Theoretical study of a four-level EIT-type system in the presence of structured coupling light for microwave field detection

Abstract

In this work, we have theoretically studied the four-level atomic system for the measurement of a microwave (MW) field. We employed the electromagnetically induced transparency (EIT) technique for finding the MW field in the presence of a Laguerre–Gaussian (LG) beam as a coupling light. We have shown that, by the application of LG modes, narrower dips for the probe absorption spectrum can be generated, which can be easily identified and gives better resolution compared with the Gaussian mode. An exact location of dips in the probe absorption spectrum is found, and it is useful in the measurement of MW fields. We have estimated the FWHM of the probe absorption spectrum for Gaussian and LG coupling cases as 3.74 × 10 5 H z and 1.07 × 10 5 H z , respectively. Based on FWHM, we have found that minimum change in MW electric field in the order of 3.32 µ V c m − 1 will be detectable in the case of the LG mode as a coupling beam.