Multi-quantum well distributed feedback and distributed Bragg reflector lasers
Unlike bulk semiconductors, quantum well (QW) structures exhibit unique optical features, because their band structure is completely different. In this paper, the authors review the applications of multi-quantum well (MQW) structures to AlGaAs/GaAs distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers. Theoretical and experimental results on the lasing characteristics of MQW DFB lasers are described, mainly focusing on linewidth. Reduction in the chirp and the alpha -parameter were measured, and a linewidth as narrow as 1.5 MHz was obtained. Next they review various characteristics of MQW DBR lasers. In these lasers, MQW structures were used both as an active layer and as a low loss passive waveguide. Highly efficient surface emission from the second-order grating was observed. They also measured the fast bistable switching and beam switching characteristics. In the last part they review the fabrication and characterisation of AlGaAs/GaAs quantum well wires grown on corrugated substrates.