An optimised AlGaAs/GaAs multiple quantum well phase modulator

Slab waveguide devices were fabricated from material grown by MOVPE, and measurements of phase change at 863 nm and contrast were made on a device 385 mu m in length. The experimental results and those predicted from the model, including the linear electro-optic effect (LEO) from the whole of the depletion region, are shown. At 6 V bias the predicted phase shift is in error by a factor of 1.7 or 0.83, depending on the sign of the LEO, and the contrast is predicted to within a factor of 1.4. As a comparison with the characteristics of the first sample modelled above, the measured results in the optimised device give a ratio of phase change to contrast of 43.6 at 6 V. In the unoptimised device for 2.5 V, the highest bias used, the phase change is 45 degrees , and the contrast is 4.4. Normalising these values to the length predicted by the model to give 50% absorption in this device gives a figure of merit of 9.2.<
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