Abstract: A solid state, electronic, optical transition device includes a multiple-layer structure of semiconductor material which supports substantially ballistic electron/hole transport at energies above/below the conduction/valance band edge. The multiple layer structure of semiconductor material includes a Fabry-Perot filter element for admitting electrons/holes at a first quasibound energy level above/below the conduction/valance band edge, and for depleting electrons/holes at a second quasibound energy level which is lower/higher than the first energy level. Such an arrangement allows common semiconductor material to be used to produce emitters and detectors and other devices which can operate at any of selected frequencies over a wide range of frequencies.