A nano-tip-based plasmonic double-gate structure (NPDS) excited by the surface plasmon polariton (SPP) resonance of the gate electrode has recently been proposed to achieve the specifications of the UV laser-induced copper cathode. The function of the NPDS is to generate a high bunch charge via nearinfrared laser-induced field emission without increasing the cathode size. In this study, we report detailed numerical studies of the proposed NPDS to elucidate the physical mechanism of SPP propagation and light-tip coupling via internal SPP resonance. The simulation results show the relationship between the internal SPP resonance and the tip-light coupling in the NPDS, and the feasibility to achieve significant field emission enhancements with the NPDS. Understanding the internal SPP field in the plasmonic double-gate structure and the light field-tip coupling process in the NPDS is of practical importance in designing field emitter devices and could become an important factor in future high-brightness free-electron laser cathodes and high-sensitivity optical biosensors.
Index Terms-Surface plasmons (SPs), Nano plasmonics, Nano structure, Free-electron laser cathodeTae Young Kang is with the