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.

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.