Abstract

Much blame has been placed on the high level of gain compression in quantum-well lasers as a factor for limiting the modulation bandwidth by “overdamping” the dynamic system.¹ To the extent that there are still some uncertainties in the origin of gain compression and hence in whether or not its high value in quantum-well lasers are fundamental, there is no clear path as yet to show how the problem can be overcome. However, by realizing that the dynamic consequence of gain compression is that of “overdamping,” one can correct the situation by introducing elements in the laser diode that “undamp” it. Such an element that is already well known is a saturable absorber, which with appropriate characteristics can cause self-pulsation in laser diodes.² It is shown theoretically and experimentally in what follows that within certain limits, incorporation of a saturable absorber by tandem-contact geometry in quantum-well lasers can reclaim a substantial portion of the “lost” bandwidth due to gain compression.

© 1991 Optical Society of America