Effect of GaAs/AlGaAs quantum-well structure on refractive index

We investigate the refractive index difference between the GaAs/AlGaAs quantum wells (QWs) and bulk AlGaAs. We find the refractive index difference is smaller when the electric field in the nominally intrinsic MQW region is larger, or when the well (GaAs) thickness of the QW's is larger, or when the Al fraction of the QWs is smaller. The maximum refractive index difference between the 100 /spl Aring/ GaAs/100 /spl Aring/ Al/sub 0.2/Ga/sub 0.8/As QWs at zero electric filed and bulk Al/sub 0.1/Ga/sub 0.9/As is about 0.044. Even with a small refractive index difference of 0.0132, the OFF-state reflectance of a normally-off MQW modulator at the designed photon wavelength will increase from the desired value of 0% to 90% when the reflectivity of the bottom mirror is 0.99.<
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