The Study Of Transmission Characteristic Of Terahertz Wave Photonic Crystal Fibers

Terahertz(THz) wave refers to electromagnetic radiation in the frequency interval from0.1THz to10THz, it occupy a relatively unexplored portion of the electromagnetic spectrum. It has very important academic and application value, so it has become the research object of many researchers in recent years. The plastic (Polyethylene, Teflon, etc) type of photonic crystal fiber have become an ideal transfer medium for THz waves because of its super smooth dispersion and low loss transmission. To guide THz waves over long distance with single mode, low dispersion and low loss, it is still a difficult task for researchers. My research work will be introduced in the following paragraphs.1. A novel type of THz-PCF with three small air holes equilateral triangle core is proposed. The shape of cladding is a standard hexagon of triangle lattice structure. The core region is introduced into three small air holes forming an equilateral triangle. Polyethylene is adopted as the basement material. The structure not only has the unique properties of photonic crystal fiber, but also more parameters can be adjusted. In addition, the lower confinement loss and waveguide dispersion can be obtained in the frequency range of single-mode transmission.2. As THz wave frequency range is very wide, achieving the endless single-mode transmission is very difficult in terahertz band. In this paper, the single-mode transmission characteristics are analyzed by using the theory of frequency normalization. The results show that the Terahertz frequency range of the single-mode transmission can be adjusted by optimizing the cladding pitch, cladding air hole, core air hole diameters and core air hole numbers. The more important thing is that the single-mode bandwidth increases as the diameter of cladding air holes, and the core air hole decreases. And it will decreases as the pitch of the cladding decreases with other parameters unchanged.3. The dispersion, loss and effective mode field area of the triangle core terahertz photonic crystal fibers are analyzed in single-mode bandwidth by the full vector finite element method. The results show that the Terahertz frequency range of the single-mode transmission can be adjusted by optimizing the diameters of cladding pitch, cladding air hole and core air hole.0.1THz～5THz broadband single-mode transmission the range of can be obtained and waveguide dispersion can be limited in+0.5ps/(nm·km)--2ps/(nm·km) for wavelength of60μm～600μm when A, d1and d2are400μm,100μm and40μm respectively. In addition, the confinement loss decreases as the frequency increase and absorption loss increases as the frequency increases, and gradually tend to be more smooth with frequency increasing in the frequency of0.1THz～5THz. Through designing structure of the fiber, the broadband, single mode, low dispersion, low loss and large mode field area can be achieved.