Theoretical Research On Bandgap Characteristics Of Two Dimensional Square Lattice Photonic Crystals

Photonic Crystals are kinds of new-style optical materials.Because of its characteristic theory, photonic crystals have been a new hotspot in research.Moreover,the most radical characteristic of photonic crystals is photonic band gap(PBG). Many applications of photonic crystals are based on the characteristic. Actually,because it is very difficult to manufacture the photonic crystals with complex structure, investigated two dimensional photonic crystals with simple structures still have practical value.The band structure of two dimensional photonic crystals with Square lattice is simulated by using plane wave expansion method(PWM) and finite-difference time-domain method(FDTD) in the paper. Several semiconductor materials including Si and Ge are used to fabricate the Square lattice photonic crystals. The effect of variety of structure parameters and dielectric refractive index on complete photonic band gap are discussed,and some rules of complete photonic band gap are found.The researchful result of the thesis as follows:(1) The simulation results indicate that the complete photonic band gap appears in Square lattice photonic crystals when circular dielectric rods with higher refractive index. For the Square lattice photonic crystals with circular air holes in dielectric, the complete photonic band gap appears when the refractive index is more than 3.30,and the ratio of air rods diameter and lattice constant has constantly stabilized at 0.97.(2) The transmission and reflection spectra of the Square lattice photonic crystals with elliptical rods are calculated by FDTD method. The calculational results show that the complete photonic band gap wavelength width is the widest for the Photonic crystals with elliptical dielectric rods when the rotation angle is 0o,the horizontal radius is 0.1μm and the vertical radius is 0.5μm. For the photonic crystals with elliptical air holes, the the widest complete photonic band gap appears when the rotation angle is 0o, the horizontal radius is 0.2μm and the vertical radius is 0.5μm.(3) For the Square lattice photonic crystal with hexagonal columns,with the decrease of the symmetry, the bandgap width of the photonic crystals is not larger than the Square lattice photonic crystals with circular rod. Even the largest bandgap width of the photonic crystals with hexagonal air holes in Ge is less than the photonic crystals with circular air holes.(4) For the Square lattice photonic crystal with square columns,the minimum refractive index is very low when the complete photonic band gap appears. The rotation angle of dielectric rods or air holes is constant when the largest bandgap width appears.