By Peter Weiss
Etching a series of concentric ridges around the lamp-on-a-chip known as a light-emitting diode, or LED, flings forward light that otherwise would be lost to the sides or back of the device. The ridges boost an LED’s brightness seven-fold compared with the same LED without the ridges, Mark Y. Su and Richard P. Mirin, both of the National Institute of Standards and Technology in Boulder, Colo., report in the July 17 Applied Physics Letters.
The physicists used experimental LEDs that they had designed to emit infrared radiation when illuminated by an infrared laser. Su says that he expects ridges to also improve performance of standard LEDs, which emit light in response to electric current. Interference among light waves passing through the ridges bends those waves’ paths in the right direction, Su explains.