Optical lithography in the last three decades has been one of the key techniques of the semiconductor industry for transferring circuits and devices images onto substrates, and it is expected that this technology will remain a reference method for at least another decade. With the advent of femtosecond laser systems, optical lithography can takes advantage of the very short pulse duration and the very high peak power, thus avoiding thermal damages to the resist and substrate. Only in the highly focused region of the beam, the photo-polymerization can be initiated by two photons absorption processes in the resist. This technology is considered one of the potential techniques for the fabrication of arbitrary three-dimensional of micro- and nanostructures. In standard (single-photon absorption) optical lithographies, the realization of a 3D structure requires the built up of layers upon layers via consecutive steps. By two-photons lithography, the 3D structures are written directly, achieving greater spatial resolution, providing deeper laser penetration in the resist media, and less photobleaching outside the focal region. Due to its versatile nature, technological advances in 3D micro- and nano-structure fabrication are interesting for several fields, incuding: (i) microfluidics, where high-aspect-ratio PDMS microstructures or even complex 3D channels can be easily prepared; (ii) photonic crystals, where the directed top-down fabrication of arbitrary 3D structures in organic materials, differently from colloidal self-assembly methods, allows a complete control of the generated 3D structures; (iii) micro-optics, micro optical devices, or beam shaping at the exit of an optical fiber. 

(Left) Concentric circles calibration of energy dose on polymeric material. (Right) One photon versus two photon excitation scheme.

For more information, please contact: Dr. Antonio A. R. Neves ( This e-mail address is being protected from spam bots, you need JavaScript enabled to view it )