Thermally diffused expanded-core fibers with gain or loss

Abstract

We investigate the modal properties of thermally diffused expanded-core fibers (TEC) with loss or gain. The corresponding Helmholtz equation with complex refractive index profile is solved numerically using Galerkin's method. The imaginary part of the modal electric field results in wave-front distortion showing that the power flows out or into the doped region according to the sign of the imaginary part of the refractive index. The spectral characteristics of the calculated gain or loss are discussed. Our results may potentially be useful to design high power fiber lasers or amplifiers using TEC technique. © 2009 Photonics Society of Poland.