A local-to-nonlocal SHG process is demonstrated on an electrically tunable metasurface, combining an LSPR at the FF with a TM-GMR at the SH to achieve independent dual tunability. Through modal-overlap engineering of the proposed scheme, a high-χ(2) MQW meta-atom delivers strong nonlinearity while achieving 2-DoF SH control with minimal trade-offs, advancing the functionality of nonlinear nonlocal metasurfaces.
Abstract
Nonlinear optical metasurfaces enable subwavelength control of light-matter interactions, yet simultaneous tunability of harmonic signal intensity and spectral response remains a fundamental challenge. Here, a local-to-nonlocal second harmonic (SH) generation process is presented, enabled by an electrically tunable polaritonic metasurface, allowing independent control of the SH spectral peak wavelength and intensity. The metasurface combines a localized surface plasmon resonance at the fundamental frequency with a transverse magnetic guided-mode resonance at the SH frequency. By engineering modal overlap within a multiple quantum well layer, voltage-controlled modulation of SH intensity and angle-controlled spectral tuning is achieved, demonstrating two decoupled degrees of freedom associated with local and nonlocal modes. Angle-resolved nonlinear reflection measurements confirm the independent tunability of the metasurface, validating the separation of excitation and emission pathways. This hybrid approach provides a general framework for nonlinear metasurfaces with enhanced flexibility and functional control, paving the way for applications in nonlinear signal processing, angle-multiplexed photonics, and entangled photon-pair generation for quantum optics.
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