Research Of Terahertz Wave Modulator Based On Graphene And Metamaterial Structure

With the development of ultrafast laser technology and terahertz detection technology,domestic and foreign universities and research institutions have put into research and development boom of the terahertz functional device,making the terahertz absorption,filtering,modulation and other functional devices have made rapid development.In recent years,with the large amount of new materials and new structures such as graphene and metamaterial have been introduced into the field of terahertz,which makes the terahertz wave control technology develop particularly fast.Based on above background and according to the back gate transistor structure and the existing semiconductor technology,we designed and fabricated a terahertz wave modulator combining graphene and metamaterial,and studied modulation performance of the modulator.In addition,we proposed two terahertz wave modulators based on flexible substrates for the practical application of the modulator.In this paper,the general transfer process of graphene was studied.By analyzing the problems encountered during the transfer,the transfer process was optimized and the graphene film with good quality was obtained.Then according to the traditional design of the transistor structure,we designed a back-gate transistor with graphene channel.By continuously adjusting the optimization process and exploring the process parameters,we made the good performance of the back gate graphene transistors.Then a terahertz wave modulator with graphene and metamaterial structure was proposed.According to the experience of preparing back-gate graphene transistors before,the terahertz wave modulator with frequency selective properties was successfully prepared.Through the electrical control,at the design of the frequency point,we got 6% of the modulation depth.Aiming at the shortcoming of easy breakdown of the silicon dioxide,we put forward the improvement scheme that used the alumina as the gate dielectric and optimized the metamaterial structure.Finally through the THz-TDS time-domain spectroscopy system test,the improved modulator's modulation depth had doubled,reaching 13%.At last,we studied the terahertz wave modulator based on flexible substrate.Among them,the multi-stage terahertz wave modulator with PET as the substrate can realize the four-level modulation by controlling the voltage application mode,the maximum modulation depth is up to 36%;The thin layer silicon terahertzwavemodulator with PDMS as the substrate is used to realize the transmission enhancement under the action of 808 nm laser.Through the thin silicon etching,the THz wave modulator can be stretched.The research content of this paper is the forefront,which provides some new ideas and new directions for the development of terahertz modulator.