Nonlinear metasurfaces

Optical metasurfaces are typically flat surfaces with an array of structures that have subwavelength dimensions (~10-1000 nm). Careful design of these features allows the phase and polarization of light to be controlled. While standard bulky optical components are typically used for these applications, this area of research, also known as "flat optics," allows for miniaturization and integration. Combining these engineered nanostructures with nonlinear materials, such as non-centrosymmetric metal oxides, allows additional tuning and enhancement of optical nonlinear properties such as electro-optic modulation and frequency conversion efficiency.

We specialize in the design, fabrication and characterization of nonlinear metasurfaces made of lithium niobate and barium titanate. Our strong background in electro-optical measurements has enabled us to show how high-speed free-space modulators can be achieved by top-down fabrication in lithium niobate on an insulator platform [Weigand et. al. 2021] and by bottom-up fabricated barium titanate metasurfaces [Weigand et. al. 2024]. Based on similar principles, enhanced light-matter interaction within a resonant structure can increase the efficiency of second harmonic generation [Talts et. al. 2023].

Examples of further work include improving modulation efficiencies, investigating novel material sources and device configurations, and in particular developing systems that combine nonlinear optical signals with fast signal modulation.