Tailoring bandgap transmission spectra of new Neodymium-doped tellurite all-solid photonic bandgap fibers with double cladding layers

摘要

Neodymium (Nd)-doped fibers are potential candidates for optical fiber amplifiers operating near the 1.3-μm spectralregion due to the ~4F_(3/2)→~4I_(13/2) transition of Nd~(3+) ions. But, there is an amplified spontaneous emission at 1.06 μm due tothe ~4F_(3/2)→~4I_(11/2) transition whose branching ratio is about 5 times larger than that at 1.3 μm. In order to suppress thetransmission of the 1.06-μm emission, we propose a new tellurite all-solid photonic bandgap fiber (ASPBF) with a singleline of high index rods and double cladding layers. Tellurite glasses of TeO_2-Li_2O-WO_3-MoO_3-Nb_2O_5 (TLWMN), TeO_2-ZnO-Na_2O-La_2O_3 (TZNL) and TeO_2-ZnO-Li_2O-K_2O-Al_2O_3-P_2O_5 (TZLKAP) are developed. High-index rods ofTLWMN and an Nd-doped TZNL rod are arranged symmetrically and horizontally in the x-axis of a hexagonal TZNLcladding. The outer cladding is made of the TZLKAP glass. The finite element method is used to calculate the modedistribution and the bandgap properties. The fiber transmission spectra are numerically investigated with the effects ofrod diameter and filling factor variation. When the core diameter is 3.0 μm, rod diameter is 2.3 μm and filling factor isfrom 0.7 to 0.8, the 1.06-μm emission which is caused by the ~4F_(3/2)→~4I_(11/2) transition can be suppressed as compared withthe 1.33-μm emission which is caused by the ~4F_(3/2)→~4I_(13/2) transition.