Laser belongs among the younger inventions of the 20^th century. Though it will be only 40 years old the next year, it became the indivisible part of our lives.

The word itself is the abbreviation of the English expression ”Light Amplification by Stimulated Emission of Radiation”. From the name it is obvious, and from our experience we know, that the laser is an apparatus that gives off the light. It differs from the common light with the fact, that it is monochromatic and coherent and it has small divergence. The coherent light has got only one frequency and phase and we can compare it to the marching military formation, while the incoherent light is like the crowd of people moving in a chaotic way in the street.

The function of the laser is based on the principal of the induced emission, which was forecasted by Albert Einstein in 1916 already. At the end of the 20´s an English, talented physicist Paul Adrien Maurice Dirac carried out even a more detailed mathematic analysis of the quantum theory of radiation further developed the Einstein’s thoughts. But first in 1958 Charles Hard Towens, later a Nobel prize winner (for physics), carried out with his fellows the right calculations, which allowed this idea to be realised. At the end of 1959 the attention of scientists started to be attracted with ruby, one of the finest precious stones. But the scientists were interested in the fact, that the ruby shows the photoluminescence. In the summer 1960 an American physicist T. Maiman polished the end sides of the fabric ruby crystal and fitted them out with a tiny layer of silver (to work it as a mirror). After illuminating the crystal with a green light, a red ray of the laser light came through one of the mirrors. So Maiman became the creator of the first – though imperfect – laser.

Since that time the laser has been constantly developed. The individual types have been innovated during the time and their parameters have been improved. Today, we can divide lasers into different categories. According to the materials, from them the laser effect can be obtained. These are above all the consistent, hydraulic and gas lasers. The lasers can draw the energy in a optic, electric, chemical way or thermodynamically. We can also divide the lasers according to the emitted wave-length: Infra-red, in the area of the visible light, ultraviolet and X-rays. Finally we can divide lasers according to their use: Scientific, measuring, medical, technological, energetic and military.

The laser pointer (Figure from the page http://www.goaegis.com/ store/laser_pointer_store.html)

Every of these lasers found its application in a different sphere of the human activity. Not every laser is suitable for all applications. The most lasers we daily meet, are the lasers of small effort. These work continually (coherently, constantly). E.g. laser pointer, laser printer, copy-machines or CD-ROM’s mechanics. The lasers working in a continual regime are also used for data transmission.

Then the lasers are used for measuring of distances, in the eye surgery (elimination or reduction of the short sight) and the like.

For welding, cutting, digging or surgery is the effort of the laser the major characteristic, therefore the impulse-lasers are being used here. The effort of the laser depends on the length of the laser pulse. The shorter the pulse is, the bigger is the effort. The reduction of the pulse-length lead to few nanoseconds, whereby the effort of small power-stations was achieved.

However the laser fast found its application also in the military sphere (guidance of the missiles) and in the espionage sphere (laser microphone).

Though the man managed a great many of problems while constructing a laser, the man didn’t beat the nature (as for the energetic effectiveness). Because the bulb converts only 3 % of the electric energy into the light, the fluorescent lamps convert about 15 % and the laser about 20 %. And an “ordinary“ glow-worm can convert nearly 100 % of its biochemical energy into light! View to this the nature beats the man in all he has achieved so far.