Simultaneous Trapping of Two Optical Pulses in an Atomic Ensemble as Stationary Light Pulses

The stationary light pulse (SLP) refers to a zero-group-velocity optical pulse in an atomic ensemble prepared by two counter-propagating driving fields. Despite the uniqueness of an optical pulse trapped within an atomic medium without a cavity, observations of SLP so far have been limited to trapping a single optical pulse due to the stringent SLP phase-matching condition, and this has severely hindered the development of SLP-based applications. In this paper, we first show theoretically that the SLP process in fact supports two phase-matching conditions and we then utilize the result to experimentally demonstrate simultaneous SLP trapping of two optical pulses for the duration from 0.8 $\mu$s to 2.0 $\mu$s. The characteristic dissipation time, obtained by the release efficiency measurement from the SLP trapping state, is 1.22 $\mu$s, which corresponds to an effective Q-factor of $2.9\times 10^9$. Our work is expected to bring forth interesting SLP-based applications, such as, efficient photon-photon interaction, spatially multi-mode coherent quantum memory, creation of exotic photonic gas states, etc.