Research Of Terahertz Wave Modulator Based On Silicon Microstructure

The terahertz wave?THz?is the last spectral spectrum band to be fully developed on the electromagnetic spectrum,and its spectral performance and application potential have attracted great attention from the academic and industrial circles.In addition to wireless communication technology,there is a great deal of research on terahertz imaging technology internationally.While the research of terahertz security imaging technology,used as a technical breakthrough,has developed rapidly from basic theory to system development in Chinese.THz modulators has become a key component of these application systems,which has a significant impact on the performance properties of the final application system.For a terahertz modulator,a large modulation depth means greater imaging clarity and accuracy,and a high modulation rate means fast imaging speed and high efficiency.Therefore,the large modulation depth and modulation rate are the two core indicators of the terahertz modulator.The purpose of this paper is to study semiconductor silicon as the main research object.Through combing semiconductor silicon and new micro-structures,a terahertz modulation device with a large modulation depth is constructed,which provides device technology support for THz imaging and wireless communication technology.Firstly,according to the equivalent refractive index theory,a silicon-based terahertz antireflection microstructure was designed and developed.Double-layered block and cylindrical microstructures have been manufactured.Experimental results have shown that the microstructure has a transmission of up to 85%for terahertz waves between0.45 THz and 0.9 THz.The transmission is increased by more 10%than the silicon substrate in the 450 GHz broadband.As a terahertz modulator,its maximum insertion loss is only 1.5 dB.In addition,the studies have shown that the two microstructures have the same transmission enhancement effect on the terahertz wave.Secondly,a THz light-control modulator combined with silicon-based antireflux microstructure and black silicon is proposed.Black silicon has a good absorption of the visible and near-infrared light,which could generate a large number of photogenerated carriers in silicon structure,so that it can achieve the role of regulation of terahertz transmission.Experimental results have shown that over 85%of the relative modulation depth can be obtained for both 638 nm and 808 nm pump lasers.Compared with ordinary silicon chips,the device can meet the needs of working under small pump laser power while increasing the modulation depth.At last,a THz electronically controlled modulator combined with a silicon-based antireflux microstructure and a vanadium dioxide phase-change film is proposed.Vanadium dioxide?VO₂?has a room temperature insulator-metal phase transition characteristic.The THz wave transmission can be modulated by the electrically controlled phase transition.The VO₂ thin film with good performance was prepared by magnetron sputtering and processed into an electronically controlled structure.The whole device has a strong transmission to the terahertz wave before the phase transition of the VO₂ thin film.However,the transmission amplitude of the terahertz wave is significantly reduced after the phase transition into the metal state.The transmittance of the modulation device changes up to 65%before and after modulation,and the relative modulation depth can reach over 76%.Both of the above THz adjustable devices can work in a wider frequency band.Besides,they have the advantages of simple processing technology,low cost,small insertion loss,large modulation depth,and so on.These adjustable devices have a good application advantages in THz wireless communication,imaging and other technical fields.