A Terahertz Metamaterial Sensor Based on Dual Resonant Mode and Enhancement of Sensing Performance

A tunable terahertz metamaterial sensor based on aluminum and silicon has been proposed in this paper. Two identical aluminum crosses are placed on either side of the silicon layer. Two substructures are formed by changing certain structural parameters, and two different resonant modes are enhanced directionally in these substructures, respectively. The refractive index sensing range for both resonant modes is 1.0-1.8. The sensitivity and figure of merit (FOM) of the electric dipole resonant mode which is centered at 2.333 THz are 117.67 and 1.07 GHz/RIU. As for the Fano mode which is centered at 3.381 THz, the calculated values are 81 and 2.53 GHz/RIU. Both resonant modes can achieve over 98% opacity. More significantly, an enhancement method of sensing capacity is realized based on perturbation theory. By placing polytetrafluoroethylene (PTFE) plates on the ends of the upper surface aluminum cross, the sensitivity of both resonant modes is improved. The optimized structure provides a sensitivity of 132.75 and 105.17 GHz/RIU for the two resonant modes, respectively. In addition, the effects of PTFE layer thickness on sensing performance are also discussed. This work opens up new prospects in the design of terahertz metamaterial sensors and provides a new method of enhancing sensing capacity.