When light waves encounter obstacles, be it a crack in a window or a tiny flaw in a fiber optic cable, they scatter. A large proportion of that light scatters out of the system, but some of it scatters back toward the source in a phenomenon called backscattering.
"There is no such thing as a perfect material," said mechanical science and engineering professor Gaurav Bahl, who led the study. "There is always a little bit of imperfection and a little bit of randomness in the materials that we use in any engineered technology. For instance, the most perfect optical fiber used for long-range data transmission might still have some invisible flaws. These flaws can be a result of manufacturing, or they can appear over time as a result of thermal and mechanical changes to the material. Ultimately, such flaws set the limits of performance for any optical system."
Previous studies have shown that undesirable backscattering can be suppressed in special materials that have certain magnetic properties. However, these are not viable options for today's optical systems that use transparent, nonmagnetic materials like silicon or silica glass, Bahl said
In this study, Bahl and graduate student Seunghwi Kim used an interaction of light with sound waves, instead of magnetic fields, to control backscattering.