Observation of Spatial Dark Waves and Solitons

Abstract

In our recent research we observed a strange phenomenon whereby a beam of light passing through a rectangular grid of wires in a nonlinear defocusing medium exhibits the formation of almost identical images of the grid cell in the far-held area, instead of a linear diffraction pattern. Our ongoing research strongly suggests that this phenomenon is due to the formation of dark waves in the nonlinear medium, and even dark solitons. It appears that, unlike temporal dark solitons, spatial dark solitons can, in principle, be easily formed in a self-defocusing nonlinear medium. In particular, we observed these waves when a single wire was placed in the beam path, as well as when a grid of wires was used. These results are also consistent with our computer simulation for both the 2-D and 3-D cases. The new phenomenon may be useful in optical computing and communication systems.