Enhanced Second Harmonic Generation in One-Dimensional WS₂ Nanoscrolls

Two-dimensional transition metal dichalcogenides (TMDs), such as WS₂, exhibit strong second harmonic generation (SHG) at the monolayer limit, making them promising candidates for frequency conversion in nonlinear optical technologies. SHG, a nonlinear process where two photons of frequency ω combine to generate one photon of frequency 2ω, is highly sensitive to crystal symmetry. For example, in the 2H-type stacking structure, which is the most stable form in bulk WS₂, inversion symmetry is restored for even-numbered layers posing challenges for scalable SHG applications.



In this study, we investigate the SHG characteristics of WS₂ and its one-dimensional nanoscroll structures through broadband SHG measurements. We analyze the dependence of SHG efficiency on the orientation and thickness of the nanoscrolls, observing a significant enhancement in SHG compared to monolayer WS₂. To precisely control the scroll thickness and orientation, we employed stacking techniques and laser patterning. The incident wavelength was varied from 1100 to 1630 nm, corresponding to SHG signals in the 550 to 815 nm range. Our findings demonstrate enhanced SHG across a wide wavelength range, including the O-band (1260–1360 nm) and L-band (1565–1625 nm), suggesting strong potential for applications in fiber based nonlinear optical devices.