Femtosecond Nonlinear Optical Properties of 2D Metallic NbS₂ in the Near Infrared

Abstract

The understanding of the nonlinear optical (NLO) properties of photonic materials is relevant and necessary for basic studies and technological developments. Among the materials with high optical nonlinearities, layered transition-metal dichalcogenides (LTMDs) have attracted considerable attention from the viewpoint of both synthesis as well as characterization and applications. We report here the third-order NLO properties of one LTMDthe metallic NbS2that was prepared by a modified redox exfoliated method, suspended in acetonitrile. The LTMD was morphologically and compositionally characterized using transmission electron microscopy, atomic force microscopy, X-ray diffraction, Raman scattering, and linear absorption. The Z-scan technique was employed to characterize the nonlinear refraction (NLR) and nonlinear absorption (NLA) behavior in the femtosecond regime. Metallic NbS2 presented a sign inversion of the nonlinear refractive index from negative (self-defocusing) to positive (self-focusing) with the increase of intensity up to 100 GW/cm2. Two distinct features characteristic of NLA, two-photon absorption and saturated absorption, were also observed for different intensity ranges, with the former evolving into the latter as the intensity increased in the same range as for the NLR measurements. The material’s band structure of NbS2 was calculated using the density functional theory, and the origin of the nonlinearities is discussed by comparison with the experimental data.

Nonlinear Optical Interactions and Relaxation in 2D Layered Transition Metal Dichalcogenides Probed by Optical and Photoacoustic Z-Scan Methods

“…This different stacking leads to different physical properties. In this study, the 2H-NbS 2 phase is present, and this is demonstrated in the TEM and Raman analysis in recent studies …”

“…It should be noticed that the NLS mechanism was also observed to contribute to the NLT process for the same NbS 2 sample studied by 800 nm optical Z-scan with 100 fs input pulses. 30 ZrTe 2 presents a semimetallic character, as confirmed recently via angle-resolved photoemission spectroscopy (ARPES), 11 besides its topological semimetal character. 31 Figure 6 shows the results for OZ-and PAZ-scans.…”

“…In this case, β OZ‑scan = 3β PAZ‑scan and the contribution of NLS to the NLT is slightly higher than in MoS 2 . It should be noticed that the NLS mechanism was also observed to contribute to the NLT process for the same NbS 2 sample studied by 800 nm optical Z-scan with 100 fs input pulses …”

“…In this study, the 2H-NbS 2 phase is present, and this is demonstrated in the TEM and Raman analysis in recent studies. 30 Figure 5a,b shows the OZ-scan normalized transmittance, and Figure 5c,d shows the normalized PAZ-scan signal for the NbS 2 suspension for two different intensities. The overall nonlinear absorption behavior is similar to that of MoS 2 , with both SA and RSA observed.…”

Initiating VB‐Group Laminated NbS2 Electromagnetic Wave Absorber toward Superior Absorption Bandwidth as Large as 6.48 GHz through Phase Engineering Modulation

“…[51] In addition, the two peaks at higher binding energies belonging to NbS 2 nanowires are observed at 207.4 and 210.2 eV, which can be assigned to Nb 5+ 3d 5/2 and Nb 5+ 3d 3/2 of Nb 2 O 5 because of oxidation on the surface. [52,53] Raman spectra for the samples are obtained using a laser with a wave length of 532 nm as the light source. As shown in Figure S4 (Supporting Information), those for sample N-4 exhibit four peaks at 312.4, 333.1, 381.2, and 449.2 cm −1 , which could be the characteristic peaks of NbS 2 corresponding to the E 1 , E 2 , A 1 , and A 2 vibration modes, [30,54] respectively.…”