Integrated photonics on the dielectrically loaded lithium niobate on insulator platform

Thin-film lithium niobate on insulator (LNOI) is emerging as one of the promising platforms for integrated photonics due to the excellent material properties of lithium niobate, which includes a strong electro-optic effect, high second-order optical nonlinearity, a large optical transparency window, and low material loss. Although direct etching of lithium niobate has been adopted more widely in recent years, it remains to be seen if it will be adopted in foundry processes due to the incompatibility with standard CMOS fabrication processes. Thus, the scalability of the LNOI platform is currently still limited when compared with other platforms such as silicon photonics. Dielectrically loaded LNOI waveguides may present an alternative. These waveguides have been used to demonstrate a range of optical components with a simplified fabrication process while demonstrating competitive performance. In this contribution, we review the recent progress in dielectrically loaded LNOI waveguides, summarize the advantages and disadvantages of different loading materials, compare the performance of different platforms, and discuss the future of these platforms for photonic integrated circuits.