Design of optimized high-speed depletion-edge-translation optical waveguide modulators in III-V semiconductors

A new first-principle theory that includes the higher order field and carrier effects in semiconductor waveguide refractive index modulators has been developed. For the first time, the relative importance of the electrorefractive, band filling, linear electro-optic, and plasma effects is shown. The theory agrees well with measurements from experimental AlGaAs/GaAs depletion-edge-translation (DET) phase modulators that have given record levels of phase shift per volt per unit length, and it suggests an improved DET device design with much larger phase shifting efficiency. The required drive voltage/bandwidth figure of merit, Vπ/ Δf, for this configuration (without including quantum wells) is lower than for any other existing optical index modulator.