2D ternary transition metal dichalcogenides (TMDCs) have been studied widely by researchers from the fields of nanotechnology to materials science because of the extraordinary chemical/physical characteristics, and significant potential in nanoscale device applications. Here, the application of Nb x Re (1−x) S 2 nanosheets in ultrafast photonics is studied. The few-layer Nb x Re (1−x) S 2 nanosheets are fabricated through liquid phase exfoliation method and a Nb x Re (1−x) S 2 -microfiber device is constructed by depositing these nanosheets onto the tapered region of a microfiber. After incorporating the Nb x Re (1−x) S 2 -microfiber saturable absorber (SA) into a net positive dispersion Er-doped fiber (EDF) laser cavity, the generation of stable dissipative soliton pulses with a pulse duration of 1.03 ps proved as polarization-locked vector solitons upon further study. With pump power growing to 900 mW, the average output power increases to 116.9 mW without pulse splitting. Besides, the pulse width can be compressed to 149.6 fs outside the cavity by using a single-mode fiber. Compared with previous works based on 2D materials-based saturable absorbers, the Nb x Re (1−x) S 2 -based mode-locked fiber laser proposed herein, reveals superior comprehensive performance.

The nonlinear optical properties of cuprous sulfide have been studied. The successful application in Er-doped fiber laser has proved cuprous sulfide as a novel, promising materials in the field of ultra-fast photonics.

Figure 6. a) The optical spectrum with a central wavelength of 1559.5 nm and a modulation period of 1.31 nm, b) oscilloscope trace of the bound state pulse sequence, c) RF spectrum of the output pulse train, d) the autocorrelation trace of the 2nd order soliton molecules, e) optical spectra of the 3rd and 4th order soliton molecules, and f) autocorrelation trace of the 3rd and 4th order soliton molecules.

Bismuthene with a similar layered lattice structure belonging to group VA is regarded as a kind of novel two-dimensional material and has excellent properties such as small indirect bandgap (less than 1 eV) and unique electronic properties, etc. Based on the large magnitude of thirdorder nonlinear susceptibility and high carrier motility, bismuthene can be considered as a promising material for various optoelectronics, electronics, and nonlinear optics. Compared with the mass research about the few-layer bismuthene, we focus on the characteristics and nonlinear optical properties of bismuthene nanosheets in this work. Bismuthene nanosheets present high modulation depth over 7.7%. The sheet-structured bismuthene as saturable absorbers (SAs) is a technically important issue in laser technology. Here, for the first time, it is demonstrated that bismuthene nanosheets can be served as an SA to readily generate a harmonic dual-wavelength mode-locked picosecond pulse in a highly nonlinear fiber laser. A harmonic mode-locked pulse order from 1st to 20th is obtained at the pump power from 43.2 to 201.5 mW. When the pump power is greater than 408 mW, a 52th harmonic dual-wavelength pulse (corresponding to the repetition of 208 MHz) has been obtained. This study demonstrates the bismuthene saturable absorption is an intrinsic property independent from the structural dimension. Our work attests the promise of bismuthene in optical communication, optical detecting, sensor systems, and material processing, etc.

Two-dimensional materials have attracted increasing attention because of their excellent mechanical, thermodynamic, magnetic, electrical and optical properties. Here, a new two-dimensional material of tin sulfide (SnS) is experimentally prepared. It is layered like black phosphorus and owns distinct optoelectronic properties, but eliminates the disadvantage of instability. The nonlinear saturable absorption characteristics of the SnS nanosheets is investigated at 1563.3 nm by the double-balanced detection method. The obtained modulation depth and saturation intensity are 5.4% and 66.3 MW/cm 2 , respectively. A passively harmonic mode-locked erbium-doped fiber laser based on the SnS saturable absorber (SA) has been demonstrated. The results show that mode-locking with fundamental frequency of 5.47 MHz is realized at pump power of 28.38 mW. With the increase of pump power, the laser can operate from fundamental frequency to high-order harmonic mode-locking. The maximum repetition rate of 412.73 MHz has been obtained, which is equivalent to the 76th harmonic mode-locking. This work reveals that SnS nanosheets is a novel and efficient SA with high damage threshold, which will find potential applications in optical communication, photoelectric detection, laser medicine, etc.