From blue light to white
White light-emitting diodes are replacing conventional light sources the world over. This was not possible without blue light-emitting diodes, development of which has now been honored with the Nobel Prize.
The Nobel Prize for Physics this year goes to the native-born Japanese Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for the development of light-emitting diodes (LEDs) emitting blue light.
Something that sounds so succinct and unspectacular is nothing short of world changing. The first LEDs (“Light Emitting Diodes”) appeared as far back as 1962 as signal lamps and in seven segment displays and were followed ten years later with orange, yellow and finally green LEDs. But blue light-emitting diodes were a long time coming despite a whole string of research groups around the world embarking on the quest for the “blue grail”. Initially, this was to use short wavelength blue laser diodes to make high data density storage discs such as are to be found in Blu-ray players. Nobody at the time had any inkling that the blue LED, as the missing piece of the “white” puzzle, only completed by combining the colors red, green and blue or yellow and blue, would one day stand the lighting industry on its head.
Outsider material gallium nitride
Zinc selenide (ZnSe) was long favored as a semiconductor material for developing the missing blue LED. But laser diodes made of the “difficult” material did not enjoy a long lifespan. In the late Eighties, the Nobel Prize laureates took a different tack by opting for gallium nitride (GaN), long held to be unworkable.
Isamu Akasaki and Hiroshi Amano were researching at the University of Nagoya in Japan. Electrical engineer Shuji Nakamura for his part was working at Nichia, a Japanese chemical company making lighting materials, also used in fluorescent tubes, and which therefore was initially not exactly enthusiastic about its colleague's “blue” ideas. But Nakamura pressed on and virtually single-handedly lay the technical foundations for blue light emitting and laser diodes. Whereas Nichia is now earning billions from the invention Nakamura, who nowadays teaches as a professor at the University of California in Santa Barbara, was fobbed off with a few million.
Now, twenty years on, the white LED is ubiquitous: it drives display illuminations, lights motorists way through the night and is downright revolutionizing the lighting industry worldwide.
“We owe these three nothing less than the reinvention of white light”, said Staffan Normark of the Royal Swedish Academy of Sciences in Stockholm. “Red and green LEDs have been around for years but blue was missing. When you combine these three colors, you get white light. That was demonstrated as far back as Isaac Newton”, said Per Delsing, Chairman of the Nobel Committee for Physics.
Congratulations from the LASER World of PHOTONICS on the Nobel Prize.