Vertical-cavity surface-emitting lasers with spatially adjustable DBR reflectivity to enable free-space photonic repeaters

We have created bidirectional high-performance top- and bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) from a single epitaxial wafer. Using a spatially selective oxidation of AlAs layers in hybrid distributed Bragg reflectors (DBRs) of a VCSEL structure, devices processed for top emission had threshold currents of 100-110 μA with slope efficiencies of 18%-20%. Devices from the same wafer processed for bottom substrate emission had thresholds of 110-120 μA and slope efficiencies of 17% and 18%. This technology will greatly simplify the use of VCSEL's in large three-dimensional (3-D) parallel interconnects, photonic repeaters, and smart pixels.