Photonic crystal electro-optic devices in engineered thin film lithium niobate substrates

We report on photonic crystal electro-optic devices formed in engineered thin film lithium niobate (TFLN™) substrates. Photonic crystal devices previously formed in bulk diffused lithium niobate waveguides have been limited in performance by the depth and aspect ratio of the photonic crystal features. We have overcome this limitation by implementing enhanced etching processes in combination with bulk thin film layer transfer techniques. Photonic crystal lattices have been formed that consist of hexagonal or square arrays of holes. Various device configurations have been explored, including Fabry Perot resonators with integrated photonic crystal mirrors and coupled resonator structures. Both theoretical and experimental efforts have shown that device optical performance hinges on the fidelity and sidewall profiles of the etched photonic crystal lattice features. With this technology, very compact photonic crystal sensors on the order of 10 μm x 10 μm in size have been fabricated that have comparable performance to a conventional 2 cm long bulk substrate device. The photonic crystal device technology will have broad application as a compact and minimally invasive probe for sensing any of a multitude of physical parameters, including electrical, radiation, thermal and chemical.