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Carl --
The technical key is that LEDs and laser diodes are close "kissing" cousins, and are getting even closer. Diode lasers can emit a LOT of light, but at the moment the high power lasers are infrared. However, we should expect that to change.
Blue LEDs are, I think, based on silicon nitride, and are themselves becoming more powerful, more reliable, and less expensive every day. Some "white" LEDs are three junctions -- red, gree, and blue -- in one package. They produce white much the way a TV or computer monitor produces white. Other white LEDs use the blue (or maybe even now, UV) emissions to excite a fluorescent material, not unlike a standard fluorescent bulb.
The problem with the optics is that LED emissions are not collimated, as are lasers. The light emits in a fan-like "spray," which is not symmetrical. Special optics must be used for beam-shaping. However, it's not difficult -- it's simply different from what's used with light bulbs today.
The key, of course, is getting the brightness. But with recent LEDs producing enough bright light to be painful, I'd guess spotlight-like brightness is just around the corner.
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Don Foster (near Cape Cod, MA)
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