In this Letter, the loss and gain characteristics of an unconventional ${\mathrm{In}}_x{\mathrm{Ga}}_{1x}\mathrm{As}/\mathrm{Ga}\mathrm{As}$ asymmetrical step well structure consisting of variable indium contents of ${\mathrm{In}}_x{\mathrm{Ga}}_{1x}\mathrm{As}$ 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 device. Unlike conventional quasi-rectangle wells, the asymmetrical step well may lead to a hybrid strain configuration containing both compressive and tensile strains and, thus, special loss and gain characteristics. The results will be very helpful in the development of multiple wavelength InGaAs-based semiconductor lasers.