Tapered-apertures for high-efficiency miniature VCSELs

Improved performance of smaller vertical cavity lasers is important for applications which require arrays of vertical cavity lasers operating at low power such as free-space optical interconnections between computer boards. If one obtains ideal scaling in which threshold current density and slope efficiency remain constant as device size shrinks, overall threshold currents should scale inversely with the device area. By engineering the shape of intra-cavity dielectric apertures it is possible to better confine the current and provide low-loss guiding of the optical mode, thereby approaching the desired scalability. More importantly, we show that the power conversion efficiency is higher at the lower output powers because the voltage can be lower despite increased resistance due to current transport through the aperture.