Effect of optical anisotropy of bismuth active centers on polarization properties of fiber laser at 1.46 µm

A bismuth-doped fiber laser emitting optical radiation near 1.46 µm in two orthogonally polarized modes is presented. The laser was realized in an all-polarization-maintaining (PM) fiber configuration based on a gain medium with bismuth active centers associated with Si atoms (BACs-Si) and a fiber Bragg grating providing high reflectivity of two orthogonal polarizations. The single- and dual-polarized laser oscillations were achieved in various configurations. The polar plots of the laser output power in each mode as a function of pump polarization angle were obtained and analyzed. The conditions for achieving lasing in single- and dual-polarized modes were determined. In addition, the numerical model taking into account absorption and emission cross-section anisotropies of BACs-Si is proposed to study the behavior of the laser characteristics. The research can be useful for designing fiber laser sources with controllable polarization properties.