Modal gain and lasing states in InAs/GaAs self-organized quantum dot lasers

The modal gain of an InAs/GaAs self-organized quantum dot laser is determin ed from a measurement of the normal incidence, interband photocurrent. The maximum modal gain of the ground state transition is shown to have a value of (7 +/- 3) cm(-1), considerably smaller than typical values for comparabl e quantum well lasers. The photocurrent technique is demonstrated to be a c onvenient and simple method for determining the spectral form of the gain a nd for comparing the modal gain of different devices. The consequences of t he small modal gain for the laser characteristics are discussed. (C) 2000 A merican Institute of Physics. [S0021-8979(00)09201-X].