History of laser technology

In the beginning there was: Albert Einstein.!! In the early 20th century, the famous physicist during his research, began to closely examine the phenomenon of light. One of his considerations centred around the idea that light could possibly be made up of individual “energy packages” (the quantum hypothesis by Planck - was already known). This resulted in what then became known as the “principle of stimulated emission”. It was upon this principle that Einstein laid the foundation for the development of the technology that we now call laser technology. However, it was more than 40 years later that the physicist Charles Townes actually put Einstein’s foundational theory into practice in terms of stimulated emission. Stimulated emission means that a laser-active medium can temporarily store energy. e.g. irradiation with light. This stored energy can be “forcefully” retrieved, creating the amplified laser beam.

From maser to laser

In the late 1940s, Townes started experimenting with microwaves and in 1951 he constructed a device that could generate and amplify these microwaves. Based on Einstein’s theory, Townes named his discovery “Maser” - an acronym for “microwave amplification by stimulated emission of radiation”. What was possible with microwaves, i.e. the amplification by stimulated emission of radiation, should also be possible for infrared or conventional light, knowing that as the wavelength decreases, the cost of constructing a laser greatly increases.

However, it was still a few more years before a “light amplification by stimulated emission of radiation”, or laser in short, was actually constructed based on this assumption. All the material required to build a laser was already known and available. A flash lamp, along with a synthetically manufactured ruby doped with chromium and a metal sleeve finally formed the first laser in the hands of the physicist Theodore Maiman in 1960. However, experts did not pay much attention to this discovery straight away. Quite the opposite: When Maiman attempted to have his findings printed in a journal, the editors refused to accept the text - the idea of combining coherent light beams with high color purity seemed too irrelevant and too meaningless.

It was only over the course of many years that it finally became clear what was truly possible with laser technology. Nowadays, a very broad range of laser systems exist. And all of these lasers are based on the same principle that Einstein predicted possible in 1917 and that Theodore Maiman experimentally demonstrated in 1960.

Evolution of the laser from the 1960s

Once the principle of laser technology was known and understood, the speed of development increased greatly. As early as in 1961, a ruby laser was used in opthalmology in the USA. It was not long before multiple uses were found for the invention and it quickly became popular, particularly in medicine as it heralded the age of minimally invasive surgery.

Just one year later, in 1962, research was being carried out in the USA on the semiconductor laser. This ultra-compact laser is capable of continuous operation and is easily integrated into electronic components. Due to the need for high laser beam power in industry, the first CO2 laser was invented by Kumar Patel in 1964. Ever since then, the CO2 laser has been used to cut, drill and weld metals. Today, more than 50 years after they were first discovered, CO2 lasers have become an indispensable part of modern day production. From 1966 onwards, laser physics became colourful with the development of the dye laser. This wavelength of laser light can be selected anywhere along a spectrum of fluorescent dyes. Since then, dye lasers have mainly been used in spectroscopy.

The laser becomes a commodity

The CDs and CD-ROMs that were made possible from 1972 onwards have now almost become extinct. The invention of the semiconductor laser, finally enabled laser physics to penetrate the mass market. Thus, from the 1980s onwards, the mass production of the advanced technology of photonics, a combination of laser diodes and glass fiber transmission, has ensured the high data speeds that we enjoy over the Internet today.

Finally, in 1998, laser diodes became even smaller than the wavelength of light that they emit. Since then, nanolasers are being used in data processing, medicine and optical signal transmission.

The laser in use today

In the medical sector, lasers are utilised to remove tumour tissue in the field of laser-induced thermotherapy, and are also used to reattach detached retinas and treat varicose veins.

In cosmetics, lasers are being used to remove old, unwanted tattoos and for permanent removal of hair through epilation. However due to the high tempertaures of heat radiation and the reactive products of the thermally altered/destroyed colour pigments, the use of lasers in removing tattoos can be risky. Nevertheless, this method has largely established itself as a standard form of treatment.

In tunnel construction, a directional beam produced by a laser provides the tunneling machines with the high accuracy and precision necessary for this process.

Further applications of laser machines

The laser is omnipresent in our everyday lives. The laser light beam burns our CDs, prints our paper or scans our purchases at the supermarket checkout. Lasers support visual presentations as laser pointers or are used to quickly and accurately measure distance.

In the industrial sector, various metals are drilled, cut, marked or welded all by the means of a laser. Where conventional processing methods such as turning or milling would fail, lasers are extremely precise even with the most complex geometries.

In research, lasers are used in mass spectrometry to excite higher atomic or molecular states or are fitted in instruments that are used to study the atmosphere.

The idea of energy production through lasers is still in its infancy. In the field of nuclear fusion, high-power lasers can produce extremely dense plasmas of high particle density and temperatures up to 1 million degrees. However, it is still not yet clear, when a stable, exothermic nuclear fusion could be established.