Subdiffraction 3D Nanolithography by Two‐Photon Two‐Step Absorption and Photoinhibition

Abstract Improving the 3D resolution is a decisive step in the transition of direct laser writing from being limited to research use to being a powerful tool. Three‐color (3CL) lithography is expected to result in significantly higher resolution with two‐color lasers initiating polymerization in two steps and one‐color laser inhibiting polymerization. However, the 3CL process increases the complexity of the system and makes the influence of chromatic aberration worse which leads to non‐ideal writing results, which is ≈80 nm linewidth (≈λ/10) at present. In this study, the 3CL lithography is improved by introducing almost one color (1CL) instead of three colors to achieve subdiffraction 3D nanolithography based on two‐photon two‐step absorption and photoinhibition (T 2 A‐PI). Using benzil as a photoinitiator, a sub‐30 nm (<λ/17.5) lateral feature size, minimum 80 nm lateral, and 160 nm axial pitches are achieved, which, to our knowledge, is the best to be fabricated using the laser in the visible region. 3D woodpile photonic crystals and other high‐quality nanostructures are fabricated, demonstrating the unique advantages over existing direct laser writing technologies.