High-energy ultra-wideband noise-like pulse emitted from a Tm-doped fiber laser

We present a high-energy, ultra-wideband noise-like pulse (NLP) based on nonlinear response and energy enhancements in a 2 μm figure-of-eight fiber laser. The nonlinear response enhancement is achieved by utilizing low-cost commercially available standard communication fiber (SMF-28) and optimizing its length in the figure-of-eight cavity. Enhancing the single-pulse energy of the ultra-wideband NLP is realized by employing a bidirectional pumping scheme. An ultra-wideband NLP with a 3 dB spectrum width of 87.6 nm and a 30 dB spectrum width of 380.1 nm is obtained at an SMF-28 length of 10 m in the nonlinear amplifying loop mirror ring and 300 m in the unidirectional ring. The highest power and pulse energy emitted from the ultra-wideband NLP fiber laser are demonstrated, reaching 429.2 mW and 700.1 nJ, respectively. Such a high-energy ultra-wideband NLP has important application prospects in improving the performance of optical coherence tomography and the flatness of the supercontinuum.