Abstract :
A sub-cyclic change in the electromagnetic properties of a medium, such as its electric permittivity or magnetic permeability, incurs angular frequency changes in the electromagnetic field propagating through the medium. Such frequency shifts have been mainly studied in context of plasmas, but rarely discussed in electromagnetics textbooks, except for the special case of the Doppler frequency shift, which is essentially a frequency change due to a moving medium (D. K. Kalluri, Electromagnetics of Time Varying Complex Media, 2nd ed. Boca Raton, FL: CRC Press, 2010). Abrupt changing in the medium electromagnetic properties in nonmoving media may thus be used to induce upshifting or downshifting in the angular frequency of the wave. This angular frequency shift is the counterpart of the wave number shift that occurs when the wave propagates through an interface between two half-spaces with different electric properties, as shown in Figure 1.
