Semiconductor multiple quantum well (MQW) modulators operating with incident light normal to the plane of the device are of considerable interest because they are the fundamental elements for spatial light modulators, and have the potential for being high speed, high dynamic range devices integrable with detector and control electronic circuits. Prior research on normal incidence multiple quantum well light modulators has concentrated on amplitude modulation, relying on a sufficient difference in the absorption coefficient between the on/off states at the operating wavelength to achieve useful contrasts. Such changes in the absorption coefficient have typically been effected by means of the quantum confined Stark effect (QCSE), Wannier Stark localization, or photoinduced excitonic absorption saturation. Unfortunately, thickness constraints due to growth considerations, coupled with the limitation that the maximum obtainable change in the excitonic absorption due to line broadening is .about.2.times.10.sup.4 cm.sup.-1, prevents the contrast ratio in a normal incidence MQW light modulator from exceeding a value of .about.10:1. This on/off ratio can be improved considerably by incorporation of the modulator structure within an asymmetric Fabry-Perot (ASFP) cavity which has a 100:1 contrast in a reflection electro-optic absorption modulator and a 27:1 contrast in an all-optical modulator. Conversely, optical modulators utilizing polarization rotation, such as liquid crystal and magneto-optic devices, have achieved significantly higher contrast ratios (&gt;10.sup.4 :1), but they are hampered by poor high frequency performance.