A terahertz signal enhancement implemented by subwavelength metallic grooves

Abstract

This research analyzes the field enhancement properties of a subwavelength metallic groove working at 0.4 terahertz (THz), which is potentially applicable as a receiver to enhance THz signals in integrated circuits. We derive the analytic formulation of the field magnification by utilizing the distinctive characteristics of the electromagnetic (EM) field inside and above the groove with the EM field continuity on the upper and lower surfaces of the groove. This method, known as the Bruijn theory, has been applied in acoustics and optics to obtain reflection and absorption coefficients. Then, the dependence of these field enhancement properties on both the groove width and depth is examined by theoretical analysis and numerical simulations consistently. Results show that the field enhancement varies periodically with the groove depth in a period of 0.5λ, featuring the typical Fabry–Perot resonance. The field enhancement is inversely proportional to the groove width due to the cavity effect. Besides, the field intensity can be further enhanced by 10% via appropriately rounding the sharp vertices at the inlet of the groove. Moreover, the incident angle effect on the field enhancing property is explored. An enhancement of >32 dB can be realized at any incident angle with a groove of dimensions 158×225μm2. These results are helpful for understanding the field enhancement mechanism and designing novel THz plasmonic devices, such as an easily manufactured antenna receiver or sensor with simple and compact configuration, as well as offering a feasible solution for the high attenuation problem of THz communications.