Abstract

Switching techniques with coherent optical sources are a challenge for telecommunications. One technique is to control the polarization eigenstate of the laser. We have examined the stability of polarized modes in quasi-isotropic laser, such as He-Ne laser at 3.39 μm¹ and have proposed a general anisotropy model with applications.² To test our calculations we have used He-Ne lasers as they are easy to construct in-house and are systems for which all the important parameters are known. For practical applications, however, it is clear that one must use more compact lasers, such as miniature solidstate lasers or semiconductor lasers. To control the polarization eigenstate of such a laser with Polarized Optical Feedback (POF), we need sources, which can run single mode and have weak anisotropies. Possible candidates that satisfy these criteria are microchip Nd:YAG lasers and Vertical Cavity Surface Emitting Lasers.³ However, the orientation of their polarization can vary from laser to laser. That could be a sign of weak anisotropy as the polarization states of quasi-isotropic lasers are highly sensitive to residual cavity anisotropies (most likely strain left during the fabrication process). Previously, we reported on the control of the polarization eigenstates of microchip YAG lasers using POF.⁴ Here we focus our study on adding POF in order to control the polarization eigenstate of gain-guided VCSELs. A schematic diagram of the experimental setup is shown in Fig. 1.

© 1994 IEEE