The Research Of Terahertz Amplitude Modulator Based On Metamaterials

Terahertz(THz) lies in the frequency gap between the microwave and infrared, the lack of efficient THz devices causes the developments of terahertz technology slowly. Electromagnetic metamaterials is a natural medium which has not possessed superior physical properties of artificial composite structure or composite medium, mainly including thin metal wires, Swiss ring, frequency selective surfaces(FSS) and split ring resonator(SRR) and variouses of structures. SRR is a kind of one or more gaps in the metal structure of graphics, which can change its structure to make an effective response to THz wave, and has broad application prospects in the terahertz technology.In this thesis, three SRR based terahertz amplitude modulators are presented, all of them have good modulating performances, which can work in THz transmission window ?(627-711GHz). The research results have certain practical and reference value.Firstly, structures of metamaterials are outlined, the equivalent medium theory is used to describe basic electromagnetic properties of metamaterials, the metamaterials electromagnetic parameters extraction method is expounded, SRR structures are theoretically analyzed by equivalent circuit method. Secondly, the modulating characteristics of SRR structures are particularly studied, the effect of FSS's material, geometry size, substrate's material, loading mode, thickness, multilayer on modulating characteristics are discussed. Finally, three novel amplitude modulators that can work in THz transmission window ? are presented. The working frequencies of the modulators are all 669 GHz, insertion losses are near 1d B, modulation depth is near 80%. Meanwhile, they show different advantages respectively, the structure the single SRR amplitude modulator is the simplest, and its post fabrication processing is convenient and the dimentional discrepancy is negligible. The dual SRR amplitude modulator has lower insertion loss, and stable modulation performance. The quadri SRR amplitude modulator whose configuration is flexible to control has higher modulation depth.In a word, the SRR based THz amplitude modulators mentioned above have good performances, which can work in THz atmospheric communication system.