AUTHORS:

Wang Y., Luo Y., Wen J., Dong Y., Wang T., Mou C., Chen W., Pang F., Zou W., Buczynski R., Peng G.-D.

ABSTRACT:

The previous studies have shown that the presence of bismuth (Bi) nanoparticles in bismuth-doped fibers (BDFs) will lead to the decrease of the luminescence responsible from bismuth active centers (BACs). To better understand the characteristics of BACs, this study examines the effect of Bi nanoparticles on the spectral intensity of BDFs from the aspects of host materials, BAC types, temperature, and excitation photon energy. A first-order reaction kinetic model incorporating the photocatalytic process of Bi nanoparticles, based on the theory of interband plasmon resonance, was established to investigate the intrinsic relation between Bi nanoparticles and BAC deactivation. By comparing the constants of thermal activation rate and thermal deactivation rate of BAC-Si in thermal annealing with dwelling time of 60 and 120 s, it was found that the latter case is significantly higher than the former at over 600 °C. Specifically, the thermal activation rate reaches up to 12.19 times at 800 °C. Such observation is resulted from the competitive interaction between the photocatalytic process of Bi nanoparticles and the thermal deactivation of BAC, associated with the valence state differences of Bi ions in BACs responsible for the same luminescence band. Additionally, it was found that the ionization of BACs caused by the photocatalytic effect of Bi nanoparticles is not only proportional to the irradiation wavelength, but also related to the local dielectric properties of BACs. By comparing the normalized ionization rates of different BACs under pumping at wavelengths ranging from 407 to 1460 nm, the values of the imaginary part of the local dielectric constant are in the order of BAC-Si < BAC-P < BAC-Al < BAC-Ge. Especially, BAC-Ge is more susceptible to ionization and inactivation due to the enhanced photocatalytic effect of Bi nanoparticles.

Optics & Laser Technology, 2025, vol. 187, art. 112844, doi: 10.1016/j.optlastec.2025.112844