The Prize:
The 2009 Nobel Prize in Physics, shared between Charles K. Kao “for groundbreaking achievements concerning the transmission of light in fibres for optical communication” and Willard S. Boyle and George E. Smith “for the invention of an imaging semiconductor circuit—the CCD sensor.”
The Science:
Modern communication (the Internet, telephone lines, cable television, and even medical imaging) is almost entirely dependent on fibre optic cables. Coupled-charged devices (CCDs) are important in research and industry, but are also the technology behind your vacation photos and favourite Youtube clips.
Talking With Light
History is full of beautiful examples of how light can be trapped in glass and water, such as the coloured glassware and crystal chandeliers.
Light can be trapped in water or glass because it travels slower in these media than it does in air. When light enters a glass of water, it slows down, causing the light beam to change direction. This explains why a straw in a glass of water looks like it has split in two. However, if the light comes from within the water out towards the air, much of the light bounces off of the surface of the water and is trapped within the aqueous substance.
Since the 1930s, doctors had been using thin glass rods to transmit light down a patient’s throat to view their stomachs, or to illuminate teeth in dental surgery. However, these glass fibres were only practical for use over short distances. They often “leaked” light, and most of the light dissipated after only a few metres.
The invention of the laser provided scientists with a beam of light that could be flashed on and off, creating the ones and zeros of binary code and providing a method for communication transmission. All they needed was a fibre that wouldn’t leak light over long distances and they would have the technology for optical communication.
When Shanghai-born engineer Charles K. Kao began working in the field of communications, the idea of light being used as a communication signal was only beginning to get attention. Communication in the 1950s and ’60s was largely via electronics or radio waves. Light was thought to be a better option than the status quo because the speed and frequencies of light lend themselves well to signal adjustment. But how to transmit the light signals over long distances?
In the 1960s, Kao began studying glass fibres at the Standard Telecommunications Laboratories. With the help of junior colleague George A. Hockham, he set a goal to improve the transmission of light through optical fibers to one per cent transmission over one kilometre. If he could meet this goal, optical communication would become feasible.
They soon discovered that poor transmission rates were a result of impure glass, and in 1966 proposed using purer starting materials for new fibres. In 1971, the American company Corning Glass Works unveiled a one-kilometre-long optical fibre that could finally promise practical transmission rates.
Today, the world has been wrapped many times over in optical fibre. It is light, strong, and flexible and can therefore be buried or run underwater, which is important for trans-Atlantic communication. Transmission rates today are as high as 95 per cent over one kilometre, leagues above Kao’s initial one per cent goal, and the amount of information travelling at the speed of light through these cables increases every day. The Internet would not be possible without them.
Much of the information travelling along the world’s optical fibres originates in devices using technology that was awarded the second half of the 2009 Nobel Prize in Physics.
The Death of Film
The CCD is today’s most popular electronic eye. You can find them in digital cameras, video recorders, microscopes, telescopes like the Hubble, and the Keppler satellites.
In 1970, Willard Boyle and George Smith, who worked at the famous Bell Labs, were approached by their boss to develop a memory device that could out-compete a device developed by another group at Bell Labs. Boyle and Smith sketched out the theory and math behind the CCD in one afternoon, and a prototype was built within a week. Although it was originally designed as a memory device, the CCD’s capabilities as a camera soon took centre stage.
The CCD uses the photoelectric effect (which won Einstein a Nobel in 1921) to sense light. A stamp-sized silicon plate acts as the light sensor that covers millions of tiny wells called photocells that are arranged in a grid. When the sensor is exposed to light (like when you open your camera’s shutter), this excites electrons in the silicon plate. These then release and collect in the photocells below. The amount of light the silicon plate is exposed to results in more or less electrons collecting in the photocells. Applying filters to the CCD can allow it to sense the colour of light shining on it.
When voltage is applied to the photocell array, the electrons can be read, converted to binary code, and used to recreate an image. Each photocell read from the array corresponds to a pixel in the final image. Early cameras and video recorders enabled with CCDs were bulky and expensive, but the drive towards an ever more digitized world pushed down cost and drove the engineering behind smaller and more efficient camera technologies.
Today, the light sensitivity and amazing resolution power of the CCD allows us to see the very small and the very large, the bottom of our oceans, and the surface of our neighbouring planets.
What You May Not Know:
Willard Boyle was born in rural Nova Scotia, and grew up in a remote logging town in Quebec where he was home schooled by his mother until he was 15. His early life shaped his desire to succeed. Although best known for his contributions to the CCD, he also helped develop the first continuously operating ruby laser (now used for tattoo removal) and the semiconductor lasers that are used in CD players. He also worked on the NASA Apollo program that put man on the moon.
