Studies on Electromagnetically Induced Transparency in $\Lambda$-systems in $^{87}Rb$ atom

Abstract

We have investigated electromagnetically induced transparency (EIT) in two different $\Lambda$-systems in $^{87}Rb$ atom in $D_{2}$ line transitions. It is found that observed EIT signals in both the systems (A) ($|5^{2}S_{1/2} F=1\rangle \rightarrow |5^{2}P_{3/2} F'=1\rangle \leftarrow |5^{2}S_{1/2} F=2\rangle$) and (B) ($|5^{2}S_{1/2} F=1\rangle \rightarrow |5^{2}P_{3/2} F'=2\rangle \leftarrow |5^{2}S_{1/2} F=2\rangle$) have different strength and lineshape which are dependent on coupling beam power. For a given coupling beam power, the EIT signal with $\Lambda$-system (B) has more symmetric lineshape and greater strength than that obtained with system (A). The experimental results are in qualitative agreement with the results of a six-level theoretical model. We have further investigated EIT in both these $\Lambda$-systems in presence of applied longitudinal magnetic field and observed that separation between Zeeman split-EIT peaks increased linearly with the strength of the magnetic field. At a fixed value of applied magnetic field, the strength of Zeeman split-EIT peaks in both the $\Lambda$-systems increases with increase in coupling beam power. In presence of magnetic field and at higher coupling power, the observed EIT signals (central peaks) have higher slope than that of signals obtained in absence of magnetic field. These studies establish that $\Lambda$-system (B) is more useful than $\Lambda$-system (A) from applications point of view.