On-chip lamp scores a bull’s-eye

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.,