College Park, MD--Optical amplifiers used in fiber-optic communications—including, of course, the ubiquitous erbium-doped fiber amplifier (EDFA)—are typically doped with rare earth elements, commonly erbium and ytterbium. Many other combinations of elements have been tried in pursuit of amplifiers operating in different communications wavebands. However, obtaining effective signal amplification with those rare-earth ions is challenging and requires advanced materials and manufacturing. And to be commercially useful, the glass must be both stable and low-loss, requiring little energy to boost signals.
Raising quantum efficiency
An experimental glass developed by a team from Dalian Polytechnic University (Dalian, China) and the City University of Hong Kong solves some of these manufacturing problems. The researchers incorporated heavy-metal and alkali/alkaline earth elements such as lead, bismuth, gallium, lithium, potassium, and barium in an oxide glass doped with trivalent samarium (Sm) rare-earth ions. Among oxide glasses, the maximum phonon energy of these materials is among the lowest, which may induce multichannel fluorescence emissions and significantly enhance Sm-ion quantum efficiency.
In laboratory tests, the Sm glass released IR energy at a wavelength of 1185 nm—within the window of fiber-optic telecommunications—as well as other wavelengths. The results, reported in the Journal of Applied Physics (published by the American Institute of Physics), indicate adding Sm to heavy metal gallate glass is worth exploring for use in both fiber-optic networks and lasers. See http://jap.aip.org/.