Two-photon photopolymerization and 3D lithographic microfabrication

This chapter attempts to give an overview of the historical development and current progress of femtosecond laser micro-nanofabrication based on multiphoton absorption, and particular emphasis is placed on two-photon photopolymerization. Femtosecond laser interaction with matter differs essentially from those with longer pulses or CW lasers in its significant nonlinearity, ultrafast characteristics and the possibility of highly localization of reaction volume. These features enable three-dimensional (3D) micronanofabrication in solid and liquid media. In two-photon photopolymerization, when a near-infrared femtosecond laser is tightly focused into a photopolymerizable resin, 3D polymer micro-nanostructures are produced by pinpoint photopolymerization of liquid precursory resins. Using this direct laser writing scheme, various photonic, micro-optical components and micromechanical devices have been readily produced. The two-photon photopolymerization technology is expected to play a similar role to that played by lithography for planar semiconductor device processing, but for micro-nanofabrication of 3D polymer-based optoelectronic devices as well for microelectromechanical systems.