Current-spreading-induced bistability in bipolar cascade vertical-cavity surface-emitting lasers

We present experimental evidence that current spreading in the cavity of two-stage bipolar cascade vertical-cavity surface-emitting lasers is responsible for the formation of bistability loops in the light versus current characteristics. The bistable behavior strongly varies with the detuning between cavity resonance and gain maximum and is attributed to the wavelength and carrier density dependent absorption coefficient. In order to explain the measured dependencies, an analytical model is presented that very well matches the light output characteristics.