The　maximum　power　conversion　efficiencies　of　the　top-emitting,　oxide-confined,　two-dimensional　integrated　2x2　and　4x4　vertical-cavity　surface-emitting　laser　(VCSEL)　arrays　with　the　oxide-apertures　of　6　mu　m,　16　mu　m,　19　mu　m,　26　mu　m,　29　mu　m,　36　mu　m,　39　mu　m,　and　46　mu　m　are　fabricated　and　characterized,　respectively.　The　maximum　power　conversion　efficiencies　increase　rapidly　with　the　augment　of　oxide-aperture　at　the　beginning　and　then　decrease　slowly.　A　maximum　value　of　27.91%　at　an　oxide-aperture　of　18.6　mu　m　is　achieved　by　simulation.　The　experimental　data　are　well　consistent　with　the　simulation　results,　which　are　analyzed　by　utilizing　an　empirical　model.