In₂Se₃ nanosheets for harmonic mode-locked fiber laser

Abstract

Two-dimensional materials with a sheet structure have excellent optical, electrical and mechanical properties, and have attracted much attention in recent years, especially In 2 Se 3 (the N-type semiconductor compound), which has a rapid development in the fields of materials science and optical communication. In this paper, the nonlinear saturation absorption characteristics of In 2 Se 3 are studied. The In 2 Se 3 nanosheet dispersion can be used in ultrafast photonics applications. The nonlinear absorption is measured by power dependent method, and the modulation depth and saturation intensity are 3.8% and 246.6 MW cm −2 , respectively. More importantly, In 2 Se 3 is used as a saturable absorber (SA) in a passively mode-locked erbium-doped fiber laser. The proposed mode-locked fiber laser is demenstrated with a center wavelength of 1529.4 nm, a fundamental frequency of 5.9 MHz, a spectral width of 3.96 nm, a pulse width of 1.38 ps, and a signal-to-noise ratio of 55 dB. For the first time, harmonic mode-locking with a high-repetition rate of 431 MHz is achieved when the pump power is 360 mW corresponding to 73rd-order harmonic mode locking. It can be seen that In 2 Se 3 is indeed a new excellent photonic material, which can be used in fiber optic communication, SAs photonics, laser material processing and light modulators.

Low-Dimensional In2Se3Compounds: From Material Preparations to Device Applications

“…ME is a common and effective method for preparing ultrathin In 2 Se 3 nanosheets down to monolayer or In 2 Se 3 -based heterojunction for the fundamental study of physical properties. ,, Besides, MBE is a powerful technique for the preparation of high-quality and thickness-controllable 2D In 2 Se 3 epitaxial films disregarding lattice-matching limits . CVD can be exploited to prepare relatively high-quality 2D films at a large scale. ,, Furthermore, using a liquid-phase method can obtain defect-free In 2 Se 3 nanostructures applied for the large-area optoelectronic devices. ,, Although preparation techniques are numerous, preparing pure-phase In 2 Se 3 is still a challenge. In the following subsection, the conditions and features of popular preparation methods for low-D In 2 Se 3 are described in detail and summarized in Table .…”

“…The physical basis is that the ultrasonication energy should match well between the solvent bond energy and the surface energy. The solvent molecules are adsorbed into the interlayer space, expand the space between interlayers, and then further weaken the vdW forces, which last leads to thin nanosheets being stripped. , …”

“…61,71,75 Furthermore, using a liquid-phase method can obtain defectfree In 2 Se 3 nanostructures applied for the large-area optoelectronic devices. 21,32,76 Although preparation techniques are numerous, preparing pure-phase In 2 Se 3 is still a challenge. In the following subsection, the conditions and features of popular preparation methods for low-D In 2 Se 3 are described in detail and summarized in Table 1.…”

“…The solvent molecules are adsorbed into the interlayer space, expand the space between interlayers, and then further weaken the vdW forces, which last leads to thin nanosheets being stripped. 32,76 In the preparation of α-In 2 Se 3 nanosheets by Wang et al, 32 5 mg of bulk α-In 2 Se 3 crystals were put into a 2 mL of solution mixed with deionized water and isopropanol volume fractions of 40%, followed by sonicating the mixture for 4 h at a power of 100 W and a frequency of 80 kHz under ambient temperature. Then, α-In 2 Se 3 thin nanosheets were separated from the dispersion by centrifugation.…”

CoS2 with 3D Valence Electron Shell Structure for Pulsed Laser Application

“…In recent years, researchers have paid great attention to nanomaterials because of their unique electrical, magnetic, and mechanical properties. − Nanomaterials have the advantages of large specific surface area and low density, which have potential applications in drug delivery, catalysis, and other fields. − Therefore, it is of great significance to carry out research on the preparation of such materials. , Novel nanomaterials exhibit novel optoelectronic properties in saturable absorbers (SAs) and optical confinement properties. − Among transition-metal sulfide (TMS) candidate materials, nickel- or cobalt-based sulfide-rich redox active sites and variable valence states have been receiving great attention. − People are dedicated to exploring TMSs, which are synthesized at low temperatures and have a controllable size and structure. − Schleich et al used transition-metal halides and alkali metal sulfides to prepare disulfides in nonaqueous solvents; Passaretti et al obtained CoS 2 crystals by vulcanizing [Co­(NH 3 ) 6 ]­Cl 2 and H 2 S at low temperatures, but the crystallization performance was not excellent. , Because CoS 2 and FeS 2 are sulfides of the same family in the same cycle, they contain similar characteristics. − The metal elements are all +2 valence styles, and the style of sulfur is −s–s– . In the natural world, CoS 2 is generally not left alone.…”