Shape‐Sensitive Second‐Harmonic Generation in Mie‐resonant TMDC Nanoparticles

The miniaturization and functionality of Mie‐tronic devices impose the use of high‐index materials with a blueshifted transparency window and high quadratic nonlinearity. In this regard, transition metal dichalcogenides (TMDCs) are promising candidates, which also exhibit excitons at room temperature. In this work, C‐exciton‐enhanced second‐harmonic generation (SHG) in single cylindrical and cubic Mie‐resonant nanoparticles made of flakes is investigated. The study shows that SHG rotational anisotropy (SHG‐RA) is sensitive to the geometric shape of nanoparticles. In particular, the rotational patterns from cuboid nanoparticles exhibit considerable two‐fold modulation, which is governed by the altering pump field distribution inside the nanoparticle as it rotates relative to the pump polarization direction. A slight deviation from the cube shape results in a strong spectral dependence of rotational patterns when tuning the wavelength through a Mie‐driven SHG resonance. These results may be important for designing and optimizing the nonlinear response of TMDC‐based metasurfaces.