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• Few-layer NiTe 2 nanosheets are prepared by combining the convenient chemical synthesis and liquid phase exfoliation. • Two-dimensional semi-metallic NiTe 2 exhibits saturable absorption properties, which has been seldom reported. • Er-doped and Tm-doped mode-locked fiber lasers are realized using NiTe 2 -based tapered fiber saturable absorber, respectively. Two-dimensional transition metal dichalcogenides (TMDs) have been widely used in ultrafast optics. However, the traditional TMDs such as MoS 2 and WS 2 have narrow operating band and slow carrier recovery time, limiting their practical application. Among various kinds of TMDs, nickel ditelluride (NiTe 2) is a special type-II Dirac semi-metallic TMD material developed recently, showing great potential in ultrafast pulse generation due to its broadband optical response, ultrafast carrier recovery time, strong light-matter interaction and high chemical stability. Nevertheless, there has been no research reported on the NiTe 2 based saturable absorber (SA) and its application in the mode-locked laser at the 1.5 and 2 μm regions. In this work, few-layer NiTe 2 nanosheets were prepared and SA device was further fabricated by depositing them on a tapered fiber. The saturable absorption property of NiTe 2 SA was confirmed by using a balanced twin-detector measurement system. With the use of NiTe 2 SA, the Er-doped mode-locked fiber laser with a central wavelength of 1567.3 nm and a pulse width of 1.07 ps was achieved. Moreover, the Tm-doped mode-locked fiber laser with a central wavelength of 1966.08 nm was also obtained based on the NiTe 2 SA. These results show that NiTe 2 is a promising SA material for ultrafast pulse laser. [ABSTRACT FROM AUTHOR]

• Two-dimensional PdTe 2 is a novel saturable absorption material which has been rarely reported. • Few-layer PdTe 2 nanosheets are prepared by the simple and effective ultrasonic liquid exfoliation method. • Yb-doped mode-locked fiber laser with a pulse width of 887.2 ps is realized using PdTe 2 /PVA as the saturable absorber. In this work, two-dimensional few-layer palladium ditelluride (PdTe 2) nanosheets are produced by the simple and effective ultrasonic liquid exfoliation method and used as novel saturable absorber in an Yb-doped mode-locked fiber laser. The results show that the prepared flexible PdTe 2 /PVA composite film has a modulation of 3.7% and a saturation intensity of 77.6 MW/cm2. The obtained Yb-doped mode-locked fiber laser based on the film shows a pulse width of 887.2 ps with a repetition and central wavelength of 8.921 MHz and 1069 nm, respectively. So far, there has been few reports on PdTe 2 as saturable absorbers to realize mode-locked fiber lasers. The results suggest that two-dimensional PdTe 2 has great potential applications in nonlinear optics and ultrafast photonics. [ABSTRACT FROM AUTHOR]

As a kind of semiconductors, tellurium has attracted much attention due to its superior optical, electrical, and thermoelectric properties. In particular, a lot of research on low-dimensional tellurium has been performed in recent years, but with relatively few work on its applications in ultrafast photonics. In this work, a femtosecond fiber laser was realized using the prepared tellurium nanowires as the saturable absorber. Tellurium nanowires were synthesized by the hydrothermal method and then deposited on the tapered optical fiber to form the tellurium saturable absorber (Te-SA). The saturable absorption property of Te-SA was tested by the two-arm balance detection method, the saturation intensity and modulation depth were determined to be 8.9 MW/cm2 and 27.0%, respectively. Then, Te-SA was applied in the erbium-doped fiber laser and a stable mode-locked fiber laser with a pulse width of 621 fs was achieved. The results indicate the great potential application of tellurium nanowires in ultrafast photonics. • Tellurium nanorods are prepared by a green and safe hydrothermal method. • The saturable absorber based on the tellurium nanorods shows strong nonlinear optical absorption property. • A mode-locked Er-doped fiber laser with of a pulse width of 621 fs was realized based on the Te-SA. [ABSTRACT FROM AUTHOR]