A Simple Wideband Dual-Slotted Circular Ring Based Linear-Circular and Linear-Cross Reflective Type Polarizer for THz Regime

The design of a wideband reflecting type linear-circular and linear-linear polarization converter in the THz frequency regime is described in depth in this work. The reflective polarizer unitcell seen here is made of a simple circular ring with two orthogonal cuts printed on top of a $\text{Si} 0_{2}$ substrate which is terminated with the ground. Post simulation results show a linearly polarized $((x/y)$ incident wave converted to its cross $(y/x)$ component in two frequency bands (7.19-11.12 THz and 15.28-15.78 THz) after reflection. The reflected wave would also be circularly polarized in the frequency bands (5.77-6.38 THz and 12.40-14.01 THz). The proposed structure has a unitcell periodicity of 0.1846 $\lambda_{\mathrm{L}}$ and an effective thickness of 0.0685 $\lambda_{\mathrm{L}}$, where $\lambda_{\mathrm{L}}$ is the lowest broadband frequency. For linear to cross conversion, the proposed design has a stable reaction up to 45°, and for linear to circular conversion, it has a stable response up to 30°. Authors are convinced that the proposed geometry has several advantages like simple, compact, and angular stable. It is used in real-time applications like polarization beam-splitters and time-domain spectroscopy, where these conversions are the primary concern.

I. Introduction

Polarization is a property of the Electromagnetic (EM) waves that specifies the spatial orientation of the electric field oscillating directions. The EM wave polarization states can be controlled and manipulated, which has already been used in various practical applications such as Radar Cross Section (RCS) reduction [1], mutual coupling reduction [2], and Quarter and half-wave plates [3]. Generally, the polarization conversion is experienced in crystals like quartz and tourmaline available in nature. However, due to the weak anisotropy of these crystals, these structures have various limitations, such as larger thickness leading to bulkier, heavier power dissipation, and it isn't easy to implement in real-time applications [4].