1T-titanium selenide (1T-TiSe2), a representative of 1T phase transition metal dichalcogenides (TMDs), exhibits semimetallic behaviour with a nearly zero bandgap structure, which makes it a promising photoelectric material. A high-quality multilayer 1T-TiSe2 saturable absorber (SA) is successfully fabricated by a combination of liquid phase exfoliation and the spin coating method. The broadband nonlinear saturable absorption properties of the prepared 1T-TiSe2 SA are investigated by using the open aperture (OA) Z-scan method. Passively Q-switched (PQS) all-solid-state lasers with different bulk crystals at the wavelengths of 1.0, 1.3, 2.0 and 2.8 μm are realised based on the 1T-TiSe2 SA. To the best of our knowledge, this is the first presentation of the application of a 1T-TiSe2 material to all-solid-state bulk lasers. The results indicate that 1T-TiSe2 could be an alternative broadband SA for solid-state pulsed lasers and exhibits promising potential applications in mode-locked ultrafast lasers.

2D van der Waals metal 3R phase niobium disulfide (3R‐NbS2) has fascinating anisotropic, magnetic, optical, and superconducting properties. Herein, few‐layered 2D 3R‐NbS2 nanosheets are fabricated by combining liquid phase exfoliation and spin‐coating methods. The first principles calculations are performed to explore their electronic band structures to reveal the metallic properties and enhanced optical absorption as thickness increased. The linear and nonlinear optical properties arising from the plasmonic effects and nonequilibrium electrons are studied through the violet–visible–near‐infrared absorption spectroscopy, polarization‐resolved optical microscopy, and open‐aperture Z‐scan methods. The nonlinear absorption coefficient and imaginary part of the third‐order susceptibility are determined to be −2.5 × 106 cm GW−1 and −2.4 × 10−6 esu at 1064 nm. Furthermore, 2D 3R‐NbS2 nanosheets based saturable absorbers are fabricated and applied in solid‐state pulsed lasers, in which a continuous‐wave mode‐locking laser operation at 1050.6 nm is demonstrated with a pulse duration of 302 fs. The results not only verify that 2D metallic materials, such as 3R‐NbS2, are excellent nonlinear optical modulators, but also will arouse a general interest in designing novel materials/structures with 2D metallic materials for electronic and photonic devices.

1T-phase titanium diselenide (1T-TiSe), a model two-dimensional (2D) transition metal dichalcogenide, has attracted much attention due to its intriguing electrical and optical properties. In this work, a 1T-TiSe-based high-quality large-area saturable absorber (SA) (1T-TiSe-SA) was successfully fabricated with the liquid-phase exfoliation method. With the as-prepared 1T-TiSe-SA, a stable, passively Q-switched laser operating at 2.95 μm was first realized. Under an absorbed pump power of 3.35 W, the maximum average output power was 130 mW with a slope efficiency of 5%. A pulse width of 160.5 ns was obtained, which is the shortest among 3.0 μm passively Q-switched lasers ever achieved with 2D materials as SAs, to the best of our knowledge. The results indicate that 1T-TiSe is a promising alternative as a nonlinear optical modulator for short-pulse laser generation near the 3.0 μm mid-infrared region.

No abstract