ELECTROOPTICAL MODULATOR USING INTRASUBBAND ABSORPTION IN A QUANTUM-WELL STRUCTURE.

Intrasubband electrooptical absorption in a quantum well with a uniform electric field has been calculated. Calculation shows that, compared to the exciton absorption, intrasubband electrooptical absorption has two distinct features for the dominant transition of states 1-2: (1) The absorption peak for the intrasubband absorption increases in energy with an increasing electric field over a wide range; For exciton absorption, the energies of the ground states of both the electrons and holes decrease, so the absorption peak decreases in energy with an increasing electric field (2) The absorption peak for intrasubband absorption also increases in magnitude with increasing electric field, so the absolute value of the overlap integral for the 1-2 transition increases. For the exciton absorption, the increasing electric field causes further separation of electrons and holes in the well and the decrease of the energy difference between the electron and hole ground states, the absolute value of the overlap integral decreases. The forbidden transition 1-3 when F equals 0 becomes allowable with an applied electric field. the basis of these physical phenomena, an IR modulator making use of intrasubband absorption has been designed.