Asymmetric double-quantum-well phase modulator using surfaceacoustic waves

摘要

An AlGaAs-GaAs asymmetric double-quantum-well (DQW) optical phasenmodulator using surface acoustic waves is investigated theoretically.nThe optimization steps of the DQW structure, which so far have not beennreported in detail, are discussed here. The optimized phase modulatornstructure is found to contain a five-period QDW active region. A surfacenacoustic wave induces a potential field which provides the phasenmodulation. Analysis of the modulation characteristics show that bynusing the asymmetric DQW, the large change of the induced potential atnthe surface and thus large modification of the quantum-well (QW)nstructure can be utilized. The modification of each QW structure isnconsistent, although this consistency is not always preserved in typicalnsurface acoustic wave devices. Consequently, the change of refractivenindex in each of the five DQW's is almost identical. Besides, the changenof effective refractive index is ten times larger here in comparison tona modulator with a five-period single QW as the active region and thusnproduces a larger phase modulation. In addition, a long wavelength and anlow surface acoustic wave power required here simplify the fabricationnof surface acoustic wave transducer and the acoustooptic phase modulator