NOnlinear LIthium niobate Metasurfaces for Integrated THz generation

The terahertz (THz) band of the electromagnetic spectrum (0.1 – 10 THz) is currently attracting massive interest due to its incredible application richness. Among others, the THz band is a key region where most of the fundamental vibrational resonances of condensed matter and proteins can be found. The utmost relevance of this strategic spectral window in fundamental physics and biology dramatically boosted the development of THz-based technologies in the last decades. Yet, several technological challenges still prevent assessing the full THz spectral window and the development of integrated devices. As a result, to date, no intense laser-based source exists in the range of 5 – 15 THz. This new ‘THz gap’ will be a major challenge for source development in the coming years. Concurrently, integrable THz platforms are extremely appealing in view of ‘portable’ THz systems, applications to integrated photonics, and development of novel hybrid systems.

NO LIMITHz proposes a potential breakthrough in this field, by developing a new family of integrated THz broadband sources with unmatched conversion efficiencies and ad-hoc wavefront shaping by means of a disruptive platform based on an innovative artificial nonlinear optical metamaterial. NO LIMITHz is based on very recent results showing that dielectric metasurfaces – two-dimensional metamaterials – enable THz light emission with efficiencies comparable to the best nonlinear optical materials in nature, but in a sub-wavelength thickness. Furthermore, it leverages our demonstrations of functional nonlinear lithium niobate metasurfaces enabling strong enhancement and dynamic control of the nonlinear optical interactions.

We will design, fabricate, and characterize novel active dielectric metasurfaces based on lithium niobate that efficiently emit THz beams over a wide bandwidth and with a well-defined polarization state. The wavefront of the generated beam can be arbitrarily set by the geometry of the metasurface enabling, for instance, the THz output to be directly focused on a specific sample location. The new approach of NO LIMITHz will enhance the THz generation efficiency from nonlinear metasurfaces by more than three orders of magnitude compared to the state-of-the-art based on plasmonic platforms. This will allow the realization of ultracompact THz sources in the 5 – 15 THz band with improved efficiency power and extended functionalities compared to existing technologies.