The self Q-switching mode-locking effect in compact red fiber laser has been investigated. The Q-switched mode-locking state can keep operating with a pump power ranging from 120.5 mW to 564.8 mW. The maximum average output power of this self Q-switched mode-locking laser is 22.5 mW, and the central wavelength of the output optical spectrum is 635.9 nm with a 3 dB bandwidth of 2.4 nm, as well as the fundamental repetition rate of mode-locking pulse trains being 25.8 MHz. This work can provide an attractive method for Q-switched mode-locking pulse generation in visible fiber lasers.

Transition metal dichalcogenides (TMDs) possess a direct bandgap in the visible frequency range and can be applied as attractive visible saturable absorbers (SAs). In this paper, a new TMDs tungsten selenide (WSe)-based red Q-switcher is fabricated and successfully used for Q-switched pulse generation in a red Pr-doped ZBLAN fiber laser. The passive Q-switching fiber laser at 635.2 nm generates a stable pulse with pulse duration of 504 ns and average output power of 4.91 mW as well as a tunable pulse repetition rate of 131.9-260.4 kHz. Furthermore, the size effect of WSe on the 635 nm passive Q-switching output performance is also investigated. Our work will provide certain significance for the optimization of passive Q-switching red fiber lasers based on TMDs.

We demonstrate, for the first time to the best of our knowledge, four wave mixing (FWM) process in a 900 nm wavelength region. A 54 m highly nonlinear photonic crystal fiber (HN-PCF) is used as nonlinear medium, and continuous wave laser diodes at near 975 nm are selected as pump sources. By simultaneously injecting two pump sources into the HN-PCF, FWM is observed with wavelength spacing of 0.4 nm and 2 nm, respectively. Compared with FWM in conventional highly nonlinear fibers, HN-PCF one possesses much higher conversion efficiency. These FWMs introduce an opportunity to extend the wavelength coverage of fiber lasers and amplifiers in 900 nm waveband, and also indicate that HN-PCFs can have great potential for FWM applications towards short wavelength regions.

A wavelength widely tunable all-fiber Tm3+-doped double clad fiber laser by using topological insulator (TI) as saturable absorber (SA), for the generation of large energy passively Q-switched pulse, is demonstrated. This 2 μm fiber laser source can generate an average output power as high as 195 mW, corresponding to a pulse energy of ∼3 μJ, and the laser wavelength can be widely tuned from 1935.42 to 2048.85 nm. This high-performance Q-switched operation is implemented by purpose laser cavity optimization and TI-SA protection. Overall, the above results can provide an easily accessible way to develop large energy wavelength tunable passively Q-switched 2 μm fiber laser sources, which possesses important applications in various fields, including manufacturing, spectroscopy, medicine, and the military.