent absorption profile with angularly-distributed lobes. Also, a spatially-varying optical transparency can be formed, due to the periodic variation of the absorption spectrum. Then, asymmetrical Laguerre-Gaussian beams are used to extend the selective spatial transparency mechanism to asymmetric spatially-structured windows, allowing for optical manipulation of spatial modes at arbitrary positions. Moreover, we investigate the influence of the asymmetric parameter on the features of the spatial inhomogeneities and show how the beams enable us to imprint the phase information of the orbital angular momentum at a desired position.