Polarization-Sensitive Scattering from Tunable Hybrid Au–Si Nanoantennas for Anticounterfeiting Applications

Polarization of light provides an additional degree of freedom in nanostructure-light interactions and delivers a wide variety of physical phenomena and applications. While relatively well-described for plasmonics and high-refractive-index nanosystems, the potential for polarization-dependent control of optical properties in hybrid nanostructures composed of two or more materials remains not fully unlocked. Here, we study the polarization-dependent scattering behavior of resonant hybrid gold–silicon nanostructures lacking inversion symmetry. We adjust the geometrical configuration and material phase of the nanostructure components through precise femtosecond laser irradiation to induce polarization-dependent changes of scattering spectra. By evaluating the color change using the color-difference (ΔE*) formula, we demonstrate ΔE* values of approximately 9.7 and 3.9 for TE- and TM-polarized oblique illumination, respectively. Notably, the latter value is close to the just noticeable difference threshold of 2.3 calculated for the studied nanosystems. Numerical simulations and semianalytical multipole decomposition techniques are applied to investigate this polarization-dependent scattering behavior, revealing that for the studied hybrid nanosystem, this phenomenon occurs at illumination angles ranging from 57° to 75°. Finally, we developed an effective defense mechanism against counterfeiting. The achieved results hold significant potential for further research into hybrid nanophotonic systems and for the development of optical chips, sensors, and anticounterfeit systems.