Ta2NiSe5 nanosheets as a novel broadband saturable absorber for solid-state pulse laser generation

Two-dimensional (2D) ternary chalcogenides have attracted great attentions because of their novel chemical and physical properties arising from the synergistic effect and stoichiometric variation with the additional third element compared with their binary counterparts. Here, high-quality 2D tantalum nickel selenide (Ta2NiSe5) nanosheets are successfully fabricated by a liquid-phase exfoliation (LPE) method. The ultrafast excited carrier relaxation time and nonlinear optical absorption response are investigated and reveal that the prepared 2D Ta2NiSe5 nanosheets have excellent broadband saturable absorption properties, which are further illustrated by three passively Q-switched (PQS) all-solid-state lasers operating at 1.0, 2.0 and 2.8 µm with the Ta2NiSe5 nanosheet-based saturable absorber (SA). Furthermore, mode-locked laser operation with the pulse width as short as 356 fs is also realized at 1.0 µm. This work not only demonstrates the excellent nonlinear optical proprieties and optical modulation performance of Ta2NiSe5, but also paves the way for exploring the photonic and optoelectronic proprieties of ternary chalcogenide materials.