PETER HAYES EXAMINES ONE OF TECHNOLOGY'S MOST UNDER PUBLICIZED ARENAS

Lasers are one of technologies most overlooked and misunderstood arenas. Without them there could be no fibre optic cables, laser/LED printers, holography or CD players - to name but four possible applications.

Infact there are figures in the industry who believe that lasers will take over from metal-based "buses" as a way of passing information through a computer. However such futuristic ideas will have to wait until another day.

The word "laser" comes from the initials of the actions a laser beam performs: Light Amplification by Stimulated Emission of Radiation. It was invented, and first demonstrated, by the American physicist Theodore H. Mainman in 1960.

At its heart, laser technology uses a particular brand of "energy packet" called a photon. These can be produced in various ways, but in essence it uses a flash unit covered in some form of man made or natural crystal.

The high burst of light transforms the crystals chromium atoms, momentarily, from it natural "low energy" state to a "high energy" state. When returning to their normal low energy state the crystal releases the all important photons.

Photons are special in that when they collide they trigger a domino effect passing on a replica of the previous model to the next photon. These "dominos" also travel in perfect straight lines. In industrial use, the red laser beam is built up of millions of these re-actions being focused and controlled by means of mirrors.

The power of lasers lies in its concentration of energy. At its most defined, powerful enough to burn through plated steel and controllable enough to be used in hospital operations.

However only selected devices need such power and most computer applications use a highly scaled down version of the process, sometimes called a semi-conductor laser.

Laser printers use these forms of low-power laser, that is invisible to the human eye, in its printing process. However nowadays many printers prefer a Light Emitting Diode (LED) process that employs highly similar principles.

Low power lasers form a vital part of telecommunications as they are the main communication medium of fibre-optic cabling. Needing little in the way of power - and therefore using semi-conductor lasers - the beam is controlled to produce short flashes of light - that is passed to the cable by way of a lens.

In CD applications the lower power laser reads the digital one's and zero's on the disc that are contained in tiny holes officially called "pits." This beam is reflected on to a device called a "photodiode" that translates the "disturbed" beam pattern into binary information. This information can be used as either computer data or translated into music or film.

Curiously holography predates lasers having been invented by the Hungarian born Professor Gabor in 1947. He combined the greek words "holos" and "grama" to mean the whole message, because it formed a complete picture.

However it would be 1961 before science harnessed lasers to create the kind of 3D image we would recognise today. A normal photography is 2D because all that is captured on film is light and shade. Holography-based photography captures depth by measuring (by laser) the distance the light has travelled and then - through a highly complicated computer procedure - translates this information to a set "fixed view" picture with small variations of the image stored in a way that they will only be displayed when the image (or human head) is moved.

The use of lasers took a sinister term with the Strategic Defence Initiative (SDI) or "Star Wars" programme - which looked for new ways of using lasers to shoot down enemy missiles from space.

For this the Americans started to develop a new form of laser using hydrogen and flourine that combines to create an extremely powerful burst of laser power.

Such a chemical formed laser - using perhaps as much as 25 megawatts of energy - could destroy an object over 2,000 miles away...