Microsphere femtosecond laser sub-50 nm structuring in far field via non-linear absorption

Creation of arbitrary features with high resolution is critically important in the fabrication nano-optoelectronic devices. Here, sub-50 nm surface structuring achieved directly on Sb2S3 thin films via microsphere femtosecond laser irradiation far field. By varying fluence and scanning speed, nano-feature sizes can be flexibly tuned. Such small patterns are attributed to co-effect focusing, two-photons absorption, top threshold effect, high-repetition-rate laser-induced incubation effect. The minimum feature size reduced down ~30 (λ/26) by manipulating film thickness. fitting analysis between ablation width depth predicts that ~15 at thickness ~10 nm. A nano-grating fabricated, which demonstrates desirable beam diffraction performance. This nano-scale would highly attractive for next-generation nano-lithography field ambient air.