Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted significant interest in various optoelectronic applications due to their excellent nonlinear optical properties. One of the most important applications of TMDs is to be employed as an extraordinary optical modulation material (e.g., the saturable absorber (SA)) in ultrafast photonics. The main challenge arises while embedding TMDs into fiber laser systems to generate ultrafast pulse trains and thus constraints their practical applications. Herein, few-layered WS with a large-area was directly transferred on the facet of the pigtail and acted as a SA for erbium-doped fiber laser (EDFL) systems. In our study, WS SA exhibited remarkable nonlinear optical properties (e.g., modulation depth of 15.1% and saturable intensity of 157.6 MW cm) and was used for ultrafast pulse generation. The soliton pulses with remarkable performances (e.g., ultrashort pulse duration of 1.49 ps, high stability of 71.8 dB, and large pulse average output power of 62.5 mW) could be obtained in a telecommunication band. To the best of our knowledge, the average output power of the mode-locked pulse trains is the highest by employing TMD materials in fiber laser systems. These results indicate that atomically large-area WS could be used as excellent optical modulation materials in ultrafast photonics.
In this Letter, high-quality WS film and MoS film were vertically stacked on the tip of a single-mode fiber in turns to form heterostructure (WS-MoS-WS)-based saturable absorbers with all-fiber integrated features. Their nonlinear saturable absorption properties were remarkable, such as a large modulation depth (∼16.99%) and a small saturable intensity (6.23 MW·cm). Stable pulses at 1.55 μm with duration as short as 296 fs and average power as high as 25 mW were obtained in an erbium-doped fiber laser system. The results demonstrate that the proposed heterostructures own remarkable nonlinear optical properties and offer a platform for adjusting nonlinear optical properties by stacking different transition-metal dichalcogenides or modifying the thickness of each layer, paving the way for engineering functional ultrafast photonics devices with desirable properties.
in the field of ultrafast photonics. Since the successful demonstration of graphene-based saturable absorber (SA) for ultrafast pulsed lasers, [7,8] 2D layered materials including black phosphorus, topological insulators, and transition metal dichalcogenides (TMDs), have recently been extensively investigated in nonlinear optical devices for the generation of ultrafast pulses via passive modelocking operation. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] In particular, the recent advancements in the development of TMDs with unique electronic and optical attributes have explored many potential applications in electronics and photonics. [24,25] The TMDs with layered structure can be exfoliated into atomic-thin layers, which advance the development of wider applications as high-performance transistors, photodetectors and nonlinear optical devices owing to their widespread bandgaps from the visible to the nearinfrared region. [24][25][26][27][28][29][30][31] Currently, nonlinear optical devices based on group VIB TMDs have been fully studied using as saturable absorbers (SA) for the successful generation of short pulses in broadband region. [17][18][19][20][21][22][23][32][33][34][35][36] Despite the previous efforts, it is still possible to optimize the SA devices toward ultrafast photonics for the admired purposes of generating laser pulse with shorter pulse width and greater output power, which can be anticipated by exploring other members of TMDs. In comparison with intensively studied group VIB TMDs, group IVB TMDs which are theoretically predicted to have superior physical properties to group VIB TMDs, have rarely been investigated yet. [37,38] For instance, single-layered HfS 2 is expected to possess much higher carrier mobility (≈1800 cm 2 V −1 s −1 ) and smaller bandgap (≈1.2 eV) than that of MoS 2 . [38,39] Owing to superior electronic properties, ultrathin HfS 2 fabricated by mechanically exfoliation or chemical vapor deposition methods presents significant potential in phototransistors and field-effect transistors. [40][41][42][43][44][45][46][47] However, to our knowledge, the nonlinear optical properties of HfS 2 and its application in ultrafast photonics remain unknown.In this contribution, we demonstrate a new function of multilayered HfS 2 nanosheets (NSs) with nonlinear optical absorption for development of ultrafast photonic devices. We prepared HfS 2 NSs via a modified liquid exfoliation approach using isopropanol (IPA) as solvent. HfS 2 dispersions are precisely deposited onto a microfiber to form a SA device by using a photonic crystal fiber (PCF) assisted deposition method. The HfS 2 SA device is found to show excellent nonlinear absorption Group IVB transition metal dichalcogenides (TMDs) have attracted significant interests in photoelectronics due to their predictable superior physical properties compared to group VIB (Mo and W) TMDs. However, the nonlinear optical properties and ultrafast photonic devices based on group IVB TMDs remained unexplored so far. Herein, the nonlinear ...
Large-area and highly crystalline transition metal dichalcogenides (TMDs) films possess superior saturable absorption compared to the TMDs nanosheet counterparts, which make them more suitable as excellent saturable absorbers (SA) for ultrafast laser technology. Thus far, the nonlinear optical properties of large-scale WSe 2 and its applications in ultrafast photonics have not yet been fully investigated. In this work, the saturable absorption of chemical vapor deposition (CVD) grown WSe 2 films with large-scale and high quality are studied and the use of WSe 2 films as a broadband SA for passively mode-locked fiber lasers at both 1.5 and 2 μm ranges is demonstrated. To enhance the light-material interaction, largearea WSe 2 film is tightly transferred onto the side wall of a microfiber to form a hybrid structure, which realizes strong evanescent wave interaction between light and WSe 2 film. The integrated microfiber-WSe 2 device shows a large modulation depth of 54.5%. Using the large-area WSe 2 as a mode-locker, stable soliton mode-locked pulse generation is achieved and the pulse durations of 477 fs (at 1.5 μm) and 1.18 ps (at 2.0 μm) are demonstrated, which suggests that the large-area and highly crystalline WSe 2 films afford an excellent broadband SA for ultrafast photonic applications. References and links 1. Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, and M. S. Strano, "Electronics and optoelectronics of two-dimensional transition metal dichalcogenides," Nat. Nanotechnol. 7(11), 699-712 (2012). 2. K. F. Mak and J. Shan, "Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides," Nat. Photonics 10, 216-226 (2016 1974-1981 (2013). 2085-2087 (2012)
Two-dimensional materials have become the focus of research for their photoelectric properties, and are employed as saturable absorption materials. Currently, the challenge is how to further improve the modulation depth of saturable absorbers (SAs) based on two-dimensional materials. In this paper, three kinds of WSe2 films with different thicknesses are prepared using the chemical vapor deposition method. The nonlinear optical responses of the WSe2 films including the nonlinear saturable absorption and nonlinear refractive index are characterized by the double-balanced detection method and Z-scan experiments. Different modulation depths are successfully obtained by controlling the thickness of the WSe2 films. We further incorporate them into an all-fiber laser to generate mode-locked pulses. The mode-locked fiber lasers with a pulse duration of 185 fs, 205.7 fs and 230.3 fs are demonstrated when the thickness of the WSe2 films is measured to be 1.5 nm, 5.7 nm and 11 nm, respectively. This work provides new prospects for WSe2 in ultrafast photonic device applications.
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