Spontaneous emission factor and waveguiding in GaAs/AlGaAs MQW lasers

The waveguiding properties of gain-guided GaAs multiple quantum-well (MQW) lasers are investigated. Near- and far-field measurements reveal that gain guiding is much stronger in the MQW lasers than in conventional double-heterostructure lasers. The index antiguiding, however, is of the same strength in both types of lasers. Due to the altered lateral waveguiding, the astigmatism factor K is very low in the MQW lasers and has a value of K=3. As a consequence, MQW lasers exhibit very narrow far fields ( theta /sub 11/ degrees ), nearly single longitudinal mode operation with a sidemode suppression ratio of 1/10 and a low linewidth enhancement factor alpha =2.< >