Thz Photonic Crystal Defect Transmission Conditions And Laws

The terahertz (THz) wave and photonic crystals have been important research contents in the field of science during recent years. The terahertz region that lies between the millimeter and infrared region in the electromagnetic spectrum is a transitional area between electronics and photonics. So it has many unique advantages, and it has potential applications in many domains including imaging, environment monitoring, medical diagnosing and broadband mobile communications. Now more and more attentions and interests focus on the THz. However, the transmission loss is too severe because the devices with low dispersion and low loss fall behind greatly. If this problem can't be solved, the research and application of THz wave will be blocked.Photonic crystals are optical structures with periodic variations of the refractive index. There are frequency bands, which called photonic bandgap, in the periodic dielectric materials. If there are dot or line or plane defects in the periodic dielectric, it will appear frequency bands in which electromagnetic wave can propagate perfectly. The photonic band gap structures have been experimentally used effectively in many domains, and can achieve special function by introducing defects in it. These performances do well in the terahertz ranges too. Besides, an important reason for design the terahertz photonic crystal propagating devices is the availability of precision manufacturing techniques in sub-millimeter, as the fabrication of a photonic crystal for the optical region can be a high technical challenge and the size of photonic crystal in microwave is too big. Therefore, analyzing the photonic crystal material and design the terahertz photonic crystal are significant in applying the THz technology.Plane wave expansion method is used in this paper to study the bandgap characteristic of the two dimensional photonic crystal in terahertz region. This paper analyzes the stuff that may be used in terahertz region as photonic material, and chooses silicon as dielectric material to study the transmission characteristic of photonic waveguide in terahertz region. Also this paper studies how the radius and the refractive index of the dielectric cylinders affect the bandgap of the photonic crystal in two dimensional rectangular photonic lattice and triangular photonic lattice and their opposite-phase structures; how the radius and the refractive index of the spheres affect the absolutely bandgap of photonic crystal in three dimensional fcc and diamond structure and their opposite-phase structures. And on the basis of former research, some waveguides are designed, including line waveguide,90°waveguide, T-junction in THz range. As a result, we find that there is a close relationship between the effectiveness of propagating and the size of photonic crystal. In other words, THz wave can propagate effectively in the waveguide when the photonic bandgap is wide enough.