Optical coupling behavior and associated effects in two-dimensional implant-defined coherently coupled vertical-cavity surface-emitting laser (VCSEL) arrays are studied via both experiments and theoretical calculations. Experiments show that optical coupling between array elements can enhance the array’s output power. Additionally, optical coupling via leaky optical fields can provide extra optical gain for the array elements, which can then reduce the thresholds of these elements. Elements can even be pumped without current injection to emit light by receiving a strong leaky optical field from other array elements. Optical coupling can also cause unusual phenomena: the central elements in large-area coherently coupled VCSEL arrays that lase prior to the outer elements when the arrays are biased, or the average injection current required for each element to lase, which is much lower than the threshold for a single VCSEL. Theoretical calculations are performed to explain the experimental results.