Abstract

Apart from the obvious advantage of having superior DC characteristics such as an ultralow threshold current, a major attraction of quantum well lasers is their predicted advantages in dynamic characteristics. These include a very high modulation speed, a low frequency chirp (α_a- parameter) and a narrow linewidth. While the low frequency chirp and the narrow linewidth are obviously related, both of them result from a small α_a-parameter which in turn is largely a consequence of a high differential gain - the derivative of the optical gain with respect to carrier density - which is also responsible for the predicted high modulation speed. The high differential gain arises primarily from a modification of the density of states functions, and thus can be regarded as a direct consequence of the quantum confinement of the carriers.

© 1996 Optical Society of America