Polarization Rotation via Asymmetric Optical Pumping

The polarization rotation of a linearly polarized optical (probe) field caused by a left-circularly polarized pumping beam is studied in an opened two-level system of a ⁸⁷Rb atom. Letting a linearly polarized optical field (probe) and left-circularly polarized pumping beams co-propagate through a Rb vapor, we observe the featurable polarization rotation signals of the linearly polarized probe field via the asymmetric optical pumping with low intensities. Based on this phenomenon, a polarization-controlled light switching can be demonstrated at a low light level. Such a scheme of polarization rotation can be extended in a solid or semi-conduct material and find a practical application in all-optical information processing.