PS Builds a LASER …and so can you

The incredible ruby ray is the hottest scientific discovery of the decade, but practical uses are still scarce. Here’s your chance to join the search

-June, 1960: Dr. T.H. Maiman, of the Hughes Aircraft Co., reports the development of the first successful ruby laser.
—November, 1964: Popular Science publishes plans for the first do-it-yourself ruby laser.

By Ronald M. Benrey

IT MAY sound like science fiction— but it’s really science fact: You can build a working ruby laser. It could be the most challenging—and rewarding— home-workshop project that you have ever tackled.

A ruby laser is a source of coherent light. All of the light waves in the pencil-thin, bright-red ruby laser beam are in phase—or in step—with each other. This extraordinary property of the laser beam—shared by no other light source—has spurred a world-wide search for practical uses.

Ordinary light sources—a light bulb, for example—generate incoherent light; the light waves are out of phase with each other.

Drop a pebble into a still pond, and the waves ripple out smoothly in all directions. This represents a single light wave from a light source. All light sources produce more than a single wave, however.

They act as if you dropped a handful of pebbles at once: You get a jumbled clutter of waves one on top of another. This clutter of waves is analogous to incoherent light.

Suppose, though, you dropped your handful of pebbles one pebble at a time, each in exactly the same spot in the pond. The waves would continuously radiate from that point. All of the wave crests would be in phase. This is coherent radiation.

A ruby laser generates a coherent light beam by a similar process. Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. Inside the ruby laser rod—heart of the ruby laser—excited atoms are stimulated to emit light waves in phase with each other.