We present the investigation of energy wavefunctions, dispersion profile, dipole momentum behavior, and optical gain for a nanoscale heterostructure formed with material layers of InAlAs/InGaAs/GaAsSb/InGaAs/InAlAs on a GaAs substrate. The designed structure is simulated with a 6 band k p formalism for the investigation. At room temperature, the 1548-nm wavelength has an optical gain of 2352/cm, making it suitable for NIR applications. The response of the designed heterostructure is also investigated with external temperature, strain, charge density, and electric field variations to report the tunability of the optical gain and wavelength. Due to its tunability in the NIR wavelength region, this structure can be used for different NIR applications without changing the material system.