Superior nonlinear optical response in non-centrosymmetric stacking edge-rich spiral MoTe${}_2$ nanopyramids

Transition metal dichalcogenides (TMDs) are of great promise for various nonlinear optical (NLO) applications due to their unique electronic and optoelectronic properties, such as tunable optical bandgap, strong spin-orbit coupling, and exciton effects. However, the desired NLO performances of regular 2H-TMDs are usually restricted by their limited absorption at atomic thickness. With this regard, a structurally novel spiral MoTe${}_2$ (s-MoTe${}_2$) nanopyramids is reported with unique and superior NLO response, enabled by their broken inversion symmetry, weak interlayer coupling, exciton resonance, and strong light-matter interaction from the edge-rich 3R-like quasi-multilayer structure. The excellent NLO response over a wide spectral range from the near-infrared to visible region is demonstrated, where second- and third-order NLO responses have been simultaneously observed. Moreover, the second-order nonlinear susceptibility of s-MoTe${}_2$ is estimated to be around 1-2 order(s) of magnitude larger than those of most reported TMDs. The demonstration of a superior NLO response in such s-MoTe${}_2$ not only paves a new way for designing the best NLO TMD structures, but also greatly prompts their practical applications in micro-nano NLO devices on chips in future. (© 2022 Wiley‐VCH GmbH)