It all started with Albert Einstein. In the early 20th century, the celebrated physicist closely studied the phenomenon of light in his research. One of his considerations revolved around the question of whether or not light could consist of individual “energy packages” (the quantum hypothesis by Planck - was already known). With the “principle of stimulated emission” emanating from these thoughts, Einstein laid the foundation for the development of a technology that we now know as laser technology. However, it was more than 40 years later that the physicist Charles Townes put Einstein’s theoretical foundations into practice in terms of stimulated emission. Stimulated emission means that a laser-active medium can briefly store energy by e.g. irradiation with light. This stored energy can be “forcefully” recovered - thus amplifying the laser beam.
Townes experimented with microwaves in the late 1940s, and in 1951 he created a device that could generate and amplify these microwaves. Based on Einstein’s theory, Townes dubbed his discovery “Maser” - an acronym for “microwave amplification by stimulated emission of radiation”. What was feasible with microwaves, i.e. the amplification by stimulated emission of radiation, should also be achievable for infrared or conventional light, knowing that with a decrease in wavelength, the cost of constructing a laser greatly increases.
However, it was several years before a “light amplification by stimulated emission of radiation,” or laser, was erected from this theory. The material needed to construct a laser was known and accessible. A flash lamp, a synthetically constructed ruby doped with chromium, and a metal sleeve finally developed the first laser through the hands of physicist Theodore Maiman in 1960. However, experts did not acknowledge this discovery immediately. Quite the contrary: When Maiman wanted to have his findings published in a journal, the editors refused to accept the text - the possibility of combining coherent light beams with high color purity seemed too trivial, too insignificant.
Throughout the years it became clear what is possible with laser technology. Now, a broad spectrum of laser systems exists. All are based on the principle that Einstein predicted in 1917 and that Theodore Maiman tested in 1960.
As soon as the principle of laser technology was known, new laser development skyrocketed. Ruby lasers were used in ophthalmology in the USA as early as 1961. Especially in medicine, the invention quickly became wide-reaching and paved the way for the age of minimally invasive surgery.
In 1962, the semiconductor laser was also studied in the USA. This ultra-compact laser may be used in continuous operation and is simple to integrate into electronic components.
Kumar Patel created the first CO2 laser system in 1964. This system utilized high beam power, and thus ideal for industrial use. Following its development, metals have been cut, drilled, marked, or welded using this laser. To this day, over 50 years after their discovery, CO2 lasers are still an essential part of contemporary production.
Since 1966, laser physics have gotten colorful. With the development of the dye laser, the wavelength of laser light along a spectrum of fluorescent dyes is openly selectable. Dye lasers have primarily been used in spectroscopy since then.
With the invention of the semiconductor laser, laser physics finally enters the mass market. Beginning in the 1980s, the new technology of photonics, a combination of laser diodes and glass fiber transmission, is fitting for mass production and secures high data speeds on the Internet today.
In 1998, the laser diodes eventually grew smaller than the wavelength of light that they emit. From then on, nanolasers have been used in data processing, medicine, or optical signal transmission.
Laser beams are capable of removing tumor tissue in the scope of laser-induced thermotherapy and are used to join detaching retina or treat varicose veins in the medical field.
In the cosmetics industry, lasers remove old, undesired tattoos or permanently remove hair through epilation. Due to the high heat radiation and the reaction outcomes of the thermally altered/destroyed color pigments, the use of lasers in removing tattoos is precarious. Nonetheless, the method is a widely established standard.
Laser machines also provide a directional beam in tunnel construction that makes the remarkably precise digging of tunneling devices possible.
The laser is also everywhere in our daily lives. They are used to burn CDs, print paper, or scan our purchases at store checkouts. Lasers are used during presentations as laser pointers or to quickly and efficiently measure distances.
In industrial applications, lasers drill, cut, mark, or weld metals. Lasers are remarkably precise even with the most complex geometries, where standard processing techniques, such as turning or milling, would fail.
Lasers are used in research to study the atmosphere or mass spectrometry to excite higher atomic or molecular states.
The concept of energy generation through lasers is still in its beginning stages. In the field of nuclear fusion, high-power lasers create extremely dense plasmas of high particle density and temperatures up to 1 million degrees. Though, it is still not clear when a stable, exothermic nuclear fusion can be established.