Gain switching enhancement in asymmetric coupled quantum wells

Optical gain switching is theoretically investigated in various InGaAs/InP coupled quantum well structures. Our calculations are based on the k . p me thod with 6 x 6 Luttinger-Kohn Hamiltonian and on the density matrix formal ism with intraband relaxation. Our results show that the gain of asymmetric coupled quantum wells (CQWs) is substantially reduced under electric field , compared with that of symmetric CQWs or single quantum well (SQW) structu res. This is mainly attributed to the increase of the differences in the do minant transition energies due to the enhanced Stark effect. The asymmetric structures were obtained by varying the width or the depth of the two well s constituting the CQWs. Using these asymmetric CQWs, gain switching at low er voltage can be achieved.