Nanofocusing resolution enhancement of superlens combing with optically induced local thermal effect

Plasmon-assisted nanofocusing has become a promising strategy to overcome the diffraction limit in optical lithography by enabling deep-subwavelength energy localization. In this work, we present a hybrid superlens architecture that integrates structural field optimization with thermally enhanced resolution. The system comprises a five-layer metal-dielectric stack (Cr-Al-PR-Al-SiO2), with surface plasmon polaritons (SPPs) excited by circularly polarized light impinging on spiral groove patterns milled in the Cr layer. Two groove configurations are analyzed-uniform-width and Gaussian-modulated-to explore the effect of geometrical tuning on SPP excitation and heat localization. Full-wave simulations reveal that Gaussian modulation improves phase matching and suppresses side lobes, leading to a reduced optical full width at half maximum (FWHM) from 53.29nm to 43.92nm. Moreover, transient thermal simulations under 15W, 10ns UV irradiation show that thermal energy is more tightly confined in the Gaussian case, shrinking the high-temperature zone at 156°C from 32.59nm to 21.46nm. This localized heating may facilitate selective photoresist crosslinking near the glass transition temperature (~156°C), effectively reducing the developed feature size. The results suggest a synergistic enhancement of resolution through combined electromagnetic and photothermal control, suggesting a viable strategy toward high-resolution maskless lithography.