Search

In this work, ultrafast Yb-doped fiber laser was realized using multi-layer palladium diselenide (PdSe2) film as the saturable absorber, which was prepared by simple selenization of palladium film deposited by magnetron sputtering method. The prepared polycrystalline PdSe2 film has a thickness of about 12 nm. At a pump power of 180 mW, the obtained mode-locked fiber laser based on the PdSe2 film has a central wavelength of 1063.75 nm, a pulse width of 615 ps, a repetition rate of 17.66 MHz, and an output power of 4.43 mW, respectively. These results indicate that PdSe2 has great potential in applications of ultrafast lasers. [ABSTRACT FROM AUTHOR]

Niobium disulfide is a kind of transition metal dichalcogenides which has the advantages of large modulation depth, short excited carrier recovery time and high carrier mobility, theoretically being very suitable for the applications in ultrafast photonics. Up to now, there are few reports on the application of NbS 2 in ultrafast optical devices, especially in the devices with long working wavelength, such as 2 µm. In this work, few-layer NbS 2 nanosheets were prepared by liquid exfoliation method and the NbS 2 -SA was prepared by covering the nanosheets on tapered fiber. The device NbS 2 -SA exhibits good nonlinear saturable absorption property with a modulation depth of 10.2 % at 1550 nm. Based on the NbS 2 -SA, both 1.5 µm and 2 µm ultrafast fiber lasers are realized. The 1.5 µm mode-locked fiber laser has a pulse width of 753 fs and the 2 µm mode-locked fiber laser has an estimated pulse width of 5.77 ps and a maximum output power of 5.56 mW. All the results prove that NbS 2 is an excellent broadband saturable absorption material. • Few-layer NbS 2 nanosheets are prepared by liquid phase exfoliation. • A NbS 2 nanosheets-based tapered fiber saturable absorber with large modulation depth is fabricated. • Mode-locked pulses are obtained in Er-doped and Tm-doped fiber lasers using the same NbS 2 saturable absorber. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rigorous mode-locking performance comparison between MoS 2 and MoSe 2 is demonstrated. • Results indicate that MoS 2 has shorter excited state carrier lifetimes than MoSe 2 in visible region. • The MoS 2 and MoSe 2 show excellent performance in achieving femtosecond fiber laser. Recently, MoS 2 and MoSe 2 have attracted significant attention in ultrafast photonics owing to their excellent nonlinear optical properties. The mode-locking performance of them were also investigated intensively. However, so far, there is still no answer to who has better mode-locking performance between MoS 2 and MoSe 2. In this work, we prepared MoS 2 and MoSe 2 nanosheets and the transient absorption spectra indicate that both have excited-state carrier lifetimes of picosecond level in the visible region, and MoS 2 has a shorter recovery time than MoSe 2. The mode-locked Er-doped fiber lasers (EDFL) based on MoS 2 and MoSe 2 were carried out in the same ring laser cavity, which allows for an accurate comparison of their mode-locked performance. The mode-locked EDFL based on MoS 2 saturable absorber (SA) shows a pulse width of 470 fs, which is much shorter than that based on MoSe 2 SA (639 fs). This suggests that MoS 2 has better mode-locking performance than MoSe 2 from the viewpoint of pulse width. [ABSTRACT FROM AUTHOR]

• 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]

• Ultrathin VSe 2 nanosheets with thickness less than 5 nm are prepared by liquid phase exfoliation. • Two-dimensional metallic layered VSe 2 exhibits saturable absorption properties. • Single- and Dual-wavelength mode-locked fiber lasers are realized using VSe 2 -based saturable absorber, respectively. Vanadium selenide (VSe 2) is a special two-dimensional (2D) transition metal dichalcogenide (TMD) material with metallic properties similar to graphene, which has been proved to have saturable absorption properties and used in mode-locked fiber lasers. As an excellent saturable absorber (SA) material, VSe 2 has advantage of ultrafast carrier recovery time and broadband optical response range. However, the potential application of VSe 2 in the field of ultrafast photonics has not been fully developed so far. In this work, the as-prepared VSe 2 nanosheets were deposited on tapered fiber by optical deposition to obtain VSe 2 SA. By inserting VSe 2 SA into an Er-doped fiber laser, the mode-locked pulses with a central wavelength of 1574.4 nm can be obtained. The pulse width of the laser is measured to be ∼680 fs which is narrowest in the reported VSe 2 SA-based lasers. In addition, the unique dual-wavelength mode-locked pulse is also obtained by further adjusting intracavity dispersion and polarization. This kind of dual-wavelength pulse is valuable in high order harmonic generation enhancement, terahertz wave generation, dense wavelength division multiplexing, dual-frequency comb and other applications. Our results show that metallic VSe 2 is of great potential value in ultrafast fiber laser. [ABSTRACT FROM AUTHOR]

Abstract Tunable multi-wavelength mode-locked ytterbium-doped fiber laser is realized by using ultrathin graphitic carbon nitride (g-C 3 N 4) nanosheets as saturable absorber. g-C 3 N 4 nanosheets with an average thickness of 3.5 nm are obtained through liquid-phase ultrasonic exfoliation of g-C 3 N 4 powder prepared by high temperature sintering. Passively mode-locked ytterbium-doped fiber laser was obtained by using the g-C 3 N 4 nanosheets coated D-shaped fiber as saturable absorber. It is interesting that tunable dual-, triple- and quadruple-wavelength mode-locked lasers were obtained by adjusting the pump power and polarization controller. And the maximum average output power of the mode-locked laser can reach 10.32 mW. The pulse width of the quadruple-wavelength mode-locked laser is 1.9 ns, with a working repetition of 11.2 MHz. To our best knowledge, this is the first time reporting this tunable multi-wavelength mode-locking phenomenon based on g-C 3 N 4. Highlights • Ultrathin g-C 3 N 4 nanosheets (~3.5 nm thick) were prepared. • Stable mode-locked laser was realized based on the prepared ultrathin g-C 3 N 4 nanosheets. • Interesting tunable dual- triple- and quadruple-wavelength mode-locked lasers based on g-C 3 N 4 were first reported. [ABSTRACT FROM AUTHOR]

Novel layered bismuth oxysulfide (Bi 2 O 2 S) has shown great potential in photoelectric detection, photocatalysis, and photochemical cells due to its excellent properties such as excellent environmental stability, high carrier mobility, and favorite band gap (about 1∼1.5 eV). These excellent physical properties also make it advantageous for applications in the field of ultrafast photonics. However, to date, there has been no reported research on Bi 2 O 2 S in ultrafast fiber lasers. In this work, we report a facile method to synthesize Bi 2 O 2 S nanosheets by a combination of the hydrothermal and liquid-phase exfoliation (LPE) methods with good crystallinity and thickness less than 10 nm. Further, stable mode-locked pulses are achieved by applying the Bi 2 O 2 S SA in Er-doped and Tm-doped fiber lasers, respectively. The Er-doped mode-locked fiber laser has a pulse width of 453.6 fs and the optical spectrum is stable, with a maximum output power of 5.1 mW in the mode-locked state. The obtained Tm-doped mode-locked fiber laser based on Bi 2 O 2 S has an estimated pulse width of 2.69 ps and a maximum output power of 7.13 mW. Our results provide new opportunities for the development of Bi 2 O 2 S together with its application in ultrafast photonics. • The application of novel Bi 2 O 2 S nanosheets in ultrafast fiber lasers are investigated for the first time. • The Er-doped mode-locked fiber laser based on Bi 2 O 2 S has the narrowest pulse width. • The Bi 2 O 2 S based Tm-doped mode-locked fiber laser has a high output power and a large slope efficiency. [ABSTRACT FROM AUTHOR]

MXenes, one of the largest families of two-dimensional (2D) materials, provide great potential in photonics, electronics and energy. Especially, MXenes are recently discovered as alternatives to conventional saturable absorbers (SAs). However, the inevitable exposure of metal atoms on surface is likely to react with oxygen or oxygen-containing groups, leading to the severe problem of environmental instability. Here, we developed a partially-controlled oxidation strategy to prepare TiO 2 @Ti 3 C 2 T x heterostructures. The dense nanosized TiO 2 on the surface of heterostructures prevent the further oxidation of the Ti 3 C 2 T x inside, enabling a stable performance in ultrafast photonics. The saturable absorption property of TiO 2 @Ti 3 C 2 T x heterostructures is verified using the balanced twin-detector measurement system. The modulation depth and saturation intensity were determined to be 14.4% and 2.929 GW/cm2 at 1550 nm, respectively. The Erbium-doped fiber laser (EDFL) with the use of TiO 2 @Ti 3 C 2 T x SAs exhibits pulse width of 552 fs. More importantly, there is no obvious degradation in saturable absorption property of the TiO 2 @Ti 3 C 2 T x based EDFL after an exposure in air for more than thirteen months, indicating the excellent environmental stability of the TiO 2 @Ti 3 C 2 T x heterostructures. This work provides an alternative approach to enhance the long-term performance of Ti 3 C 2 T x optoelectronic devices, which may shed light on the material synthesis and device design of MXenes. • A facile strategy to synthesis the TiO 2 @Ti 3 C 2 T x heterostructures. • TiO 2 @Ti 3 C 2 T x SA exhibits an excellent performance in EDFL. • TiO 2 @Ti 3 C 2 T x heterostructures enable a stable performance in 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]

• 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]