Research Of Terahertz Modulation Properties Based On Ba_0.6Sr_0.4TiO₃ Ferroelectric Materials

The research of terahertz(THz) modulator is one of the key points in THz technology, and the research of tunable material in THz region is the basis of Thz modulator. In this paper, it is devoted to study the optics induced modulating characteristics of ferroelectrics like Ba0.6Sr0.4TiO3 in THz region, and the design of electrically tunable THz metamaterials. The main content include:1. It is introduced that the basic characteristics of ferroelectrics, the models of dielectric response of ferrolectrics and photo-ferroelectric effects. The experimental facility of 0.4Ba0.6Sr0.4TiO3-0.6La(Mg0.5Ti0.5)O3(BST-LMT) ceramic based optical tuning experiment, and the process of acquiring complex refractive index and complex dielectric constant of BST-LMT. The preparation of BST-LMT ceramic is introduced, and the transmitted waveform, frequency spectrum, transmittance,dielectric constant and absorption coefficient of BST-LMT under different levels of laser power is analyzed. And the XPS spectrum of BST-LMT is also analyzed, it shows that the Ti3+ and Ti4+ coexist in BST-LMT, and these ions have significant contribution to the optical tuning process.2. The experiment result of optical tuning of dielectric properties of KTaO3,SrTiO3, SrTiO3:Fe is analyzed. In these materials, the effect of external optical field has a similar effect as that in BST-LMT ceramic. For different levels of green laser power, the real part of dielectric constant of these five crystals decrease as the laser power increasing, while the imaginary part changes a little. The mechanism of the optical tuning process is similar to that in BST-LMT ceramic, despite that different ions play a role in this process.3. It is sumarrized that the development of tunable THz functional devices first.Then based on the research of H. T. Chen et al., we designed a new kind of THz elecrically tunable metamaterial, combining the interdigital electrode and the split resonant ring. It is further analyzed that the effect of electric field on the change of dielectric constant of BST, and its influence on the transmitted THz wave. Using the software CST MWS, we simulated the influence of the thickness of BST film on the resonance absorption peak of transmitted THz wave.