| It is a hot spot to look for a kind of high performance material to realize its high efficiency modulation in the practical application of terahertz communication system at the present stage.The excellent electro-optical properties caused by the deflection of the domain structure in the ferroelectric material can ensure that the dielectric constant of the ferroelectric material is remarkably changed under the induction of the external field,thereby effectively modulating the THz wave.In this paper,it is devoted to study the structural properties and its dielectric modulation properties in the THz band of the new-type ternary relaxer ferroelectric single crystal[0.24Pb(In1/2Nb1/2)O3-0.43Pb(Mg1/3Nb2/3)O3-0.33 Pb Ti O3,(0.24PIN-0.43PMN-0.33PT)].The concrete research content is as follows:1.The scheme and its feasibility of modulating THz wave using ferroelectric single crystals are systematically investigated and analyzed based on ferroelectric materials and the advantages of THz wave.The phase structure of ferroelectrics is discussed and the dielectric response model of ferroelectrics is proposed based on the analysis of the research status of THz modulation technology.The dielectric properties of the 0.24PIN-0.43PMN-0.33 PT single crystal were discussed,which provides a theoretical basis for the study of THz dielectric properties in the field.Also the method of Raman spectroscopy is introduced,which provides effective spectroscopy test for the study of material structure.2.The phase structure and phase transition characteristics of the materials were studied by Raman scattering spectroscopy.Raman spectra of 0.24PIN-0.43PMN-0.33 PT single crystal which having a MPB component was analyzed by Gaussian fitting,and the position and number of Raman spectra were determined to be monoclinic structure at room temperature.The monoclinic structure of the single crystal is determined by analyzing the position and number of Raman mode.The Raman spectra of MB monoclinic structure of the material under different electricfield were analyzed,the result showed that a phase transition from MB to MC monoclinic phase structure has occurred in the crystal and the MC monoclinic structure is more stable than MB monoclinic structure.At the same time,the deflection of the ferroelectric domains caused by the field-induced phase transition makes the material show strong dielectric properties in the THz band,which provided a reliable theoretical basis for the study of modulation characteristics of material in THz wave.3.The materials were tested by terahertz time-domain spectroscopy,and the dielectric properties of the single crystal were simulated and analyzed by the finite-difference time-domain method under different conditions.The transmission and reflection THz time-domain spectra of the single-crystal were measured at room temperature and the dielectric spectra were obtained from the established model and the flourier transform.The effect of different thickness and different electric field on the permittivity of the material in the range of 0.1-1.0THz and its influence on the modulation characteristics of the terahertz wave are simulated and studied by FDTD,which provides a valuable reference for finding the ideal material for studying the modulation characteristics of terahertz wave. |
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