Effects of thermal treatment on photoluminescence properties of bismuth/erbium co-doped optical fibers

The effects of thermal annealing on the photoluminescence (PL) properties of bismuth/erbium co-doped multicomponent optical fiber (BEDFs) in a temperature range of from room temperature (RT) up to 1100 °C are clarified by PL, Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) measurements. When pumped by an 830 nm laser diode, the fiber exhibits a broad near-infrared (NIR) emission band consisting of three distinctive peaks at the wavelengths of 1100, 1420 and 1530 nm, originating from different luminescence centers, viz., Al-related, Si-related bismuth active centers (BACs) and Er3+, respectively. The relative emission intensities of the BACs and Er3+ vary in distinctively different manners with thermal treatment temperature are comprehensively studied. Three temperature regions, i.e., RT ∼ 300 °C, 300-800 °C, and 800-1100 °C can be distinguished accordingly. The instability of the BACs, formation of non-luminous bismuth centers and crystallization of the fiber are proposed to account for the thermal effects on the PL behaviors of the different luminescent centers in the fiber. A first-ever piece of information is also given concerning the PL reversibility of the various luminescence centers in the BEDFs.