Comparisons With VCSELs
Unlike a VCSEL, in which two high-reflecting mirrors are incorporated into the laser structure to form the optical cavity, in a VECSEL one of the two mirrors is external to the diode structure. As a result, the cavity includes a free-space region. A typical distance from the diode to the external mirror would be 1 cm. Several workers demonstrated optically pumped 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.) because of their unusually high power (see below) and efficiency when pumped by multi-mode diode laser bars. These lasers are in the process of challenging conventional high power lasers such as solid state (e.g., Nd:YAG) and carbon dioxide lasers for machining operations.
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. Mooradian formed a company, Novalux, Inc., which was the first to demonstrate VECSELs (which they called "NECSELs"). Applications for electrically pumped VECSELs include frequency doubling of near-IR VECSEL emitters to attain compact powerful sources of single-mode blue and green light for projection display purposes.
Read more about this topic: Vertical-external-cavity Surface-emitting-laser
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“I don’t like comparisons with football. Baseball is an entirely different game. You can watch a tight, well-played football game, but it isn’t exciting if half the stadium is empty. The violence on the field must bounce off a lot of people. But you can go to a ball park on a quiet Tuesday afternoon with only a few thousand people in the place and thoroughly enjoy a one-sided game. Baseball has an aesthetic, intellectual appeal found in no other team sport.”
—Bowie Kuhn (b. 1926)