Integrated thermo-optic micro-ring resonator in Z-cut lithium niobate thin film with isolation trenches

We propose and demonstrate a thermally tuned micro-ring resonator in a Z-cut lithium niobate on insulator platform. The ring cavity is heated by a thermal electrode placed above the waveguide. In addition, to improve the thermal insulation, we introduce trenches around the heating area. An excellent extinction ratio of 25 dB and a Q-factor of 12,000 are measured from the micro-ring resonator. The improvement associated with the trench structure is about 1.5-fold compared with the structure without trenches. The proposed isolation structure can be widely introduced to thermo-optic devices, significantly reducing fabrication difficulty.