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The Laser User Magazine
Issue 051 - Summer 2008
Two-photon polymerisation: technique and system
Author: Sven Passinger, Aleksandr Ovsianikov, Andreas Ostendorf, and Boris N. Chichkov
Rapid progress in the performance of ultra-short pulse laser systems has created exciting possibilities for two-photon polymerisation (2PP), a promising 3D microfabrication method that requires high and precise localization of femtosecond laser pulses in both time and space.
As can be seen in Figure 1, which shows an example of what can be achieved by 2PP, the process offers high resolution and the capability of real 3-dimensional structuring, providing unprecedented freedom in the fabrication of complex micro- and nanostructures.
Benefits of the two-photon process
In operation 2PP is somewhat similar to that of the traditional stereo-lithography technique, but provides much better structural resolution and quality. In each case the process involved is the curing of photosensitive materials; the critical distinction is in the mechanism by which the laser beam initiates the process. In the case of 2PP the process employs near infrared laser beams and requires the simultaneous absorption of two photons, whereas in traditional stereolithography a laser beam is used and the process is initiated by the absorption of a single ultraviolet photon. Because many photosensitive materials are transparent in the near infrared and are highly absorptive at ultraviolet wavelengths, one can initiate polymerisation with near infrared laser pulses within the volume and fabricate 3D structures, whereas with ultraviolet laser radiation polymerisation occurs at the surface.