Dispersion of Generalized Surface Phonon Polaritons on α‐Quartz Observed by Attenuated Total Reflection

Real and virtual excitation generalized surface polaritons are investigated on a 45° cut of an α‐quartz crystal. For the wave vector of the surface polariton coplanar with the normal to the surface and the optical axis they are transverse magnetic polarized extra‐ordinary waves. The experimental results agree with calculated dispersion curves. By attenuated total reflection for transverse magnetic polarized radiation it is shown that virtual excitation generalized surface polaritons exist only for certain ranges of the angle between the surface and the optical axis.