Two-dimensional material-based saturable absorbers: towards compact visible-wavelength all-fiber pulsed lasers

TLDR

Passive Q‑switching or mode‑locking using a saturable absorber inside the laser cavity is a highly effective pulse‑generation technique, yet most existing absorbers fail in the visible spectrum, hindering visible‑wavelength pulsed fibre lasers. The study reports visible‑wavelength saturable absorbers based on 2D transition‑metal dichalcogenides (WS₂, MoS₂, MoSe₂) and demonstrates compact red‑light Q‑switched Pr³⁺‑doped all‑fibre lasers. The performance arises from the ultrafast saturable absorption of layered TMDs in the visible and a compact all‑fibre cavity incorporating a dielectric‑mirror‑coated fibre end facet. Passive Q‑switching at 635 nm produced stable 200 ns pulses with 28.7 nJ energy and 232–512 kHz repetition, indicating a promising route toward high‑performance visible and ultraviolet pulsed lasers.

Abstract

Passive Q-switching or mode-locking by placing a saturable absorber inside the laser cavity is one of the most effective and popular techniques for pulse generation. However, most of the current saturable absorbers cannot work well in the visible spectral region, which seriously impedes the progress of passively Q-switched/mode-locked visible pulsed fibre lasers. Here, we report a kind of visible saturable absorber-two-dimensional transition-metal dichalcogenides (TMDs, e.g. WS2, MoS2, MoSe2), and successfully demonstrate compact red-light Q-switched praseodymium (Pr(3+))-doped all-fibre lasers. The passive Q-switching operation at 635 nm generates stable laser pulses with ∼200 ns pulse duration, 28.7 nJ pulse energy and repetition rate from 232 to 512 kHz. This achievement is attributed to the ultrafast saturable absorption of these layered TMDs in the visible region, as well as the compact and all-fibre laser-cavity design by coating a dielectric mirror on the fibre end facet. This work may open a new route for next-generation high-performance pulsed laser sources in the visible (even ultraviolet) range.