Abstract

High-aspect-ratio micro- or nano-objects are elements of many innovative devices, such as photonic crystals. For two-dimensional columns-in- air photonic crystals, aspect ratios higher than 3.0 are typical for practical applications. However, it is not easy for conventional photolithography to fabricate high-aspect-ratio objects smaller than the diffraction limit. Nonlinear absorption to femtosecond pulses provides an attractive solution. The fabrication of three-dimensional micro-structures through multiphoton-absorption photopolymerization (MAP) using femtosecond lasers has been demonstrated.^2,3,4 in addition, femtosecond pulses can produce sub-diffraction-limit features by careful control of the pulse energy such that only the beam center has intensity larger than the threshold of multiphoton absorption.^5,6

© 2002 Optical Society of America