Several workers demonstrated optically pumped [1] VECSELs, and they continue to be developed for many applications including very high power diode laser sources for use in industrial machining (cutting, punching, etc.)
However, electrically pumped VECSELs (another matter entirely), were the brainchild of Aram Mooradian, an engineer known for fundamental contributions to diode laser linewidth studies, who worked for many years at MIT Lincoln Laboratory in Lexington, Massachusetts.
In contrast, a conventional in-plane semiconductor laser entails light propagation over distances of from 250 μm upward to 2 mm or longer.
The significance of the short propagation distance is that it minimizes the effect of "antiguiding" nonlinearities (the same phenomenon is coincidentally quantified by the linewidth enhancement factor relating to Mooradian's above-mentioned earlier work) in the diode laser gain region.
In a VECSEL, the external mirror permits a significantly greater area of the diode to participate in generating light in a single mode, resulting in much higher power than otherwise attainable.