Electrorefraction in GaAs and InGaAsP and its application to phase modulators

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Abstract
A Kramers–Kronig analysis is used to calculate the refractive index change induced by changes in the shape of the fundamental absorption edge when a strong electric field is applied to a semiconductor. Calculations are made for GaAs and InGaAsP over the 0.9 to 1.55 μm wavelength range. For GaAs, we find that the electrorefraction is Δn=7.9×10−4 at λ=1.06 μm when the electric field is 400 kV/cm, but decreases to Δn=1.3×10−4 at λ=1.55 μm for the same electric field strength. For wavelengths far below the band gap, the refractive index change has a quadratic dependence on the applied electric field. The electrorefraction effect will have important applications for optical waveguide phase modulators.