1917

Laser

Albert Einstein (1879–1955)

Laser pointers, laser scanners, laser printers, giant laser weapons … Why are lasers so common? A good part of it comes in the name: Light Amplification by Stimulated Emission of Radiation, or LASER. The Stimulated Emission part is important: laser light is usually a single, pure color with a single phase and a narrow beam that stays that way over long distances. As light goes, this is about as organized as it gets. Light from a normal bulb has photons with all different colors, all different directions, and all different phases.

When engineers got hold of organized laser light, they were able to do things they could not do with disorganized light. For example, the tight beam of the laser lets engineers shoot it at a tiny spot on the mirror surface of a DVD or CD and see whether the light reflects off cleanly. If it does, that represents a 1, if not, a 0. The tight beam and concentrated light also lets a laser cut paper, wood, or metal very precisely. The beam can contain hundreds of watts of power all concentrated into a pinprick of light.

Lasers make fiber optics possible. The basic idea is simple—a light at one end of the fiber turns on and off to send 1s and 0s to the other end. Lasers can switch on and off very quickly. The focused, powerful beam can travel dozens of miles through modern fiber before needing a repeater. And because of the precise color, it is possible to put multiple colors of laser light through the same fiber to multiply capacity. Massive amounts of data can flow through a single fiber—something that would be impossible without lasers.

Laser light shows us something interesting about engineers. Once the fundamental discovery is made (in this case by Albert Einstein, who set down the foundations for lasers and masers in a paper published in 1917), engineers often find many different ways to exploit it. The original laser sources were quite crude. Engineers find ways to make them smaller, faster, brighter, cheaper. These improvements open up new uses for lasers, and soon we find that engineers have built lasers into hundreds of products. It’s the engineering way.

SEE ALSO Compass (1040), Trinity Nuclear Bomb (1945), Fiber Optic Communication (1970).

The laser guide star (LGS) at Yepun, one of the four individual telescopes that comprise the Very Big Telescope (VBT) in the Atacama Desert in Chile.