LIGHT EMITTING DIODES
The Chou group at Princeton fabricated emitting structures with gratings with no effect on
performance , clearly differentiating imprint from conventional patterning. They also showed
that the dye molecules oriented on imprint (Wang 1999-2).
A group at ITES have shown that the light output from OLEDS can be increased by adding
imprint structures (Kozaki 2005)
Lumileds have shown that photonic crystals can be used to increase the light output from
LEDS's (Wierer 2004). These were fabricated by electron beam direct write, a much lower
cost manufacturing process in needed for this to be a viable solution for lighting
applications. One of the challenges for imprint on LED is that the wafers are typically non flat
in part due to thermal expansion mismatch between the active layers and substrates either
silicon carbide or sapphire.
This is one of the most exciting opportunities for imprint. The latest developments in
increased light output are described in Strategies in Light 2006 conference report.
Heptagon have described how imprinted micro-optics can be used in LED packages
(Stager 2004, and Rossi 2006)
Toshiba reported improved light output using a self assembled block copolymers to create
the pattern (Fujimoto 2005).
Polymeric solar cells with controlled phase separation have been reported by (Brabec 2000
CNRC have built plastic solar cells by direct imprint (Cui 2004)
A team at National Taiwan University have reported some very high efficiency solar cells
devices that structured surfaces to improve coupling into surfaces (Chen 2005)
A team from University of Electro communications have created nanotextured TiO2 for solar
cells (Diguna 2005 and other papers in conference), suggesting an opportunity for imprint.
The Chou group have reported on Ga As photdectors have been fabricated by imprint
Omron described an in house thermal S&R tool that would imprint on 1 x 1 meter display
glass. They showed 2 tiered imprints with 100 nm wide 200 nm high posts on 10 um wide
bars (Okuno 2005). The devices were designed as a light guide for cell phone displays.
Other opportunities in displays include orientation of liquid crystals (Sharf 2002), and
fabrication of devices such as OLED's.
One ultimate dream is an all plastic display combining OLED's or LC's, drive electronics
with organic TFT, and backlight.
Discussed in Storage
Camera chips have an insitu micro lens made by a reflow process. Imprint would seem
solution for improved feature control.
A team at CSEM have integrated optics into VCSEL's (Gimkeiwitz)
A team at U Denmark built a polymer micro dye cavity laser fabricated by imprint (Nilsson
Fabrication of dual grating reflectors for high power laser diodes by a team from U Central
Florida (O'Daniel 2006)
Tunable microcavities in planar photonic crystals from U.Neuchatel (Marki 2006).
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Optical Device Applications