[Concept] : Laser and Hologram

A laser beam can cut through steel as easily as knife cuts through butter. A laser is a device that produces a powerful beam of light. The word ‘laser’ stands for Light Amplification by Stimulated Emission of Radiation.

All lasers produce coherent light. Coherent light is very pure, which means that all the light waves have the same wavelength, they are all “in step” with one another, and they are all travelling in exactly the same direction. Laser light can be used to create three dimensional photographs called holograms.

 How a laser works

The heart of a laser is a material called lasing medium. The lasing medium is given energy, usually by an electric current or by light from device called a flash tube. The atoms of the lasing medium absorb energy and then give it out again as waves of coherent light. The light reflects back and forth between two mirrors, becoming more and more intense, until it emerges from one of the mirrors (which is only partly reflective) as a laser beam.

Application of lasers

Lasers have many uses, because they produce a powerful beam of uniform light that will not spread out over long distances and that can be directed very precisely. Lasers are used to read supermarket bar codes, play compact disks, guide weapons, and send signals along optical fibres.

Metal cutting

A powerful infrared laser beam can generate enough heat to cut through metals or to weld (join) them together by melting them.

Laser surgery

Surgeons can control lasers with great precision to burn away cancer cells or delicately trim the lens of an eye to improve a person’s sight.

Light show

Laser beams always follow a straight line, so they can be used to produce stunning visual effects at rock concerts and other special events.

Holograms

Holograms are photographs that appear three dimensional. This effect is produced by taking a photograph using two different sets of light waves from a laser beam. Holograms have many uses because they allow people to see an object from different angles.

Making holograms

To make a hologram, a laser beam is split into two parts, one called an object beam and the other a reference beam. Only the object beam reflects off the object that is to be photographed. Both beams strike a plate of photographic film, where they interfere and create a three dimensional looking image.

Famous personality

Theodore Maiman

In 1953, US physicist Charles Townes invented a device called a maser, which produced microwaves. In 1960, his fellow US physicist Theodore Maiman used the principle of Townes’ device to build a laser. Maiman’s laser used a ruby crystal as the lasing medium.