Acoustic, microwave and photonic devices in thin film lithium niobate
Abstract: Lithium niobate (LN) is studied for a long time due to its exceptional electro-, nonlinear- and acousto-optic properties, as well as its wide transparency window and large refractive index. For instance, LN electro-optic modulators are the workhorse for the optical communication industry, while the periodically poled lithium niobate (PPLN) is mainly used for wavelength conversion and photon pair generation. Despite its great properties, the LN platform could not compete with the other integrated photonics platforms due to the problems related to material processing and integration. As a point, the traditional LN devices are formed with titanium diffusion which resulted in bulky devices. These devices have weak optical confinement and show reduced non-linear efficiencies. Due to these problems, the previous LN devices remained bulky, and could not find a place among other integrated photonic platforms. Recently, the high-quality thin-film LN wafers have been made commercially available paving way for nanophotonic devices with this platform. In this talk, I will talk about my development of the nanophotonic lithium niobate platform at UIUC (Q factors reaching 3.5 million at 1550 nm). Then, I will demonstrate novel electro-optic and acousto-optic devices that realize optical isolation and back-scattering suppression with this platform. Finally, I will talk about other old optical materials that can be successfully re-fabricated as a thin film on oxide (similar to thin film LN).