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 ofa STRb 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 al1-optical information processing.