Barrier strain influence on the high-speed properties of compressively strained InGaAsP multiquantum-well laser structures

We report on an extensive experimental study of the barrier strain influence on the high-speed properties of compressively strained quaternary (InGaAsP) multiquantum-well (MQW) lasers emitting at 1.55 μm. In the design of strained MQW laser structure emitting at 1.55 μm, the main effect of varying the barrier strain amount is to modify the effective well/barrier height for both electrons and holes. In this paper, it is shown experimentally from MQW structures with different barrier strain values, that a strong decrease of the nonlinear gain coefficient can be obtained when the barrier strain is reduced, leading to quantum-well (QW) laser structures with a damping coefficient (called the K-factor) as low as 0.18 ns, i.e., theoretical damping limited bandwidth as high as 50 GHz. This result appears to be qualitatively well explained by a substantial reduction of the carrier capture time to escape time ratio, due to an increase of the well/barrier offset in the conduction and valence bands