20 DB CONTRAST GAAS/ALGAAS MULTIPLE QUANTUM-WELL NONRESONANT MODULATORS

We report a successful fabrication of nonresonant GaAs/AlGaAs multiple quantum well (MQW) modulators with a contrast ratio of more than 20 dB and a wide bandwidth of 3 nm. The optical path, as long as 8-mu-m, is attained by fabricating a high purity thick MQW layer with a residual carrier concentration of less than 10(14) cm-3 and introducing a high-reflectivity AlAs/AlGaAs quarter-wavelength mirror. The driving wavelengths are located at the absorption edge, resulting in the low-absorption loss.