Recent developments in femtosecond laser－induced three－dimensional microstructures

Femtosecond lasers have two characteristics: ultrashort pulse length and ultrahigh electric field. They are widely used in the analysis of dynamic processes of various physicochemical reactions and fine processing with minimal thermal effects. They can also be used for three－dimensional microstructure modifications due to the nonlinear interaction between light and matter. We review the application of femtosecond lasers to three－dimensional rewriteable optical memories with ultrahigh storage density, the formation of colored three－dimensional images, the fabrication of integrated optical switches, and other related areas. We also suggest future research directions in this area.