Enhanced Second Harmonic Generation from Ferroelectric HfO2-Based Hybrid Metasurfaces

Integrated nonlinear metasurfaces leading to high-efficiency optical second harmonic generation (SHG) are highly desirable for optical sensing, imaging, and quantum photonic systems. Compared to traditional metal-only metasurfaces, their hybrid counterparts, where a noncentrosymmetric nonlinear photonic material is incorporated in the near-field of a metasurface, can significantly boost SHG efficiency. However, it is difficult to integrate such devices on-chip due to material incompatibilities, thickness scaling challenges, and the narrow band gaps of nonlinear optical materials. Here, we demonstrate significantly enhanced SHG in on-chip integrated metasurfaces by using nanometer thin films of ferroelectric Y:HfO2. This material has the merit of CMOS compatibility, ultraviolet transparency up to 250 nm, and significant scalability down to sub-10 nm when deposited on silicon. We observe a 20-fold magnitude enhancement of the SHG intensity from the hybrid metasurface compared to a bare ferroelectric HfO2 th...