We report on the electric-field dependent band-gap energy and near-gap absorption coefficient of a specially designed strained-layer superlattice (SLS) employing tensile strained quantum wells and having a band-gap wavelength near 1.3 &mgr;m. The SLS was grown by molecular-beam epitaxy on an InP substrate and consists ofIn0.43Ga0.57Aswells (4.5-nm-thick) andIn0.6Al0.4Asbarriers (6.75-nm-thick). For applied fields from zero up to at least2.5×105 V/cm, the band-edge absorption exhibits a single peak, which we attribute to a field-independent superpositioning of the heavy- and light-hole ground states. This result agrees with tunneling resonance calculations, which predict these hole states to have the same zero-field energy and to undergo nearly identical Stark shifts. Absorption–coefficient changes of up to104 cm−1were readily achieved with applied biases under 15 V, suggesting potential applications to optical modulator devices. ©1997 American Institute of Physics.