Transmittive-type triple-band linear to circular polarization conversion in THz region using graphene-based metasurface

This paper reports an elaborated study of a graphene-based transmittive-type triple-band linear to circular polarization converter (TTLCPC) within the lower mid infrared (MIR) region, covering the terahertz gap. The linearly polarized incident electromagnetic wave undergoes conversion into the circular polarization at three distinct frequencies viz., 5.72 THz, 13.49 THz and 18.90 THz. The axial ratios (AR) at these three THz bands are under 3 dB till 40°incident angles of the electromagnetic wave. The circular polarized nature of the transmitted electromagnetic wave was verified by generating the polarization ellipses at the three distinct frequency bands. The proposed prototype is designed in the sub-wavelength region by maintaining a thickness of λ/26.11 and a periodicity of λ/4.35 with respect to the lowest frequency band; making the proposed device ultra-thin and compact in nature. The proposed TTLCPC can be useful for electromagnetic measurement, THz detection, THz sensing, THz imaging, THz antenna and stealth technology, etc. [Display omitted] •The graphene metasurface design exhibits linear to circular polarization conversion.•The axial ratios are less than 3 dB till 40°incident angles at three distinct THz bands.•Polarization ellipses confirm circular polarized nature of the transmitted wave.•The design evolution has been studied in details in the light of field distribution.