DOUBLY-RESONANT COHERENT COUPLING OF INFRARED RADIATION VIA INTERSUBBAND TRANSITIONS IN QUANTUM-WELLS

The influence of a strong coupling field on the linear response of a modulation-doped quantum well to a weak probe field is studied theoretically for the case when the coupling field frequencies are comparable to those of bound-bound and bound-quasi-bound transitions within the conduction subbands. Model calculations suggest that line-center reductions in the ground-to-coupled-excited-subband absorption of up to 80 % can be coherently induced with CO2 laser intensities of approximately 20 MW/cm2. The effect requires the infrared coupling field to be polarized in the growth direction, and the nature of the modifications in the linear response depends strongly on the parity and relaxation rates of the excited subband states.