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:
“Throughout the history of commercial life nobody has ever quite liked the commission man. His function is too vague, his presence always seems one too many, his profit looks too easy, and even when you admit that he has a necessary function, you feel that this function is, as it were, a personification of something that in an ethical society would not need to exist. If people could deal with one another honestly, they would not need agents.”
—Raymond Chandler (1888–1959)
“Boys forget what their country means by just reading “the land of the free” in history books. Then they get to be men, they forget even more. Liberty’s too precious a thing to be buried in books.”
—Sidney Buchman (1902–1975)
“In history the great moment is, when the savage is just ceasing to be a savage, with all his hairy Pelasgic strength directed on his opening sense of beauty;—and you have Pericles and Phidias,—and not yet passed over into the Corinthian civility. Everything good in nature and in the world is in that moment of transition, when the swarthy juices still flow plentifully from nature, but their astrigency or acridity is got out by ethics and humanity.”
—Ralph Waldo Emerson (1803–1882)