High ytterbium concentration Yb/Al/P/Ce co-doped silica fiber for 1-μm ultra-short cavity fiber laser application
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We demonstrate a high ytterbium concentration Yb/Al/P/Ce co-doped silica fiber by conventional modified chemical vapor deposition (MCVD) technology and solution doping process. The fiber has a Yb concentration of about 2.5 wt%, and the corresponding core absorption coefficient is measured to be ~1400 dB/m at 976 nm. The gain coefficient was measured to be approximately 1.0 dB/cm. It is found that the Yb/Al/P/Ce co-doped silica shows a lower photodarkening-induced equilibrium loss of 52 dB/m at 633nm than the Yb/Al/P co-doped silica fiber of 117 dB/m. Using the heavily Yb3+-doped silica fiber, a compact and robust ultrashort cavity single-frequency fiber laser was achieved with a maximum output power of 75 mW and a linewidth of 14 kHz. Furthermore, a compact passively mode-locked fiber laser (MLFL) with a repetition rate of 1.23 GHz was also proposed using our developed Yb-doped fiber. The laser properties of the proposed lasers were systematically investigated, demonstrating the superior performance of this fiber in terms of photodarkening resistance and ultrashort-cavity laser application. Furthermore, utilizing an all-fiber structure based on silica-based fiber offers the significant advantage of high stability and reliability.
我们通过传统改良化学气相沉积（modified chemical vapor deposition, MCVD）工艺与溶液掺杂法，制备出高镱掺杂浓度的Yb/Al/P/Ce共掺石英光纤。该光纤的镱掺杂浓度约为2.5 wt%，对应纤芯在976 nm处的吸收系数经测试约为1400 dB/m，增益系数经测试约为1.0 dB/cm。研究发现，相较于Yb/Al/P共掺石英光纤（其633 nm处光致暗化平衡损耗为117 dB/m），本次制备的Yb/Al/P/Ce共掺石英在633 nm处的光致暗化平衡损耗更低，仅为52 dB/m。利用该高掺Yb³+石英光纤，我们实现了一款结构紧凑、性能稳定的超短腔单频光纤激光器，其最大输出功率可达75 mW，线宽仅为14 kHz。此外，基于本课题组开发的掺镱石英光纤，我们还研制出一款重复频率为1.23 GHz的紧凑型被动锁模光纤激光器（passively mode-locked fiber laser, MLFL）。我们对两款激光器的激光特性开展了系统性研究，结果表明该光纤在抗光致暗化性能与超短腔激光应用方面均表现优异。此外，采用基于石英基光纤的全光纤结构，可显著提升系统的稳定性与可靠性。
