POLARIZATION-INDEPENDENT STRAINED INGAAS/INGAALAS QUANTUM-WELL PHASE MODULATORS

We demonstrate for the first time polarization-independent phase modulation in In1-xGaxAs / InGaAlAs multiple-quantum-well waveguides. We show 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 DELTAn(TM) can be made to approach that in the TE polarization DELTAn(TE). At 1.523 mum, we achieve the ratio DELTAn(TM)/DELTAn(TE) = 1 for x = 0.7 with a phase shift coefficient 17.4-degrees/V-mm. Polarization independence is maintained over the entire range of reverse bias voltage.