extractor. Such an intensity pattern can
allow designers to develop very thin back-lights that, in turn, can result in significantly thinner LCD monitors and televisions.
Apart from their angular emission pattern, photonic crystal LEDs also feature
significantly enhanced surface brightness—
which makes them attractive for general
space lighting applications. A photonic crystal white LED from Luminus is targeted
at the general illumination market. This
device is a large-chip LED (emitting area
of 3 mm 3 3 mm). It demonstrates the fact
that the photonic crystal approach becomes
ever more attractive as the device area increases.
Large-area LEDs are set to replace conventional light sources in the future,
and equipping them with etched
photonic crystal patterns appears
to be the way to increase their
brightness even more.
approach is being
used to develop
for thin flat-panel
more power, while the latter allows them to
emit light in preferred directions.
Now that affordable production techniques are under development, the scene is
set for the large-scale production of these
devices for both the display and general
illumination markets. Manufacturers such
as Luminus of the United States and
LuxtalTek of Taiwan see great promise in
LEDs integrated with photonic crystal light
extraction structures. Large-area photonic
crystal LEDs may usher in the era
of general-purpose solid-state
lighting in the not-too-distant
future and thus become
one of the most familiar
devices to us. t
The principal attractiveness of photonic crystal LEDs is their combination of
enhanced brightness and a customizable
angular emission profile. The former allows these
devices to appear brighter without consuming any
The author would like to
thank the Photonic Quasicrys-
tal LEDs for Display Illumination
(PQLDI) consortium funded by the
Technology Strategy Board (TSB) for permis-
sion to reproduce the images in this article.
Phlatlite LED from
Faiz Rahman ( email@example.com) is with
the department of electronics and electrical
engineering at the University of Glasgow,
Glasgow, United Kingdom.
[ Holes in a photonic crystal ]
Atomic force microscope image of holes that form a
photonic crystal. Proper dry etching produces round
holes with vertical walls.
[ Light emission from a photonic crystal LED ]
Institute of Photonics, University of Strathclyde and Ian Watson
The anode and cathode contacts are to the right and left of
the emitting area.