Super resolution direct laser writing in ITX resist inspired by STED microscopy

Direct laser writing (DLW) has become a routine tool for fabricating microstructures through two photon polymerization. Due to the diffraction limit, the resolution is usually larger than a quarter of a wavelength. In this article, by using stimulated emission depletion (STED) inspired lithography, we fabricate nanodot of 81 nm in diameter and nanoline of 93 nm in width in resist with initiator of isopropyl thioxanthone (ITX). An 800 nm, 75-MHz fs laser works as the polymerization light and a 532 nm donut mode continuous wave (CW) laser as the depletion light. This technology is potentially useful for fabrication of super resolution nanostructures.