Microwave-synchronized fine-tuning of electromagnetically induced chirality in atomic media

This paper investigates the microwave-synchronized fine-tuning of electromagnetically induced chirality in a four-level atomic system. The system is driven by two optical fields and one microwave field in an extended double-Λ configuration. Under low-density conditions, the system exhibits double electromagnetically induced transparency (EIT), which can be controlled by adjusting the amplitudes of coupling fields and the phase of the microwave field. We show that, under suitable conditions of the coupling field amplitudes and microwave phase, the double EIT reduces to a single EIT as a result of multi-path quantum interference. These optical processes are elucidated using dressed-state analysis. In this context, we also examine the magnetic susceptibility and chiral coefficients. Furthermore, by incorporating local-field corrections for a high-density medium, we demonstrate broadband absorption-free negative refraction of the probe field, where neither the effective permittivity nor the permeability is required to be simultaneously negative.