Παρασκευή, 10 Οκτωβρίου 2014

The 2014 Nobel prizes: Physics: Blue's brothers

This year’s prize is awarded for work that will ultimately light up the world

THE Nobel prizes were instituted as a means to reward individuals or organisations who, as Alfred Nobel's will had it, "have conferred the greatest benefit on mankind". Often in the field of physics, the benefit is a measure of understanding of the very small or the very distant: a light shone into the vast darkness of our ignorance about how the universe is composed, and how it works. This year, by contrast, the physics prize has been awarded for an actual light. But it is a light that has already conferred great benefit on mankind, and promises yet more. Japanese researchers Isamu Akasaki of Meijo University, Hiroshi Amano of Nagoya University, and Shuji Nakamura of the University of California, Santa Barbara shared in cracking the problem of making diodes that give off blue light.

The light and the heat of fire gave way to the incandescent bulb in the early 19th century, but such bulbs still squander a great deal of electrical energy as heat. A light-emitting diode, first posited in the 1920s, accomplishes the trick of converting electrical energy with almost perfect efficiency into light. It pairs semiconductor materials that create an imbalance of electrons and their counterparts, called holes. When the twain meet, out comes a discrete burst of light.

However, LEDs tend to make light in narrow bands of colour, dictated by the properties of the semiconductor. Red LEDs proved relatively easy to manufacture in the early 1960s, but orchestrating the dance of electrons and holes to elicit green light took until the end of that decade. A blue LED required a material that hadn't been tamed for industrial use. That took until the early 1990s, when Drs Akasaki, Amano and Nakamura figured out how to make pristine films of the semiconductor gallium nitride, with just the right recipe of impurities that created electron-hole pairs suitable for a blue hue.

It would now be hard to enumerate all of the applications that make use of blue LEDs, principally because they are joined with their green and red brethren to make the light to which people are most accustomed: white. LED-based lighting is finding its way into more and more global markets as it becomes cheaper; already it is in the flash of cameras and smartphones. But blue light has made its own way as well. Blue diodes lie at the heart of DVD and the aptly named Blu-Ray players. By using the same approach, slightly more energetic ultraviolet light can be made—a boon for sterilising surfaces and drinking water using little energy. Communications and computing seem inexorably headed to a future that makes more use of light's properties, and blue light's short wavelength is best for ever-smaller technologies. As the members of the Sweden's Royal Academy of Science put it during their press conference, this year's award is more an "invention" prize than a "discovery" prize. But it is an invention, they said, that would have made Alfred Nobel happy.

Source: The Economist

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