Shedding light on the future

What's so special about a laser?

The word laser is an acronym as each letter making up the name stands for another word: light amplification (by) stimulated emission (of) radiation. The acronym was first used by US scientist Gordon Gould who tried, unsuccessfully, for many years to patent the laser. He did though, after years of legal battling, obtain the patents for many laser applications, and so died a rich man.

The light produced by a laser is very different from the light produced by normal sources such as a light bulb, a candle flame or the Sun. Light from normal sources is divergent, or spreads out in all directions, while the light from a laser travels in a narrow beam in one direction with very little divergence.

Laser light is usually monochromatic, which means it contains only one color, whereas ``white'' light contains different colors, and can be split into the colors of the spectrum as described by Sir Isaac Newton.

Laser light is also coherent. This means that all the individual light waves add up to make it extremely bright, unlike normal light which is incoherent.

Lasers in everyday life

Holograms are three-dimensional images which are produced using laser light. Most credit cards and some bfbank notesnf (such as the 1,000 baht note) now have holographic images to help guard against forgery, since the holograms are difficult to reproduce.

Whenever you visit a supermarket, convenience store or bookshop you will see the bar code readers which work by reflecting red laser light from the black and white bar code on the label. This light is reflected to a sensor which turns it into a digital code. This is used by the store's computer to calculate the price, print an itemized receipt and update stock records or even place an order for more of that product.

Compact discs (CD) and Digital versatile discs (DVD) have data burned onto them using a very narrow beam of laser light. The reading of the data on the spinning disc is similar to the way in which the barcode reader works, except that by focusing the laser light down to a very tiny spot the disc can be made to contain a lot more information. This information is in the form of a digital code, some of which is used to create a picture and some to create sound.

Lasers in medicine

Surgeons nowadays often use a `laser scalpel' to cut through skin and muscle. It has the advantage that it cuts quickly, with little bleeding and causes less damage to the surrounding tissue.

Lasers are used in eye surgery too. One of the most common procedures is to repair blind spots caused when the retina becomes detached from the back of the eye. There are also treatments such as Lasik surgery which involve re-shaping the cornea, the transparent front of the eye. This enables vision to be improved so that many people no longer need to wear glasses.

Dermatology, or the treatment of the skin, has advanced a great deal since the introduction of lasers. They can be used to remove birthmarks, scars, tattoos, and aging skin. The laser can be set to remove just a single layer of cells at a time, without damaging healthy cells underneath. After you've had your skin treated why not have your teeth whitened by laser too?

Other things lasers do

Lasers have been used for many years to cut materials quickly and accurately - from sheets of steel to the cloth for a suit and the individual components on a silicon chip to diamonds, the hardest material. Famously, in the film ``Goldfinger,'' a laser beam very nearly cut the hero, James Bond, in half!

Laser printers have made high quality, fast printing available to all at a relatively low cost while air pollution can be monitored by measuring tiny changes in a laser beam as it passes through the air.

The non-divergence of laser light makes it useful for pointers, but lasers are also useful in tracking satellites. A pulse of laser light is directed at the satellite and the time it takes for the reflected light to return can be used to calculate the height of the satellite. On a larger scale, the distance to the Moon has been measured very accurately in the same way, by shining lasers at special reflectors placed on the Moon by astronauts.

Lasers in the future

Laser technology has advanced a great deal. The first lasers were huge machines requiring a lot of power and large cooling systems. Today scientists are trying to make a silicon chip which could contain millions of tiny lasers. If this could be done then instead of computers using streams of electrons (electricity) to carry out their calculations they could use tiny pulses of light, greatly increasing computing speeds.

The highest power lasers are being used to start nuclear fusion reactions in the laboratory. These are the same processes that take place in the Sun, and many people think that this could be the key to future, almost unlimited, clean power for the world.

Laser light can be focused onto a very small area, so that for a short time the ``energy density'' in that area is huge, similar to the energy density just after the Big Bang. This gives physicists an opportunity to study the conditions of the very early Universe and perhaps determine its future.

One thing is for sure, even though its inventors didn't know what to do with it; the laser has become an indispensable part of the modern world and is here to stay.

Next time: Why old people squint and other facts about our eyes.

Corrin Funnell is a laser physicist with a specialty in laser spectroscopy. He has taught in the UK, Egypt, at Thailand's own Harrow International School, where he became head of the physics department. Currently, he is head of Physics at Island School, Hong Kong.