Abstract The effects of large deformation have been studied by preparing thin (20–30 μm) membranes with quantum-well layers on top. A small gas pressure of a few bar deforms the membrane substantially and changes the optical spectra of the quantum wells. Tensile and compressive strains can be obtained. Biaxial deformations can be studied in the middle of the membrane, uniaxial deformations at its edge. We present the results of the photoluminescence and absorption from GaAs/AlGaAs and from InGaAs/GaAs quantum wells.