Modulation of visible light by AlAs-AlGaAs multiple-quantum-well p-i-n structures

We report measurements on the modulation of visible light by a multiple-quantum-well (MQW) modulator designed for normal incidence. The MQW structure is composed of AlAs-Al/sub x/Ga/sub 1-x/As with an Al concentration x=0.41. The structure exhibits an exciton absorption peak at 608 nm in the visible part of the spectrum. The phase and amplitude modulation properties of this structure mere studied using a Michelson interferometer that employed a novel double lock-in detection technique. Phase and amplitude modulation were studied as a function of the wavelength to determine their maxima. In our structure, phase modulation up to 200 and amplitude modulation up to 8% were observed. These values are comparable to what is typically achieved by using waveguide geometry.