All-optical generation of structured light via microwave-field-controlled spontaneous emission

Abstract

We propose a scheme for achieving spatially dependent spontaneous emission by using vortex light beams (OAM) in a five level atomic configuration. It consists of an upper excited level and four lower metastable levels. The excited level is simultaneously coupled to two ground levels by a coherent probe field and a vortex field, respectively. In addition, a microwave field couples two of the ground levels. The excited state is assumed to be coupled by the vacuum modes in the free space and eventually decays to a fifth metastable level. It is found that by manipulating key parameters such as the strength of the Laguerre–Gauss beams, the Rabi frequency and detuning of an external microwave field, and the initial state of the atoms, we can achieve highly tunable spontaneous emission spectra. A wide variety of spatiospectral behavior, including two-dimensional spectral-peak narrowing, spectral-peak enhancement and spontaneous emission quenching is obtained.