What makes laser light unusual
The word laser began as an acronym for light amplification by stimulated emission of radiation. Ordinary lamps give off light in all directions, with many wavelengths mixed together and the waves out of step with each other. A laser produces light with three useful properties.
- Nearly one wavelength. The light is very close to a single color, which matters in measurement and in communications.
- Coherence. The light waves are in step with each other, which allows precise interference effects and tight focusing.
- Low spreading. The beam stays narrow over long distances, so a laser pointer can make a small spot far away.
These properties are what make a laser a tool rather than just a bright light. A low-power laser can read a code in barcode scanners or the surface of a disc, while a high-power one can cut metal, and the difference lies mainly in power and wavelength rather than in the basic principle.
From theory to device
The theory goes back to Albert Einstein, who in 1917 described how an atom in an excited state could be prompted by passing light to release a matching photon. That idea, stimulated emission, was a theoretical result that few people thought could be exploited for decades. The same Einstein who explained the photoelectric effect, which later underpinned solar panels, therefore also set the groundwork for the laser, though he did not predict the device itself.
In the 1950s, Charles Townes and colleagues at Columbia University built the maser, an amplifier that worked on microwaves using stimulated emission. Independent work by Nikolay Basov and Aleksandr Prokhorov in the Soviet Union led to related results. In 1958 Arthur Schawlow and Townes published a paper describing how the idea could be extended to visible light. In 1960 Theodore Maiman, at Hughes Research Laboratories in California, demonstrated the first working laser using a ruby crystal. Those steps get closer attention in separate histories, so here the point is simply the sequence: a theory from 1917, a microwave device in the 1950s and a light version in 1960.
The main families of lasers
After Maiman’s ruby laser, the number of laser types grew quickly. They are usually grouped by the material that amplifies the light.
- Solid-state lasers use a crystal or glass doped with particular atoms. The ruby laser was the first. Neodymium-based lasers later became common in industry and research.
- Gas lasers use gases such as a helium-neon mixture or carbon dioxide. The helium-neon laser, demonstrated in 1960, became familiar in laboratories and supermarkets, and carbon dioxide lasers are widely used for cutting.
- Semiconductor lasers, or laser diodes, were first demonstrated in 1962 by several groups and are tiny, efficient and cheap. They drive most laser devices that people meet in daily life.
- Dye, fiber and excimer lasers fill more specialized roles, such as tunable light for research, high-power industrial work, or very short ultraviolet pulses.
A tool for many trades
Within a few decades, lasers became part of equipment in widely different fields. Without going deep into any one of them:
- Communications use laser diodes to send signals through glass fiber. Optical fibre carries a large share of long-distance data traffic.
- Industry uses lasers for cutting, welding, marking and measuring.
- Science uses them for spectroscopy, precise timing and cooling atoms.
- Medicine uses them in surgery, dermatology and eye care.
- Consumer devices use them in disc players, laser printers and pointers.
- Manufacturing uses them in stereolithography and in 3D scanners, among other machines.
Each of these has a separate history, and some are treated in their own articles on this site.
A technology that grew with its uses
When lasers first appeared, many scientists saw them mostly as laboratory instruments. The surprise was how many fields found a use for them. Part of the reason was the arrival of laser diodes, which could be mass-produced like electronic components. Costs fell, power requirements dropped and lasers could be built into products that were sold to the public.
Safety and responsibility
Lasers can damage eyes and skin, even at modest power if the beam is focused on the retina. For that reason, laser products are classified by power, and devices intended for consumers are built with limits and warning labels. Users are generally advised to follow manufacturer instructions. It is also an area where reputable regulations exist, which differ by country.
A short summary of the story
The laser is an unusual case of a device that was predicted in theory long before anyone built it, built in 1960 after years of related work on masers, and then rapidly adapted to uses nobody had clearly anticipated. Its history is a reminder that basic research often finds its applications later and in unexpected places.