Research On Propagation Characteristics Of Terahertz Photonic Crystal Fiber

The terahertz (THz) region that lies between the millimeter and infrared region in the electromagnetic spectrum, with frequencies ranging from 100 GHz to 10 THz, is an important region. This is because various characteristic parameters of materials, such as phonons, excitons, and cooper pairs exist in this region. To date, progress in THz spectroscopy has been enormous such as THz-radiation emitters and detectors. THz spectroscopy techniques uses mainly free space propagation of this far-infrared electromagnetic (EM) wave and it is to some extent difficult to control and guide.On the other hand, photonic crystal fibers (PCF) has engendered growing interest over the past few years since they offer the opportunity to create new means of THz wave guiding, compared to the conventional optical fibers, such as broadband single-mode operation and air guiding.Based on the study and analysis of photonic crystal fibers, this paper presents the design and analysis of several new configurations of PCF. Beginning with existing commonly used numerical methods, this research choose the frequency and time domain methods the plane wave method (PWM) and the finite difference time domain method (FDTD) to model and simulate the new configuration PCFs. PWM, FDTD and the applicability to the periodical 2D PCF are discussed.A new configuration of single-polarization single-mode (SPSM) PCF is proposed. The properties of the fundamental space-filling mode (FSM) are analyzed in detail by the PWM, and give a criterion of SPSM PCFs. By FDTD method, numerical modeling of the electromagnetic in time domain is analyzed, and then the dispersion properties under the influence of the fiber structural parameters are examined.Based on the analyzed of SPSM PCF, highly birefringent enlarged holes rectangular lattice PCF is proposed. Birefringent property meets the anticipation. Another phenomenon is that for these structures, there is a frequency point at which the group-velocity dispersion of the two polarization states are both zero.At last, the first THz polyethylene photonic crystal fiber (PPCF) using perfusion technics was fabricated. It is a two-dimensional triangular PPCF. At the center of the structure, one hole is missing to create a high refractive index defect.