The Incredible Rocket-Engine Laser [Scanning Our Past]

Abstract

By JEFF HECHT C harles Townes's original laser proposal envisioned a low-power coherent light source for communications. Theodore Maiman's demonstration of the first laser at Hughes Research Laboratories in 1960 produced bright pulses of red light and gave great hopes for bigger and better things, especially in the Pentagon. Two years later, a Sunday newspaper supplement feature titled "The Incredible Laser: Death Ray or Hope" illustrated with science-fictional laser cannons, opined: The laser may have greater impact than any discovery so far in the burgeoning field of electronics, which has already brought us radar, transistors, satellite tracking networks, [and] TV. The technological revolution it brings about may dwarf any in the past [1]. This historical article traces the invention of the gas-dynamic laser, how it successfully generated high powers, and how it failed to meet the requirements for usable directed-energy weapons and became, in the words of one observer, "a ten-ton watch." Behind closed doors, military laboratories tried to scale up Maiman's design, in which bursts of light from a coiled flash lamp powered a tiny ruby rod. Hughes Research Laboratories tried making bigger ruby lasers (quoted in [2]). AT&T's Bell Telephone Laboratories developed crystals doped with the rare-earth neodymium, which emitted more light than ruby, but crystals were small and hard to grow [3]. Then Elias Snitzer at American Optical Company added neodymium to optical glass, first in the form of millimeter-thick fibers [4], and later-prompted by military interest-as laser rods a few inches thick [5]. Those advances led the Pentagon to budget $5 million-big money in the early 1960s-for Project SEASIDE to develop pulsed solid-state laser weapons [6]. Air Force Chief of Staff, General Curtis E. LeMay, became a laser enthusiast, briefing a reporter that a speed-of-light laser beam would be invaluable for intercepting Soviet ICBMs [7, pp. 6-7]. A firm called Technology Markets Inc. envisioned a $1.25 billion market in 1970 for "huge lasers, not unlike the anti-aircraft searchlights of World War II, that would roam the heavens, seeking out incoming missiles and destroying or diverting them with the powerful beams of light" [8, p. 25].