Short-wavelength bottom-emitting vertical-cavity lasers

Abstract

Bottom-emitting vertical-cavity surface-emitting lasers (VCSELs), which emit through a transparent substrate have several advantages over conventional top-emitting lasers such as accessibility of the laser output at both facets, the ability to fashion optical elements such as lenses into the substrate, and the suitability of this structure to flip-chip bonding for hybrid microelectronic integration. Relatively-long-wavelength VCSELs are required to emit through a GaAs substrate. Currently, bottom-emitting VCSELs at shorter wavelengths appropriate for Si photodetectors rely upon etching deep via holes or removal of the GaAs substrate, both of which can compromise the underlying distributed Bragg reflector mirror. VCSELs at 850-nm grown directly on transparent AlGaAs substrates are to date inferior to those grown on GaAs substrates. We report high-performance 850-nm selectively oxidized VCSEL arrays bonded to GaP and AlGaAs transparent substrates using a simple wafer fusion process to enable emission through the substrate.