EurekAlert December 8, 2020
Researchers in the UK re-examined the refractive index and found a general way to calculate the direction-dependent refractive index and the condition for zero index in a given direction. By analogy with linear versus circular polarization, they showed that when the zero-index direction is complex-valued, a material supports waves that can propagate in only one sense, for example, clockwise. They showed that there is an infinite family of both time-reversible and time-irreversible homogeneous electromagnetic media that support unidirectional propagation for a particular polarization. The work extends the concept of the refractive index, shedding new light on the understanding of topological photonics and providing new sets of material parameters, and reproduces many of the findings derived using topology…read more. TECHNICAL ARTICLE
Dispersion relation and polarization for electromagnetic waves in materials as the index is reduced to zero. Credit: Nature Physics (2020)