Problem: Vertical-cavity surface-emitting lasers, or VCSELs, are commonly used in telecommunications networks, but they behave in ways scientists don’t completely understand. Specifically, the polarization of the light they emit–the orientation of its magnetic field–fluctuates unpredictably. Moreover, a little optical feedback, such as light reflected from network equipment, may result in chaotic changes in the power or wavelength of the light emitted by the lasers. Engineers would like to harness all of these fluctuations to increase the data-carrying capacity of light.
Solution: Marc Sciamanna, a professor at the École Supérieure d’Électricité in Paris, has developed a theoretical explanation of the lasers’ chaotic behavior. He has also suggested different techniques for controlling VCSEL polarization and chaotic laser dynamics in general; in particular, he demonstrated that optical feedback can be used to regularize polarization. More recently, he showed that increasing the amount of noise, or random fluctuation, in the electrical current that powers the lasers would make the variations in polarization more predictable and also stabilize the chaotic output. If light polarization and chaotic dynamics were subject to engineers’ control, they could be used to encode digital information–significantly expanding Internet bandwidth.