Refractive femtosecond laser beam shaping for two-photon polymerization

Three dimensional microstructure fabrication by two-photon polymerization is an established technique that normally uses single beam serial writing. Recently the use of a micro-optical element, to give multipoint beam delivery, was reported to give a degree of parallel processing. The authors describe an alternative approach to parallel processing using an axicon lens. This is a refractive element that, in combination with a high power microscope objective, efficiently transforms the laser beam from a Gaussian spot to an annulus. The authors demonstrate that the beam can polymerize a three dimensional shape, with nanoscale resolution. The use of more sophisticated refractive beam shaping is also discussed.