Formation of field induced absorption in the probe response signal of a four-level V type atomic system a theoretical study

TL;DR

This paper presents a theoretical model analyzing how a four-level V-type atomic system exhibits field-induced absorption in the probe response, revealing conditions under which absorption dips occur within transparency windows.

Contribution

The study develops an analytical density matrix model for a four-level V system, highlighting new absorption phenomena not present in simpler three-level systems.

Findings

Absorption dip appears at the center of the transparency window under Doppler broadening.

EIT window appears only under Doppler-free conditions.

Probe absorption depends on control field Rabi frequency, population transfer, and temperature.

Abstract

A density matrix based analytical model is developed to study the coherent probe field propagation through a four-level V type system in presence of a coherent control field. The model allows coupling of the probe field from the upper ground level to both of the excited levels keeping the control field locked to a particular transition. The addition of an extra ground level to a conventional three-level V type system creates extra decay paths to the ground levels for the upper level population. A set of sixteen density matrix based equations are formed and then solved analytically under rotating wave approximation to study the probe response under steady state condition. The simulated probe absorption spectra shows absorption dip at the centre of a transparency window only under Doppler broadened condition although the conventional EIT window appears under Doppler free condition. The dependence of the field induced absorption signal on the Rabi frequency of the control field, population transfer rate among the ground levels and temperature of the vapour medium has been studied in details.