Higher Gain of Single-Mode Cr-Doped Fibers Employing Optimized Molten-Zone Growth

Enhancement of Tetrahedral Chromium (Cr4+) Concentration for High-Gain in Single-Mode Crystalline Core Fibers

“…A gross gain of 8-dB on a fiber length of 27-cm for a 300-nm broadband SCCF using a thermal annealing technique is demonstrated. In comparison with previous reports [7], [15], this study has improved in the fiber length and gain performance of the SCCFs. The 8-dB gain and 27-cm fiber length are the highest yet reported of the SCCFs.…”

“…The transmission losses of the SCCF were measured by the cutback method, which was similar to the absorption spectra. The measured transmission loss with and without annealing were 0.32 dB/cm and 0.23 dB/cm at the wavelength of 1.4 μm, respectively [7].…”

“…An aligned optimization LHPG system to fabricate the SCCFs was used and integrated with a 60W-CW CO 2 laser heat source, along with few reflective mirrors, two CCDs, a power controller, and a growth chamber [6], [7]. We optimized the molten zone like a trapezoid during the fiber growth process.…”

“…The gain simulation model of the SCCF was evaluated as the gross gain as function of optimized fiber length, transmission loss, and annealing process. In the simulation of the SCCFs, the background loss of the SCCF with annealing at 1000°C was about 0.36 dB/cm and the absorption coefficient of the Cr 4+ -ions was 0.85 cm −1 at 1064 nm wavelength [7]. The ground-state absorption and ESA cross section were set as 22 × 10 −19 and 7 × 10 −20 cm 2 , respectively [22].…”

“…Therefore, it is advisable to develop a fiber amplifier with broad covering of the low-loss transmitted bandwidth. Recently, Cr-doped fibers have been demonstrated the possible functions as broadband amplifiers for use in the next-generation fiber amplifiers [5]- [7]. The core material of the Cr-doped fiber was a single crystal of Cr 4+ :YAG (chromium doped yttrium aluminum garnet) with a glass cladding.…”