Design Of A Terahertz Filter In Two Dimension Photonic Crystal

Terahertz(THz) is a electromagnetic waves which frequency bands is between infrared wave and microwave. It is also known as sub-millimeter and far-infrared waves. Terahertz science and technology is a complex frontier discipline. Since the1980 s, the research of the generation of THz wave have made a great development.The progress of THz generation mechanism and modern quantum cascade laser leads to the development of the generation of THz wave. Meanwhile, the THz detection technology have greatly developed. The Terahertz science and technology research is booming across the world. The application of THz technology needs the THz devices to control terahertz wave. For example, the THz devices used to transmission and filter THz wave. The devolopment of the terahertz demand for these devices.Photonic crystal is a now optical material which has band gap structure, and photonic crystal is composed of dielectric material with dielectric constant changed periodically. We can introduce defect to change structure and adjust parameter to realize specific function. We can also change the constant of lattice so that the devices can be applied in Terahertz region. The application of photonic crystal is one of the popular research fields in terahertz technology.In this dissertation, we introduce the application, the generation, the transmission and detection of terahertz. The theoretical calculation methods were researched. The plane wave expansion method which can be used to calculate the photonic band gap structure and the finite difference time domain method can be used to analysis transmission property. The band gap structure of the rectangular lattice and the triangle lattice photonic crystal is analyzed with the plane wave expansion method. For example, we choose a rectangular two-dimensional photonic crystal with circular dielectric rods to study the properties of the point-defect cavity and linear-defect waveguide. Finally, the three-port resonant channel drop filter with a resonant reflection cavity is designed in THz region. Meanwhile, we demonstrate the terahertz filter that provides filtering functionality in the terahertz frequencyregime by coupled mode theory and the finite element method. Meanwhile, the energy of reflection to input port is close to zero, so that it will not lead to severe noise to other components if the designed structure is integrated.