Vertical-cavity surface-emitting lasers for free-space interconnects

Vertical-cavity surface-emitting lasers have emerged as viable optical sources for lowpower, low-cost interconnects. Work over the past few years has involved the use of several different structures, including etched-mesa, proton-implanted and dielectric apertured types. Although much of the development work aimed at manufacture has focused on the proton-implanted structure, more recent work suggests that lower threshold, higher-efficiency configurations may be more desirable for future applications. In this review, we briefly outline the different structures, introduce a general design formalism, overview growth and fabrication issues, summarize some integration work, and finally review some applications that have been identified. Free-space interconnects with AlGaAs/GaAs-based materials will be emphasized including a brief summary of recent work on links using integrated microlenses on the VCSELs and detectors to avoid external optics. For completeness, we shall also include some discussion of the progress in long-wavelength InP-based (1.3 - 1.55 μm) and short-wavelength AlInGaP/GaAsbased (0.8 - 0.6 μm) VCSELs as well as guided-wave data links.