Polarization-insensitive graphene-based THz rasorber with ATA characteristics

This paper presents a polarization-insensitive rasorber implemented with absorption-transmission-absorption(ATA)characteristics over three consecutive frequency ranges in the terahertz(THz)band. The proposed rasorber is made of a two-layer periodic structure. These two layers are separated by a spacer made of glass substrate. The unit cells of the top layer have a modified swastika geometry metallization, which is loaded with graphene strips to make it lossy and provide dual-band absorption. In the bottom plane frequency selective surface(FSS), a square ring is engraved on the metal layer to obtain bandpass characteristics between two stopbands provided by the top layer. The designed rasorber works in the -0.2 1.2 THz frequency range. It provides wideband absorption with a|S-11| < - S10 dB from 0.274 to 1.094 THz with a fractional bandwidth(BW)of around118%.An in-band transmission window is designed with a|S-21| > -S3 dB in the frequency of 0.615 to 0.719 THz provides a large BW of 104 GHz (15.59%)for THz communication. Within this transmission band, the lowest insertion loss of 0.27 dB is obtained at 0.686 THz. It provides the absorption of more than80%in both the lower band(-0.276 0.442THz, 46.24 % BW) and the higher band(-0.861 1.094 THz, 23.83 % BW). The simulated response of the designed rasorber using a full-wave electromagnetic simulator and calculated through ECM are found to be in good agreement.