Nonlocal optical field effects in metal nanoplasmonics influenced by dielectric environments

Metal nanoplasmonics has emerged as a transformative platform for sub-diffraction-limited light manipulation, owing to its unique capability to confine and enhance optical fields at the nanoscale. While significant progress has been made in understanding plasmon-enhanced phenomena over the past two decades, theoretical investigations into how nanoscale dielectric environments influence the optical properties of metallic plasmonic nanostructures remain limited. In this work, we employ the quantum hydrodynamic model to develop a unified approach for analyzing nonlocal optical field effects in metal–dielectric nanowire systems. Our findings demonstrate that dielectric permittivity exerts a long-range influence on the resonance frequency of plasmonic nanostructures, with higher dielectric constants inducing a redshift in plasmon resonance frequency. Furthermore, the inter-wire spacing between metallic and dielectric nanowires critically affects optical field distribution and enhancement. Notably, decreasing the dielectric–metal proximity does not universally enhance light-field amplification. A primary factor contributing to this observation is that interfacial dielectric screening alters the plasmon mode’s effective wavelength. These results promise to establish foundational design principles for advanced nanophotonic devices.