We report the demonstration of normal incidence infrared (3–5 &mgr;m) electroabsorption modulation utilizing the Stark effect to induce &Ggr;‐Ltransitions in asymmetrically stepped AlSb/InAs/Al0.4Ga0.6Sb/GaSb/AlSb quantum wells grown on a GaSb substrate by molecular beam epitaxy. The measurements were performed using a Fourier transform infrared spectrometer at 77 K. The largest infrared absorption at 5 &mgr;m with an absorption coefficient of 3200 cm−1has been obtained at 14 V reverse bias. The results indicate the potential of this novel structure for application as a normal incidence infrared modulator. ©1995 American Institute of Physics.