Higher-Gain Broadband Single-Mode Chromium-Doped Fiber Amplifiers by Tetrahedral-Chromium Enhancement

The net gains of 5.1 and 4.4-dB for a 300-nm broadband single-mode Cr-doped crystalline core fiber (SMCDCCF) are in demonstration with and without thermal annealing, respectively. The gain improvement was mainly achieved by enhancing the tetrahedral chromium (Cr
⁴⁺
(tetra))-ions up to 17% in the SMCDCCF annealing.