Bismuthene Nanosheets for 1 µm Multipulse Generation.

Bismuthene, as a new two-dimensional material made up of diazo metal elements, has drawn massive attention for its unique electronic, mechanical, quantum, and nonlinear optical properties. In recent years, researchers have increasingly turned their attention to the ultrafast photonics fields based on bismuthene. However, the internal ultrashort pulse dynamics has seldom been explored yet. In this work, the nonlinear optical properties of bismuthene nanosheets have been studied and applied in a passively mode-locked fiber laser. The saturation intensity and modulation depth of a saturable absorber (SA) device are about 2.4 MW/cm2 and 1%, respectively. Thanks to the narrow band gap of bismuthene and tapered fiber structure, a special kind of noise-like multipulses has been obtained. The evolution of the pulsed laser is also studied. This proposed pulsed fiber laser based on a bismuthene SA device is well suitable for some applications such as material processing, optical logics, and so forth.

Multi-wavelength output based on gold nanoparticles in erbium-doped fiber lasers.

A multi-wavelength fiber laser can be used as an ideal light source device for optical communication of wavelength-division multiplexing. A type of combined filter composed of a gold nanoparticle saturated absorber and three-wave polarization controller was constructed. Its multi-wavelength laser output is realized in an erbium-doped fiber ring laser. We studied the degradation of single-wavelength, dual-wavelength, and triple-wavelength output in the range of 1555-1565 nm, the tunability of three wavelengths, and the spectral periodicity of 1 min 57 s. The interesting phenomena of subregional transmission of gold nanoparticles were discovered. We have a clearer understanding of the filtering process of gold nanosaturable absorbers and the special state between pulsed and non-pulsed when using them to achieve ultra-short pulsed lasers.

SnSe2 Nanosheets for Subpicosecond Harmonic Mode-Locked Pulse Generation.

Tin diselenide (SnSe2 ) nanosheets as novel 2D layered materials have excellent optical properties with many promising application prospects, such as photoelectric detectors, nonlinear optics, infrared photoelectric devices, and ultrafast photonics. Among them, ultrafast photonics has attracted much attention due to its enormous advantages; for instance, extremely fast pulse, strong peak power, and narrow bandwidth. In this work, SnSe2 nanosheets are fabricated by using solvothermal treatment, and the characteristics of SnSe2 are systemically investigated. In addition, the solution of SnSe2 nanosheets is successfully prepared as a fiber-based saturable absorber by utilizing the evanescent field effect, which can bear a high pump power. 31st-order subpicosecond harmonic mode locking is generated in an Er-doped fiber laser, corresponding to the maximum repetition rate of 257.3 MHz and pulse duration of 887 fs. The results show that SnSe2 can be used as an excellent nonlinear photonic device in many fields, such as frequency comb, lasers, photodetectors, etc.

Fe3O4 nanoparticle-enabled mode-locking in an erbium-doped fiber laser.

In this paper, we have proposed and demonstrated the generation of passively mode-locked pulses and dissipative soliton resonance in an erbium-doped fiber laser based on Fe3O4 nanoparticles as saturable absorbers. We obtained self-starting mode-locked pulses with fundamental repetition frequency of 7.69 MHz and center wavelength of 1561 nm. The output of a pulsed laser has spectral width of 0.69 nm and pulse duration of 14 ns with rectangular pulse profile at the pump power of 190 mW. As far as we know, this is the firsttimethatFe3O4 nanoparticles have been developed as low-dimensional materials for passive mode-locking with rectangular pulse. Our experiments have confirmed that Fe3O4 has a wide prospect as a nonlinear photonics device for ultrafast fiber laser applications.

Cu2S nanosheets for ultrashort pulse generation in the near-infrared region.

2D metal chalcogenide materials have received enormous attention due to their extraordinary bio-chemical, electronic, magnetic, thermal and optical properties. Compared with the typical two-dimensional transition metal dichalcogenides (TMDs) and topological insulators, cuprous sulfide (Cu2S) has very different two-dimensional lattice structures, along with excellent electro-catalysis and high conductivity. However, the nonlinear optical properties of Cu2S have never been studied until now. Here, the nonlinear photonics characteristics of Cu2S and its application in ultrafast lasers have been systematically studied for the first time. Through optical deposition of Cu2S nanosheets on a tapered fiber, the nonlinear optical properties of Cu2S nanosheets are measured through the interaction with the evanescent field. The results indicate that superior nonlinear saturable absorption properties with a modulation depth of 0.51% are achieved. An erbium-doped fiber (EDF) laser is constructed to verify the performance of the Cu2S saturable absorber (SA). The results show that an output pulse with 8.06 MHz repetition rate, 1.04 ps pulse duration, 1530.4 nm central wavelength and 3.1 nm spectral width without an obvious Kelly sideband is obtained. Considering the diversity of the metal chalcogenide family, various engineering applications may be developed from the nonlinear saturable absorption characteristics of Cu2S, including optical fiber communication/sensing, precision optical metrology, material processing and nonlinear optics.

Fe3O4 nanoparticles as a saturable absorber for giant chirped pulse generation.

Fe3O4 nanoparticles (FONPs) are magnetic materials with a small band gap and have well-demonstrated applications in ultrafast photonics, medical science, magnetic detection, and electronics. Very recently, FONPs were proposed as an ideal candidate for pulse generation in fiber-based oscillators. However, the pulses obtained to date are on the order of microseconds, which is too long for real application in communication. Here, we report the use of FONPs synthesized by a sol-hydrothermal method and used as a saturable absorber (SA) to achieve nanosecond pulses in an erbium-doped fiber laser (EDFL) for the first time. The proposed fiber laser is demonstrated to have a narrow spectral width of around 0.8 nm and a fixed fundamental repetition rate (RPR) of 4.63 MHz, whose spectra and pulse dynamics are different from the mode-locked lasers reported previously. It is demonstrated that the proposed fiber laser based on a FONP SA operates in the giant-chirp mode-locked regime. The most important result is the demonstration of a pulse duration of 55 ns at an output power of 16.2 mW, which is the shortest pulse based on FONPs for EDFLs reported to date. Our results demonstrate that the FONP dispersion allows for an excellent photonic material for application in ultrafast photonics devices, photoconductive detectors, and optical modulators.