Fiber lasers and amplifiers can do incredible things, but the technology is not as new as you think. Half a century ago, Elias Snitzer and a handful of colleagues at the American Optical Company's Research Center in Southbridge, MA pioneered both technologies. On October 26, 2012, I attended the dedication of plaque recognizing the achievement as a Milestone in electrical technology by the Institute of Electrical and Electronics Engineers.
Founded in the 19th century to make spectacles, American Optical in 1954 became the first company to try to develop practical fiber-optic imaging bundles, which were first demonstrated by academics and an independent inventor working on shoestring budgets. Initially funded by the Central Intelligence Agency to develop image scrambling bundles for secure messaging, AO later developed imaging bundles.
AO hired Snitzer to work on fiber optics in 1959. At his job interview, he recognized the puzzling patterns in a fiber bundle as evidence of lateral modes, and later published the first analysis of single-mode transmission. Interested in the laser, Snitzer took advantage of AO's glass expertise to make a solid-state laser of glass rather than crystals. He formed barium crown glass doped with 2% neodymium oxide into a three-inch rod thinner than a millimeter, covered with a low-index glass cladding to improve light transmission. Pumping with a coiled flashlamp like the one Theodore Maiman used in the ruby laser, Snitzer demonstrated pulsed lasing in the stiff neodymium-doped fiber at room temperature in 1961.
In 1963, Snitzer and Charles Koester amplified pulses by up to a factor of 50,000 in a meter-long fiber laser without reflective end coatings, coiled around a linear flashlamp. Their goal was to measure gain dynamics, but the demonstration also showed the potential of fiber amplifiers.
The lack of good pump diodes kept fiber lasers and amplifiers from being practical until the 1980s. Snitzer played an important role in that development, developing doped fiber sensors, demonstrating 1480 nm diode pumping for erbium-fiber amplifiers and developing dual-core fibers now used in high-power fiber lasers. Snitzer died in May, but lived to see developments including multi-kilowatt fiber lasers and high-speed communications through fiber amplifiers in the global telecommunications network. Four of his children who attended the Milestone dedication were pleased by the recognition of the man they knew as "dad."
IEEE Milestone for fiber lasers and amplifiers, across the street from former American Optical headquarters in Southbridge, MA. (Courtesy of Dick Whitney)
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