  The dielectric response of transparent conductive oxides near the bulk
plasmon frequency is characterized by a refractive index less than vacuum. In
analogy with x-ray optics, it is shown that this regime results in total
external reflection and air-guiding of light. In addition, the strong reduction
of the wavevector in the ITO below that of free space enables a new surface
plasmon polariton mode which can be excited without requiring a prism or
grating coupler. Ultrafast control of the surface plasmon polariton mode is
achieved with a modulation amplitude reaching 20%.
