We proposed a passively stabilized Q-switched E r : L u 2 O 3 laser at 2845 nm, applying a MXene N b 2 C T x nanosheets saturable absorber prepared by the liquid-phase exfoliation method. The surface morphology and nonlinear properties of this nanosheet were systematically characterized. Average output power of 542 mW for the Q-switched laser was obtained under 7.26 W of absorbed pump power. Meanwhile, the Q-switched pulse duration was measured to be 223.7 ns with 142.9 kHz repetition rate corresponding to a peak power of 16.96 W.

In the current study, layered metallic vanadium disulfide (VS₂) is fabricated by a liquid-phase exfoliation method, and its microstructures as well as optical characteristics are investigated. Based on first-principles calculations, the band structure and density of the states of both bulk T-VS₂ and monolayer H-VS₂ are illustrated, showing the metallic behavior with a zero band gap. By using VS₂ as the saturable absorber in a doubly Q-switched Tm:YAP laser with an EOM, the Q-switching laser pulses at 2 μm with 22 ns and 200 Hz are generated, corresponding to the single pulse energy of 755 μJ and the peak power of 34.3 kW. The coupled rate equations of the doubly Q-switched laser are given, and the numerical simulations agree with the experimental results. The results indicate that VS₂ is a promising nanomaterial due to its nonlinear optical property. The doubly Q-switched laser demonstrates a high level of performance in reducing pulse width and enhancing pulse peak power.

Abstract We firstly propose a roadmap for the design of high repetition rate (~100 MHz) Tm-doped ultrafast fiber laser with an emission wavelength above 2000 nm. This roadmap is confirmed by both theoretical simulation and experimental verification. The designed Tm-doped fiber oscillator not only operates in continuous wave regime with a broad tunable wavelength range of ~ 100 nm, but also in mode-locking regime with an emission wavelength > 2000 nm (up to 2020 nm). A 470-fs laser pulse with a pulse repetition rate of ~96 MHz and the maximum average power of 50 mW are achieved at the output wavelength of 2007 nm, matching well with the theoretical prediction. In a further step, the seed laser pulse is amplified to 3.3 W, accompanied by a Raman frequency shift of the output wavelength to 2346 nm. The homogeneous intense broadband spectrum with a bandwidth of 240-nm centered at 2200 nm is also observed.

An ytterbium-doped, single-stage, double-pass nonlinear fiber amplification system was fabricated for amplifying an 1100-nm mode-locking fiber laser. Pre-chirp managed amplification (PCMA) was applied in realizing the nonlinear amplification process with an all-polarization-maintaining (PM) fiber construction. The system can deliver 19.8-nJ, 58.7-fs, 24.4-MHz amplified signal pulses with a 10-dB spectral range spanning from 1049 nm to 1130 nm. Further experimental investigations were conducted in exploring the dynamics of the double-pass nonlinear amplification process. This compact 1100-nm ultrafast fiber laser can be implemented for multi-photon microscopy (MPM) with deep penetration depth.

High-power, single-frequency lasers are important in the applications of coherent optical communication, Doppler wind lidar, and remote sensing. Here, a 10-kHz, 353-μJ, single-frequency, 574-ns, 1548-nm fiber laser system was demonstrated based on the optical pulse modulation. The 1548-nm, single-frequency seed laser with the linewidth of 1.25 kHz was modulated by two acousto-optic modulators (AOMs) into a 10-kHz pulsed laser. Two cascaded fiber amplifiers were spliced after the AOMs to scale up the pulse energy. The amplified spontaneous emission (ASE) was inhibited by the multistage amplification construction and the optical bandpass filters. A customized pulse profile was proposed to pre-compensate the temporal modulation and inhibit the stimulated Brillouin scattering (SBS) effect. The pulse duration of the amplified single-frequency pulse was 574 ns, with the peak power of 753 W. A numerical model was also built for investigating the dynamic of the interaction process inside the power amplifier. The simulated results indicate the maximum output power of the 10-kHz, customized single-frequency laser can be 3.984 W with a pulse duration of 381 ns.