We　have　investigated　the　dependence　of　modal　behavior　on　the　structures　of　2-D　implant-defined　coherently　coupled　vertical　cavity　surface-emitting　laser　(VCSEL)　arrays　experimentally　and　theoretically.　2-D　VCSEL　arrays　with　different　interelement　spacing　have　been　designed　and　fabricated.　Through　the　experimental　analysis　of　near-field　and　far-field　distribution,　in-phase　and　out-of-phase　mode　are　obtained　from　the　arrays,　depending　on　the　interelement　spacing.　Considering　the　effect　of　thermal　and　carrier　injection,　the　refractive　index　distribution　of　the　arrays　under　operation　is　calculated.　Then,　FDTD　Solutions　software　is　employed　to　calculate　the　near-field　distributions　of　the　arrays　through　establishing　a　simplified　refractive　index　model.　The　simulation　results　agree　well　with　the　experiments.　Meanwhile,　according　to　the　phase　characteristics　of　in-phase　and　out-of-phase　mode,　as　observed　from　the　near-field　profiles,　the　far-field　distributions　are　calculated,　in　an　excellent　agreement　with　the　experiments.