We experimentally demonstrate a passively harmonic mode locked (PHML) Er-doped fiber laser with pump power efficiency up to 17 MHz/mW operating at L-band based on single walled carbon nanotubes polyvinyl alcohol (SWCNTs-PVA) film. Under 233 mW pump power, the stable pulse train at 1594.97 nm with 40.5 dB side mode suppression ratio (SMSR) and 742 fs pulse duration is obtained at a repetition rate of 1.923 GHz, corresponding to 170th harmonic of the fundamental frequency. Under optimized intracavity conditions, the pulses frequency is able to scale up to 2.415 GHz with a high level of 40 dB SMSR, which to the best of our knowledge, is the highest value yet reported from a L-band PHML fiber laser incorporating SWCNTs as saturable absorber (SA). Such high repetition rate and stable fiber laser operating at L band may be desirable for various applications.

中文翻译：

---

基于碳纳米管薄膜的2.4 GHz L波段被动谐波锁模光纤激光器

我们通过实验证明了一种基于单壁碳纳米管聚乙烯醇 (SWCNTs-PVA) 薄膜的无源谐波锁模 (PHML) 掺铒光纤激光器，其泵浦功率效率高达 17 MHz/mW。在 233 mW 泵浦功率下，在 1.923 GHz 的重复频率下获得了 1594.97 nm 处的稳定脉冲序列，具有 40.5 dB 边模抑制比 (SMSR) 和 742 fs 脉冲持续时间，对应于基频的 170 次谐波。在优化的腔内条件下，脉冲频率能够扩展到 2.415 GHz，具有 40 dB SMSR 的高水平，据我们所知，这是结合 SWCNT 的 L 波段 PHML 光纤激光器报告的最高值饱和吸收体（SA）。