In this Letter, the loss and gain characteristics of an unconventional InxGa1?xAs/GaAs asymmetrical step well structure consisting of variable indium contents of InxGa1?xAs materials are measured and analyzed for the first time, to the best of our knowledge. This special well structure is formed based on the indium-rich effect from the material growth process. The loss and gain are obtained by optical pumping and photoluminescence (PL) spectrum measurement at dual facets of an edge-emitting devi
