VCSELs with optically controlled current confinement: experiments and analysis

We have devised a novel oxide-free and regrowth-free approach for optically controlled current confinement in vertical-cavity surface-emitting lasers (VCSELs). This is realized with a monolithically integrated phototransistor (PT), which is configured as an optical switch and embedded between the two Bragg reflectors. We have fabricated functional PT-VCSELs by one-step epitaxial growth plus metal deposition with different top contact sizes. We present light current voltage characteristics of the lasers as well as a simple theoretical model explaining the occurrence of a distinct turn-on point and clarify epitaxial design requirements to reach strong optically controlled current confinement.