The physicists were specifically interested in what happens to a light pulse as it travels through the array at different velocities in the presence of a defect. If the light is scattered by the defect, it means dissipative processes have occurred. If the light pulse moves through the defect without changing its shape (i.e., without losing collectivity), there is no dissipation and the light has superfluid motion. Through their calculations, the physicists showed that, for certain low velocities, the transverse motion of light is superfluid with zero dissipation. When the velocity increases, dissipative processes occur that destroy the collectivity of the light's oscillations, and superfluidity breaks down.
Wednesday, October 27, 2010
Physicists show that superfluid light is possible: In this study, Leboeuf and Moulieras have shown that a superfluid critical velocity does exist in a nonlinear medium. They explain how superfluid light can be observed in an array of waveguides. From a dynamical point of view, light propagating through a nonlinear medium is formally equivalent to a Bose gas of interacting massive particles. Light can travel straight along the waveguides in the longitudinal direction, or it can tunnel between adjacent guides in the transverse direction. The benefit of this set-up is that it allows the scientists to engineer different characteristics of the array and control the light's flow.