Tuning silicon-on-insulator ring resonators with in-plane switching liquid crystals

We show that the resonance wavelength of silicon-on-insulator ring resonators can be tuned when a top cladding of liquid crystal is present. In-plane strip electrodes are used to generate an electric field that reorients the liquid crystal director in the plane parallel to the chip surface. This causes the resonance wavelength to shift toward longer wavelengths. The magnitude of this shift is about $1\mathrm{nm}$, which is twice as large as previously reported shifts. The experimental results are verified extensively with our simulation tools, where a calculation of the director orientation is combined with a fully anisotropic mode solver. From this, we get a clear view of the mechanism behind the tuning.