Terahertz Frequency-Selective Surface With Polarization Selection and Conversion Characteristics

In this paper, a novel frequency selective surface (FSS) with polarization selection and dual-band polarization conversion characteristics is proposed for terahertz applications. The FSS is composed of two layers of metallic periodic arrays separated by a polymer dielectric spacer. The top and bottom arrays provide bandpass and bandstop characteristics for TE- and TM-polarized incidences, respectively. Geometrical parameters of the top and bottom arrays are tuned such that the phase differences of the TE and TM transmissions at the lower (f₁) and upper (f₂) crossover frequency points are -90° and +90°, respectively. Therefore, for normal incidence, a 45o linearly-polarized incident wave is converted into a right-handed circularly-polarized and left-handed circularly polarized transmitted wave at f₁ and f₂, respectively. Equivalent circuit models are established to explain the operation principle of the proposed FSS. A prototype is fabricated using micromachining with its transmission characteristics, namely, polarization selectivity and dual-band polarization conversion, validated by time-domain and frequency-domain measurements.