History
The predecessor of the atomic line filter was the infrared quantum counter, designed in the 1950s by Nicolaas Bloembergen. This was a quantum mechanical amplifier theorized by Joseph Weber to detect infrared radiation with very little noise. Zero spontaneous emission was already possible for x-ray and gamma ray amplifiers and Weber thought to bring this technology to the infrared spectrum. Bloembergen described such a device in detail and dubbed it the "infrared quantum counter".
The media of these devices were crystals with transition metal ion impurities, absorbing low-energy light and re-emitting it in the visible range. By the 1970s, atomic vapors were used in atomic vapor quantum counters for detection of infrared electromagnetic radiation, as they were found to be superior to the metallic salts and crystals that had been used.
The principles hitherto employed in infrared amplification were put together into a passive sodium ALF. This design and those that immediately followed it were primitive and suffered from low quantum efficiency and slow response time. As this was the original design for ALFs, many references use only the designation "atomic line filter" to describe specifically the absorption-re-emission construction. In 1977, Gelbwachs, Klein and Wessel created the first active atomic line filter.
Faraday filters, developed sometime before 1978, were "a substantial improvement" over absorption-re-emission atomic line filters of the time. The Voigt filter, patented by James H. Menders and Eric J. Korevaar on August 26, 1992, was more advanced. Voigt filters were more compact and " be easily designed for use with a permanent magnet". By 1996, Faraday filters were being used for LIDAR.
Read more about this topic: Atomic Line Filter
Famous quotes containing the word history:
“It would be naive to think that peace and justice can be achieved easily. No set of rules or study of history will automatically resolve the problems.... However, with faith and perseverance,... complex problems in the past have been resolved in our search for justice and peace. They can be resolved in the future, provided, of course, that we can think of five new ways to measure the height of a tall building by using a barometer.”
—Jimmy Carter (James Earl Carter, Jr.)
“All things are moral. That soul, which within us is a sentiment, outside of us is a law. We feel its inspiration; out there in history we can see its fatal strength.”
—Ralph Waldo Emerson (1803–1882)
“For a transitory enchanted moment man must have held his breath in the presence of this continent, compelled into an aesthetic contemplation he neither understood nor desired, face to face for the last time in history with something commensurate to his capacity for wonder.”
—F. Scott Fitzgerald (1896–1940)