The intensity of two-photon induced fluorescent shows quadratic dependency to the excitation intensity, as a result, one can achieve optical sectioning in fluorescent microscopy without the use of a confocal aperture. When the excitation power is properly adjusted, the fluorescent and photobleached volume is restricted to the vicinity of the focal points; therefore, it is possible to use this mechanism to achieve 3D data storage and microstructure fabrication (stereolithography).

The recording medium used in this experiment was poly-HEMA block doped with a high efficient two-photon fluorophore, APSS, (4-[N-(2-hydroxyethyl)-N-methyl) amino phenyl]-4’-(6-hydroxyhexyl sulfonyl) stilbene). The block was made by dissolving APSS in HEMA with an initiator, 2,2’-azobisisobutyronitril (AiBN) (1% mole ratio) and polymerized at 60° C for 48 hours. The polymer was then trimmed into a small rectangular block (3×5×1 mm3) and surfaced by using a ultramicrotome with a glass knife. A modified Biorad MC500 LSM equipped with a home-made computer controlled stage scanner was used for both writing (stage scanning) and read-back (beam scanning).