It's a sunny day on the campus of the University of California, Santa Barbara, but little light penetrates the labs and offices of Shuji Nakamura. Shades sheathe the windows in part because, Nakamura says, "I worry about unknown people around here-that they will include a spy."

That sounds farfetched until you consider that Nakamura, who played a lead role in the development of blue light-emitting materials, is now back for a second act. In the 1990s Nakamura gained fame by cooking up the first semiconductor materials to emit bright blue light-a boon for displays and data storage-and sparked a global race to perfect the materials. He made those trailblazing lasers and their glowing cousins, light-emitting diodes (LEDs), at Tokushima, Japan-based Nichia-and became a sort of national folk hero in the process. (When Nakamura is in Tokyo, subway riders accost him for his autograph.)

Now, having moved to an academic post in the United States, he is at it again-caught up in an intense worldwide competition. That's because the bright blue emitting devices that are the progeny of his original inventions provide a key stepping stone in a high-stakes effort to produce white-light LEDs that are sufficiently cheap, pleasing, and efficient to crush Edison's almighty light bulb-and radically transform the
$40 billion general-illumination industry.

Briskly crossing a courtyard, Nakamura enters a semiconductor test room, and grad student John Kaeding hands him a plastic container bearing a translucent Oreo-size disc. Nakamura sits on a stool and touches a test electrode to a spot near the disc's center. The disc is made of sapphire and coated with at least 30 invisibly thin layers of materials whose fundamental workings are not fully understood but whose properties astonish. Instantly, a bluish-green glow emanates. Nakamura lifts the electrode and touches a spot closer to the disc's edge; it shines a grassy green. A third spot is dimly aquamarine; a fourth, violet; a fifth, bright blue-the color needed to create a solid-state device that produces white light.