Aug 1, 2006 Nanoetching makes LEDs brighter Researchers in the
US claim to have made a resonant cavity LED (RCLED) seven times
brighter over a 130 nm bandwidth by etching circular Bragg
gratings into the device structure (Applied Physics Letters 89
033105). The technique could have applications in displays as
well as medical imaging - in particular, say the researchers,
optical coherence tomography (OCT). "We have demonstrated a 7.5x
enhancement of light extraction from a RCLED, which in turn has
an enhancement factor of 2.7x over a conventional LED," Mark Su,
lead author of the paper, told optics.org. "Whereas only around
2% of the light generated within a conventional LED can be
collected, we estimate that we harvested 41% of the light
generated within the LED." A resonant cavity is a way to improve
the light extraction of a regular LED by placing a mirror below
the active layer. However, even in this configuration, most of
the emitted light is waveguided below the semiconductor surface
and lost. "We used a