Dirk Englund, professor of electrical engineering and applied physics at Columbia University, says that the dark pulses created by the scientists at NIST and JILA are similar to well-known quasi-particles called “dark solitons.” Regular solitons are pulses of light that are passed through a special optical material that keeps them from dispersing, or losing energy over a distance. Dark solitons are the “absence of energy in a continuous beam background,” Englund says.
But it is difficult to generate dark solitons, which is why the technique hasn’t been used in telecommunications, says Mirin. The setup is cumbersome, and sometimes only a single dark soliton is produced. The new dark pulse laser makes it easier to produce a soliton-like effect, says Mirin.
“While it does not appear that these dark pulses are actually solitons,” says Englund, “they are similar and could prove useful in communications and optical measurements applications.”
It is too early to promise that dark pulses will revolutionize telecommunications, Mirin says. Since today’s communications systems use bright pulses of light, optical fibers have been engineered to reduce the amount of energy lost due to dispersion, which means dark pulses couldn’t travel effectively along existing fiber. Dark pulse lasers would need their own specially engineered type of fiber. Still, he’s encouraged that the discovery of a compact and reliable source of dark pulses could open up new areas of research.