<title>Small-signal response of a lamba/4-shifted MQW DFB laser as a three-level system</title>

Abstract

The small-signal response of a X/4-shifted multiple-quantum well (MQW) distributed feedback (DFB) laser is investigated. The gain spectrum shows two major peaks located at the lowest heavy-hole and light-hole transitions. Therefore, the MQW DFB laser is treated as a three-level system. In the low-power range the heavy-hole transition dominates, while in the high-power range there is a mixing of the heavy-hole and the light-hole transitions. It is shown that the dynamic response of the MQW DFB laser is significantly affected by the contribution due to the light-hole transition. Its dependence on the number of quantum wells and on the coupling coefficient of the grating (K) is also discussed.