Investigation Of Optical Controlled Terahertz Transmission Characteristics Based On WO₃ And MoO₃ Films

Terahertz wave（THz）usually refers to the electromagnetic radiation,which is in the transition region between macro electronics and micro photonics.Terahertz wave has important applications in many fields.Because of the significant change of physical effect when the existing high-frequency electronic devices or optical devices are applied to the terahertz frequency band,it is important to study the electronic functional materials and devices available in the terahertz frequency band.Because the principle of optically pumped terahertz modulation is based on the generation of carriers in the material under the external excitation light,the transfer of carriers leads to the change of the dielectric constant of the material,thus changing the transmission of terahertz wave,but there are few reports about the application of photovoltaic materials in the field of Terahertz modulation.In this background,we selected the materials of tungsten oxide（WO₃）and molybdenum oxide（MoO₃）to prepare the thin film,and measured its transmission characteristics in terahertz band and its terahertz modulation ability under the excitation of pump light.Subsequently,WO₃ with better modulation performance is combined with metamaterials to simulate and design a terahertz modulation device with good modulation performance.Firstly,WO₃ and MoO₃ films were prepared,and their properties were characterized after annealing.The thickness of the film was measured by atomic force microscope（AFM）.The absorption spectrum of the film was measured by UV-Vis spectrophotometer,from which the most suitable excitation wavelength was obtained.The transmission characteristics of THz wave in the films and the modulation effect of material film on THz wave are studied.With the increase of pump power,the modulation depth decreases gradually.The modulation range of WO₃ film is larger,about 73%of MF value and 1521.4%of real dielectric constant In the fabrication depth,the virtual part has 256.1%modulation depth,the MF value of MoO₃film is about10%,the real part of dielectric constant has 11.55%modulation,and the virtual part has 25.6%modulation effect.Finally,a terahertz metamaterial based on the open-loop structure is designed by CST simulation software.The influence of the size of the open-loop structure and the side length of the periodic element structure on the structure performance is studied.Based on the simulation design of THz modulation device of WO₃ film with better performance.Using the complex permittivity of WO₃ film with different pump power,the absorption curve of the absorber is simulated.With the increase of the pump power,the absorption frequency of the absorber moves slightly to the low frequency direction,and the absorption frequency changes 45.2%with the 260m W pump power,which shows that the absorber has certain tunability.