▎ 摘　　要

We report a SPR based gas sensor using doped graphene monolayer employing the ATR technique via modified Otto coupling configuration. The proposed gas sensor is an approach different from the already reported Otto geometry for SP excitation in terahertz frequencies where the air gap has been replaced by a dielectric spacer layer (organic material) of refractive index (n(d)) 1.44, 1.50 and 1.54 at operating terahertz frequency of 5 THz. The performance of the sensor with respect to key system parameters such as the thickness of the dielectric layer, sensitivity, detection accuracy and FOM are investigated in the paper using angular interrogation via Transfer matrix method. It is observed that with increasing refractive index of spacer dielectric, the proposed gaseous sensor exhibits trade off between sensitivity and detection accuracy. However, the FOM is approximately equal for refractive indices 1.44 and 1.50 of spacer material, which is similar to 20 % higher than that at n(d) = 1.54. The FOM for n(d) = 1.44, increases from 527 (analyte refractive index = 1.00) to 741 RIU-1 (analyte refractive index = 1.10).