We present a two-color (956 and 985 nm) InGaAs/AlGaAs laser structure epitaxially stacked through a low-resistance (10(-5)-10(-4) Ohm cm(2)) Esaki junction, exhibiting two threshold characteristics. It is shown that this structure can be considered as a bipolar cascade laser. (C) 1997 American Institute of Physics. [S0003-6951(97)00952-2].