Bell Telephone Laboratories - Coherent Light
August 1962 Radio-Electronics

August 1962 Radio-Electronics [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

"Multichannel light highways for communications are still far from realization. But with continuous sources of coherent light available, it becomes possible to explore the problems of modulating, transmitting, detecting, amplifying and, in general, controlling light for possible communications applications." That claim was made in a 1962 Bell Telephone Laboratories (Bell Labs) info ad in Radio-Electronics magazine. More than six decades later, the job is being handled by microcircuits with integrated laser transmitters and receivers. High quality optical fiber provides information transport across the neighborhood, city, state, country and world. A big list of other Bell Labs innovations is at the page bottom. Created a century ago in 1925, Bell Telephone Laboratories' name has been Nokia Bell Labs (Finnish) since 2016, and was under the auspices of Alcatel (French) from 2006 until the sale to Nokia. Alcatel also owns Lucent Technologies. Seems the number of foundational American companies not owned by foreign concerns is dwindling into nonexistence. "C'est la vie," or I should now say "Se on elämää."

Bell Telephone Laboratories Ad

Exploring the Possibilities in Coherent Light

At Bell Laboratories, Donald F. Nelson studies a beam of coherent red light produced by a continuously operating ruby optical maser. The heart of the device is a uniquely shaped ruby crystal immersed in liquid nitrogen in the tubular glass dewar extending from upper left to center. Light from the mercury arc lamp (lower center) is reflected by round mirror at left to mirror at right and then is focused on the ruby crystal to produce maser action. Coherent light emerging from end of dewar is picked up by a detector.

Is it feasible to take advantage of the enormous bandwidth available at optical frequencies? Could coherent light, for example, be sent through protecting pipes to provide high-capacity communication channels between cities?

To study such possibilities it is, first of all, necessary to have a source of continuous coherent radiation at optical frequencies. Such a source was first produced when Bell Laboratories scientists developed the gaseous optical maser.

Recently, our scientists demonstrated the generation of continuous coherent light by solid materials. Using a crystal of neodymium-doped calcium tungstate, a material developed at Bell Laboratories, continuous optical maser action was obtained in the near infrared. It has also been attained with visible light, using a new optical "pumping" arrangement to excite a ruby crystal. (See illustration above.)

Multichannel light highways for communications are still far from realization. But with continuous sources of coherent light available, it becomes possible to explore the problems of modulating, transmitting, detecting, amplifying and, in general, controlling light for possible communications applications.

Bell Telephone Laboratories

World center of communications research and development.