Microlens-integrated vertical-cavity surface-emitting lasers for large-tolerant fiber optic coupling

We have fabricated microlens-integrated vertical-cavity surface-emitting lasers (VCSELs) by selective oxidation of composition-graded digital alloy AlGaAs. Microlens-integrated VCSELs with self-aligned structure was fabricated using standard VCSEL processing without additional process steps, due to the simultaneous formation of a microlens and oxide aperture. The output beam from the oxide-buried and oxide-removed AlGaAs microlens-integrated VCSELs has a beam radius of 3.7 µm and 3.5 µm at a distance of about 25 µm and 15 µm, respectively, from the surface of the VCSEL. From the calculation of VCSEL-to-SM fiber coupling efficiency, the oxide-buried lensed-VCSELs exhibited 1-dB axial alignment tolerance range of about 40 µm.