Optically-pumped vertical-cavity surface-emitting laser structures with anisotropic spontaneous emission characteristics

Almost all vertical-cavity surface-emitting lasers (VCSEL´s) have been fabricated from device structures grown on (100) GaAs substrates. Optical-pumping experiments on these laser structures show no polarization dependence on the state of the pump. One of the problems of current surface-emitting lasers is that the state of polarization of the emitted light cannot, in general, be determined a priori. It is important to seek some methods to control the polarization of the light emitted from these devices for polarization-sensitive applications such as coherent optical signal processing. We have conducted preliminary experiments designed to understand how one could effect the control of the state of polarization of these lasers. Our experiments consist of optically pumping a VCSEL structure with light from an Ar⁺ ion laser and monitoring the polarization of the spontaneous emission. The laser structures on which our experiments are performed consist of 2 strained In_0.2Ga_0.8As quantum wells each of 8 nm wide with 10 nm GaAs barriers