研究目的
To develop single-mode large-mode-area Er–Yb fibers with a core based on phosphorosilicate glass highly doped with fluorine to achieve high pump-to-signal conversion efficiency and true single-mode operation.
研究成果
The developed technology enables the fabrication of single-mode Er–Yb fibers with a core diameter up to 20 μm and a slope efficiency of 34% in laser configuration. The fibers exhibit true single-mode operation and low amplified spontaneous emission near 1030 nm, making them suitable for high-power applications without mode instability issues.
研究不足
The maximum Yb concentration is limited to below 2 wt.% to avoid glass devitrification and high scattering loss. The Er concentration is constrained by concentration quenching above 0.1–0.2 wt.%. The core NA reduction limits the P2O5 content, affecting the excitation transfer efficiency. The technique may not achieve perfectly flat refractive index profiles due to central dips from the MCVD process.
1：Experimental Design and Method Selection:
The study used an all-gas-phase modified chemical vapor deposition (MCVD) method to fabricate fiber preforms. The design aimed to reduce the core numerical aperture (NA) to 0.07–0.08 for single-mode operation with a large core diameter. A W-shaped refractive index profile was employed to reduce the cut-off wavelength.
2：07–08 for single-mode operation with a large core diameter. A W-shaped refractive index profile was employed to reduce the cut-off wavelength.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Fiber preforms were fabricated with cores based on F–Yb2O3–Er2O3–P2O5–SiO2 glass, doped with varying concentrations of Er and Yb. Samples were analyzed using energy-dispersive x-ray spectroscopy (EDXS) and scanning electron microscopy (SEM).
3：List of Experimental Equipment and Materials:
Precursors included SiCl4, POCl3, SiF4, Er(thd)3, and Yb(thd)3. Equipment included a JEOL JSM-5910LV SEM for chemical analysis, an EXPO NR9200HR fiber analyzer for refractive index profiling, and laser setup components such as pump diodes, combiners, and beam quality measurement systems (e.g., Thorlabs M2MS-BP209IR).
4：Equipment included a JEOL JSM-5910LV SEM for chemical analysis, an EXPO NR9200HR fiber analyzer for refractive index profiling, and laser setup components such as pump diodes, combiners, and beam quality measurement systems (e.g., Thorlabs M2MS-BP209IR).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Preforms were fabricated by depositing layers using MCVD, followed by jacketing and drawing into fibers. Fibers were tested in copropagating amplifier and laser schemes. Pump and signal powers were measured, and beam quality was assessed.
5：Data Analysis Methods:
Data on gray loss, excitation transfer efficiency (ETE), and pump-to-signal conversion efficiency (PCE) were analyzed. Statistical methods included spline interpolation for gray loss dependence and comparative analysis of fiber performance.
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