Control of terahertz transmission through sub-wavelength copper film gratings deposited on RF-4 substrates

Abstract

Low cost terahertz filters (copper gratings) have been fabricated by using plastic substrates and printed circuit board processes. The optical properties of these gratings have been investigated. These sub-wavelength copper film gratings with various periods display remarkably enhanced transmission over the terahertz wavelength range. The maximum amplitude transmission efficiency reaches 86% for the grating with a period of 500 μm. The resonance peaks shift to lower frequencies on increasing the period of the gratings. By analyzing three kinds of models, we demonstrate that the excitation of surface plasmons on the upper and lower interfaces of the grating is the prime mechanism responsible for the extraordinary transmission. Various phase shifts between samples and the bare substrate have been detected, leading to the transmission dip frequencies of our experimental results deviating from the theoretical predictions of a surface plasmon polariton model. In addition, apparent angle-dependent behaviors have been observed in the transmission spectra of the grating with the period of 500 μm and the slit width of 180 μm, which confirms that the copper film grating is a promising geometry for producing terahertz polarizers.