Dielectric‐Compatible Thermal Scanning Probe Lithography for Grayscale Chiral Metasurfaces

ABSTRACT All‐dielectric chiral metasurfaces, exploiting broken in‐plane or out‐of‐plane symmetry to manipulate circular polarized light, offer immense potential applications for chiral emission, sensing, and nonlinear optics. While their low loss and multipolar resonances surpass metallic counterparts in efficiency and design freedom, realizing flexible design and full capabilities has been constrained by suitable high‐precision 3D nanofabrication approaches. Here, we overcome this critical barrier by developing dielectric‐compatible thermal scanning probe lithography (t‐SPL) for high‐index dielectric metasurfaces with grayscale topography and exceptional vertical resolution (<10 nm). Therefore, grayscale‐engineered 3D chiral metasurfaces can be designed and precisely fabricated, showcasing the chiral quasi‐bound states in the continuum with high quality factors (Q‐factor>100) and giant intrinsic chirality. In addition, the resulting 3D geometries provide independent control over both chirality and Q‐factor through tailored asymmetric parameters. By developing the dielectric‐compatible t‐SPL as a promising pathway for complex high‐index all‐dielectric 3D architectures, this work enables the practical realization of high‐efficiency chiral optical devices—accelerating progress in integrated quantum photonics, ultrasensitive biosensing, and compact polarization‐engineered systems.