Study On The Modulator Based On Graphene And Metamaterial

In recent years, with the development of terahertz technology, THz wave has been widely used in many fields such as information communication, high definition imaging, sensing,security and disease detection. However, these applications need not only reliable THz sources and effective detectors, but also high performance terahertz devices and the modulator is one of the most important devices in many functional devices. Graphene has been used to improve the performance of terahertz optoelectronic devices due to its prominent modulation of electric field or magnetic field and special optoelectronic properties in the terahertz band. The THz devices such as absorbers, sensors, modulators, etc. have been researched and validated. At room temperature, the high carrier mobility of graphene provides the improvement of modulator modulation rate with a solid basis. But graphene on the terahertz wave absorption is very limited, resulting in modulation depth modulator is greatly limited, and it also reduces the resistance to interference. Metamaterial as a kind of artificial material absorbs THz wave by the collective oscillation of metal surface carrier. At the same time, graphene perform as metal when the imaginary part of its dielectric constant is greater than 0. And this provides a basis for the combination of graphene and metamaterials improving the modulation rate. In this paper, based on the characteristics of the electrical tuning of graphene and the resonance absorption of metamaterials, we studied modulator of tunable modulation depth based on graphene metamaterial, tunable plasmon induced transparency metamaterial based on graphene and tunable modulator based on polarization direction of incident light.The main contents and conclusions of this paper are shown as follows:1. A modulator of tunable modulation depth based on graphene metamaterial has been proposed. The model structure of double layer graphene complementary structure and dielectric is established, and a series of modulation depth corresponding to the frequency of 11.85THz is obtained through CST simulation. Where the maximum modulation depth is greater than 96%. The series of modulation depth can be modulated and transformed by bias voltage regulating graphene Fermi level. This will greatly promote the application of modulator in the wave shaping, such as generating sine wave, triangle wave and square wave.In addition, the transmission law is analyzed by using the harmonic oscillator model.2. Study the tunable plasmon induced transparency metamaterial based on graphene in the terahertz frequency range. Based on the simulation, the transmission of the transparency window is over 0.82 at graphene Fermi level 1.5eV. When the Fermi level is adjusted from 1.2eV to 1.6eV, the transparency window changes from 1.7THz to 2.0THz, achieving significant tunability. This indicates that the structure we design can be used in tunable THz devices. We establish the coupling Lorenz oscillator model to analyze the interference between the bright and the dark modes of the structure. The theoretical results are consistent with the simulations.