Polarization-independent strained InGaAs/InGaAlAs quantum-wellphase modulators

Polarization-independent phase modulation in In_1-xGa _xAs/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 Δn_TM can be made to approach that in the TE polarization Δn _TE. At 1.523 μm, the ratio Δn_TM /Δn_TE=1 for x=0.7 with a phase shift coefficient of 17.4°/V-mm was achieved. Polarization independence was maintained over the entire range of reverse bias voltage