Theory and characterization of elliptically polarized modes in vertical-cavity surface-emitting lasers

The polarization of the beam emitted from telecom-wavelength vertical-cavity surface-emitting lasers (VCSELs) is studied in detail. Stokes parameters are extracted separately for the two polarization sub-modes of the fundamental spatial mode LP01. This characterization was performed at room temperature and for a significant number of devices. This led to the discovery of stable optical modes with a polarization that differs from the linear case. This crucial result was obtained without immersing the devices in an external magnetic field or driving them under external optical injection. In addition, the polarization can be tuned directly with the drive current. Moreover, the polarization handedness can be switched electrically. A theoretical investigation shows that some of the equations forming the basis of the spin-flip model should be reconsidered. In particular, a generalization of this theory is discussed and fantastic agreement is found with the experimental results. This work paves the way for a broad range of novel applications with the VCSEL technology, in particular for spintronics, bio-chemical sensing and telecommunication.