Stabilization of the longitudinal mode against spatial hole burning in lambda /4-shifted DFB lasers by quantum size effect

A novel method for stabilizing the spectral properties of lambda /4-shifted distributed-feedback (DFB) lasers against the longitudinal spatial hole burning by using the quantum size effect in MQW structures is proposed and demonstrated experimentally and theoretically. The effect of the longitudinal spatial hole burning on the spectral behavior is shown to be determined by the alpha parameter, not by the differential index or by the optical confinement in the active layer. The reduction of the alpha parameter is found to be very effective in suppressing the spectral instabilities induced by the longitudinal spatial hole burning.<>