Research On Terahertz Multi-pixel Wavefront Modulator

In the past ten years,terahertz technology has developed rapidly with the advent of terahertz sources and terahertz detectors.Terahertz imaging technology has shown its significant practical value in material properties analysis,airport security inspection,biological tissue diagnosis,radar imaging and other fields.Terahertz imaging technology based on compressive sensing technology has the advantages of fast sampling rate,low sampling rate,and high resolution,and has received extensive attention from researchers from all walks of life.The multi-pixel terahertz wavefront modulator studied in this paper has the modulation rate of the electronic switch to ensure the high sampling rate of the imaging process;and in the imaging system,the vector-matrix or matrix-matrix and the multiplication between the images are realized.Linear sampling of image information ensures low sampling rates in the imaging process.Therefore,this paper mainly focuses on the combination of the wavefront modulator coding system and the theory of compressive sensing to study high-precision,fast-sampling terahertz imaging theory;design and simulation of high-efficiency,high-segment-degree devices;and three aspects of device processing and testing on wavefronts.Modulators have undergone a more comprehensive study.The main contents and results of this thesis are as follows:1?Combined with the terahertz wavefront modulation coding system,the imaging principle of the terahertz imaging system based on the compressive sensing technology is mainly studied;from the basic theory of compressed sensing and the signal sparse representation of the compressive sensing theory,the coding measurement matrix design,and the reconstruction algorithm Three aspects of the design study and design of a terahertz imaging system incorporating a multiphase element wavefront modulator.2?The structural unit suitable for the multi-pixel wavefront modulator is studied and designed,and the regulation characteristics of the unit structure are analyzed.The cell structure is mainly a micro-structure with EIT phenomenon and an HEMT I-shaped micro-structure,and analysis and comparison are made from the aspects of the resonance intensity,modulation rate,and modulation depth of the structure,and the modulation efficiency reaches over 90% with low parasitic parameters.HEMT I-shaped microstructure.3?Aiming at the dynamic regulation characteristics of HEMT-based multi-pixel arrays.Firstly,the independent modulation capability of different pixel array modulators is analyzed by electromagnetic simulation;the influence of the cell structure parameters on the resonant frequency points is further analyzed,and the reasons for finding solutions to the problems are analyzed;and the mutual coupling between the subunit structures and the modulator transmission is further studied.The effect of the coefficient.Through research,a cross-dislocation distributed structure is designed.This structure effectively eliminates crosstalk between sub-cell structures under the condition of ensuring multi-phase modulation without frequency deviation,and provides a good design scheme for device implementation.4?A 4×4 pixel array wavefront modulator with a working frequency band of 220 GHz was designed and a reasonable circuit design was performed.Then,micro-nano processing was used to process the device and an experimental system was set up for experiment.The test results show that the modulator has an independent modulation capability for each pixel,and the individual cell modulation efficiency is greater than 70%.