Terahertz Amplitude And Space Modulation Based On Phase Change Vanadium Dioxide

Terahertz?THz?wave has many proven characteristics,such as high permeability,low energy,fingerprint spectrum characteristics,broad spectrum,transient,coherence,high absorption of polar molecules.Generation,transmission,modulation and detection of THz radiation constitute the key technologies in THz science.How to modulate THz wave effectively is the basis of THz radiation applications,such as communication,signal processing and other fields.At present,the research of THz Science is not as mature as that of infrared and microwave,so the modulation means of THz wave are relatively scarce,which greatly limits the application of THz technology in various fields.In this paper,we mainly study the THz spatial light modulator and filter based on vanadium dioxide.The specific research contents are as follows:1.The characteristics,applications and functional devices of THz are systematically studied.Secondly,the theory of metamaterials and common modulation methods are studied,which lay a theoretical foundation for the research of filter and spatial light modulator.The phase transformation mechanism and fabrication method of vanadium dioxide are studied.The application of vanadium dioxide in various fields is expounded.It is a good knowledge reserve for modulation filters and spatial light modulators.2.A multi-band THz bandpass fifilter based on vanadium dioxide?VO₂?hybrid metamaterialis experimentally demonstrated.From bottom to top of the fifilter,they are650 nm-thick high resistance silicon substrate,100 nm-thick Silicon nitride,125 nm-thick VO2,500 nm-thick Silicon nitride,and 200 nm-thick aluminium pattern.When the incident THz wave polarized along with they direction,the filter has three tunable passbands whose central frequencies locate at 0.32,0.70 and 0.94 THz,respectively.Under bias current of 0.22 mA,the transmission of the three bands can be electrically modulated and their modulation depths are 97%,97.5%and 96%,respectively.When the THz wave polarized in x direction,there is only one tunable passband with central frequency of 0.73THz,and the modulation depth achieves 96.5%.The tunable mechanism is due to the Joule heat induced isolator-to-metal transition?IMT?of the VO₂ film.The proposed approach provides a promising platform for THz frequency selection.The surface current distribution is simulated by CST electromagnetic simulation software,and the causes of each absorption peak are analyzed.The samples are tested by Z-3 THz time domain spectroscopy system.The experimental results show that the composite simulation achieves the desired modulation effect.This THz wave filter based on vanadium dioxide has simple structure,small volume,deep modulation depth and fast reaction speed.It has important application value in THz field.3.A THz spatial light modulator based on vanadium dioxide is proposed.By charging different pixels,the modulator makes the transmission of THz wave of different pixels different by local heating,and achieves spatial modulation effect.Although the effect is not ideal,the modulation difference of adjacent pixels heated by a single pixel is only 14%,but it can achieve better effect by optimization and improvement.