News | April 1, 2002

The Airborne Laser from Theory to Reality: An Insider’s Account

By Hans Mark Defense Horizons 12

Introduction and Scientific Background 

Defense Horizons 12Albert Einstein spent World War I in Berlin, where he developed a theory that described electromagnetic radiation in equilibrium with atoms that could emit and absorb radiation. The innovation in Einstein’s work, which was published in 1916 and 1917, was that he used the newly developed quantum theory to obtain his results. The most important result was not only that the atoms in the assembly could absorb and emit radiation spontaneously but also that atoms in certain excited states could be induced to emit radiation.1 Einstein called this discovery the stimulated emission of radiation. Einstein’s discovery provided the basis for the development of lasers, though the phenomenon would not be observed in the laboratory for many years. 

The development of radar during World War II required intensive research in microwave radiation. The need for highly sensitive radar receivers led to isolating and observing for the first time Einstein’s stimulated emission of radiation. In 1954, Charles H. Townes, J.P. Gordon, and H.J. Zeiger were the first to amplify a microwave signal by using stimulated emission.2 They called their device the maser, which stood for Microwave Amplification by the Stimulated Emission of Radiation. This work led many to speculate about applying the same principles to radiation in other regions of the electromagnetic spectrum. This effort turned out to be successful, and 6 years later, a positive result was achieved with visible light.

READ MORE >>