We demonstrate a novel piezoelectric-barrier heterostructure designed for efficient all-optical light modulation. The modulation mechanism relies upon drastic photocarrier separation by the piezoelectric field in the barrier layers. We present room temperature results showing that an optical “control” power of 70W/cm2creates in the heart of the structure a space-charge field of about 30 kV/cm, which induces large spectral shifts (≈100 nm) in the photoluminescence spectra of a CdHgTe quantum well in the 1.5 &mgr;m range. ©1998 American Institute of Physics.