Steven G. Johnson

A fundamental relation between phase and group velocity, and application to the failure of perfectly matched layers in backward-wave structures

Loh, Po-Ru; Skorobogatiy, Maksim; Oskooi, Ardavan; Johnson, Steven (American Physical Society, 2009-06-11)

We demonstrate that the ratio of group to phase velocity has a simple relationship to the orientation of the electromagnetic field. In nondispersive materials, opposite group and phase velocity corresponds to fields that ...