Negative group delay times in frustrated Gires-Tournois and Fabry-Perot interferometers

It is demonstrated in this paper that a Gires-Tournois interferometer illuminated with an angle of incidence greater than the critical angle for total internal reflection introduces a negative group delay time, whatever the orientation of the electric field vector of the wave with respect to the plane of incidence, when the evanescent wave in the dielectric layer is reflected by a dielectric substrate whose refractive index is between those of the incident medium and of the dielectric layer. When the evanescent wave in the dielectric layer is reflected by a nonabsorbing metal, the group delay time is negative when the electric field vector is in the plane of incidence and positive when the electric field vector is perpendicular to the plane of incidence. Similarly, a frustrated Fabry-Perot interferometer shows negative group delay times for angles of incidence greater than specific p-wave and s-wave critical angles.