Zeeman optical pumping of Rb atoms in a hollow-core photonic crystal fiber.

Preparation of an atomic ensemble in a particular Zeeman state is a critical step of many protocols for implementing quantum sensors and quantum memories. These devices can also benefit from optical fiber integration. In this work we describe experimental results supported by a theoretical model of single-beam optical pumping of Rb atoms within a hollow-core photonic crystal fiber. The observed 50% population increase in the pumped F = 2, m = 2 Zeeman substate along with the depopulation of remaining Zeeman substates enabled us to achieve a threefold improvement in the relative population of the m = 2 substate within the F = 2 manifold, with 60% of the F = 2 population residing in the m = 2 dark sublevel. Based on theoretical model, we propose methods to further improve the pumping efficiency in alkali-filled hollow-core fibers.