Spectrum and Polarization-Resolved Nonlinear Optical Near-Field Imaging of Plasmonic Nanoantennas
Y. Liu, Jiajun Wang, Bingbing Zhu, Xinhao Wang, Sheng Zhang, Weifeng Liu, Lei Shi, Zhensheng Tao
Abstract
Plasmonic nanoantennas, which support surface plasmon resonances enabling the concentration of electromagnetic energy into subwavelength volumes, have emerged as versatile tools for a wide range of applications. However, achieving high-resolution near-field imaging with polarization and temporal sensitivity remains a significant challenge. In this work, we present a novel nonlinear optical microscopy technique based on degenerate four-wave mixing to enable spectrum- and polarization-resolved near-field imaging of plasmonic nanoantennas. By using a mid-infrared pump and near-infrared probe, we capture detailed spatial distributions of plasmon-enhanced near-field intensity and polarization characteristics, revealing distinct polarization patterns and frequency-dependent enhancements. Our method enables the observation of resonance-induced spectral shifts and subwavelength spatial resolution, offering valuable insights into plasmonic field behaviors, particularly in the mid-infrared range. This approach provides a powerful tool for exploring and understanding the complexities of plasmonic nanostructures, with significant potential for advancing nano-optics applications.