Asymmetric tunnel coupled quantum wells with built-in resonant second order nonlinearity were designed and fabricated within the antimonide material system. The quantum wells demonstrated intensive photo- and electroluminescence responses associated with optical transitions between two tunnel-split conduction band subbands and one valence band subband. The thickness of the tunnel barrier defined the optical gain bandwidth and resonance energy for the difference frequency generation. The test diode lasers based on asymmetric quantum wells with a conduction subband splitting of about 25 meV operated near 2.1 μm at room temperature and demonstrated high differential gain and excellent performance parameters. The experimental modal gain spectra showed relatively flat top and an extended bandwidth at high pumping levels.