Thermo-optic tuning of quasi bound state in continuum in lithium niobate thin film hetero-nanograting

Lithium niobate (LN) is difficult to etch precisely due to its stable physical and chemical properties. In recent years, more and more research has focused on etchless thin film lithium niobate (TFLN). Here, a one-dimensional SiO 2 nanograting structure fabricated on lithium niobate on insulator (LNOI) platform is designed in this study. This nanograting can generate one-dimensional diffraction waves. Then quasi-bound state in the continuum (q-BIC) can be introduced by aligning with the waveguide mode supported by the TFLN, which can achieve a high-quality factor and strong field enhancement, thus improving the interaction between light and matter. Furthermore, we validate the polarization characteristics of the nanograting structure, and measure the thermo-optical tuning sensitivity of the device to be 26.67 pm/K. This finding opens up potential avenues for realizing multi-dimensional tunable and dynamic photonic devices.