Solid-state lighting continues to gain popularity as an efficient replacement for conventional incandescent and fluorescent illumination. The light sources typically combine an LED that emits in the blue or near-UV with one or more phosphors that are excited by the LED and emit at longer wavelengths. When an LED is driven at high current densities, however, its efficiency falls off steeply (see Physics Today, July 2013, page 12) and the spectral outputs of the LED and the nearby phosphors shift. But as Kristin Denault, Michael Cantore, and colleagues at the University of California, Santa Barbara (UCSB), report, laser diodes are developing into an attractive alternative to LEDs. The coherent laser output doesn’t droop or shift, and the phosphors can be placed far enough away and kept cool so that their spectral contributions also remain stable. In two of the UCSB devices, a commercial near-UV laser diode excited red,...

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