Ultra-low voltage GaAs/AlGaAs Mach-Zehnder intensity modulators

In this paper Mach-Zehnder modulators with 0.3 V drive voltage were presented. These modulators use substrate removed very compact GaAs/AlGaAs optical waveguides for tight optical confinement and buried doped QWs as electrodes. Separation between the doped QW electrodes is only 0.15 mum. This allows the creation of very large modulating electric fields with low voltages. Such large fields create large index changes due to linear electro-optic effect and carrier depletion. Furthermore very strong optical confinement improves the optical overlap hence large material index changes can be utilized very efficiently.