The search for new applications for laser light beams

Light can blind or distort colours, or confuse one with chiaroscuros. But it can have greater usefulness if its properties, characteristics, how it is created, etcetera are better understood.

At the Department of Applied Physics at the University of the Basque Country School of Engineering they are using laser light in studies to look for new applications.

There is more than one kind of laser beam but, basically, the process of its creation is the same:

Initially, photons– light particles – are needed and, to this end, electricity or another source of light is used, for example, a flash. The photons thus created reach a state that is known as ‘active species’ their electrons being in an excited state. The photons join with the ‘active species’ electrons, thus boosting their energy levels. This situation causes the electrons to jump to a higher energy level; they are said to be in an excited state.

But the electrons cannot last very long in this state and spontaneously return to their fundamental level, thereby liberating the accumulated energy in the form of photons. These released photons have greater energy and longer wavelength than the initial photons – these liberated photons are those that create a laser light beam.

There exists the possibility that the energy accumulated by the electrons is not released in the form of photons but as heat. This happens with glass when photons from the sun’s rays hit it. The electrons in the glass are excited but, on returning to their fundamental level, they release energy in the form of heat and not as light.

The ‘active species’ photons are released in all directions, but some of these can be trapped by two mirrors judiciously juxtapositioned. A to-and-fro movement is initiated with the photons bouncing back and forth from one mirror to the other. Moreover, while they are trapped, they continue influencing other electrons, thus creating ever more high-energy photons, i.e. evermore laser light.

The released ‘active species’ photons tend to line up and group together so they have even greater energy level. When a certain energy level is reached, a series of photons escapes through one of the mirrors – this is a laser light beam, continuous and pulsating.

The colour of the laser will fundamentally depend on the ‘active species’, given that each species liberates photons of a specific wavelength, creating green, red, yellow or invisible laser beams.

In the laboratory they are investigating active species and materials by subjecting them to laser.

Knowledge of the optical properties of materials can be used for an infinite number of applications. For example, in the Applied Physics laboratory they have created crystals of a special composition that could be used in medicine. Once the size of the crystals is reduced, they can be introduced into cells as markers, in order to discriminate between different types of cells or even between components of a cell. The laser beam falling on the crystals will illuminate them thus signalling their exact position or they will initiate specific cell processes which would result in the death of cancer cells, for example. All this calls for, needless to say, precise knowledge of lasers and, above all, of the crystals to be used.

It is not science fiction, but science fact and in there amongst other, very real bodies, is the School of Engineering.