Polarization-independent strained InGaAs/InGaAlAs quantum-well phase modulators

Polarization-independent phase modulation in In/sub 1-x/Ga/sub x/As/InGaAlAs multiple-quantum-well waveguides is demonstrated for the first time. It is shown that by increasing the Ga fraction and hence the tensile strain in the quantum well the electric-field-induced refractive index change in the TM polarization Delta n/sub TM/ can be made to approach that in the TE polarization Delta n/sub TE/. At 1.523 mu m, the ratio Delta n/sub TM// Delta n/sub TE/=1 for x=0.7 with a phase shift coefficient of 17.4 degrees /V-mm was achieved. Polarization independence was maintained over the entire range of reverse bias voltage.<
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