Coherent population trapping (CPT) versus electromagnetically induced transparency (EIT)

We discuss the differences between two well-studied and related phenomena---coherent population trapping (CPT) and electromagnetically induced transparency (EIT). Many differences between the two---such as the effect of power in the beams, detuning of the beams from resonance, and the use of vapor cells filled with buffer gas---are demonstrated experimentally. The experiments are done using magnetic sublevels of the $ 1 \rightarrow 1 $ transition in the D$_2$ line of $^{87}$Rb.