Monolithic wavelength-graded VCSEL and resonance-enhanced photodetector arrays for parallel optical interconnects

The key components in many wavelength-multiplexed optical interconnect architectures consists of monolithic arrays of uniformly-wavelength-graded optical sources and wavelength-selective photodetectors. These arrays can minimize optical crosstalk in a parallel free-space optical interconnect, increase the data throughput in a wavelength-multiplexed fiber channel, or enhance the functionality of an optical interconnect by providing wavelength-controlled optical routing. Multi-wavelength VCSEL arrays have been achieved by varying the thickness of only the active layer, which resulted in varying mirror losses and non-uniform device characteristics. We describe a wavelength-grading scheme that scales the thickness of all the layers within the resonance structure, which reduces the loss dispersion and improves device uniformity. We show that wavelength-graded arrays of VCSELs and resonance-enhanced photodetectors (REPDs) can be produced in a repeatable and uniform manner by controlling the local MOCVD growth rate of the epilayers on a topographically patterned substrate. We further show that wavelength-graded arrays of VCSELs and REPDs can be monolithically integrated on the same substrate, thus improving the wavelength matching between the source and detector arrays