C. Wu, C. Wang, G. You and J. Cao
ACS Applied Optical Materials (2023)
The Drude model successfully quantifies the optical constants for bulk matter, but it is not suitable for subwavelength objects. In this paper, terahertz near-field optical microscopy and finite element simulation are used to study gallium-etching-fabricated gold patches. Electron transport is discovered to determine the optical signal strength. However, the signal from the substrate is complicated and not fully understood. When the etching area decreases, the near-field interaction is not dominated by the doping concentration, and a higher signal is observed near connected metals. Simulation is used to discuss the anomalous enhancement phenomenon, which includes electric field distribution and electromagnetic heating. This work lays the foundation for more sophisticated simulations and further experimental verification in the future.