The reduction of dumping factor at well-in-well quantum well lasers

A quantum well design for controlling of the carrier relaxation process and reducing of the gain damping effect was investigated for improvement of high speed direct modulation semiconductor lasers. The proposed Well-in-Well structure decreases the carrier relaxation time into an active well by carefully designed wave function which relates to the LO phonon scattering rate. The decrease of relaxation time and the increase of modulation bandwidth was analyzed numerically. The reduction of damping factor γ was also demonstrated by experimental measurement of the relative intensity noise spectrum.