Crystalline Phase Effects on the Nonlinear Optical Response of MoS₂ and WS₂ Nanosheets: Implications for Photonic and Optoelectronic Applications

Abstract

In the present work, some MoS 2 and WS 2 nanosheets were prepared and characterized. Depending on the preparation procedures, trigonal prismatic (2H) or octahedral (1T) coordination of the metal atoms was obtained, exhibiting metallic (1T) or semiconducting (2H) character. Both MoS 2 and WS 2 nanosheets were found exhibiting large nonlinear optical (NLO) responses, strongly dependent on their metallic (1T) or semiconducting (2H) character. Therefore, the semiconducting character of MoS 2 and WS 2 exhibits positive nonlinear absorption and strong self-focusing behavior, while their metallic character counterparts exhibit strong negative nonlinear absorption and important self-defocusing behavior. In addition, the semiconducting MoS 2 and WS 2 were found exhibiting important and very broadband optical limiting (OL) action extending from 450 to 1750 nm. Therefore, by selecting the crystalline phase of the nanosheets, that is, their semiconduction/metallic character, their NLO response can be greatly modulated. The results of the present work demonstrate unambiguously that the control of the crystalline phase of MoS 2 and WS 2 provides an efficient strategy for 2D nanostructures with custom-made NLO properties for specific optoelectronic and photonic applications such as OL, saturable absorption, and optical switching.

Phthalocyanine‐Based 2D Polymer for Ultrafast Nonlinear Optical Application

“…According to the theoretical fit, the values of the nonlinear refractive index ( n 2 ) are ‐0.16 and ‐0.42 cm 2 GW −1 for PET devices, and ‐0.15 and ‐0.59 cm 2 GW −1 for quartz device, respectively. The n 2 of Pc‐2DP devices were much higher than some typical 2D materials, such as MXene, MoS 2 , and WS 2 , [ 74,75 ] and only slightly lower than that of BP (Figure S23, Supporting Information ). [ 76 ]…”

Modelling the structural disorder in trigonal-prismatic coordinated transition metal dichalcogenides

“…The octahedral coordination of Mo in MoS 2 was observed as a consequence of intercalation with different guests (Petkov et al, 2002;Acerce et al, 2015;Wang et al, 2017;Stavrou et al, 2022) or as a result of special preparation techniques (Parilla et al, 2004;Geng et al, 2017;Ding et al, 2019); the variety of reported structural details is probably related to preparation routes and to materials composition.…”

Strong Ultrafast Saturable Absorption and Nonlinear Refraction of Some Non-van der Waals 2D Hematene and Magnetene Nanoplatelets for Ultrafast Photonic Applications

“…The strong optical nonlinearities along with their ultrafast response (typically in the femtosecond time scale) are some of the key properties of 2D materials, raising their high potential for optoelectronics and photonics. Because of these characteristics, they can be used in various photonic devices, e.g., as pulsed lasers, optical power limiters, − ultrafast all-optical switches/modulators, , photodetectors, etc. In particular, the most studied van der Waals 2D materials, i.e., graphene, transition metal dichalcogenides (TMDs) like MoS 2 , WS 2 , and MoSe 2 , black phosphorus (BP), and MXenes (Ti 3 C 2 T x ), − have revealed exceptional saturable absorption (SA) properties, such as large NLO absorption coefficient, large modulation depth, and low saturation intensity.…”