The impact of the relative phase on the transient optical properties of a four-level EIT medium

This Letter investigates the transient phenomena in a four-level electromagnetically induced transparency (EIT) system when strong coupling fields are rapidly switched on or off. We analyze transient properties of a probe field absorption and dispersion by studying the system evolution from transient EIT into steady-state EIT. It is shown that the absorption and dispersion can dramatically be affected by the relative phase between applied fields.