Researchers with Philips Lumileds have developed a monochromatic nitride diode that closes the yellow light-emitting diode (LED) gap. The phosphor-converted (PC) amber LED demonstrated by Regina Mueller-Mach and her colleagues uses the down-conversion of blue light from an indium-gallium-nitride (InGaN) LED to longer-wavelength light by a phosphor, in a variation of a well-established process for producing cold or warm white light from blue LED light.