Study On Absorption Of Terahertz Tunable Metamaterials And Ultrathin Metal Films

Terahertz detector is a key component of the research and application of terahertz technology,which directly affects the development and application process of terahertz technology.Metamaterials are composed of ordered and reasonably arrayed subwavelength artificial structures with nearly perfect absorption properties and can be used in the absorption structure of terahertz detection systems.This article focuses on research work on terahertz metamaterial detectors.Based on the microbolometer of the terahertz detection system,a metamaterial absorbing structure matched with the microbridge structure was designed and fabricated in this thesis.First of all,the thesis designs the cross structure metamaterial with the length of 40 ?m lattice unit and analyses the magnetic field and electric field resonance distribution with the structure at 2.52 THz resonant frequency.The corresponding positions of the metamaterial 's top structure are therefore expanded in the direction of field resonance and Magnetic resonance respectively.The cross structure metamaterial and the tetrafoliate structure metamaterial with the length of 28 ?m and 35 ?m of lattice unit are also devised.Besides,through the combination of the two dimensional plane of the top layer,the metamaterial of the complementary structure of the broad frequency absorption(0.5 THz)is formulated.After analyzing the key parameters of the superstructure,the corresponding superstructure is prepared and the absorption properties of the superstructure are tested.Theoretically,the paper analyzes the differences between simulation results and test results.Based on the design and preparation of metamaterial structure,the thesis tunes the electromagnetic response of metamaterials and changes the electromagnetic response between the lattice elements of a metamaterial by means of mechanical movement.Three kinds of tunable metamaterial structures based on mechanical movements were designed and simulated to calculate the electromagnetic resonance performance,and their tuning effects were studied.They have frequency tuning ranges of 1.3 THz,1.5 THz,and 0.45 THz,respectively.The preparation and testing methods of this tuning method were designed and the preparation and testing were completed.A tunable metamaterial structure based on variable surface square resistance was proposed,and the tuning performance of the metamaterial structure under the tuning method was simulated.The tuning range was 1 THz.On the basis of the test of reflection transmission absorption characteristics of ultrathin NiCr thin films with different thickness after thinning of RIE technology,the thesis designs composite absorption structure of ultrathin metallic film and superstructure.The absorption of single film is hence improved by using 8nm and 20 nm ultrathin NiCr thin film.In addition,the multigroup photo absorption peak is obtained after the segmentation of the resonator of the metamaterial.At 8 nm film thickness,there is an absorption rate between 5 % and 15 % at 0.5 THz to 1.75 THz,besides we get multiple sets of resonant absorption peaks;at 20 nm film thickness,on the condition of 0.5 THz to 1.75 THz there are multiple sets of resonant absorption peaks between 10 % and 20 % absorption rate.