The article evaluates a surface plasmon resonance (SPR) sensor that uses a graphene microribbon (GMR) array on a silicon waveguide to detect benzoic acid in terahertz (THz) frequencies. The graphene micro-strips are periodically spaced to efficiently excite SPR in THz. The application of planar waveguide technologies enables the development of miniature and compact multisensor devices that can connect to instrumentation using optical fibers, providing the ability for remote operation. Here, the impact of modifying variables as ribbon width (r_w) and the number of ribbons (num_rib) are examined for a specific structure of GMR, tuned to E_F = 0.45 eV and Γ = 3.7 meV with periodicity λ = 4 µm, deposited on a silicon waveguide of h = 15 µm and SiO_2 substrate. The results show that the manipulation of these variables enhances the plasmon formation, but also highly affect the plasmonic modal distribution along the array. The article concludes that the balance between these features can lead to the sensor's performance optimization. Therefore, changing the analyte refractive index with the acid concentration, a very high sensitivity sensor of 8658 nm/RIU is presented for r_w = 3 µm and num_rib = 200.
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