Longitudinal-mode characteristics of weakly index-guided buried-stripe type 980-nm laser diodes with and without substrate-mode-induced phenomena

We have carried out a systematic experimental study of the longitudinal-mod e characteristics of 980-nm laser diodes with a weakly index-guided buried- stripe structure at high optical output powers. For comparison, we have pre pared devices with 1.5- and 2.5-mum cladding layers. We found large differe nces in the longitudinal-mode characteristics and light output linearity be tween the two types of devices, We think that these differences result from whether or not there is coupling between the ordinary laser-mode and an un usual substrate-mode. In addition, our results show an improvement in laser diode characteristics when the substrate-mode is suppressed.