Everyone’s
heard of blue lasers by now.  Some people have them in their
homes.  The reason they are important, is that blue light has
a shorter wavelength than the red lasers that were used in the first CD
and DVD devices.  The shorter wavelength means that the laser
can see smaller dots.  Smaller dots mean that more information
can be packed into the same space.  That means more
information can be put on a DVD is a blue laser is used, compared to a
red laser.

The technical details?  

Previous
attempts to make such devices used gallium nitride.  But it
turns out that plain old zinc oxide works better.  

href="http://spectrum.ieee.org/mar07/4946">Ultraviolet
lasers and LEDs made from zinc oxide are on their way
IEEE Spectrum
March 2007

…First-generation discs relying on red lasers could store about 5
gigabytes of data, and blue lasers have taken that to 50 GB. But if
disc-player laser wavelengths could be pushed down into the ultraviolet
part of the spectrum, disc densities could be hiked up to as much as
250 GB…

…A practical deep-ultraviolet LED would be especially valuable
because “if you have UV, you can excite anything in the
visible,” says David Look, director of the semiconductor
research center at Wright State University, in Dayton, Ohio.
“You could have pure red, blue, and green phosphors. Then you
excite them in any proportion to get any color.”

The key to making UV-­emitting devices is likely to be zinc
oxide: it’s a better material than gallium nitride for making
these devices, because it naturally emits (and absorbs) at those
wavelengths more efficiently. Plus it is cheap and abundant…

It
turns out that it has been a challenge to find a way to make this work,
to make devices with a useful service lifetime, and to do it cheaply.
 But the IEEE article indicates that there problems are being
overcome.  

The potential payoff:

face="Helvetica, Arial, sans-serif"> href="http://www.jetro.go.jp/en/market/trend/topic/2005_05_led.html">World’s
First Blue LED Made with Zinc Oxide

What’s more, the new LEDs also will deliver 10 times the light-emitting
efficiency. With the way now opened up for low-cost, mass-produced
LEDs, and also laser diodes and other devices using zinc oxide, it is
believed that the LED and laser diode market could expand by as much as
several trillion yen.

LEDs are used as light sources in applications requiring high
luminance, long service life and high efficiency, such as large outdoor
displays, traffic signals, liquid-crystal display backlighting and
illuminations. Laser diodes are used in infrared applications, such as
optical communications devices, and in the red through blue domain they
are used in information read/write light sources.

LED lighting is already promising, already efficient, but expensive.
 It remains to be seen how inexpensively these devices could
be made for illumination purposes, but if they are ten times more
efficient, it almost doesn’t matter what they cost.