Polarization- and Modal-Control in a Vertical-Cavity Surface-Emitting Laser With an External-Cavity Formed by a Liquid Crystal Overlay

By utilizing a fully-vectorial three-dimensional cold-cavity optical simulation, we analyze the spectral, polarization, and modal-losses behavior of a vertical-cavity surface-emitting laser with a nematic liquid-crystal (LC) overlay. We identify phenomena responsible for mode and polarization selectivities and show how they can be controlled by varying design geometry parameters, such as LC thickness and oxide aperture diameter, or by electrooptically tuning the LC director. We present possibility of achieving voltage-controlled polarization switching of a fundamental mode or transverse mode switching within the same polarization. Furthermore, we show that it is theoretically possible to obtain improved single-mode operation by means of increased higher order transverse mode discrimination. Finally, we point out a way to destabilize the diode by equalizing the modal losses of all the analyzed modes.