Investigations on photocurrent bi-stability of a two-color mode-locked quantum dot laser

In this paper, state-of-the-art research on two-color passively mode-locked InAs/InGaAs quantum dot lasers is reviewed with a focus on the influence of resistor Self-Electro-Optical Effect absorber biasing on emission-state transitions and on absorber photocurrent bi-stability. We start with the recently studied absorber photocurrent characteristics of quantum dot lasers with two different gain-bandwidth chirping and in particular the emissionstate-transition from sole ground-state lasing to two-color ground-state and excited-state lasing of the strongly chirped laser. By modifying the degree of chirping and the operating conditions, we extend this two-color lasing to a regime with a z-shaped emission-state and photocurrent transition. Finally, we find a z-shaped emissionstate and an absorber photocurrent bi-stability and hysteresis without the transition via a two-color operation regime. The emission-state and absorber photocurrent bi-stability and its dependences on biasing conditions are explained qualitatively.