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Light Emitting Diodes (LEDs) have
long been known for their compact bright light, robustness, environmental
friendliness and long lifetime. The market and applications for
LEDs has been growing significantly in the last couple of decades
where many barriers in efficiency and packaging have been broken.
Applications in high-brightness LEDs currently cover a diverse range
from mobile phones and automotives to display backlighting and traffic
signalling.
Dramatic growth in the sales of
LEDs is expected once the overall light efficiency of the LED approaches
that of fluorescent lighting and the vast general illumination market
is penetrated.
The cost of LEDs is currently prohibitive for many applications
mainly due to the packaging costs associated with the modification
of the light emission profile to suit the application as well as
heat management.
Photonic Crystals and LEDs
One method of increasing the light extraction efficiency from a
surface emitting LED is by the use of periodic patterning of the
diode surface. Early Photonic
Crystal patterned LED structures of this type have been shown
to increase the light extraction efficiency by several times [Erchak,
A. A. et al. "Enhanced coupling to vertical radiation using
a 2D Photonic Crystal in a semiconductor LED", Appl. Phys.
Lett. 78, no. 5, 2001, Pg 563].
Photonic Quasicrystals and LEDs
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| SEM
micrograph of a high order symmetry Pinwheel Photonic Quasicrystal
structure defined using a selection of tiling rules highlighting
the complex non-periodic orientation of the pattern. |
As well as increased light extraction efficiency extra
benefits such as tailored LED light emission profiles can be achieved
by the use of Photonic
Quasicrystal LED patterned structures. Quasicrystal patterns
are precisely defined at a small scale, but appear to lack order
when examined on a larger scale. Precise tiling rules are
employed to arrange the patterns across the surface allowing the
high symmetry nature of the quasicrystals to form bespoke far-field
emission profiles.
Mesophotonics now offers LED manufacturers a comprehensive
design service for complex photonic crystal structures for enhancing
LED emission. Based on over 10 year experience in the design
of photonic crystal structures especially those based on quasicrystals,
Mesophotonics is also able to offer licenses to its extensive IP
portfolio in this area.
Further information regarding the incorporation of
photonic quasicrystals into LEDs can be found here
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