Broadband 1T-polytype tantalum disulfide saturable absorber for solid-state bulk lasers

Abstract

1T-polytype tantalum disulfide ( 1 T-TaS 2 ), 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, 1 T-TaS 2 shows considerable potential for applications in broadband optoelectronic devices. However, its NLO characteristics and related applications have rarely been explored. Here, 1 T-TaS 2 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 ± 0.52 cm MW − 1 under 1030 nm, which is larger than that of other typical 2D saturable absorber (SA) materials (graphene, black phosphorus, and MoS 2 ) under similar experimental conditions. Based on these findings, using 1 T-TaS 2 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 1 T-TaS 2 for broadband optical modulators and provide a potential candidate material system for mid-IR nonlinear optical applications.