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Figure 19: Cavity resonance shifting due to a change in material index of refraction. Using a standard index of 3.4 (red) as our base, to comply with Si or GaAs substrates, switching the barrier regions of our heterostructured cavity to an index of 3.3 (yellow) offers negligible overlap between “barrier” cavity resonances and the waveguide bandwidth (grey). Further confinement would be possible with lower switched index but is less physically reasonable.