Beam bombs or eve-surgerv?

Previously, the road to the H-bomb was long and expensive and therefore barred to all but a handful of countries.

The development of a lasertriggered bomb would require an explosive charge, a comparatively simple and cheap laser, plus associated electronic circuitry, and some heavy water.

make a bomb of this sort.

Laser beams, a form of radiation first demonstrated in 1960, can be compared to light beams with power densities many millions of times greater than those found on the surface of the sun.

'Light' is not perhaps the right word to use, because today lasers also produce beams in the infrared and ultra-violet domains which are not visible to the naked eye.

The first laser did, however, produce a visible, red beam and the name laser—standing for Light Amplification by Stimulated Emission of Radiation - has been generally accepted.

The first laser took the form of a synthetic ruby crystal mounted between two mirrors.

When this crystal was illuminated by short, intense bursts of white light, a red light beam of enormous power started to bounce back and forth between the mirrors increasing in strength each time it passed through the ruby.

One of the mirrors was partially transparent and from this mirror emerged the intense parallel shaft of red light that was the first laser beam.

Since then a number of other crystals have been used in lasers and the technique has been extended to lasers using a gas or liquid.

Between them the various types of laser can produce beams of widely differing characteristics; some suitable for one particular field of application and some for others.

It is, for example, the ruby laser's ability to produce intense, short light pulses that makes it so useful to the ophthalmic surgeon.

The intense light pulses from a suitable laser will pass through the outer transparent regions of the eye, the cornea, the lens, etc. without causing damage.

They can then be used to 'spot weld' back into place a retina that has become detached.

No anaesthetic need be used because each weld can be completed in a few thousandths of a second.

No heat is produced: the welding is completed and the laser switched off again, long before any movement of the eye can take place.

What are the unique characteristics of laser light that makes it much more useful —and possibly more deadlythan light from conventional sources?

First of all there is its extreme directionality.

The light output from a laser is transmitted in a beam which is many millions of times more concentrated than the beam from the best searchlight.

A laser beam directed from the earth to the moon, for example, will illuminate an area only two miles in diameter on the lunar surface. Power density Secondly there is the extraordinary density of the power within the beam.

This is a result of the 'synchronized' nature of the process by which the light is generated.

Light energy is always generated in small 'packets'. Each packet is produced by a single atom in the generating material and the packets of light from the millions of atoms add together to give the total output.

In conventional light sources, the individual atoms produce their packets of energy with random timing.

In a laser each atom is stimulated to produce its packet by the packets of light from the other atoms.

It is because the emissions A laser beam can be focused to a It can selectively destroy smaller the corpuscle. dimensional photographs probably the most impressive result of the laser's properties, since such photographs possess quite unusual features.

No special glasses are required and two effects not found in conventional photographs are present. Seeing behind An observer can, by moving his position, look around objects in the foreground of the picture to see what is behind them, in exactly the same way as when viewing the original scene.

Moreover, an observer has to refocus his eyes to look at distant objects after looking at those in the foreground of the photograph!

conventional photography, all the expanding light waves reflected from each point in the object are concentrated back into a point in the plane of the photographic ilm by means of a lens.

In laser photography-called holography-laser light is used without a lens and, in effect, the light waves are 'frozen' in the emulsion on the photographic plate.

When the plate is then illuminated by laser light, the light waves are 'unfrozen' and start travelling again towards the eye of the observer.

The viewer, therefore, cannot differentiate between the reconstructed image and the real object.

The uses of lasers for communications and holography are refinements which bring us some distance from the mere ability of these beams to focus massive doses of energy onto small areas.

They have been used, with some success, in cutting, welding and drilling metal and other materials.

In the case of hard rock, a preliminary 'softening-up' with about five seconds from a carbon dioxide gas laser, causes severe damage and reduces considerably the wear on tunnelling machinery.

Man has, in the laser, found a source of radiation with qualities so unusual and unique that many years of intensive work will be needed before all its potential uses have been fully explored.

In the early 1960s, the laser was called 'a solution in search of a problem' The early 1970s may reveal it as the means for cheap thermo-nuclear oblivion - an urgent problem for mankind in search of a revolutionary solution. spot, smaller than a red i orpuscle. parts as well as the who le