A universal route to efficient non-linear response via Thomson scattering in linear solids

Non-linear materials are cornerstones of modern optics and electronics. Strong dependence on the intrinsic properties of particular materials, however, inhibits the at-will extension of demanding non-linear effects, especially those second-order ones, to widely adopted centrosymmetric materials (for example, silicon) and technologically important burgeoning spectral domains (for example, terahertz frequencies). Here we introduce a universal route to efficient non-linear responses enabled by exciting non-linear Thomson scattering, a fundamental process in electrodynamics that was known to occur only in relativistic electrons in metamaterial composed of linear materials. Such a mechanism modulates the trajectory of charges, either intrinsically or extrinsically provided in solids, at twice the driving frequency, allowing second-harmonic generation at terahertz frequencies on crystalline silicon with extremely large non-linear susceptibility in our proof-of-concept experiments. By offering a substantially material- and frequency-independent platform, our approach opens new possibilities in the fields of on-demand non-linear optics, terahertz sources, strong field light-solid interactions and integrated photonic circuits. Metamaterials featuring locally enhanced non-linear Thomson scattering offer a practical and universal method for efficiently stimulating non-linear responses in linear solid materials.

Automated summary

Non-linear materials, although widely used in optics and electronics, have limitations in extending demanding non-linear effects to widely used centrosymmetric materials (such as silicon) and technologically important spectral domains (such as terahertz frequencies). In this study, the researchers introduce a universal method called non-linear Thomson scattering to efficiently stimulate non-linear responses in linear solid materials, allowing for second-harmonic generation at terahertz frequencies on materials like crystalline silicon. This approach offers a material- and frequency-independent platform for various applications in non-linear optics, terahertz sources, light-solid interactions, and integrated photonic circuits.