Stable single filament laser action in constricted double heterostructure (CDH) AlGaAs diodes

Stable single filament lasing has been obtained from stripe contact, double heterostructure (AlGa)As devices with constricted active layers (tapered thickness active layers with a minimum thickness region). In one constricted layer geometry, the filaments appear essentially round (≲ 2 µm diameter) and do not change shape or position all the way to catastrophic damage levels (~ 85 mW/facet in pulsed operation). Observed far fields are circular with a beam divergence of about 20°. In another geometry, elliptically shaped filaments emit pulsed powers up to at least 100 mW/facet without "kinks" in the power-current profile. A model of the constricted double heterostructure (CDH) laser is outlined and utilized to discuss the design and behavior of the round filament device.