Effect of excited-state-mediated capture of carriers into the lasing ground state on the modulation bandwidth of quantum-dot lasers with asymmetric barrier layers

Abstract

The parasitic electron-hole recombination outside of a quantum-confined active region still presents a challenge in conventional injection lasers. The use of asymmetric barrier layers (ABLs) (one on each side of the active region) should efficiently suppress this recombination. However, even in lasers with ABLs, excited states may be present in the active region in addition to the ground state. Excited states may strongly affect delivery of charge carriers to the lasing ground state. In this work, dynamic properties of quantum dot (QD) lasers with ABLs are studied in the presence of excited states in QDs. The situation is considered when the carrier capture into the lasing ground state in QDs is excited-state-mediated. It is shown that the modulation bandwidth of the ABL QD laser can be considerably impacted by excited-to-ground state relaxation delay in QDs. Hence a strict control of the intradot relaxation time will be required to enhance the modulation bandwidth in ABL QD lasers.