在二氧化硅中掺入适量GeO2可增大折射率,用其作为光子晶体光纤的纤芯时易于将光场捕获在纤芯中,形成稳定的传输模式.本文通过有限差分法数值解亥姆霍兹方程,研究了空气孔呈三角形典型结构排列的光子晶体光纤的特性.当纤芯及空气孔的大小都相同时,纤芯掺杂比例越高,光子晶体光纤的有效折射率就越高,色散则会向负向增长.此外,在这种高折射纤芯的光子晶体光纤中,当纤芯的大小及折射率均固定仅增大周围空气孔时,光子晶体光纤的色散增大,有效折射率趋于降低,模场有效面积也趋于减小.

When the core index is increased by using doped GeO2 technology in photonic crystal fiber (PCF), light is more easily confined by not only the air holes, but also the raised-index core. By numerical solving Helmholtz equation with finite differential (FD) method, some performances were studied about PCF that transverse cross sections consist of a central high-index defect in a regular triangular array of air holes. The dispersion difference is visible under all kind of doped proportion in core when the core and air hole sizes are fixed. Higher doped proportion in core will bring higher effective index of PCF and make the dispersion parameter decreasing. Furthermore, increasing the air hole sizes with fixed core size and index will make the dispersion become higher, effective index decreasing and effective area of modal field decreasing. Especially, the changing trend is little different under all kinds of doped proportion in core.