SPATIAL FEEDBACK EFFECTS IN NARROW-STRIPE INDEX-GUIDED SEMICONDUCTOR-LASERS

We demonstrate experimentally that spatial effects of feedback are imp ortant in determining the operating characteristics of index-guided se miconductor lasers, It is in fact the inflexibility of the index-guide d mode that makes the laser susceptible to small misalignments of the external cavity, which can induce power variations of nearly 40% of th e solitary laser power with feedback levels of less than 2% (-17 dB), With a simple model, we calculate the modification of the feedback wav efront as a function of the external cavity length and shelf that the power variations are induced through changes in the cavity loss brough t on by the interference of the feedback field with the field reflecte d off the laser facet, By experimental comparison to a partly gain-gui ded laser, we conclude that these large-scale variations will be signi ficantly reduced or absent in purely gain-guided lasers.