Diodes, devices which control the flow of electricity, are used in instruments for detecting, measuring, and studying microwave radiation. The Maser and the Laser Discoveries Townes and other scientists wanted to obtain stronger radiation with even shorter wavelengths using sources other than vacuum tubes. In 1916 Albert Einstein had shown theoretically that atoms stimulated by radiation could emit, as well as absorb, radiation. In 1951 Townes showed how useful radio waves only a centimeter long could be obtained form ammonia molecules. On display is a focuser from one of Townes' earlier maser set-ups.
All gases contain some high-energy molecules.
As molecules inside the cavity return to a lower energy level, they release microwave radiation. This radiation, reflecting inside the cavity, stimulates additional molecules to radiate energy. This process amplifies, or intensifies, the microwave radiation, which is then emitted. Other scientists developed masers based on Townes' research and proposals. Nicholaas Bloembergen, at Harvard, provided an idea for an effective solid-state maser.