The Field and Energy Distributions of the Fundamental Mode in the Solid-Core Photonic Crystal Fibers for Different Geometric Parameters

For a solid core photonic crystal fiber with the triangular lattice, the field and energy distributions of fundamental mode are considered at 1.55？μm wavelength. The silica core is constituted by removing the 7 air holes. The cladding consists of the two-dimensional silica-air photonic crystal with the 4 rings of air holes. The field and energy distributions were investigated for three different values of . Here, d and represent the diameter of air holes and the pitch length, respectively. The simulations show that, for the fixed , the increase in ratio does not cause the considerable changes in the field and energy intensity distributions, but for the fixed , the increase in this ratio affects the intensity distributions reasonably. 1. Introduction In recent years, the photonic crystal fibers (PCFs) have been of significant interest due to their unique structures and new properties [1–6]. Generally, photonic crystal fibers consist of an arrangement of air holes in the cladding extending the whole length of the fiber. Photonic crystal fibers are categorized into two groups according to light guiding mechanism. One is the index guiding photonic crystal fiber, and the other is the photonic band gap PCF. In the index guiding PCFs, the core region is solid and the light is confined in the central core as in the conventional fibers. The photonic crystal fiber consists of the pure silica fiber with an array of the air holes along the length of the fiber. The core is constituted by removing the central hole from the structure. The higher effective refractive index of the surrounding holes forms cladding in which leading the index guiding mechanism analogous to total internal reflection. Consequently, the light guiding can be explained by the total internal reflection which is also the way light is guided in step index fibers. If around the central air hole there is the two-dimensional photonic crystal cladding which consists of a periodic array of the silica and air, such fibers are called the photonic band gap photonic crystal fibers. The central hole in these fibers acts as the core, and in this place the light is guided by the photonic band gap effect. The frequencies within the band gap of the structure will expose to the multiple Bragg reflection that leads to the destructive interference of the light trying to propagate away from the air core. The function of the air core is to provide a defect at the periodic structure that the propagation of the frequencies within the photonic band gap is really allowed. Therefore, it is not needed for the core indexes