Abstract

The electromagnetic field of a semi-conductor laser is usually linearly polarized because the guide is anisotropic. In a Vertical-Cavity Surface-Emitting Laser (VCSEL), the polarization could be random from one component to another or bias-current dependent. This is a sign of weak anisotropy. We showed that the polarization states of such lasers could be controlled by a polarized optical feedback ([1]-[3]). Using the frequency chirp, modulation of the current enables control of the polarization up to 50 Mhz in VCSEL’s. We explained this value by the experimental measurement of the chirp-frequency transfer function and propose here way to increase this bandwidth, using an integrated design. Recently, it has been shown [4] that a VCSEL with external feedback could have its polarization self-modulated up to 6 GHz. In figure 1, the axes of the inserted quarter-wavelength plate are at 45° with respect to the laser axes. However, no theoretical account was given. Here, we give experimental accounts and explained why traces are slightly different from [4] (figure 2).

© 1996 IEEE