*blinks*

This is something out of science fiction. Specifically Robert Heinlein's story from the early 1940s, Let there be Light.
It is a radio antenna for visible light. They mention that you could use it as an efficient solar electric collection system or to recieve light based radio. What they fail to mention is that every antenna is also a transmitter. You can hook these beasties up to a power source and give off light, probably at high efficiencies and lowe temperatures as well as extrememly long lifetimes.