Terahertz Metamaterial Absorber and Equivalent Circuit Model for Refractive Index Sensing

Area of Science:

• Metamaterials
• Terahertz Technology
• Sensing Applications

Background:

• Terahertz metamaterial absorbers (TMAs) are crucial functional devices for electromagnetic wave absorption.
• TMAs have diverse applications, driving research into their design and performance.
• Refractive index sensing is a key application area for advanced optical devices.

Purpose of the Study:

• To design and investigate a terahertz metamaterial absorber (TMA) for narrow-band absorption.
• To evaluate the TMA's performance for refractive index sensing applications.
• To analyze the absorption mechanism and the impact of structural parameters.

Main Methods:

• Designed a TMA composed of circular and square metal ring resonators.
• Performed simulations to determine absorptivity at specific terahertz frequencies.
• Analyzed electromagnetic field energy distribution to understand absorption mechanisms.
• Investigated the influence of structural parameters on absorption.
• Evaluated refractive index sensing performance, including sensitivity, Q-factor, and FOM.
• Developed an RLC equivalent circuit model (ECM) for the TMA.

Main Results:

• Achieved high absorptivity over 68.8% at 1.926 THz and 93.27% at 4.413 THz.
• Demonstrated high sensitivity (S) of 2.537 THz/RIU for refractive index sensing.
• Obtained a maximal quality factor (Q-factor) of 234.73 and figure of merit (FOM) of 147.67 RIU⁻¹.
• Validated the RLC equivalent circuit model (ECM) against simulation results.

Conclusions:

• The designed TMA exhibits excellent performance for narrow-band absorption and refractive index sensing.
• The coupling of ring resonators is crucial for achieving high sensing sensitivity.
• The RLC equivalent circuit model provides a valuable tool for further investigation and optimization of TMAs for sensing.