Theoretical Study of Terahertz Near-Field Enhancement Assisted by Shape Resonance in Rectangular Hole Arrays in Metal Films

We report a theoretical investigation on terahertz near-field enhancement in a rectangular hole array on a metal film driven by a shape resonance. The analytic model is constructed by boundary snatching the Rayleigh wave expansion and the modal expansion of electromagnetic waves. Simulation results reveal that the enhancement factor depends on the inverse coverage, reaching more than 1000 in a sub-micron wide rectangular hole. We also show that the resonance frequency is predominantly determined by the length of the rectangles while variations in the width and the thickness cause minor shifts in the resonant frequency.