Metal-Dielectric Hybrid Nonlinear Plasmonic Antenna for Efficient THz Field Measurement

A bull's-eye plasmonic antenna is exploited to enhance the terahertz (THz) field detection sensitivity by boosting nonlinear interaction efficiency in an electro-optic sampling (EOS) scheme. The device design is based on numerical simulations optimizing spatiotemporal overlap between a near-infrared gating pulse and a locally enhanced THz field inside a gallium phosphide crystal. The metallic bull's-eye antenna is fabricated with a maskless laser direct writing technique. We experimentally demonstrate broadband EOS detection with 2.5 times higher sensitivity.