Investigating the Polarization Properties of Vertical-Cavity Surface-Emitting Lasers

Vertical-cavity surface-emitting lasers (VCSELs) are a new type of semiconductor laser that have emerged as an economical alternative to conventional edge-emitting lasers. Anisotropies within these lasers, such as birefringence and dichroism, cause their optical output to favor one of two orthogonal linear polarizations; however, other optical outputs such as elliptical polarization and polarization coexistence are possible under some circumstances. When using these lasers in real systems, optical feedback (from a fiber-optic cable or CD) is almost unavoidable. Numerical simulations suggest that under optical feedback conditions, VCSELs lose their polarization stability and descend into chaotic behavior. These complex dynamics, however, are extremely sensitive to the relaxation rates of the system, especially the so-called “spin-flip” decay rate. In addition, recent work at Mount Holyoke College suggests that extremely short external cavities can heavily influence the behavior of VCSELs. My thesis will focus on two separate investigations. In the first, I will develop a model to simulate the polarization dynamics of VCSELs in short external cavities, to complement the work that has been done at Mount Holyoke. In the second, I will experimentally investigate how VCSELs react to optical feedback in two “extreme” conditions — extremely short external cavities, and cryogenic operation.