Polarization Effects on the Brightness Waves of Electroluminescence

Electroluminescence excited by sinusoidal fields yields two maxima per half-period of the field. The intensity ratio of these maxima depends on field frequency and on the superposition of ultraviolet-excited luminescence. These observations are shown to be related to the existence of polarization effects, which are treated theoretically by extending previous theories of polarization effects in semiconductors (Jaff\'e and others), taking into account periodic excitations of centers by the field.