Terahertz Thermal Sensing by Using a Defect-Containing Periodically Corrugated Gold Waveguide

Featured Application We used the "COMSOL Multiphysics" software in the simulation process. This software enables the researcher to study the combined effect of a multitude of physical parameters in just one calculation (and for a specific model system). It has unparalleled capabilities, so that all physical phenomena can be perfectly reproduced by using the computer. A terahertz (THz) thermal sensor has been developed by using a periodically corrugated gold waveguide. A defect was positioned in the middle of this waveguide. The periodicities of waveguides can result in Bragg and non-Bragg gaps with identical and different transverse mode resonances, respectively. Due to the local resonance of the energy concentration in the inserted tube, a non-Bragg defect state (NBDS) was observed to arise in the non-Bragg gap. It exhibited an extremely narrow transmission peak. The numerical results showed that by using the here proposed waveguide structure, a NBDS would appear at a resonance frequency of 0.695 THz. In addition, a redshift of this frequency was observed to occur with an increase in the ambient temperature. It was also found that the maximum sensitivity can reach 11.5 MHz/K for an optimized defect radius of 0.9 times the mean value of the waveguide inner tube radius, and for a defect length of 0.2 (or 0.8) times the corrugation period. In the present simulations, a temperature modification of the Drude model was also used. By using this model, the thermal sensing could be realized with an impressive sensitivity. This THz thermal sensor is thereby very promising for applications based on high-precision temperature measurements and control.