High-performance gain-coupled distributed-feedback semiconductor lasers with absorptive gratings

Improved characteristics of gain-coupled distributed feedback (DFB) semiconductor lasers are obtained by optimizing the duty cycle of the absorptive grating and using an absorptive conduction-type-inverted grating. Low threshold current cw operation is achieved at 10 mA lower than lasers without conduction-type-inverting. Furthermore, improved linear oscillation and a narrow linewidth are demonstrated. For gain-coupled DFB semiconductor lasers based on absorptive gratings, ultralow chirping operation under gain switching conditions is obtained for the first time.