1T-polytype tantalum disulfide (1T-TaS2), an emerging strongly correlated material, features a narrow bandgap of 0.2 eV, bridging the gap between zero-bandgap graphene and large-bandgap 2D nonlinear optical (NLO) materials. Combined with its intense light absorption, high carrier concentration, and high mobility, 1T-TaS2 shows considerable potential for applications in broadband optoelectronic devices. However, its NLO characteristics and related applications have rarely been explored. Here, 1T-TaS2 nanosheets are prepared by chemical vapor deposition. The ultrafast carrier dynamics in the 400–1100 nm range and broadband NLO performance in the 515–2500 nm range are systematically studied using femtosecond lasers. An obvious saturable absorption phenomenon is observed in the visible to IR range. The nonlinear absorption coefficient is measured to be -22.60±0.52cmMW-1 under 1030 nm, which is larger than that of other typical 2D saturable absorber (SA) materials (graphene, black phosphorus, and MoS2) under similar experimental conditions. Based on these findings, using 1T-TaS2 as a new SA, passively Q-switched laser operations are successfully performed at 1.06, 1.34, and 1.94 μm. The results highlight the promise of 1T-TaS2 for broadband optical modulators and provide a potential candidate material system for mid-IR nonlinear optical applications.

We report on a power-scalable sub-100-fs laser in the 2-μm spectral range using a Tm³⁺-doped ‘mixed’ (Lu,Sc)₂O₃ sesquioxide ceramic as an active medium. Pulses as short as 58 fs at 2076 nm with an average output power of 114 mW at a pulse repetition rate of approximately 82.9 MHz are generated by employing single-walled carbon nanotubes as a saturable absorber. A higher average power of 350 mW at 2075 nm is obtained at the expense of the pulse duration (65 fs). A maximum average power of 486 mW is achieved for a pulse duration of 98 fs and an optical conversion efficiency of 22.3%, representing the highest value ever reported from sub-100-fs mode-locked Tm lasers.

Structured ultrashort-pulse laser beams, and in particular eigenmodes of the paraxial Helmholtz equation, are currently extensively studied for novel potential applications in various fields, e.g., laser plasma acceleration, attosecond science, and fine micromachining. To extend these prospects further, in the present work we push forward the advancement of such femtosecond structured laser sources into the 2-μm spectral region. Ultrashort-pulse Hermite– and Laguerre–Gaussian laser modes both with a pulse duration around 100 fs are successfully produced from a compact solid-state laser in combination with a simple single-cylindrical-lens converter. The negligible beam astigmatism, the broad optical spectra, and the almost chirp-free pulses emphasize the high reliability of this laser source. This work, as a proof of principle study, paves the way toward few-cycle pulse generation of optical vortices at 2 μm. The presented light source can enable new research in the fields of interaction with organic materials, next generation optical detection, and optical vortex infrared supercontinuum.

We report on a high-power Ho:YAG single-crystal fiber (SCF) laser inband pumped by a high-brightness Tm-fiber laser at 1908 nm. The Ho:YAG SCF grown by the micro-pulling-down technique exhibits a propagation loss of $0.05\pm 0.005~\text{cm}^{-1}$ at $2.09~\unicode[STIX]{x03BC}\text{m}$. A continuous-wave output power of 35.2 W is achieved with a slope efficiency of 42.7%, which is to the best of our knowledge the highest power ever reported from an SCF-based laser in the 2 $\unicode[STIX]{x03BC}\text{m}$ spectral range.

For the first time, a group-VI single element nanomaterial was used as the optical saturable absorber (SA) to generate laser pulses. With two-dimensional (2D) tellurene as a passive Q-switch, 1.06 μm and 1.3 μm pulse laser operations were realized from a diode-pumped Nd:YAG crystal. The shortest pulse widths were 98 ns and 178 ns, and the highest peak powers were 2.68 W and 2.45 W, respectively. Our research determines that tellurene is an excellent SA material in the near-infrared region.

With tin diselenide (SnSe₂) film as a saturable absorber (SA), the passively Q-switched self-frequency doubling (SFD) lasers were realized in Nd³⁺:ReCa₄O(BO₃)₃ (Re = Y, Gd) crystals. For Nd:YCa₄O(BO₃)₃ crystal, the maximum average output power at 532 nm was 19.6 mW, and the corresponding pulse repetition frequency, pulse duration, single pulse energy, and peak power were 17.6 kHz, 91.9 ns, 1.1 μJ, and 12.1 W, respectively. For Nd:GdCa₄O(BO₃)₃ crystal, these values were 14.5 mW, 22.1 kHz, 48.7 ns, 0.66 μJ, and 13.5 W.

For the first time to our knowledge, graphitic carbon nitride (g-C3N4) nanosheets are found to be an excellent saturable absorber material in the visible waveband. g-C3N4 exhibits much stronger saturable absorption in this region than in the near-infrared region, unlike other two-dimensional materials such as graphene and black phosphorus. By the Z-scan method, the nonlinear absorption coefficient β of the material is first measured at three visible wavelengths, and for g-C3N4 it is 2.05, 0.34, and 0.11 cm·GW 1 at 355, 532, and 650 nm, respectively. These are much larger than 0.06 cm·GW 1 at 1064 nm.

Owing to the small differences between the cross-sections of the four emission peaks around 1.3 μm, an efficient four-wavelength synchronous launched laser is demonstrated using a Nd:GdLuAG crystal. The laser has no special resonator design. The maximum output power is 4.28 W, which corresponds to a conversion efficiency of 45.6%. For the Q-switching, the laser operated in dual-wavelength mode, and the single pulse energy is maintained at ～80 μJ. By calculating the population inversion density, multi-wavelength emission characteristics in both continuous wave and Q-switching lasers are discussed.