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Terahertz metamaterials: Refractive index, sensing, and resonances

Singh, Leena
Engineering of high refractive index metamaterials at terahertz frequencies have been presented. Applications of terahertz metamaterials as sensor and polarization convertor have also been introduced. The metamaterials under study have been fabricated using conventional photolithography techniques in class 1000 cleanroom on free-standing, flexible substrates made of mylar/polyimide. The experimental investigations have been carried out with 8F confocal, photoconductive switch-based terahertz time-domain spectroscopy. All the simulation work has been carried out using commercially available software CST Microwave Studio and Matlab.
The main finding in this work is the deep sub wavelength coupling technique used to achieve high refractive index value of about 41.8 at 2.026 THz. This work also presents two simple linear equations utilized for further enhancement of the refractive index values at the desired terahertz frequencies. Despite the strong absorption terahertz frequencies in presence of water, this study successfully demonstrates the ability of terahertz metamaterials for sensing of chemical and biological samples in aqueous solution using terahertz spectroscopy systems with sensitivity as high as 305 GHz/RIU. A terahertz metamaterial-based polarization converter has also been presented. It demonstrates broad bandwidth and transmission efficiency as high as 80% by coupling multiple responses.