Terahertz Absorbers Based On Metamaterials

Metamaterial is a kind of artificial material which consists of an array of unit cells in a certain pattern. In theory, arbitrary electromagnetic parameters can be achieved by tailoring the metamaterial unit cell. Nowadays, metamaterial becomes more and more popular in the absorber design due to its high loss at the resonance frequency.This dissertation will detailly investigate the design, simulation, fabrication, and measurement of THz metamaterial absorbers, which includes following contents:(1) The THz technologies are introduced, which contains Thz generation, THz detection, fabrication and measurement of THz devices.(2) Single-layer multiband THz absorbers based on snowflake-type resonators and bi-layer multiband THz absorbers based on square-ring resonators are designed, during which both the Fabry-Perot model and digital simulations are used to elaborate the wave-absorbing mechanism. Comparing with square-ring type absorbers, snowflake type absorbers have better performance in eliminating the absorption peaks deriving from higher-harmonic resonances in the frequency band we focus. Finally the experiment results also demonstrate that the multiband absorbers we design are polarization insensitive and capable of working at a large incidence angle.(3) Both single-layer and bi-layer wideband absorbers are designed through using unit cells with similar sizes, all of which will resonate in the frequency band we focus. This kind of design brings down the reflectivity on account of impedance matching, which generates a wideband absorption.