Efficiently tunable and fabrication tolerant double-slot microring resonators incorporating nematic liquid crystal as claddings

An efficiently tunable and fabrication tolerant microring resonator (MRR) based on a double-slot waveguide with nematic liquid crystal (LC) upper cladding layer is proposed. Two electrodes are disposed horizontally on both sides of the waveguide for electrically tuning the director of the LC highly confined in the slots, which could significantly change the effective refractive index of the TE mode. The numerical results show that a double-slot wavguide of ~0.1 in the effective refractive index change is realized with an ultralow operation voltage of only 5 V, meanwhile, a 25-μm-radius double-slot LC MRR could achieve a relatively large dynamic wavelength tuning range of 81.4 nm. In addition, the tunable double-slot LC MRR could keep the wavelength tuning range over about 60 nm even if considering that key structure parameters design such as slot width, slot position, and large fabrication tolerances of the device are also demonstrated.