Abstract

Unexpectedly strong damping has recently been reported for strained 1-μm single-quantum-well lasers¹ and strained 1.5-μm four-quantum-well lasers.² The damping-limited maximum 3-dB bandwidth is 4 GHz for the single-quantum- well lasers, negating the expected improvement due to enhanced differential gain. The large value of k (defined as the ratio of the damping rate to the square of the resonance frequency) is shown to be independent of the chip length and, thus, also of the carrier density in these lasers. This result, in combination with the recent finding that k varies significantly with the number of wells,³ suggests that a new mechanism causes nonlinear gain in some quantum-well lasers. To explain these findings, a mechanism is proposed involving a redistribution of carriers between the wells and the barriers caused by stimulated emission in the wells.

© 1991 Optical Society of America