Gain Switching in Coupled Quantum Wells

Optical gain switching in coupled quantum wells is studied theoretically. Our analysis is based on the multiband effective mass theory and the density matrix formalism with the intraband relaxation taken into account. Significant enhancement of the Stark effect on the gain of the coupled quantum wells is predicted. Comparison with the single quantum well shows that the gain is substantially more reduced for the coupled quantum wells at the same electric field because of enhanced charge separation in this structure. These results may allow low-voltage operation of the recently proposed field-effect quantum-well laser.