Observations of negative resistance associated with superlinear emission characteristics of (Al, Ga) As double-heterostructure lasers

Observations are reported of the electrical and optical behavior exhibited by stripe-geometry, proton-bombardment-delineated, (Al, Ga)As double-heterostructure junction lasers, whose output power shows an abrupt, nearly discontinuous increase as a function of input current. When operated within this superlinear regime (in addition to exhibiting self-induced intensity pulsations) the output power averaged over many pulsations fluctuates randomly between levels corresponding to the intensities at either end of the superlinear range. A negative resistance which is light induced and associated with the lasing optical field accompanies the superlinearity, as does motion of the lasing filament along the junction plane. The low temperature behavior of the negative resistance shows that non-ohmic conduction mechanisms are present in the laser material. However, axially nonuniform changes in the luminescence observed through the substrate indicate that saturable optical absorption in the active layer at the laser mirror faces may be the predominate cause of the superlinearity and negative resistance. The development of these effects with aging may be arrested by mirror facet coatings applied before bonding.