The transmission speed of data communication systems is forecast to increase exponentially over the next decade. Development of both Si-based high-speed drivers as well as III-V-semiconductor-based high-speed vertical cavity surface emitting lasers (VCSELs) are prerequisites for future ultrahigh data-rate systems. This thesis presents: - a survey of the present state of the art of VCSELs - a systematic investigation of the various effects limiting present VCSELs - a catalogue of solutions to overcome present limits - detailed progress in modelling, fabricating and testing the currently most advanced VCSELs at the two commercially most important wavelengths.