Towards visible-wavelength passively mode-locked lasers in all-fibre format

Mode-locked fibre lasers (MLFLs) are fundamental building blocks of many photonic systems used in industrial, scientific and biomedical applications. To date, 1–2 μm MLFLs have been well developed; however, passively mode-locked fibre lasers in the visible region (380–760 nm) have never been reported. Here, we address this challenge by demonstrating an all-fibre visible-wavelength passively mode-locked picosecond laser at 635 nm. The 635 nm mode-locked laser with an all-fibre figure-eight cavity uses a Pr/Yb codoped ZBLAN fibre as the visible gain medium and a nonlinear amplifying loop mirror as the mode-locking element. First, we theoretically predict and analyse the formation and evolution of 635 nm mode-locked pulses in the dissipative soliton resonance (DSR) regime by solving the Ginzburg-Landau equation. Then, we experimentally demonstrate the stable generation of 635 nm DSR mode-locked pulses with a pulse duration as short as ~96 ps, a radio-frequency signal-to-noise ratio of 67 dB and a narrow spectral bandwidth of 1 nm) and modulated optical spectrum. This work represents an important step towards miniaturized ultrafast fibre lasers in the visible spectral region. Chinese scientists have demonstrated a low-cost and compact ultrafast passively mode-locked laser that operates in the visible light spectrum and could see use in a range of industrial, scientific, and biomedical applications. Although Mode-locked fibre lasers (MLFLs) are the fundamental building blocks of many photonic systems, ultrafast lasers in the visible light spectral region are costly and challenging to make. For the first time, Zhengqian Luo and colleagues from Xiamen University in China have demonstrated a visible-wavelength passively mode-locked all-fibre laser that operates in the dissipative soliton resonance regime. The laser generates picosecond pulses of light at 635 nanometres and represents an essential step towards miniaturized ultrafast fibre lasers in the visible light range. The work lays the foundations for photonic devices for use in applications such as material processing, medicine, spectroscopy, and optical communications.