A Modified Transmission Line Model for Extraordinary Optical Transmission Through Sub-wavelength Slits

A modified transmission line model with the equivalent capacitors is proposed to describe extraordinary optical transmission (EOT) of the sub-wavelength slit with different inner walls. The equivalent capacitors can effectively explain the discontinuity of the interface at which the surface wave propagates. The transmittance calculated with this model is in accordance with finite difference time domain (FDTD) calculations. This modified analytical model provides a methodology to analyze the transmission properties of sub-wavelength slits with different inner walls. The results show that if well-designed and manufactured, sub-wavelength curved slits have the ability to enhance the optical transmission in the visible region or the infrared region.