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.