We take advantage of the near-resonant enhancement of the third-order nonlinear response to engineer a two-photon polymerization photoinitiator with optimized efficiency in regard to literature benchmarks. We study in detail its linear and resonant third-order nonlinear optical properties, with particular focus on photoinduced radical generation. Careful choice of peripheral substituents enables its direct solubilization into a mixture of commercial multifunctional acrylic monomers, resulting in a homogeneous photoresist with good optical transparency upon simple mixing. When submitted to sub-nanosecond pulsed laser irradiation at 532 nm, the resulting photoresist displays a polymerization threshold up to eight times lower than that obtained with the classically used two-photon initiators, giving rise to sub-100 nm line width at 250 nm interline separation and resulting in highly defined three-dimensional structures.

Synthesis of novel photoinitiators, spectroscopic (UV vis, fluorescence, steady state and time resolved), electrochemical and EPR studies of their photoinduced radical generation mechanisms, Z-scan measurements of their two-photon absorption cross section, two-photon polymerization at 532 nm, with a pulsed ns laser, material evaluation by scanning electron microscopy<br>