Vertical-cavity laser diode polarization switching and control

It is demonstrated that the polarization characteristics of VCSEL (vertical cavity surface emitting laser) diodes can be uniquely influenced by the geometric transverse cavity shape. The laser output polarization direction is controlled by intentionally introducing anisotropy in VCSEL diodes using novel transverse cavity shapes. Orthogonal polarization switching of the VCSEL fundamental transverse optical mode is demonstrated. Whereas circular VCSELs can have competing orthogonal polarizations in the fundamental mode, a single polarization in an arbitrary direction can be selected and maintained using a rhombus-shaped cavity. Cross-shaped VCSELs provide a means for modulating the fundamental mode between orthogonal polarizations.