816 nm All-Fiber Mode-Locked Tm-Doped Laser in Noise-Like Pulse Regime

We report, to the best of our knowledge, the first all-fiber passively mode-locked laser around 800 nm wavelength. The laser with a figure-9 cavity configuration consists of a homemade 1146 nm Raman fiber laser as pump source, a 2.1 m-length Tm
$^{3+}$
-doped ZBLAN fiber, a 0.8/
$1.15~\mu \text{m}$
fiber end-facet dichroic mirror, and a nonlinear optical loop mirror (NOLM). The NOLM is not only employed as the output cavity mirror, and also initiates passive mode-locking. The mode-locked center wavelength is 816 nm with a 3-dB bandwidth of ~0.35 nm. The mode-locked rectangular pulse in the noise-like regime has a pulse duration of 486.7 ps with the 7.826 MHz repetition rate. The maximum average power is as high as 488.5 mW and the pulse energy is 62.4 nJ. This work represents an important step towards ~800 nm short-wavelength ultrafast fiber lasers and may has potential applications in biological imaging and medical treatment.